sv-dependency-builds: osx/include/opus/opusfile.h comparison

comparison osx/include/opus/opusfile.h @ 154:4664ac0c1032

Add Opus sources and macOS builds

author	Chris Cannam <cannam@all-day-breakfast.com>
date	Wed, 23 Jan 2019 13:48:08 +0000
parents
children

comparison

equal deleted inserted replaced

-:84bc3a5ec321
+:4664ac0c1032
+/********************************************************************
+*                                                                  *
+* THIS FILE IS PART OF THE libopusfile SOFTWARE CODEC SOURCE CODE. *
+* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
+* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
+* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
+*                                                                  *
+* THE libopusfile SOURCE CODE IS (C) COPYRIGHT 1994-2012           *
+* by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
+*                                                                  *
+********************************************************************
+function: stdio-based convenience library for opening/seeking/decoding
+last mod: $Id: vorbisfile.h 17182 2010-04-29 03:48:32Z xiphmont $
+********************************************************************/
+#if !defined(_opusfile_h)
+# define _opusfile_h (1)
+/**\mainpage
+\section Introduction
+This is the documentation for the <tt>libopusfile</tt> C API.
+The <tt>libopusfile</tt> package provides a convenient high-level API for
+decoding and basic manipulation of all Ogg Opus audio streams.
+<tt>libopusfile</tt> is implemented as a layer on top of Xiph.Org's
+reference
+<tt><a href="https://www.xiph.org/ogg/doc/libogg/reference.html">libogg</a></tt>
+and
+<tt><a href="https://mf4.xiph.org/jenkins/view/opus/job/opus/ws/doc/html/index.html">libopus</a></tt>
+libraries.
+<tt>libopusfile</tt> provides several sets of built-in routines for
+file/stream access, and may also use custom stream I/O routines provided by
+the embedded environment.
+There are built-in I/O routines provided for ANSI-compliant
+<code>stdio</code> (<code>FILE *</code>), memory buffers, and URLs
+(including <file:> URLs, plus optionally <http:> and <https:> URLs).
+\section Organization
+The main API is divided into several sections:
+- \ref stream_open_close
+- \ref stream_info
+- \ref stream_decoding
+- \ref stream_seeking
+Several additional sections are not tied to the main API.
+- \ref stream_callbacks
+- \ref header_info
+- \ref error_codes
+\section Overview
+The <tt>libopusfile</tt> API always decodes files to 48&nbsp;kHz.
+The original sample rate is not preserved by the lossy compression, though
+it is stored in the header to allow you to resample to it after decoding
+(the <tt>libopusfile</tt> API does not currently provide a resampler,
+but the
+<a href="http://www.speex.org/docs/manual/speex-manual/node7.html#SECTION00760000000000000000">the
+Speex resampler</a> is a good choice if you need one).
+In general, if you are playing back the audio, you should leave it at
+48&nbsp;kHz, provided your audio hardware supports it.
+When decoding to a file, it may be worth resampling back to the original
+sample rate, so as not to surprise users who might not expect the sample
+rate to change after encoding to Opus and decoding.
+Opus files can contain anywhere from 1 to 255 channels of audio.
+The channel mappings for up to 8 channels are the same as the
+<a href="http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9">Vorbis
+mappings</a>.
+A special stereo API can convert everything to 2 channels, making it simple
+to support multichannel files in an application which only has stereo
+output.
+Although the <tt>libopusfile</tt> ABI provides support for the theoretical
+maximum number of channels, the current implementation does not support
+files with more than 8 channels, as they do not have well-defined channel
+mappings.
+Like all Ogg files, Opus files may be "chained".
+That is, multiple Opus files may be combined into a single, longer file just
+by concatenating the original files.
+This is commonly done in internet radio streaming, as it allows the title
+and artist to be updated each time the song changes, since each link in the
+chain includes its own set of metadata.
+<tt>libopusfile</tt> fully supports chained files.
+It will decode the first Opus stream found in each link of a chained file
+(ignoring any other streams that might be concurrently multiplexed with it,
+such as a video stream).
+The channel count can also change between links.
+If your application is not prepared to deal with this, it can use the stereo
+API to ensure the audio from all links will always get decoded into a
+common format.
+Since <tt>libopusfile</tt> always decodes to 48&nbsp;kHz, you do not have to
+worry about the sample rate changing between links (as was possible with
+Vorbis).
+This makes application support for chained files with <tt>libopusfile</tt>
+very easy.*/
+# if defined(__cplusplus)
+extern "C" {
+# endif
+# include <stdarg.h>
+# include <stdio.h>
+# include <ogg/ogg.h>
+# include <opus_multistream.h>
+/**@cond PRIVATE*/
+/*Enable special features for gcc and gcc-compatible compilers.*/
+# if !defined(OP_GNUC_PREREQ)
+#  if defined(__GNUC__)&&defined(__GNUC_MINOR__)
+#   define OP_GNUC_PREREQ(_maj,_min) \
+((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min))
+#  else
+#   define OP_GNUC_PREREQ(_maj,_min) 0
+#  endif
+# endif
+# if OP_GNUC_PREREQ(4,0)
+#  pragma GCC visibility push(default)
+# endif
+typedef struct OpusHead          OpusHead;
+typedef struct OpusTags          OpusTags;
+typedef struct OpusPictureTag    OpusPictureTag;
+typedef struct OpusServerInfo    OpusServerInfo;
+typedef struct OpusFileCallbacks OpusFileCallbacks;
+typedef struct OggOpusFile       OggOpusFile;
+/*Warning attributes for libopusfile functions.*/
+# if OP_GNUC_PREREQ(3,4)
+#  define OP_WARN_UNUSED_RESULT __attribute__((__warn_unused_result__))
+# else
+#  define OP_WARN_UNUSED_RESULT
+# endif
+# if OP_GNUC_PREREQ(3,4)
+#  define OP_ARG_NONNULL(_x) __attribute__((__nonnull__(_x)))
+# else
+#  define OP_ARG_NONNULL(_x)
+# endif
+/**@endcond*/
+/**\defgroup error_codes Error Codes*/
+/*@{*/
+/**\name List of possible error codes
+Many of the functions in this library return a negative error code when a
+function fails.
+This list provides a brief explanation of the common errors.
+See each individual function for more details on what a specific error code
+means in that context.*/
+/*@{*/
+/**A request did not succeed.*/
+#define OP_FALSE         (-1)
+/*Currently not used externally.*/
+#define OP_EOF           (-2)
+/**There was a hole in the page sequence numbers (e.g., a page was corrupt or
+missing).*/
+#define OP_HOLE          (-3)
+/**An underlying read, seek, or tell operation failed when it should have
+succeeded.*/
+#define OP_EREAD         (-128)
+/**A <code>NULL</code> pointer was passed where one was unexpected, or an
+internal memory allocation failed, or an internal library error was
+encountered.*/
+#define OP_EFAULT        (-129)
+/**The stream used a feature that is not implemented, such as an unsupported
+channel family.*/
+#define OP_EIMPL         (-130)
+/**One or more parameters to a function were invalid.*/
+#define OP_EINVAL        (-131)
+/**A purported Ogg Opus stream did not begin with an Ogg page, a purported
+header packet did not start with one of the required strings, "OpusHead" or
+"OpusTags", or a link in a chained file was encountered that did not
+contain any logical Opus streams.*/
+#define OP_ENOTFORMAT    (-132)
+/**A required header packet was not properly formatted, contained illegal
+values, or was missing altogether.*/
+#define OP_EBADHEADER    (-133)
+/**The ID header contained an unrecognized version number.*/
+#define OP_EVERSION      (-134)
+/*Currently not used at all.*/
+#define OP_ENOTAUDIO     (-135)
+/**An audio packet failed to decode properly.
+This is usually caused by a multistream Ogg packet where the durations of
+the individual Opus packets contained in it are not all the same.*/
+#define OP_EBADPACKET    (-136)
+/**We failed to find data we had seen before, or the bitstream structure was
+sufficiently malformed that seeking to the target destination was
+impossible.*/
+#define OP_EBADLINK      (-137)
+/**An operation that requires seeking was requested on an unseekable stream.*/
+#define OP_ENOSEEK       (-138)
+/**The first or last granule position of a link failed basic validity checks.*/
+#define OP_EBADTIMESTAMP (-139)
+/*@}*/
+/*@}*/
+/**\defgroup header_info Header Information*/
+/*@{*/
+/**The maximum number of channels in an Ogg Opus stream.*/
+#define OPUS_CHANNEL_COUNT_MAX (255)
+/**Ogg Opus bitstream information.
+This contains the basic playback parameters for a stream, and corresponds to
+the initial ID header packet of an Ogg Opus stream.*/
+struct OpusHead{
+/**The Ogg Opus format version, in the range 0...255.
+The top 4 bits represent a "major" version, and the bottom four bits
+represent backwards-compatible "minor" revisions.
+The current specification describes version 1.
+This library will recognize versions up through 15 as backwards compatible
+with the current specification.
+An earlier draft of the specification described a version 0, but the only
+difference between version 1 and version 0 is that version 0 did
+not specify the semantics for handling the version field.*/
+int           version;
+/**The number of channels, in the range 1...255.*/
+int           channel_count;
+/**The number of samples that should be discarded from the beginning of the
+stream.*/
+unsigned      pre_skip;
+/**The sampling rate of the original input.
+All Opus audio is coded at 48 kHz, and should also be decoded at 48 kHz
+for playback (unless the target hardware does not support this sampling
+rate).
+However, this field may be used to resample the audio back to the original
+sampling rate, for example, when saving the output to a file.*/
+opus_uint32   input_sample_rate;
+/**The gain to apply to the decoded output, in dB, as a Q8 value in the range
+-32768...32767.
+The <tt>libopusfile</tt> API will automatically apply this gain to the
+decoded output before returning it, scaling it by
+<code>pow(10,output_gain/(20.0*256))</code>.
+You can adjust this behavior with op_set_gain_offset().*/
+int           output_gain;
+/**The channel mapping family, in the range 0...255.
+Channel mapping family 0 covers mono or stereo in a single stream.
+Channel mapping family 1 covers 1 to 8 channels in one or more streams,
+using the Vorbis speaker assignments.
+Channel mapping family 255 covers 1 to 255 channels in one or more
+streams, but without any defined speaker assignment.*/
+int           mapping_family;
+/**The number of Opus streams in each Ogg packet, in the range 1...255.*/
+int           stream_count;
+/**The number of coupled Opus streams in each Ogg packet, in the range
+0...127.
+This must satisfy <code>0 <= coupled_count <= stream_count</code> and
+<code>coupled_count + stream_count <= 255</code>.
+The coupled streams appear first, before all uncoupled streams, in an Ogg
+Opus packet.*/
+int           coupled_count;
+/**The mapping from coded stream channels to output channels.
+Let <code>index=mapping[k]</code> be the value for channel <code>k</code>.
+If <code>index<2*coupled_count</code>, then it refers to the left channel
+from stream <code>(index/2)</code> if even, and the right channel from
+stream <code>(index/2)</code> if odd.
+Otherwise, it refers to the output of the uncoupled stream
+<code>(index-coupled_count)</code>.*/
+unsigned char mapping[OPUS_CHANNEL_COUNT_MAX];
+};
+/**The metadata from an Ogg Opus stream.
+This structure holds the in-stream metadata corresponding to the 'comment'
+header packet of an Ogg Opus stream.
+The comment header is meant to be used much like someone jotting a quick
+note on the label of a CD.
+It should be a short, to the point text note that can be more than a couple
+words, but not more than a short paragraph.
+The metadata is stored as a series of (tag, value) pairs, in length-encoded
+string vectors, using the same format as Vorbis (without the final "framing
+bit"), Theora, and Speex, except for the packet header.
+The first occurrence of the '=' character delimits the tag and value.
+A particular tag may occur more than once, and order is significant.
+The character set encoding for the strings is always UTF-8, but the tag
+names are limited to ASCII, and treated as case-insensitive.
+See <a href="http://www.xiph.org/vorbis/doc/v-comment.html">the Vorbis
+comment header specification</a> for details.
+In filling in this structure, <tt>libopusfile</tt> will null-terminate the
+#user_comments strings for safety.
+However, the bitstream format itself treats them as 8-bit clean vectors,
+possibly containing NUL characters, so the #comment_lengths array should be
+treated as their authoritative length.
+This structure is binary and source-compatible with a
+<code>vorbis_comment</code>, and pointers to it may be freely cast to
+<code>vorbis_comment</code> pointers, and vice versa.
+It is provided as a separate type to avoid introducing a compile-time
+dependency on the libvorbis headers.*/
+struct OpusTags{
+/**The array of comment string vectors.*/
+char **user_comments;
+/**An array of the corresponding length of each vector, in bytes.*/
+int   *comment_lengths;
+/**The total number of comment streams.*/
+int    comments;
+/**The null-terminated vendor string.
+This identifies the software used to encode the stream.*/
+char  *vendor;
+};
+/**\name Picture tag image formats*/
+/*@{*/
+/**The MIME type was not recognized, or the image data did not match the
+declared MIME type.*/
+#define OP_PIC_FORMAT_UNKNOWN (-1)
+/**The MIME type indicates the image data is really a URL.*/
+#define OP_PIC_FORMAT_URL     (0)
+/**The image is a JPEG.*/
+#define OP_PIC_FORMAT_JPEG    (1)
+/**The image is a PNG.*/
+#define OP_PIC_FORMAT_PNG     (2)
+/**The image is a GIF.*/
+#define OP_PIC_FORMAT_GIF     (3)
+/*@}*/
+/**The contents of a METADATA_BLOCK_PICTURE tag.*/
+struct OpusPictureTag{
+/**The picture type according to the ID3v2 APIC frame:
+<ol start="0">
+<li>Other</li>
+<li>32x32 pixels 'file icon' (PNG only)</li>
+<li>Other file icon</li>
+<li>Cover (front)</li>
+<li>Cover (back)</li>
+<li>Leaflet page</li>
+<li>Media (e.g. label side of CD)</li>
+<li>Lead artist/lead performer/soloist</li>
+<li>Artist/performer</li>
+<li>Conductor</li>
+<li>Band/Orchestra</li>
+<li>Composer</li>
+<li>Lyricist/text writer</li>
+<li>Recording Location</li>
+<li>During recording</li>
+<li>During performance</li>
+<li>Movie/video screen capture</li>
+<li>A bright colored fish</li>
+<li>Illustration</li>
+<li>Band/artist logotype</li>
+<li>Publisher/Studio logotype</li>
+</ol>
+Others are reserved and should not be used.
+There may only be one each of picture type 1 and 2 in a file.*/
+opus_int32     type;
+/**The MIME type of the picture, in printable ASCII characters 0x20-0x7E.
+The MIME type may also be <code>"-->"</code> to signify that the data part
+is a URL pointing to the picture instead of the picture data itself.
+In this case, a terminating NUL is appended to the URL string in #data,
+but #data_length is set to the length of the string excluding that
+terminating NUL.*/
+char          *mime_type;
+/**The description of the picture, in UTF-8.*/
+char          *description;
+/**The width of the picture in pixels.*/
+opus_uint32    width;
+/**The height of the picture in pixels.*/
+opus_uint32    height;
+/**The color depth of the picture in bits-per-pixel (<em>not</em>
+bits-per-channel).*/
+opus_uint32    depth;
+/**For indexed-color pictures (e.g., GIF), the number of colors used, or 0
+for non-indexed pictures.*/
+opus_uint32    colors;
+/**The length of the picture data in bytes.*/
+opus_uint32    data_length;
+/**The binary picture data.*/
+unsigned char *data;
+/**The format of the picture data, if known.
+One of
+<ul>
+<li>#OP_PIC_FORMAT_UNKNOWN,</li>
+<li>#OP_PIC_FORMAT_URL,</li>
+<li>#OP_PIC_FORMAT_JPEG,</li>
+<li>#OP_PIC_FORMAT_PNG, or</li>
+<li>#OP_PIC_FORMAT_GIF.</li>
+</ul>*/
+int            format;
+};
+/**\name Functions for manipulating header data
+These functions manipulate the #OpusHead and #OpusTags structures,
+which describe the audio parameters and tag-value metadata, respectively.
+These can be used to query the headers returned by <tt>libopusfile</tt>, or
+to parse Opus headers from sources other than an Ogg Opus stream, provided
+they use the same format.*/
+/*@{*/
+/**Parses the contents of the ID header packet of an Ogg Opus stream.
+\param[out] _head Returns the contents of the parsed packet.
+The contents of this structure are untouched on error.
+This may be <code>NULL</code> to merely test the header
+for validity.
+\param[in]  _data The contents of the ID header packet.
+\param      _len  The number of bytes of data in the ID header packet.
+\return 0 on success or a negative value on error.
+\retval #OP_ENOTFORMAT If the data does not start with the "OpusHead"
+string.
+\retval #OP_EVERSION   If the version field signaled a version this library
+does not know how to parse.
+\retval #OP_EIMPL      If the channel mapping family was 255, which general
+purpose players should not attempt to play.
+\retval #OP_EBADHEADER If the contents of the packet otherwise violate the
+Ogg Opus specification:
+<ul>
+<li>Insufficient data,</li>
+<li>Too much data for the known minor versions,</li>
+<li>An unrecognized channel mapping family,</li>
+<li>Zero channels or too many channels,</li>
+<li>Zero coded streams,</li>
+<li>Too many coupled streams, or</li>
+<li>An invalid channel mapping index.</li>
+</ul>*/
+OP_WARN_UNUSED_RESULT int opus_head_parse(OpusHead *_head,
+const unsigned char *_data,size_t _len) OP_ARG_NONNULL(2);
+/**Converts a granule position to a sample offset for a given Ogg Opus stream.
+The sample offset is simply <code>_gp-_head->pre_skip</code>.
+Granule position values smaller than OpusHead#pre_skip correspond to audio
+that should never be played, and thus have no associated sample offset.
+This function returns -1 for such values.
+This function also correctly handles extremely large granule positions,
+which may have wrapped around to a negative number when stored in a signed
+ogg_int64_t value.
+\param _head The #OpusHead information from the ID header of the stream.
+\param _gp   The granule position to convert.
+\return The sample offset associated with the given granule position
+(counting at a 48 kHz sampling rate), or the special value -1 on
+error (i.e., the granule position was smaller than the pre-skip
+amount).*/
+ogg_int64_t opus_granule_sample(const OpusHead *_head,ogg_int64_t _gp)
+OP_ARG_NONNULL(1);
+/**Parses the contents of the 'comment' header packet of an Ogg Opus stream.
+\param[out] _tags An uninitialized #OpusTags structure.
+This returns the contents of the parsed packet.
+The contents of this structure are untouched on error.
+This may be <code>NULL</code> to merely test the header
+for validity.
+\param[in]  _data The contents of the 'comment' header packet.
+\param      _len  The number of bytes of data in the 'info' header packet.
+\retval 0              Success.
+\retval #OP_ENOTFORMAT If the data does not start with the "OpusTags"
+string.
+\retval #OP_EBADHEADER If the contents of the packet otherwise violate the
+Ogg Opus specification.
+\retval #OP_EFAULT     If there wasn't enough memory to store the tags.*/
+OP_WARN_UNUSED_RESULT int opus_tags_parse(OpusTags *_tags,
+const unsigned char *_data,size_t _len) OP_ARG_NONNULL(2);
+/**Performs a deep copy of an #OpusTags structure.
+\param _dst The #OpusTags structure to copy into.
+If this function fails, the contents of this structure remain
+untouched.
+\param _src The #OpusTags structure to copy from.
+\retval 0          Success.
+\retval #OP_EFAULT If there wasn't enough memory to copy the tags.*/
+int opus_tags_copy(OpusTags *_dst,const OpusTags *_src) OP_ARG_NONNULL(1);
+/**Initializes an #OpusTags structure.
+This should be called on a freshly allocated #OpusTags structure before
+attempting to use it.
+\param _tags The #OpusTags structure to initialize.*/
+void opus_tags_init(OpusTags *_tags) OP_ARG_NONNULL(1);
+/**Add a (tag, value) pair to an initialized #OpusTags structure.
+\note Neither opus_tags_add() nor opus_tags_add_comment() support values
+containing embedded NULs, although the bitstream format does support them.
+To add such tags, you will need to manipulate the #OpusTags structure
+directly.
+\param _tags  The #OpusTags structure to add the (tag, value) pair to.
+\param _tag   A NUL-terminated, case-insensitive, ASCII string containing
+the tag to add (without an '=' character).
+\param _value A NUL-terminated UTF-8 containing the corresponding value.
+\return 0 on success, or a negative value on failure.
+\retval #OP_EFAULT An internal memory allocation failed.*/
+int opus_tags_add(OpusTags *_tags,const char *_tag,const char *_value)
+OP_ARG_NONNULL(1) OP_ARG_NONNULL(2) OP_ARG_NONNULL(3);
+/**Add a comment to an initialized #OpusTags structure.
+\note Neither opus_tags_add_comment() nor opus_tags_add() support comments
+containing embedded NULs, although the bitstream format does support them.
+To add such tags, you will need to manipulate the #OpusTags structure
+directly.
+\param _tags    The #OpusTags structure to add the comment to.
+\param _comment A NUL-terminated UTF-8 string containing the comment in
+"TAG=value" form.
+\return 0 on success, or a negative value on failure.
+\retval #OP_EFAULT An internal memory allocation failed.*/
+int opus_tags_add_comment(OpusTags *_tags,const char *_comment)
+OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Replace the binary suffix data at the end of the packet (if any).
+\param _tags An initialized #OpusTags structure.
+\param _data A buffer of binary data to append after the encoded user
+comments.
+The least significant bit of the first byte of this data must
+be set (to ensure the data is preserved by other editors).
+\param _len  The number of bytes of binary data to append.
+This may be zero to remove any existing binary suffix data.
+\return 0 on success, or a negative value on error.
+\retval #OP_EINVAL \a _len was negative, or \a _len was positive but
+\a _data was <code>NULL</code> or the least significant
+bit of the first byte was not set.
+\retval #OP_EFAULT An internal memory allocation failed.*/
+int opus_tags_set_binary_suffix(OpusTags *_tags,
+const unsigned char *_data,int _len) OP_ARG_NONNULL(1);
+/**Look up a comment value by its tag.
+\param _tags  An initialized #OpusTags structure.
+\param _tag   The tag to look up.
+\param _count The instance of the tag.
+The same tag can appear multiple times, each with a distinct
+value, so an index is required to retrieve them all.
+The order in which these values appear is significant and
+should be preserved.
+Use opus_tags_query_count() to get the legal range for the
+\a _count parameter.
+\return A pointer to the queried tag's value.
+This points directly to data in the #OpusTags structure.
+It should not be modified or freed by the application, and
+modifications to the structure may invalidate the pointer.
+\retval NULL If no matching tag is found.*/
+const char *opus_tags_query(const OpusTags *_tags,const char *_tag,int _count)
+OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Look up the number of instances of a tag.
+Call this first when querying for a specific tag and then iterate over the
+number of instances with separate calls to opus_tags_query() to retrieve
+all the values for that tag in order.
+\param _tags An initialized #OpusTags structure.
+\param _tag  The tag to look up.
+\return The number of instances of this particular tag.*/
+int opus_tags_query_count(const OpusTags *_tags,const char *_tag)
+OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Retrieve the binary suffix data at the end of the packet (if any).
+\param      _tags An initialized #OpusTags structure.
+\param[out] _len  Returns the number of bytes of binary suffix data returned.
+\return A pointer to the binary suffix data, or <code>NULL</code> if none
+was present.*/
+const unsigned char *opus_tags_get_binary_suffix(const OpusTags *_tags,
+int *_len) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Get the album gain from an R128_ALBUM_GAIN tag, if one was specified.
+This searches for the first R128_ALBUM_GAIN tag with a valid signed,
+16-bit decimal integer value and returns the value.
+This routine is exposed merely for convenience for applications which wish
+to do something special with the album gain (i.e., display it).
+If you simply wish to apply the album gain instead of the header gain, you
+can use op_set_gain_offset() with an #OP_ALBUM_GAIN type and no offset.
+\param      _tags    An initialized #OpusTags structure.
+\param[out] _gain_q8 The album gain, in 1/256ths of a dB.
+This will lie in the range [-32768,32767], and should
+be applied in <em>addition</em> to the header gain.
+On error, no value is returned, and the previous
+contents remain unchanged.
+\return 0 on success, or a negative value on error.
+\retval #OP_FALSE There was no album gain available in the given tags.*/
+int opus_tags_get_album_gain(const OpusTags *_tags,int *_gain_q8)
+OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Get the track gain from an R128_TRACK_GAIN tag, if one was specified.
+This searches for the first R128_TRACK_GAIN tag with a valid signed,
+16-bit decimal integer value and returns the value.
+This routine is exposed merely for convenience for applications which wish
+to do something special with the track gain (i.e., display it).
+If you simply wish to apply the track gain instead of the header gain, you
+can use op_set_gain_offset() with an #OP_TRACK_GAIN type and no offset.
+\param      _tags    An initialized #OpusTags structure.
+\param[out] _gain_q8 The track gain, in 1/256ths of a dB.
+This will lie in the range [-32768,32767], and should
+be applied in <em>addition</em> to the header gain.
+On error, no value is returned, and the previous
+contents remain unchanged.
+\return 0 on success, or a negative value on error.
+\retval #OP_FALSE There was no track gain available in the given tags.*/
+int opus_tags_get_track_gain(const OpusTags *_tags,int *_gain_q8)
+OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Clears the #OpusTags structure.
+This should be called on an #OpusTags structure after it is no longer
+needed.
+It will free all memory used by the structure members.
+\param _tags The #OpusTags structure to clear.*/
+void opus_tags_clear(OpusTags *_tags) OP_ARG_NONNULL(1);
+/**Check if \a _comment is an instance of a \a _tag_name tag.
+\see opus_tagncompare
+\param _tag_name A NUL-terminated, case-insensitive, ASCII string containing
+the name of the tag to check for (without the terminating
+'=' character).
+\param _comment  The comment string to check.
+\return An integer less than, equal to, or greater than zero if \a _comment
+is found respectively, to be less than, to match, or be greater
+than a "tag=value" string whose tag matches \a _tag_name.*/
+int opus_tagcompare(const char *_tag_name,const char *_comment);
+/**Check if \a _comment is an instance of a \a _tag_name tag.
+This version is slightly more efficient than opus_tagcompare() if the length
+of the tag name is already known (e.g., because it is a constant).
+\see opus_tagcompare
+\param _tag_name A case-insensitive ASCII string containing the name of the
+tag to check for (without the terminating '=' character).
+\param _tag_len  The number of characters in the tag name.
+This must be non-negative.
+\param _comment  The comment string to check.
+\return An integer less than, equal to, or greater than zero if \a _comment
+is found respectively, to be less than, to match, or be greater
+than a "tag=value" string whose tag matches the first \a _tag_len
+characters of \a _tag_name.*/
+int opus_tagncompare(const char *_tag_name,int _tag_len,const char *_comment);
+/**Parse a single METADATA_BLOCK_PICTURE tag.
+This decodes the BASE64-encoded content of the tag and returns a structure
+with the MIME type, description, image parameters (if known), and the
+compressed image data.
+If the MIME type indicates the presence of an image format we recognize
+(JPEG, PNG, or GIF) and the actual image data contains the magic signature
+associated with that format, then the OpusPictureTag::format field will be
+set to the corresponding format.
+This is provided as a convenience to avoid requiring applications to parse
+the MIME type and/or do their own format detection for the commonly used
+formats.
+In this case, we also attempt to extract the image parameters directly from
+the image data (overriding any that were present in the tag, which the
+specification says applications are not meant to rely on).
+The application must still provide its own support for actually decoding the
+image data and, if applicable, retrieving that data from URLs.
+\param[out] _pic Returns the parsed picture data.
+No sanitation is done on the type, MIME type, or
+description fields, so these might return invalid values.
+The contents of this structure are left unmodified on
+failure.
+\param      _tag The METADATA_BLOCK_PICTURE tag contents.
+The leading "METADATA_BLOCK_PICTURE=" portion is optional,
+to allow the function to be used on either directly on the
+values in OpusTags::user_comments or on the return value
+of opus_tags_query().
+\return 0 on success or a negative value on error.
+\retval #OP_ENOTFORMAT The METADATA_BLOCK_PICTURE contents were not valid.
+\retval #OP_EFAULT     There was not enough memory to store the picture tag
+contents.*/
+OP_WARN_UNUSED_RESULT int opus_picture_tag_parse(OpusPictureTag *_pic,
+const char *_tag) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Initializes an #OpusPictureTag structure.
+This should be called on a freshly allocated #OpusPictureTag structure
+before attempting to use it.
+\param _pic The #OpusPictureTag structure to initialize.*/
+void opus_picture_tag_init(OpusPictureTag *_pic) OP_ARG_NONNULL(1);
+/**Clears the #OpusPictureTag structure.
+This should be called on an #OpusPictureTag structure after it is no longer
+needed.
+It will free all memory used by the structure members.
+\param _pic The #OpusPictureTag structure to clear.*/
+void opus_picture_tag_clear(OpusPictureTag *_pic) OP_ARG_NONNULL(1);
+/*@}*/
+/*@}*/
+/**\defgroup url_options URL Reading Options*/
+/*@{*/
+/**\name URL reading options
+Options for op_url_stream_create() and associated functions.
+These allow you to provide proxy configuration parameters, skip SSL
+certificate checks, etc.
+Options are processed in order, and if the same option is passed multiple
+times, only the value specified by the last occurrence has an effect
+(unless otherwise specified).
+They may be expanded in the future.*/
+/*@{*/
+/**@cond PRIVATE*/
+/*These are the raw numbers used to define the request codes.
+They should not be used directly.*/
+#define OP_SSL_SKIP_CERTIFICATE_CHECK_REQUEST (6464)
+#define OP_HTTP_PROXY_HOST_REQUEST            (6528)
+#define OP_HTTP_PROXY_PORT_REQUEST            (6592)
+#define OP_HTTP_PROXY_USER_REQUEST            (6656)
+#define OP_HTTP_PROXY_PASS_REQUEST            (6720)
+#define OP_GET_SERVER_INFO_REQUEST            (6784)
+#define OP_URL_OPT(_request) ((_request)+(char *)0)
+/*These macros trigger compilation errors or warnings if the wrong types are
+provided to one of the URL options.*/
+#define OP_CHECK_INT(_x) ((void)((_x)==(opus_int32)0),(opus_int32)(_x))
+#define OP_CHECK_CONST_CHAR_PTR(_x) ((_x)+((_x)-(const char *)(_x)))
+#define OP_CHECK_SERVER_INFO_PTR(_x) ((_x)+((_x)-(OpusServerInfo *)(_x)))
+/**@endcond*/
+/**HTTP/Shoutcast/Icecast server information associated with a URL.*/
+struct OpusServerInfo{
+/**The name of the server (icy-name/ice-name).
+This is <code>NULL</code> if there was no <code>icy-name</code> or
+<code>ice-name</code> header.*/
+char        *name;
+/**A short description of the server (icy-description/ice-description).
+This is <code>NULL</code> if there was no <code>icy-description</code> or
+<code>ice-description</code> header.*/
+char        *description;
+/**The genre the server falls under (icy-genre/ice-genre).
+This is <code>NULL</code> if there was no <code>icy-genre</code> or
+<code>ice-genre</code> header.*/
+char        *genre;
+/**The homepage for the server (icy-url/ice-url).
+This is <code>NULL</code> if there was no <code>icy-url</code> or
+<code>ice-url</code> header.*/
+char        *url;
+/**The software used by the origin server (Server).
+This is <code>NULL</code> if there was no <code>Server</code> header.*/
+char        *server;
+/**The media type of the entity sent to the recepient (Content-Type).
+This is <code>NULL</code> if there was no <code>Content-Type</code>
+header.*/
+char        *content_type;
+/**The nominal stream bitrate in kbps (icy-br/ice-bitrate).
+This is <code>-1</code> if there was no <code>icy-br</code> or
+<code>ice-bitrate</code> header.*/
+opus_int32   bitrate_kbps;
+/**Flag indicating whether the server is public (<code>1</code>) or not
+(<code>0</code>) (icy-pub/ice-public).
+This is <code>-1</code> if there was no <code>icy-pub</code> or
+<code>ice-public</code> header.*/
+int          is_public;
+/**Flag indicating whether the server is using HTTPS instead of HTTP.
+This is <code>0</code> unless HTTPS is being used.
+This may not match the protocol used in the original URL if there were
+redirections.*/
+int          is_ssl;
+};
+/**Initializes an #OpusServerInfo structure.
+All fields are set as if the corresponding header was not available.
+\param _info The #OpusServerInfo structure to initialize.
+\note If you use this function, you must link against <tt>libopusurl</tt>.*/
+void opus_server_info_init(OpusServerInfo *_info) OP_ARG_NONNULL(1);
+/**Clears the #OpusServerInfo structure.
+This should be called on an #OpusServerInfo structure after it is no longer
+needed.
+It will free all memory used by the structure members.
+\param _info The #OpusServerInfo structure to clear.
+\note If you use this function, you must link against <tt>libopusurl</tt>.*/
+void opus_server_info_clear(OpusServerInfo *_info) OP_ARG_NONNULL(1);
+/**Skip the certificate check when connecting via TLS/SSL (https).
+\param _b <code>opus_int32</code>: Whether or not to skip the certificate
+check.
+The check will be skipped if \a _b is non-zero, and will not be
+skipped if \a _b is zero.
+\hideinitializer*/
+#define OP_SSL_SKIP_CERTIFICATE_CHECK(_b) \
+OP_URL_OPT(OP_SSL_SKIP_CERTIFICATE_CHECK_REQUEST),OP_CHECK_INT(_b)
+/**Proxy connections through the given host.
+If no port is specified via #OP_HTTP_PROXY_PORT, the port number defaults
+to 8080 (http-alt).
+All proxy parameters are ignored for non-http and non-https URLs.
+\param _host <code>const char *</code>: The proxy server hostname.
+This may be <code>NULL</code> to disable the use of a proxy
+server.
+\hideinitializer*/
+#define OP_HTTP_PROXY_HOST(_host) \
+OP_URL_OPT(OP_HTTP_PROXY_HOST_REQUEST),OP_CHECK_CONST_CHAR_PTR(_host)
+/**Use the given port when proxying connections.
+This option only has an effect if #OP_HTTP_PROXY_HOST is specified with a
+non-<code>NULL</code> \a _host.
+If this option is not provided, the proxy port number defaults to 8080
+(http-alt).
+All proxy parameters are ignored for non-http and non-https URLs.
+\param _port <code>opus_int32</code>: The proxy server port.
+This must be in the range 0...65535 (inclusive), or the
+URL function this is passed to will fail.
+\hideinitializer*/
+#define OP_HTTP_PROXY_PORT(_port) \
+OP_URL_OPT(OP_HTTP_PROXY_PORT_REQUEST),OP_CHECK_INT(_port)
+/**Use the given user name for authentication when proxying connections.
+All proxy parameters are ignored for non-http and non-https URLs.
+\param _user const char *: The proxy server user name.
+This may be <code>NULL</code> to disable proxy
+authentication.
+A non-<code>NULL</code> value only has an effect
+if #OP_HTTP_PROXY_HOST and #OP_HTTP_PROXY_PASS
+are also specified with non-<code>NULL</code>
+arguments.
+\hideinitializer*/
+#define OP_HTTP_PROXY_USER(_user) \
+OP_URL_OPT(OP_HTTP_PROXY_USER_REQUEST),OP_CHECK_CONST_CHAR_PTR(_user)
+/**Use the given password for authentication when proxying connections.
+All proxy parameters are ignored for non-http and non-https URLs.
+\param _pass const char *: The proxy server password.
+This may be <code>NULL</code> to disable proxy
+authentication.
+A non-<code>NULL</code> value only has an effect
+if #OP_HTTP_PROXY_HOST and #OP_HTTP_PROXY_USER
+are also specified with non-<code>NULL</code>
+arguments.
+\hideinitializer*/
+#define OP_HTTP_PROXY_PASS(_pass) \
+OP_URL_OPT(OP_HTTP_PROXY_PASS_REQUEST),OP_CHECK_CONST_CHAR_PTR(_pass)
+/**Parse information about the streaming server (if any) and return it.
+Very little validation is done.
+In particular, OpusServerInfo::url may not be a valid URL,
+OpusServerInfo::bitrate_kbps may not really be in kbps, and
+OpusServerInfo::content_type may not be a valid MIME type.
+The character set of the string fields is not specified anywhere, and should
+not be assumed to be valid UTF-8.
+\param _info OpusServerInfo *: Returns information about the server.
+If there is any error opening the stream, the
+contents of this structure remain
+unmodified.
+On success, fills in the structure with the
+server information that was available, if
+any.
+After a successful return, the contents of
+this structure should be freed by calling
+opus_server_info_clear().
+\hideinitializer*/
+#define OP_GET_SERVER_INFO(_info) \
+OP_URL_OPT(OP_GET_SERVER_INFO_REQUEST),OP_CHECK_SERVER_INFO_PTR(_info)
+/*@}*/
+/*@}*/
+/**\defgroup stream_callbacks Abstract Stream Reading Interface*/
+/*@{*/
+/**\name Functions for reading from streams
+These functions define the interface used to read from and seek in a stream
+of data.
+A stream does not need to implement seeking, but the decoder will not be
+able to seek if it does not do so.
+These functions also include some convenience routines for working with
+standard <code>FILE</code> pointers, complete streams stored in a single
+block of memory, or URLs.*/
+/*@{*/
+/**Reads up to \a _nbytes bytes of data from \a _stream.
+\param      _stream The stream to read from.
+\param[out] _ptr    The buffer to store the data in.
+\param      _nbytes The maximum number of bytes to read.
+This function may return fewer, though it will not
+return zero unless it reaches end-of-file.
+\return The number of bytes successfully read, or a negative value on
+error.*/
+typedef int (*op_read_func)(void *_stream,unsigned char *_ptr,int _nbytes);
+/**Sets the position indicator for \a _stream.
+The new position, measured in bytes, is obtained by adding \a _offset
+bytes to the position specified by \a _whence.
+If \a _whence is set to <code>SEEK_SET</code>, <code>SEEK_CUR</code>, or
+<code>SEEK_END</code>, the offset is relative to the start of the stream,
+the current position indicator, or end-of-file, respectively.
+\retval 0  Success.
+\retval -1 Seeking is not supported or an error occurred.
+<code>errno</code> need not be set.*/
+typedef int (*op_seek_func)(void *_stream,opus_int64 _offset,int _whence);
+/**Obtains the current value of the position indicator for \a _stream.
+\return The current position indicator.*/
+typedef opus_int64 (*op_tell_func)(void *_stream);
+/**Closes the underlying stream.
+\retval 0   Success.
+\retval EOF An error occurred.
+<code>errno</code> need not be set.*/
+typedef int (*op_close_func)(void *_stream);
+/**The callbacks used to access non-<code>FILE</code> stream resources.
+The function prototypes are basically the same as for the stdio functions
+<code>fread()</code>, <code>fseek()</code>, <code>ftell()</code>, and
+<code>fclose()</code>.
+The differences are that the <code>FILE *</code> arguments have been
+replaced with a <code>void *</code>, which is to be used as a pointer to
+whatever internal data these functions might need, that #seek and #tell
+take and return 64-bit offsets, and that #seek <em>must</em> return -1 if
+the stream is unseekable.*/
+struct OpusFileCallbacks{
+/**Used to read data from the stream.
+This must not be <code>NULL</code>.*/
+op_read_func  read;
+/**Used to seek in the stream.
+This may be <code>NULL</code> if seeking is not implemented.*/
+op_seek_func  seek;
+/**Used to return the current read position in the stream.
+This may be <code>NULL</code> if seeking is not implemented.*/
+op_tell_func  tell;
+/**Used to close the stream when the decoder is freed.
+This may be <code>NULL</code> to leave the stream open.*/
+op_close_func close;
+};
+/**Opens a stream with <code>fopen()</code> and fills in a set of callbacks
+that can be used to access it.
+This is useful to avoid writing your own portable 64-bit seeking wrappers,
+and also avoids cross-module linking issues on Windows, where a
+<code>FILE *</code> must be accessed by routines defined in the same module
+that opened it.
+\param[out] _cb   The callbacks to use for this file.
+If there is an error opening the file, nothing will be
+filled in here.
+\param      _path The path to the file to open.
+On Windows, this string must be UTF-8 (to allow access to
+files whose names cannot be represented in the current
+MBCS code page).
+All other systems use the native character encoding.
+\param      _mode The mode to open the file in.
+\return A stream handle to use with the callbacks, or <code>NULL</code> on
+error.*/
+OP_WARN_UNUSED_RESULT void *op_fopen(OpusFileCallbacks *_cb,
+const char *_path,const char *_mode) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2)
+OP_ARG_NONNULL(3);
+/**Opens a stream with <code>fdopen()</code> and fills in a set of callbacks
+that can be used to access it.
+This is useful to avoid writing your own portable 64-bit seeking wrappers,
+and also avoids cross-module linking issues on Windows, where a
+<code>FILE *</code> must be accessed by routines defined in the same module
+that opened it.
+\param[out] _cb   The callbacks to use for this file.
+If there is an error opening the file, nothing will be
+filled in here.
+\param      _fd   The file descriptor to open.
+\param      _mode The mode to open the file in.
+\return A stream handle to use with the callbacks, or <code>NULL</code> on
+error.*/
+OP_WARN_UNUSED_RESULT void *op_fdopen(OpusFileCallbacks *_cb,
+int _fd,const char *_mode) OP_ARG_NONNULL(1) OP_ARG_NONNULL(3);
+/**Opens a stream with <code>freopen()</code> and fills in a set of callbacks
+that can be used to access it.
+This is useful to avoid writing your own portable 64-bit seeking wrappers,
+and also avoids cross-module linking issues on Windows, where a
+<code>FILE *</code> must be accessed by routines defined in the same module
+that opened it.
+\param[out] _cb     The callbacks to use for this file.
+If there is an error opening the file, nothing will be
+filled in here.
+\param      _path   The path to the file to open.
+On Windows, this string must be UTF-8 (to allow access
+to files whose names cannot be represented in the
+current MBCS code page).
+All other systems use the native character encoding.
+\param      _mode   The mode to open the file in.
+\param      _stream A stream previously returned by op_fopen(), op_fdopen(),
+or op_freopen().
+\return A stream handle to use with the callbacks, or <code>NULL</code> on
+error.*/
+OP_WARN_UNUSED_RESULT void *op_freopen(OpusFileCallbacks *_cb,
+const char *_path,const char *_mode,void *_stream) OP_ARG_NONNULL(1)
+OP_ARG_NONNULL(2) OP_ARG_NONNULL(3) OP_ARG_NONNULL(4);
+/**Creates a stream that reads from the given block of memory.
+This block of memory must contain the complete stream to decode.
+This is useful for caching small streams (e.g., sound effects) in RAM.
+\param[out] _cb   The callbacks to use for this stream.
+If there is an error creating the stream, nothing will be
+filled in here.
+\param      _data The block of memory to read from.
+\param      _size The size of the block of memory.
+\return A stream handle to use with the callbacks, or <code>NULL</code> on
+error.*/
+OP_WARN_UNUSED_RESULT void *op_mem_stream_create(OpusFileCallbacks *_cb,
+const unsigned char *_data,size_t _size) OP_ARG_NONNULL(1);
+/**Creates a stream that reads from the given URL.
+This function behaves identically to op_url_stream_create(), except that it
+takes a va_list instead of a variable number of arguments.
+It does not call the <code>va_end</code> macro, and because it invokes the
+<code>va_arg</code> macro, the value of \a _ap is undefined after the call.
+\note If you use this function, you must link against <tt>libopusurl</tt>.
+\param[out]    _cb  The callbacks to use for this stream.
+If there is an error creating the stream, nothing will
+be filled in here.
+\param         _url The URL to read from.
+Currently only the <file:>, <http:>, and <https:>
+schemes are supported.
+Both <http:> and <https:> may be disabled at compile
+time, in which case opening such URLs will always fail.
+Currently this only supports URIs.
+IRIs should be converted to UTF-8 and URL-escaped, with
+internationalized domain names encoded in punycode,
+before passing them to this function.
+\param[in,out] _ap  A list of the \ref url_options "optional flags" to use.
+This is a variable-length list of options terminated
+with <code>NULL</code>.
+\return A stream handle to use with the callbacks, or <code>NULL</code> on
+error.*/
+OP_WARN_UNUSED_RESULT void *op_url_stream_vcreate(OpusFileCallbacks *_cb,
+const char *_url,va_list _ap) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/**Creates a stream that reads from the given URL.
+\note If you use this function, you must link against <tt>libopusurl</tt>.
+\param[out] _cb  The callbacks to use for this stream.
+If there is an error creating the stream, nothing will be
+filled in here.
+\param      _url The URL to read from.
+Currently only the <file:>, <http:>, and <https:> schemes
+are supported.
+Both <http:> and <https:> may be disabled at compile time,
+in which case opening such URLs will always fail.
+Currently this only supports URIs.
+IRIs should be converted to UTF-8 and URL-escaped, with
+internationalized domain names encoded in punycode, before
+passing them to this function.
+\param      ...  The \ref url_options "optional flags" to use.
+This is a variable-length list of options terminated with
+<code>NULL</code>.
+\return A stream handle to use with the callbacks, or <code>NULL</code> on
+error.*/
+OP_WARN_UNUSED_RESULT void *op_url_stream_create(OpusFileCallbacks *_cb,
+const char *_url,...) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+/*@}*/
+/*@}*/
+/**\defgroup stream_open_close Opening and Closing*/
+/*@{*/
+/**\name Functions for opening and closing streams
+These functions allow you to test a stream to see if it is Opus, open it,
+and close it.
+Several flavors are provided for each of the built-in stream types, plus a
+more general version which takes a set of application-provided callbacks.*/
+/*@{*/
+/**Test to see if this is an Opus stream.
+For good results, you will need at least 57 bytes (for a pure Opus-only
+stream).
+Something like 512 bytes will give more reliable results for multiplexed
+streams.
+This function is meant to be a quick-rejection filter.
+Its purpose is not to guarantee that a stream is a valid Opus stream, but to
+ensure that it looks enough like Opus that it isn't going to be recognized
+as some other format (except possibly an Opus stream that is also
+multiplexed with other codecs, such as video).
+\param[out] _head     The parsed ID header contents.
+You may pass <code>NULL</code> if you do not need
+this information.
+If the function fails, the contents of this structure
+remain untouched.
+\param _initial_data  An initial buffer of data from the start of the
+stream.
+\param _initial_bytes The number of bytes in \a _initial_data.
+\return 0 if the data appears to be Opus, or a negative value on error.
+\retval #OP_FALSE      There was not enough data to tell if this was an Opus
+stream or not.
+\retval #OP_EFAULT     An internal memory allocation failed.
+\retval #OP_EIMPL      The stream used a feature that is not implemented,
+such as an unsupported channel family.
+\retval #OP_ENOTFORMAT If the data did not contain a recognizable ID
+header for an Opus stream.
+\retval #OP_EVERSION   If the version field signaled a version this library
+does not know how to parse.
+\retval #OP_EBADHEADER The ID header was not properly formatted or contained
+illegal values.*/
+int op_test(OpusHead *_head,
+const unsigned char *_initial_data,size_t _initial_bytes);
+/**Open a stream from the given file path.
+\param      _path  The path to the file to open.
+\param[out] _error Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want the
+failure code.
+The failure code will be #OP_EFAULT if the file could not
+be opened, or one of the other failure codes from
+op_open_callbacks() otherwise.
+\return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_file(const char *_path,int *_error)
+OP_ARG_NONNULL(1);
+/**Open a stream from a memory buffer.
+\param      _data  The memory buffer to open.
+\param      _size  The number of bytes in the buffer.
+\param[out] _error Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want the
+failure code.
+See op_open_callbacks() for a full list of failure codes.
+\return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_memory(const unsigned char *_data,
+size_t _size,int *_error);
+/**Open a stream from a URL.
+This function behaves identically to op_open_url(), except that it
+takes a va_list instead of a variable number of arguments.
+It does not call the <code>va_end</code> macro, and because it invokes the
+<code>va_arg</code> macro, the value of \a _ap is undefined after the call.
+\note If you use this function, you must link against <tt>libopusurl</tt>.
+\param         _url   The URL to open.
+Currently only the <file:>, <http:>, and <https:>
+schemes are supported.
+Both <http:> and <https:> may be disabled at compile
+time, in which case opening such URLs will always
+fail.
+Currently this only supports URIs.
+IRIs should be converted to UTF-8 and URL-escaped,
+with internationalized domain names encoded in
+punycode, before passing them to this function.
+\param[out]    _error Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want
+the failure code.
+See op_open_callbacks() for a full list of failure
+codes.
+\param[in,out] _ap    A list of the \ref url_options "optional flags" to
+use.
+This is a variable-length list of options terminated
+with <code>NULL</code>.
+\return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_vopen_url(const char *_url,
+int *_error,va_list _ap) OP_ARG_NONNULL(1);
+/**Open a stream from a URL.
+\note If you use this function, you must link against <tt>libopusurl</tt>.
+\param      _url   The URL to open.
+Currently only the <file:>, <http:>, and <https:> schemes
+are supported.
+Both <http:> and <https:> may be disabled at compile
+time, in which case opening such URLs will always fail.
+Currently this only supports URIs.
+IRIs should be converted to UTF-8 and URL-escaped, with
+internationalized domain names encoded in punycode,
+before passing them to this function.
+\param[out] _error Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want the
+failure code.
+See op_open_callbacks() for a full list of failure codes.
+\param      ...    The \ref url_options "optional flags" to use.
+This is a variable-length list of options terminated with
+<code>NULL</code>.
+\return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_url(const char *_url,
+int *_error,...) OP_ARG_NONNULL(1);
+/**Open a stream using the given set of callbacks to access it.
+\param _stream        The stream to read from (e.g., a <code>FILE *</code>).
+This value will be passed verbatim as the first
+argument to all of the callbacks.
+\param _cb            The callbacks with which to access the stream.
+<code><a href="#op_read_func">read()</a></code> must
+be implemented.
+<code><a href="#op_seek_func">seek()</a></code> and
+<code><a href="#op_tell_func">tell()</a></code> may
+be <code>NULL</code>, or may always return -1 to
+indicate a stream is unseekable, but if
+<code><a href="#op_seek_func">seek()</a></code> is
+implemented and succeeds on a particular stream, then
+<code><a href="#op_tell_func">tell()</a></code> must
+also.
+<code><a href="#op_close_func">close()</a></code> may
+be <code>NULL</code>, but if it is not, it will be
+called when the \c OggOpusFile is destroyed by
+op_free().
+It will not be called if op_open_callbacks() fails
+with an error.
+\param _initial_data  An initial buffer of data from the start of the
+stream.
+Applications can read some number of bytes from the
+start of the stream to help identify this as an Opus
+stream, and then provide them here to allow the
+stream to be opened, even if it is unseekable.
+\param _initial_bytes The number of bytes in \a _initial_data.
+If the stream is seekable, its current position (as
+reported by
+<code><a href="#opus_tell_func">tell()</a></code>
+at the start of this function) must be equal to
+\a _initial_bytes.
+Otherwise, seeking to absolute positions will
+generate inconsistent results.
+\param[out] _error    Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want
+the failure code.
+The failure code will be one of
+<dl>
+<dt>#OP_EREAD</dt>
+<dd>An underlying read, seek, or tell operation
+failed when it should have succeeded, or we failed
+to find data in the stream we had seen before.</dd>
+<dt>#OP_EFAULT</dt>
+<dd>There was a memory allocation failure, or an
+internal library error.</dd>
+<dt>#OP_EIMPL</dt>
+<dd>The stream used a feature that is not
+implemented, such as an unsupported channel
+family.</dd>
+<dt>#OP_EINVAL</dt>
+<dd><code><a href="#op_seek_func">seek()</a></code>
+was implemented and succeeded on this source, but
+<code><a href="#op_tell_func">tell()</a></code>
+did not, or the starting position indicator was
+not equal to \a _initial_bytes.</dd>
+<dt>#OP_ENOTFORMAT</dt>
+<dd>The stream contained a link that did not have
+any logical Opus streams in it.</dd>
+<dt>#OP_EBADHEADER</dt>
+<dd>A required header packet was not properly
+formatted, contained illegal values, or was missing
+altogether.</dd>
+<dt>#OP_EVERSION</dt>
+<dd>An ID header contained an unrecognized version
+number.</dd>
+<dt>#OP_EBADLINK</dt>
+<dd>We failed to find data we had seen before after
+seeking.</dd>
+<dt>#OP_EBADTIMESTAMP</dt>
+<dd>The first or last timestamp in a link failed
+basic validity checks.</dd>
+</dl>
+\return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.
+<tt>libopusfile</tt> does <em>not</em> take ownership of the stream
+if the call fails.
+The calling application is responsible for closing the stream if
+this call returns an error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_callbacks(void *_stream,
+const OpusFileCallbacks *_cb,const unsigned char *_initial_data,
+size_t _initial_bytes,int *_error) OP_ARG_NONNULL(2);
+/**Partially open a stream from the given file path.
+\see op_test_callbacks
+\param      _path  The path to the file to open.
+\param[out] _error Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want the
+failure code.
+The failure code will be #OP_EFAULT if the file could not
+be opened, or one of the other failure codes from
+op_open_callbacks() otherwise.
+\return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_file(const char *_path,int *_error)
+OP_ARG_NONNULL(1);
+/**Partially open a stream from a memory buffer.
+\see op_test_callbacks
+\param      _data  The memory buffer to open.
+\param      _size  The number of bytes in the buffer.
+\param[out] _error Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want the
+failure code.
+See op_open_callbacks() for a full list of failure codes.
+\return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_memory(const unsigned char *_data,
+size_t _size,int *_error);
+/**Partially open a stream from a URL.
+This function behaves identically to op_test_url(), except that it
+takes a va_list instead of a variable number of arguments.
+It does not call the <code>va_end</code> macro, and because it invokes the
+<code>va_arg</code> macro, the value of \a _ap is undefined after the call.
+\note If you use this function, you must link against <tt>libopusurl</tt>.
+\see op_test_url
+\see op_test_callbacks
+\param         _url    The URL to open.
+Currently only the <file:>, <http:>, and <https:>
+schemes are supported.
+Both <http:> and <https:> may be disabled at compile
+time, in which case opening such URLs will always
+fail.
+Currently this only supports URIs.
+IRIs should be converted to UTF-8 and URL-escaped,
+with internationalized domain names encoded in
+punycode, before passing them to this function.
+\param[out]    _error  Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want
+the failure code.
+See op_open_callbacks() for a full list of failure
+codes.
+\param[in,out] _ap     A list of the \ref url_options "optional flags" to
+use.
+This is a variable-length list of options terminated
+with <code>NULL</code>.
+\return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_vtest_url(const char *_url,
+int *_error,va_list _ap) OP_ARG_NONNULL(1);
+/**Partially open a stream from a URL.
+\note If you use this function, you must link against <tt>libopusurl</tt>.
+\see op_test_callbacks
+\param      _url    The URL to open.
+Currently only the <file:>, <http:>, and <https:>
+schemes are supported.
+Both <http:> and <https:> may be disabled at compile
+time, in which case opening such URLs will always fail.
+Currently this only supports URIs.
+IRIs should be converted to UTF-8 and URL-escaped, with
+internationalized domain names encoded in punycode,
+before passing them to this function.
+\param[out] _error  Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want the
+failure code.
+See op_open_callbacks() for a full list of failure
+codes.
+\param      ...     The \ref url_options "optional flags" to use.
+This is a variable-length list of options terminated
+with <code>NULL</code>.
+\return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_url(const char *_url,
+int *_error,...) OP_ARG_NONNULL(1);
+/**Partially open a stream using the given set of callbacks to access it.
+This tests for Opusness and loads the headers for the first link.
+It does not seek (although it tests for seekability).
+You can query a partially open stream for the few pieces of basic
+information returned by op_serialno(), op_channel_count(), op_head(), and
+op_tags() (but only for the first link).
+You may also determine if it is seekable via a call to op_seekable().
+You cannot read audio from the stream, seek, get the size or duration,
+get information from links other than the first one, or even get the total
+number of links until you finish opening the stream with op_test_open().
+If you do not need to do any of these things, you can dispose of it with
+op_free() instead.
+This function is provided mostly to simplify porting existing code that used
+<tt>libvorbisfile</tt>.
+For new code, you are likely better off using op_test() instead, which
+is less resource-intensive, requires less data to succeed, and imposes a
+hard limit on the amount of data it examines (important for unseekable
+streams, where all such data must be buffered until you are sure of the
+stream type).
+\param _stream        The stream to read from (e.g., a <code>FILE *</code>).
+This value will be passed verbatim as the first
+argument to all of the callbacks.
+\param _cb            The callbacks with which to access the stream.
+<code><a href="#op_read_func">read()</a></code> must
+be implemented.
+<code><a href="#op_seek_func">seek()</a></code> and
+<code><a href="#op_tell_func">tell()</a></code> may
+be <code>NULL</code>, or may always return -1 to
+indicate a stream is unseekable, but if
+<code><a href="#op_seek_func">seek()</a></code> is
+implemented and succeeds on a particular stream, then
+<code><a href="#op_tell_func">tell()</a></code> must
+also.
+<code><a href="#op_close_func">close()</a></code> may
+be <code>NULL</code>, but if it is not, it will be
+called when the \c OggOpusFile is destroyed by
+op_free().
+It will not be called if op_open_callbacks() fails
+with an error.
+\param _initial_data  An initial buffer of data from the start of the
+stream.
+Applications can read some number of bytes from the
+start of the stream to help identify this as an Opus
+stream, and then provide them here to allow the
+stream to be tested more thoroughly, even if it is
+unseekable.
+\param _initial_bytes The number of bytes in \a _initial_data.
+If the stream is seekable, its current position (as
+reported by
+<code><a href="#opus_tell_func">tell()</a></code>
+at the start of this function) must be equal to
+\a _initial_bytes.
+Otherwise, seeking to absolute positions will
+generate inconsistent results.
+\param[out] _error    Returns 0 on success, or a failure code on error.
+You may pass in <code>NULL</code> if you don't want
+the failure code.
+See op_open_callbacks() for a full list of failure
+codes.
+\return A partially opened \c OggOpusFile, or <code>NULL</code> on error.
+<tt>libopusfile</tt> does <em>not</em> take ownership of the stream
+if the call fails.
+The calling application is responsible for closing the stream if
+this call returns an error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_callbacks(void *_stream,
+const OpusFileCallbacks *_cb,const unsigned char *_initial_data,
+size_t _initial_bytes,int *_error) OP_ARG_NONNULL(2);
+/**Finish opening a stream partially opened with op_test_callbacks() or one of
+the associated convenience functions.
+If this function fails, you are still responsible for freeing the
+\c OggOpusFile with op_free().
+\param _of The \c OggOpusFile to finish opening.
+\return 0 on success, or a negative value on error.
+\retval #OP_EREAD         An underlying read, seek, or tell operation failed
+when it should have succeeded.
+\retval #OP_EFAULT        There was a memory allocation failure, or an
+internal library error.
+\retval #OP_EIMPL         The stream used a feature that is not implemented,
+such as an unsupported channel family.
+\retval #OP_EINVAL        The stream was not partially opened with
+op_test_callbacks() or one of the associated
+convenience functions.
+\retval #OP_ENOTFORMAT    The stream contained a link that did not have any
+logical Opus streams in it.
+\retval #OP_EBADHEADER    A required header packet was not properly
+formatted, contained illegal values, or was
+missing altogether.
+\retval #OP_EVERSION      An ID header contained an unrecognized version
+number.
+\retval #OP_EBADLINK      We failed to find data we had seen before after
+seeking.
+\retval #OP_EBADTIMESTAMP The first or last timestamp in a link failed basic
+validity checks.*/
+int op_test_open(OggOpusFile *_of) OP_ARG_NONNULL(1);
+/**Release all memory used by an \c OggOpusFile.
+\param _of The \c OggOpusFile to free.*/
+void op_free(OggOpusFile *_of);
+/*@}*/
+/*@}*/
+/**\defgroup stream_info Stream Information*/
+/*@{*/
+/**\name Functions for obtaining information about streams
+These functions allow you to get basic information about a stream, including
+seekability, the number of links (for chained streams), plus the size,
+duration, bitrate, header parameters, and meta information for each link
+(or, where available, the stream as a whole).
+Some of these (size, duration) are only available for seekable streams.
+You can also query the current stream position, link, and playback time,
+and instantaneous bitrate during playback.
+Some of these functions may be used successfully on the partially open
+streams returned by op_test_callbacks() or one of the associated
+convenience functions.
+Their documention will indicate so explicitly.*/
+/*@{*/
+/**Returns whether or not the stream being read is seekable.
+This is true if
+<ol>
+<li>The <code><a href="#op_seek_func">seek()</a></code> and
+<code><a href="#op_tell_func">tell()</a></code> callbacks are both
+non-<code>NULL</code>,</li>
+<li>The <code><a href="#op_seek_func">seek()</a></code> callback was
+successfully executed at least once, and</li>
+<li>The <code><a href="#op_tell_func">tell()</a></code> callback was
+successfully able to report the position indicator afterwards.</li>
+</ol>
+This function may be called on partially-opened streams.
+\param _of The \c OggOpusFile whose seekable status is to be returned.
+\return A non-zero value if seekable, and 0 if unseekable.*/
+int op_seekable(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+/**Returns the number of links in this chained stream.
+This function may be called on partially-opened streams, but it will always
+return 1.
+The actual number of links is not known until the stream is fully opened.
+\param _of The \c OggOpusFile from which to retrieve the link count.
+\return For fully-open seekable streams, this returns the total number of
+links in the whole stream, which will be at least 1.
+For partially-open or unseekable streams, this always returns 1.*/
+int op_link_count(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+/**Get the serial number of the given link in a (possibly-chained) Ogg Opus
+stream.
+This function may be called on partially-opened streams, but it will always
+return the serial number of the Opus stream in the first link.
+\param _of The \c OggOpusFile from which to retrieve the serial number.
+\param _li The index of the link whose serial number should be retrieved.
+Use a negative number to get the serial number of the current
+link.
+\return The serial number of the given link.
+If \a _li is greater than the total number of links, this returns
+the serial number of the last link.
+If the stream is not seekable, this always returns the serial number
+of the current link.*/
+opus_uint32 op_serialno(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+/**Get the channel count of the given link in a (possibly-chained) Ogg Opus
+stream.
+This is equivalent to <code>op_head(_of,_li)->channel_count</code>, but
+is provided for convenience.
+This function may be called on partially-opened streams, but it will always
+return the channel count of the Opus stream in the first link.
+\param _of The \c OggOpusFile from which to retrieve the channel count.
+\param _li The index of the link whose channel count should be retrieved.
+Use a negative number to get the channel count of the current
+link.
+\return The channel count of the given link.
+If \a _li is greater than the total number of links, this returns
+the channel count of the last link.
+If the stream is not seekable, this always returns the channel count
+of the current link.*/
+int op_channel_count(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+/**Get the total (compressed) size of the stream, or of an individual link in
+a (possibly-chained) Ogg Opus stream, including all headers and Ogg muxing
+overhead.
+\warning If the Opus stream (or link) is concurrently multiplexed with other
+logical streams (e.g., video), this returns the size of the entire stream
+(or link), not just the number of bytes in the first logical Opus stream.
+Returning the latter would require scanning the entire file.
+\param _of The \c OggOpusFile from which to retrieve the compressed size.
+\param _li The index of the link whose compressed size should be computed.
+Use a negative number to get the compressed size of the entire
+stream.
+\return The compressed size of the entire stream if \a _li is negative, the
+compressed size of link \a _li if it is non-negative, or a negative
+value on error.
+The compressed size of the entire stream may be smaller than that
+of the underlying stream if trailing garbage was detected in the
+file.
+\retval #OP_EINVAL The stream is not seekable (so we can't know the length),
+\a _li wasn't less than the total number of links in
+the stream, or the stream was only partially open.*/
+opus_int64 op_raw_total(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+/**Get the total PCM length (number of samples at 48 kHz) of the stream, or of
+an individual link in a (possibly-chained) Ogg Opus stream.
+Users looking for <code>op_time_total()</code> should use op_pcm_total()
+instead.
+Because timestamps in Opus are fixed at 48 kHz, there is no need for a
+separate function to convert this to seconds (and leaving it out avoids
+introducing floating point to the API, for those that wish to avoid it).
+\param _of The \c OggOpusFile from which to retrieve the PCM offset.
+\param _li The index of the link whose PCM length should be computed.
+Use a negative number to get the PCM length of the entire stream.
+\return The PCM length of the entire stream if \a _li is negative, the PCM
+length of link \a _li if it is non-negative, or a negative value on
+error.
+\retval #OP_EINVAL The stream is not seekable (so we can't know the length),
+\a _li wasn't less than the total number of links in
+the stream, or the stream was only partially open.*/
+ogg_int64_t op_pcm_total(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+/**Get the ID header information for the given link in a (possibly chained) Ogg
+Opus stream.
+This function may be called on partially-opened streams, but it will always
+return the ID header information of the Opus stream in the first link.
+\param _of The \c OggOpusFile from which to retrieve the ID header
+information.
+\param _li The index of the link whose ID header information should be
+retrieved.
+Use a negative number to get the ID header information of the
+current link.
+For an unseekable stream, \a _li is ignored, and the ID header
+information for the current link is always returned, if
+available.
+\return The contents of the ID header for the given link.*/
+const OpusHead *op_head(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+/**Get the comment header information for the given link in a (possibly
+chained) Ogg Opus stream.
+This function may be called on partially-opened streams, but it will always
+return the tags from the Opus stream in the first link.
+\param _of The \c OggOpusFile from which to retrieve the comment header
+information.
+\param _li The index of the link whose comment header information should be
+retrieved.
+Use a negative number to get the comment header information of
+the current link.
+For an unseekable stream, \a _li is ignored, and the comment
+header information for the current link is always returned, if
+available.
+\return The contents of the comment header for the given link, or
+<code>NULL</code> if this is an unseekable stream that encountered
+an invalid link.*/
+const OpusTags *op_tags(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+/**Retrieve the index of the current link.
+This is the link that produced the data most recently read by
+op_read_float() or its associated functions, or, after a seek, the link
+that the seek target landed in.
+Reading more data may advance the link index (even on the first read after a
+seek).
+\param _of The \c OggOpusFile from which to retrieve the current link index.
+\return The index of the current link on success, or a negative value on
+failure.
+For seekable streams, this is a number between 0 (inclusive) and the
+value returned by op_link_count() (exclusive).
+For unseekable streams, this value starts at 0 and increments by one
+each time a new link is encountered (even though op_link_count()
+always returns 1).
+\retval #OP_EINVAL The stream was only partially open.*/
+int op_current_link(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+/**Computes the bitrate of the stream, or of an individual link in a
+(possibly-chained) Ogg Opus stream.
+The stream must be seekable to compute the bitrate.
+For unseekable streams, use op_bitrate_instant() to get periodic estimates.
+\warning If the Opus stream (or link) is concurrently multiplexed with other
+logical streams (e.g., video), this uses the size of the entire stream (or
+link) to compute the bitrate, not just the number of bytes in the first
+logical Opus stream.
+Returning the latter requires scanning the entire file, but this may be done
+by decoding the whole file and calling op_bitrate_instant() once at the
+end.
+Install a trivial decoding callback with op_set_decode_callback() if you
+wish to skip actual decoding during this process.
+\param _of The \c OggOpusFile from which to retrieve the bitrate.
+\param _li The index of the link whose bitrate should be computed.
+Use a negative number to get the bitrate of the whole stream.
+\return The bitrate on success, or a negative value on error.
+\retval #OP_EINVAL The stream was only partially open, the stream was not
+seekable, or \a _li was larger than the number of
+links.*/
+opus_int32 op_bitrate(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+/**Compute the instantaneous bitrate, measured as the ratio of bits to playable
+samples decoded since a) the last call to op_bitrate_instant(), b) the last
+seek, or c) the start of playback, whichever was most recent.
+This will spike somewhat after a seek or at the start/end of a chain
+boundary, as pre-skip, pre-roll, and end-trimming causes samples to be
+decoded but not played.
+\param _of The \c OggOpusFile from which to retrieve the bitrate.
+\return The bitrate, in bits per second, or a negative value on error.
+\retval #OP_FALSE  No data has been decoded since any of the events
+described above.
+\retval #OP_EINVAL The stream was only partially open.*/
+opus_int32 op_bitrate_instant(OggOpusFile *_of) OP_ARG_NONNULL(1);
+/**Obtain the current value of the position indicator for \a _of.
+\param _of The \c OggOpusFile from which to retrieve the position indicator.
+\return The byte position that is currently being read from.
+\retval #OP_EINVAL The stream was only partially open.*/
+opus_int64 op_raw_tell(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+/**Obtain the PCM offset of the next sample to be read.
+If the stream is not properly timestamped, this might not increment by the
+proper amount between reads, or even return monotonically increasing
+values.
+\param _of The \c OggOpusFile from which to retrieve the PCM offset.
+\return The PCM offset of the next sample to be read.
+\retval #OP_EINVAL The stream was only partially open.*/
+ogg_int64_t op_pcm_tell(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+/*@}*/
+/*@}*/
+/**\defgroup stream_seeking Seeking*/
+/*@{*/
+/**\name Functions for seeking in Opus streams
+These functions let you seek in Opus streams, if the underlying stream
+support it.
+Seeking is implemented for all built-in stream I/O routines, though some
+individual streams may not be seekable (pipes, live HTTP streams, or HTTP
+streams from a server that does not support <code>Range</code> requests).
+op_raw_seek() is the fastest: it is guaranteed to perform at most one
+physical seek, but, since the target is a byte position, makes no guarantee
+how close to a given time it will come.
+op_pcm_seek() provides sample-accurate seeking.
+The number of physical seeks it requires is still quite small (often 1 or
+2, even in highly variable bitrate streams).
+Seeking in Opus requires decoding some pre-roll amount before playback to
+allow the internal state to converge (as if recovering from packet loss).
+This is handled internally by <tt>libopusfile</tt>, but means there is
+little extra overhead for decoding up to the exact position requested
+(since it must decode some amount of audio anyway).
+It also means that decoding after seeking may not return exactly the same
+values as would be obtained by decoding the stream straight through.
+However, such differences are expected to be smaller than the loss
+introduced by Opus's lossy compression.*/
+/*@{*/
+/**Seek to a byte offset relative to the <b>compressed</b> data.
+This also scans packets to update the PCM cursor.
+It will cross a logical bitstream boundary, but only if it can't get any
+packets out of the tail of the link to which it seeks.
+\param _of          The \c OggOpusFile in which to seek.
+\param _byte_offset The byte position to seek to.
+This must be between 0 and #op_raw_total(\a _of,\c -1)
+(inclusive).
+\return 0 on success, or a negative error code on failure.
+\retval #OP_EREAD    The underlying seek operation failed.
+\retval #OP_EINVAL   The stream was only partially open, or the target was
+outside the valid range for the stream.
+\retval #OP_ENOSEEK  This stream is not seekable.
+\retval #OP_EBADLINK Failed to initialize a decoder for a stream for an
+unknown reason.*/
+int op_raw_seek(OggOpusFile *_of,opus_int64 _byte_offset) OP_ARG_NONNULL(1);
+/**Seek to the specified PCM offset, such that decoding will begin at exactly
+the requested position.
+\param _of         The \c OggOpusFile in which to seek.
+\param _pcm_offset The PCM offset to seek to.
+This is in samples at 48 kHz relative to the start of the
+stream.
+\return 0 on success, or a negative value on error.
+\retval #OP_EREAD    An underlying read or seek operation failed.
+\retval #OP_EINVAL   The stream was only partially open, or the target was
+outside the valid range for the stream.
+\retval #OP_ENOSEEK  This stream is not seekable.
+\retval #OP_EBADLINK We failed to find data we had seen before, or the
+bitstream structure was sufficiently malformed that
+seeking to the target destination was impossible.*/
+int op_pcm_seek(OggOpusFile *_of,ogg_int64_t _pcm_offset) OP_ARG_NONNULL(1);
+/*@}*/
+/*@}*/
+/**\defgroup stream_decoding Decoding*/
+/*@{*/
+/**\name Functions for decoding audio data
+These functions retrieve actual decoded audio data from the stream.
+The general functions, op_read() and op_read_float() return 16-bit or
+floating-point output, both using native endian ordering.
+The number of channels returned can change from link to link in a chained
+stream.
+There are special functions, op_read_stereo() and op_read_float_stereo(),
+which always output two channels, to simplify applications which do not
+wish to handle multichannel audio.
+These downmix multichannel files to two channels, so they can always return
+samples in the same format for every link in a chained file.
+If the rest of your audio processing chain can handle floating point, the
+floating-point routines should be preferred, as they prevent clipping and
+other issues which might be avoided entirely if, e.g., you scale down the
+volume at some other stage.
+However, if you intend to consume 16-bit samples directly, the conversion in
+<tt>libopusfile</tt> provides noise-shaping dithering and, if compiled
+against <tt>libopus</tt>&nbsp;1.1 or later, soft-clipping prevention.
+<tt>libopusfile</tt> can also be configured at compile time to use the
+fixed-point <tt>libopus</tt> API.
+If so, <tt>libopusfile</tt>'s floating-point API may also be disabled.
+In that configuration, nothing in <tt>libopusfile</tt> will use any
+floating-point operations, to simplify support on devices without an
+adequate FPU.
+\warning HTTPS streams may be be vulnerable to truncation attacks if you do
+not check the error return code from op_read_float() or its associated
+functions.
+If the remote peer does not close the connection gracefully (with a TLS
+"close notify" message), these functions will return #OP_EREAD instead of 0
+when they reach the end of the file.
+If you are reading from an <https:> URL (particularly if seeking is not
+supported), you should make sure to check for this error and warn the user
+appropriately.*/
+/*@{*/
+/**Indicates that the decoding callback should produce signed 16-bit
+native-endian output samples.*/
+#define OP_DEC_FORMAT_SHORT (7008)
+/**Indicates that the decoding callback should produce 32-bit native-endian
+float samples.*/
+#define OP_DEC_FORMAT_FLOAT (7040)
+/**Indicates that the decoding callback did not decode anything, and that
+<tt>libopusfile</tt> should decode normally instead.*/
+#define OP_DEC_USE_DEFAULT  (6720)
+/**Called to decode an Opus packet.
+This should invoke the functional equivalent of opus_multistream_decode() or
+opus_multistream_decode_float(), except that it returns 0 on success
+instead of the number of decoded samples (which is known a priori).
+\param _ctx       The application-provided callback context.
+\param _decoder   The decoder to use to decode the packet.
+\param[out] _pcm  The buffer to decode into.
+This will always have enough room for \a _nchannels of
+\a _nsamples samples, which should be placed into this
+buffer interleaved.
+\param _op        The packet to decode.
+This will always have its granule position set to a valid
+value.
+\param _nsamples  The number of samples expected from the packet.
+\param _nchannels The number of channels expected from the packet.
+\param _format    The desired sample output format.
+This is either #OP_DEC_FORMAT_SHORT or
+#OP_DEC_FORMAT_FLOAT.
+\param _li        The index of the link from which this packet was decoded.
+\return A non-negative value on success, or a negative value on error.
+Any error codes should be the same as those returned by
+opus_multistream_decode() or opus_multistream_decode_float().
+Success codes are as follows:
+\retval 0                   Decoding was successful.
+The application has filled the buffer with
+exactly <code>\a _nsamples*\a
+_nchannels</code> samples in the requested
+format.
+\retval #OP_DEC_USE_DEFAULT No decoding was done.
+<tt>libopusfile</tt> should do the decoding
+by itself instead.*/
+typedef int (*op_decode_cb_func)(void *_ctx,OpusMSDecoder *_decoder,void *_pcm,
+const ogg_packet *_op,int _nsamples,int _nchannels,int _format,int _li);
+/**Sets the packet decode callback function.
+If set, this is called once for each packet that needs to be decoded.
+This can be used by advanced applications to do additional processing on the
+compressed or uncompressed data.
+For example, an application might save the final entropy coder state for
+debugging and testing purposes, or it might apply additional filters
+before the downmixing, dithering, or soft-clipping performed by
+<tt>libopusfile</tt>, so long as these filters do not introduce any
+latency.
+A call to this function is no guarantee that the audio will eventually be
+delivered to the application.
+<tt>libopusfile</tt> may discard some or all of the decoded audio data
+(i.e., at the beginning or end of a link, or after a seek), however the
+callback is still required to provide all of it.
+\param _of        The \c OggOpusFile on which to set the decode callback.
+\param _decode_cb The callback function to call.
+This may be <code>NULL</code> to disable calling the
+callback.
+\param _ctx       The application-provided context pointer to pass to the
+callback on each call.*/
+void op_set_decode_callback(OggOpusFile *_of,
+op_decode_cb_func _decode_cb,void *_ctx) OP_ARG_NONNULL(1);
+/**Gain offset type that indicates that the provided offset is relative to the
+header gain.
+This is the default.*/
+#define OP_HEADER_GAIN   (0)
+/**Gain offset type that indicates that the provided offset is relative to the
+R128_ALBUM_GAIN value (if any), in addition to the header gain.*/
+#define OP_ALBUM_GAIN    (3007)
+/**Gain offset type that indicates that the provided offset is relative to the
+R128_TRACK_GAIN value (if any), in addition to the header gain.*/
+#define OP_TRACK_GAIN    (3008)
+/**Gain offset type that indicates that the provided offset should be used as
+the gain directly, without applying any the header or track gains.*/
+#define OP_ABSOLUTE_GAIN (3009)
+/**Sets the gain to be used for decoded output.
+By default, the gain in the header is applied with no additional offset.
+The total gain (including header gain and/or track gain, if applicable, and
+this offset), will be clamped to [-32768,32767]/256 dB.
+This is more than enough to saturate or underflow 16-bit PCM.
+\note The new gain will not be applied to any already buffered, decoded
+output.
+This means you cannot change it sample-by-sample, as at best it will be
+updated packet-by-packet.
+It is meant for setting a target volume level, rather than applying smooth
+fades, etc.
+\param _of             The \c OggOpusFile on which to set the gain offset.
+\param _gain_type      One of #OP_HEADER_GAIN, #OP_ALBUM_GAIN,
+#OP_TRACK_GAIN, or #OP_ABSOLUTE_GAIN.
+\param _gain_offset_q8 The gain offset to apply, in 1/256ths of a dB.
+\return 0 on success or a negative value on error.
+\retval #OP_EINVAL The \a _gain_type was unrecognized.*/
+int op_set_gain_offset(OggOpusFile *_of,
+int _gain_type,opus_int32 _gain_offset_q8) OP_ARG_NONNULL(1);
+/**Sets whether or not dithering is enabled for 16-bit decoding.
+By default, when <tt>libopusfile</tt> is compiled to use floating-point
+internally, calling op_read() or op_read_stereo() will first decode to
+float, and then convert to fixed-point using noise-shaping dithering.
+This flag can be used to disable that dithering.
+When the application uses op_read_float() or op_read_float_stereo(), or when
+the library has been compiled to decode directly to fixed point, this flag
+has no effect.
+\param _of      The \c OggOpusFile on which to enable or disable dithering.
+\param _enabled A non-zero value to enable dithering, or 0 to disable it.*/
+void op_set_dither_enabled(OggOpusFile *_of,int _enabled) OP_ARG_NONNULL(1);
+/**Reads more samples from the stream.
+\note Although \a _buf_size must indicate the total number of values that
+can be stored in \a _pcm, the return value is the number of samples
+<em>per channel</em>.
+This is done because
+<ol>
+<li>The channel count cannot be known a priori (reading more samples might
+advance us into the next link, with a different channel count), so
+\a _buf_size cannot also be in units of samples per channel,</li>
+<li>Returning the samples per channel matches the <code>libopus</code> API
+as closely as we're able,</li>
+<li>Returning the total number of values instead of samples per channel
+would mean the caller would need a division to compute the samples per
+channel, and might worry about the possibility of getting back samples
+for some channels and not others, and</li>
+<li>This approach is relatively fool-proof: if an application passes too
+small a value to \a _buf_size, they will simply get fewer samples back,
+and if they assume the return value is the total number of values, then
+they will simply read too few (rather than reading too many and going
+off the end of the buffer).</li>
+</ol>
+\param      _of       The \c OggOpusFile from which to read.
+\param[out] _pcm      A buffer in which to store the output PCM samples, as
+signed native-endian 16-bit values at 48&nbsp;kHz
+with a nominal range of <code>[-32768,32767)</code>.
+Multiple channels are interleaved using the
+<a href="http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9">Vorbis
+channel ordering</a>.
+This must have room for at least \a _buf_size values.
+\param      _buf_size The number of values that can be stored in \a _pcm.
+It is recommended that this be large enough for at
+least 120 ms of data at 48 kHz per channel (5760
+values per channel).
+Smaller buffers will simply return less data, possibly
+consuming more memory to buffer the data internally.
+<tt>libopusfile</tt> may return less data than
+requested.
+If so, there is no guarantee that the remaining data
+in \a _pcm will be unmodified.
+\param[out] _li       The index of the link this data was decoded from.
+You may pass <code>NULL</code> if you do not need this
+information.
+If this function fails (returning a negative value),
+this parameter is left unset.
+\return The number of samples read per channel on success, or a negative
+value on failure.
+The channel count can be retrieved on success by calling
+<code>op_head(_of,*_li)</code>.
+The number of samples returned may be 0 if the buffer was too small
+to store even a single sample for all channels, or if end-of-file
+was reached.
+The list of possible failure codes follows.
+Most of them can only be returned by unseekable, chained streams
+that encounter a new link.
+\retval #OP_HOLE          There was a hole in the data, and some samples
+may have been skipped.
+Call this function again to continue decoding
+past the hole.
+\retval #OP_EREAD         An underlying read operation failed.
+This may signal a truncation attack from an
+<https:> source.
+\retval #OP_EFAULT        An internal memory allocation failed.
+\retval #OP_EIMPL         An unseekable stream encountered a new link that
+used a feature that is not implemented, such as
+an unsupported channel family.
+\retval #OP_EINVAL        The stream was only partially open.
+\retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+did not have any logical Opus streams in it.
+\retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+required header packet that was not properly
+formatted, contained illegal values, or was
+missing altogether.
+\retval #OP_EVERSION      An unseekable stream encountered a new link with
+an ID header that contained an unrecognized
+version number.
+\retval #OP_EBADPACKET    Failed to properly decode the next packet.
+\retval #OP_EBADLINK      We failed to find data we had seen before.
+\retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+a starting timestamp that failed basic validity
+checks.*/
+OP_WARN_UNUSED_RESULT int op_read(OggOpusFile *_of,
+opus_int16 *_pcm,int _buf_size,int *_li) OP_ARG_NONNULL(1);
+/**Reads more samples from the stream.
+\note Although \a _buf_size must indicate the total number of values that
+can be stored in \a _pcm, the return value is the number of samples
+<em>per channel</em>.
+<ol>
+<li>The channel count cannot be known a priori (reading more samples might
+advance us into the next link, with a different channel count), so
+\a _buf_size cannot also be in units of samples per channel,</li>
+<li>Returning the samples per channel matches the <code>libopus</code> API
+as closely as we're able,</li>
+<li>Returning the total number of values instead of samples per channel
+would mean the caller would need a division to compute the samples per
+channel, and might worry about the possibility of getting back samples
+for some channels and not others, and</li>
+<li>This approach is relatively fool-proof: if an application passes too
+small a value to \a _buf_size, they will simply get fewer samples back,
+and if they assume the return value is the total number of values, then
+they will simply read too few (rather than reading too many and going
+off the end of the buffer).</li>
+</ol>
+\param      _of       The \c OggOpusFile from which to read.
+\param[out] _pcm      A buffer in which to store the output PCM samples as
+signed floats at 48&nbsp;kHz with a nominal range of
+<code>[-1.0,1.0]</code>.
+Multiple channels are interleaved using the
+<a href="http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9">Vorbis
+channel ordering</a>.
+This must have room for at least \a _buf_size floats.
+\param      _buf_size The number of floats that can be stored in \a _pcm.
+It is recommended that this be large enough for at
+least 120 ms of data at 48 kHz per channel (5760
+samples per channel).
+Smaller buffers will simply return less data, possibly
+consuming more memory to buffer the data internally.
+If less than \a _buf_size values are returned,
+<tt>libopusfile</tt> makes no guarantee that the
+remaining data in \a _pcm will be unmodified.
+\param[out] _li       The index of the link this data was decoded from.
+You may pass <code>NULL</code> if you do not need this
+information.
+If this function fails (returning a negative value),
+this parameter is left unset.
+\return The number of samples read per channel on success, or a negative
+value on failure.
+The channel count can be retrieved on success by calling
+<code>op_head(_of,*_li)</code>.
+The number of samples returned may be 0 if the buffer was too small
+to store even a single sample for all channels, or if end-of-file
+was reached.
+The list of possible failure codes follows.
+Most of them can only be returned by unseekable, chained streams
+that encounter a new link.
+\retval #OP_HOLE          There was a hole in the data, and some samples
+may have been skipped.
+Call this function again to continue decoding
+past the hole.
+\retval #OP_EREAD         An underlying read operation failed.
+This may signal a truncation attack from an
+<https:> source.
+\retval #OP_EFAULT        An internal memory allocation failed.
+\retval #OP_EIMPL         An unseekable stream encountered a new link that
+used a feature that is not implemented, such as
+an unsupported channel family.
+\retval #OP_EINVAL        The stream was only partially open.
+\retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+did not have any logical Opus streams in it.
+\retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+required header packet that was not properly
+formatted, contained illegal values, or was
+missing altogether.
+\retval #OP_EVERSION      An unseekable stream encountered a new link with
+an ID header that contained an unrecognized
+version number.
+\retval #OP_EBADPACKET    Failed to properly decode the next packet.
+\retval #OP_EBADLINK      We failed to find data we had seen before.
+\retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+a starting timestamp that failed basic validity
+checks.*/
+OP_WARN_UNUSED_RESULT int op_read_float(OggOpusFile *_of,
+float *_pcm,int _buf_size,int *_li) OP_ARG_NONNULL(1);
+/**Reads more samples from the stream and downmixes to stereo, if necessary.
+This function is intended for simple players that want a uniform output
+format, even if the channel count changes between links in a chained
+stream.
+\note \a _buf_size indicates the total number of values that can be stored
+in \a _pcm, while the return value is the number of samples <em>per
+channel</em>, even though the channel count is known, for consistency with
+op_read().
+\param      _of       The \c OggOpusFile from which to read.
+\param[out] _pcm      A buffer in which to store the output PCM samples, as
+signed native-endian 16-bit values at 48&nbsp;kHz
+with a nominal range of <code>[-32768,32767)</code>.
+The left and right channels are interleaved in the
+buffer.
+This must have room for at least \a _buf_size values.
+\param      _buf_size The number of values that can be stored in \a _pcm.
+It is recommended that this be large enough for at
+least 120 ms of data at 48 kHz per channel (11520
+values total).
+Smaller buffers will simply return less data, possibly
+consuming more memory to buffer the data internally.
+If less than \a _buf_size values are returned,
+<tt>libopusfile</tt> makes no guarantee that the
+remaining data in \a _pcm will be unmodified.
+\return The number of samples read per channel on success, or a negative
+value on failure.
+The number of samples returned may be 0 if the buffer was too small
+to store even a single sample for both channels, or if end-of-file
+was reached.
+The list of possible failure codes follows.
+Most of them can only be returned by unseekable, chained streams
+that encounter a new link.
+\retval #OP_HOLE          There was a hole in the data, and some samples
+may have been skipped.
+Call this function again to continue decoding
+past the hole.
+\retval #OP_EREAD         An underlying read operation failed.
+This may signal a truncation attack from an
+<https:> source.
+\retval #OP_EFAULT        An internal memory allocation failed.
+\retval #OP_EIMPL         An unseekable stream encountered a new link that
+used a feature that is not implemented, such as
+an unsupported channel family.
+\retval #OP_EINVAL        The stream was only partially open.
+\retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+did not have any logical Opus streams in it.
+\retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+required header packet that was not properly
+formatted, contained illegal values, or was
+missing altogether.
+\retval #OP_EVERSION      An unseekable stream encountered a new link with
+an ID header that contained an unrecognized
+version number.
+\retval #OP_EBADPACKET    Failed to properly decode the next packet.
+\retval #OP_EBADLINK      We failed to find data we had seen before.
+\retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+a starting timestamp that failed basic validity
+checks.*/
+OP_WARN_UNUSED_RESULT int op_read_stereo(OggOpusFile *_of,
+opus_int16 *_pcm,int _buf_size) OP_ARG_NONNULL(1);
+/**Reads more samples from the stream and downmixes to stereo, if necessary.
+This function is intended for simple players that want a uniform output
+format, even if the channel count changes between links in a chained
+stream.
+\note \a _buf_size indicates the total number of values that can be stored
+in \a _pcm, while the return value is the number of samples <em>per
+channel</em>, even though the channel count is known, for consistency with
+op_read_float().
+\param      _of       The \c OggOpusFile from which to read.
+\param[out] _pcm      A buffer in which to store the output PCM samples, as
+signed floats at 48&nbsp;kHz with a nominal range of
+<code>[-1.0,1.0]</code>.
+The left and right channels are interleaved in the
+buffer.
+This must have room for at least \a _buf_size values.
+\param      _buf_size The number of values that can be stored in \a _pcm.
+It is recommended that this be large enough for at
+least 120 ms of data at 48 kHz per channel (11520
+values total).
+Smaller buffers will simply return less data, possibly
+consuming more memory to buffer the data internally.
+If less than \a _buf_size values are returned,
+<tt>libopusfile</tt> makes no guarantee that the
+remaining data in \a _pcm will be unmodified.
+\return The number of samples read per channel on success, or a negative
+value on failure.
+The number of samples returned may be 0 if the buffer was too small
+to store even a single sample for both channels, or if end-of-file
+was reached.
+The list of possible failure codes follows.
+Most of them can only be returned by unseekable, chained streams
+that encounter a new link.
+\retval #OP_HOLE          There was a hole in the data, and some samples
+may have been skipped.
+Call this function again to continue decoding
+past the hole.
+\retval #OP_EREAD         An underlying read operation failed.
+This may signal a truncation attack from an
+<https:> source.
+\retval #OP_EFAULT        An internal memory allocation failed.
+\retval #OP_EIMPL         An unseekable stream encountered a new link that
+used a feature that is not implemented, such as
+an unsupported channel family.
+\retval #OP_EINVAL        The stream was only partially open.
+\retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+that did not have any logical Opus streams in it.
+\retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+required header packet that was not properly
+formatted, contained illegal values, or was
+missing altogether.
+\retval #OP_EVERSION      An unseekable stream encountered a new link with
+an ID header that contained an unrecognized
+version number.
+\retval #OP_EBADPACKET    Failed to properly decode the next packet.
+\retval #OP_EBADLINK      We failed to find data we had seen before.
+\retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+a starting timestamp that failed basic validity
+checks.*/
+OP_WARN_UNUSED_RESULT int op_read_float_stereo(OggOpusFile *_of,
+float *_pcm,int _buf_size) OP_ARG_NONNULL(1);
+/*@}*/
+/*@}*/
+# if OP_GNUC_PREREQ(4,0)
+#  pragma GCC visibility pop
+# endif
+# if defined(__cplusplus)
+}
+# endif
+#endif

Mercurial > hg > sv-dependency-builds

comparison osx/include/opus/opusfile.h @ 154:4664ac0c1032