The rest of the set functions should only be called if the client needs exact control over how the audio is compressed; thorough understanding of the FLAC format is necessary to achieve good results.
The program initializes the instance to validate the settings and prepare for encoding using
The program finishes the encoding with FLAC__stream_encoder_finish(), which causes the encoder to encode any data still in its input pipe, update the metadata with the final encoding statistics if output seeking is possible, and finally reset the encoder to the uninitialized state.
Chris@1: In more detail, the stream encoder functions similarly to the stream decoder , but has fewer callbacks and more options. Typically the client will create a new instance by calling FLAC__stream_encoder_new(), then set the necessary parameters with FLAC__stream_encoder_set_*(), and initialize it by calling one of the FLAC__stream_encoder_init_*() functions.
Chris@1: Unlike the decoders, the stream encoder has many options that can affect the speed and compression ratio. When setting these parameters you should have some basic knowledge of the format (see the user-level documentation or the formal description). The FLAC__stream_encoder_set_*() functions themselves do not validate the values as many are interdependent. The FLAC__stream_encoder_init_*() functions will do this, so make sure to pay attention to the state returned by FLAC__stream_encoder_init_*() to make sure that it is FLAC__STREAM_ENCODER_INIT_STATUS_OK. Any parameters that are not set before FLAC__stream_encoder_init_*() will take on the defaults from the constructor.
Chris@1: There are three initialization functions for native FLAC, one for setting up the encoder to encode FLAC data to the client via callbacks, and two for encoding directly to a file.
Chris@1: For encoding via callbacks, use FLAC__stream_encoder_init_stream(). You must also supply a write callback which will be called anytime there is raw encoded data to write. If the client can seek the output it is best to also supply seek and tell callbacks, as this allows the encoder to go back after encoding is finished to write back information that was collected while encoding, like seek point offsets, frame sizes, etc.
Chris@1: For encoding directly to a file, use FLAC__stream_encoder_init_FILE() or FLAC__stream_encoder_init_file(). Then you must only supply a filename or open FILE*; the encoder will handle all the callbacks internally. You may also supply a progress callback for periodic notification of the encoding progress.
Chris@1: There are three similarly-named init functions for encoding to Ogg FLAC streams. Check FLAC_API_SUPPORTS_OGG_FLAC to find out if the library has been built with Ogg support.
Chris@1: The call to FLAC__stream_encoder_init_*() currently will also immediately call the write callback several times, once with the fLaC signature, and once for each encoded metadata block. Note that for Ogg FLAC encoding you will usually get at least twice the number of callbacks than with native FLAC, one for the Ogg page header and one for the page body.
Chris@1: After initializing the instance, the client may feed audio data to the encoder in one of two ways:
Chris@1:
Chris@1:
Channel separate, through FLAC__stream_encoder_process() - The client will pass an array of pointers to buffers, one for each channel, to the encoder, each of the same length. The samples need not be block-aligned, but each channel should have the same number of samples.
Channel interleaved, through FLAC__stream_encoder_process_interleaved() - The client will pass a single pointer to data that is channel-interleaved (i.e. channel0_sample0, channel1_sample0, ... , channelN_sample0, channel0_sample1, ...). Again, the samples need not be block-aligned but they must be sample-aligned, i.e. the first value should be channel0_sample0 and the last value channelN_sampleM.
Chris@1:
Chris@1: Note that for either process call, each sample in the buffers should be a signed integer, right-justified to the resolution set by FLAC__stream_encoder_set_bits_per_sample(). For example, if the resolution is 16 bits per sample, the samples should all be in the range [-32768,32767].
Chris@1: When the client is finished encoding data, it calls FLAC__stream_encoder_finish(), which causes the encoder to encode any data still in its input pipe, and call the metadata callback with the final encoding statistics. Then the instance may be deleted with FLAC__stream_encoder_delete() or initialized again to encode another stream.
Chris@1: For programs that write their own metadata, but that do not know the actual metadata until after encoding, it is advantageous to instruct the encoder to write a PADDING block of the correct size, so that instead of rewriting the whole stream after encoding, the program can just overwrite the PADDING block. If only the maximum size of the metadata is known, the program can write a slightly larger padding block, then split it after encoding.
Chris@1: Make sure you understand how lengths are calculated. All FLAC metadata blocks have a 4 byte header which contains the type and length. This length does not include the 4 bytes of the header. See the format page for the specification of metadata blocks and their lengths.
Chris@1:
Note:
If you are writing the FLAC data to a file via callbacks, make sure it is open for update (e.g. mode "w+" for stdio streams). This is because after the first encoding pass, the encoder will try to seek back to the beginning of the stream, to the STREAMINFO block, to write some data there. (If using FLAC__stream_encoder_init*_file() or FLAC__stream_encoder_init*_FILE(), the file is managed internally.)
Chris@1: The "set" functions may only be called when the encoder is in the state FLAC__STREAM_ENCODER_UNINITIALIZED, i.e. after FLAC__stream_encoder_new() or FLAC__stream_encoder_finish(), but before FLAC__stream_encoder_init_*(). If this is the case they will return true, otherwise false.
Chris@1: A function pointer matching this signature must be passed to FLAC__stream_encoder_init_ogg_stream() if seeking is supported. The supplied function will be called when the encoder needs to read back encoded data. This happens during the metadata callback, when the encoder has to read, modify, and rewrite the metadata (e.g. seekpoints) gathered while encoding. The address of the buffer to be filled is supplied, along with the number of bytes the buffer can hold. The callback may choose to supply less data and modify the byte count but must be careful not to overflow the buffer. The callback then returns a status code chosen from FLAC__StreamEncoderReadStatus.
Chris@1: Here is an example of a read callback for stdio streams:
In general, FLAC__StreamEncoder functions which change the state should not be called on the encoder while in the callback.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
The encoder instance calling the callback.
Chris@1:
buffer
A pointer to a location for the callee to store data to be encoded.
Chris@1:
bytes
A pointer to the size of the buffer. On entry to the callback, it contains the maximum number of bytes that may be stored in buffer. The callee must set it to the actual number of bytes stored (0 in case of error or end-of-stream) before returning.
Chris@1:
client_data
The callee's client data set through FLAC__stream_encoder_set_client_data().
Chris@1: A function pointer matching this signature must be passed to FLAC__stream_encoder_init*_stream(). The supplied function will be called by the encoder anytime there is raw encoded data ready to write. It may include metadata mixed with encoded audio frames and the data is not guaranteed to be aligned on frame or metadata block boundaries.
Chris@1: The only duty of the callback is to write out the bytes worth of data in buffer to the current position in the output stream. The arguments samples and current_frame are purely informational. If samples is greater than 0, then current_frame will hold the current frame number that is being written; otherwise it indicates that the write callback is being called to write metadata.
Chris@1:
Note:
Unlike when writing to native FLAC, when writing to Ogg FLAC the write callback will be called twice when writing each audio frame; once for the page header, and once for the page body. When writing the page header, the samples argument to the write callback will be 0.
Chris@1: In general, FLAC__StreamEncoder functions which change the state should not be called on the encoder while in the callback.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
The encoder instance calling the callback.
Chris@1:
buffer
An array of encoded data of length bytes.
Chris@1:
bytes
The byte length of buffer.
Chris@1:
samples
The number of samples encoded by buffer. 0 has a special meaning; see above.
Chris@1:
current_frame
The number of the current frame being encoded.
Chris@1:
client_data
The callee's client data set through FLAC__stream_encoder_init_*().
Chris@1: A function pointer matching this signature may be passed to FLAC__stream_encoder_init*_stream(). The supplied function will be called when the encoder needs to seek the output stream. The encoder will pass the absolute byte offset to seek to, 0 meaning the beginning of the stream.
Chris@1: Here is an example of a seek callback for stdio streams:
Chris@1: A function pointer matching this signature may be passed to FLAC__stream_encoder_init*_stream(). The supplied function will be called when the encoder needs to know the current position of the output stream.
Chris@1:
Warning:
The callback must return the true current byte offset of the output to which the encoder is writing. If you are buffering the output, make sure and take this into account. If you are writing directly to a FILE* from your write callback, ftell() is sufficient. If you are writing directly to a file descriptor from your write callback, you can use lseek(fd, SEEK_CUR, 0). The encoder may later seek back to these points to rewrite metadata after encoding.
Chris@1: Here is an example of a tell callback for stdio streams:
Chris@1: A function pointer matching this signature may be passed to FLAC__stream_encoder_init*_stream(). The supplied function will be called once at the end of encoding with the populated STREAMINFO structure. This is so the client can seek back to the beginning of the file and write the STREAMINFO block with the correct statistics after encoding (like minimum/maximum frame size and total samples).
Chris@1:
Note:
In general, FLAC__StreamEncoder functions which change the state should not be called on the encoder while in the callback.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
The encoder instance calling the callback.
Chris@1:
metadata
The final populated STREAMINFO block.
Chris@1:
client_data
The callee's client data set through FLAC__stream_encoder_init_*().
Chris@1: A function pointer matching this signature may be passed to FLAC__stream_encoder_init*_file() or FLAC__stream_encoder_init*_FILE(). The supplied function will be called when the encoder has finished writing a frame. The total_frames_estimate argument to the callback will be based on the value from FLAC__stream_encoder_set_total_samples_estimate().
Chris@1:
Note:
In general, FLAC__StreamEncoder functions which change the state should not be called on the encoder while in the callback.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
The encoder instance calling the callback.
Chris@1:
bytes_written
Bytes written so far.
Chris@1:
samples_written
Samples written so far.
Chris@1:
frames_written
Frames written so far.
Chris@1:
total_frames_estimate
The estimate of the total number of frames to be written.
Chris@1:
client_data
The callee's client data set through FLAC__stream_encoder_init_*().
Chris@1: If the encoder gets into any other state besides FLAC__STREAM_ENCODER_OK or FLAC__STREAM_ENCODER_UNINITIALIZED, it becomes invalid for encoding and must be deleted with FLAC__stream_encoder_delete().
Enumeration values:
Chris@1:
Chris@1:
FLAC__STREAM_ENCODER_OK
Chris@1: The encoder is in the normal OK state and samples can be processed.
Chris@1:
FLAC__STREAM_ENCODER_UNINITIALIZED
Chris@1: The encoder is in the uninitialized state; one of the FLAC__stream_encoder_init_*() functions must be called before samples can be processed.
Chris@1:
FLAC__STREAM_ENCODER_OGG_ERROR
Chris@1: An error occurred in the underlying Ogg layer.
Chris@1: The encoder has an invalid setting for bits-per-sample. FLAC supports 4-32 bps but the reference encoder currently supports only up to 24 bps.
Chris@1: FLAC__stream_encoder_init_*() was called when the encoder was already initialized, usually because FLAC__stream_encoder_finish() was not called.
Chris@1: Create a new stream encoder instance. The instance is created with default settings; see the individual FLAC__stream_encoder_set_*() functions for each setting's default.
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__StreamEncoder*
NULL if there was an error allocating memory, else the new instance.
Chris@1: Set the "verify" flag. If true, the encoder will verify it's own encoded output by feeding it through an internal decoder and comparing the original signal against the decoded signal. If a mismatch occurs, the process call will return false. Note that this will slow the encoding process by the extra time required for decoding and comparison.
Chris@1:
Default Value:
false
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
Flag value (see above).
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: Set the Subset flag. If true, the encoder will comply with the Subset and will check the settings during FLAC__stream_encoder_init_*() to see if all settings comply. If false, the settings may take advantage of the full range that the format allows.
Chris@1: Make sure you know what it entails before setting this to false.
Chris@1:
Default Value:
true
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
Flag value (see above).
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: The compression level is roughly proportional to the amount of effort the encoder expends to compress the file. A higher level usually means more computation but higher compression. The default level is suitable for most applications.
Chris@1: Currently the levels range from 0 (fastest, least compression) to 8 (slowest, most compression). A value larger than 8 will be treated as 8.
Chris@1: This function automatically calls the following other _set_ functions with appropriate values, so the client does not need to unless it specifically wants to override them:
Chris@1: Set to true to enable mid-side encoding on stereo input. The number of channels must be 2 for this to have any effect. Set to false to use only independent channel coding.
Chris@1:
Default Value:
false
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
Flag value (see above).
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: Set to true to enable adaptive switching between mid-side and left-right encoding on stereo input. Set to false to use exhaustive searching. Setting this to true requires FLAC__stream_encoder_set_do_mid_side_stereo() to also be set to true in order to have any effect.
Chris@1:
Default Value:
false
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
Flag value (see above).
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: Sets the apodization function(s) the encoder will use when windowing audio data for LPC analysis.
Chris@1: The specification is a plain ASCII string which specifies exactly which functions to use. There may be more than one (up to 32), separated by ';' characters. Some functions take one or more comma-separated arguments in parentheses.
Chris@1: The available functions are bartlett, bartlett_hann, blackman, blackman_harris_4term_92db, connes, flattop, gauss(STDDEV), hamming, hann, kaiser_bessel, nuttall, rectangle, triangle, tukey(P), welch.
Chris@1: For gauss(STDDEV), STDDEV specifies the standard deviation (0<STDDEV<=0.5).
Chris@1: For tukey(P), P specifies the fraction of the window that is tapered (0<=P<=1). P=0 corresponds to rectangle and P=1 corresponds to hann.
Chris@1: Example specifications are "blackman" or "hann;triangle;tukey(0.5);tukey(0.25);tukey(0.125)"
Chris@1: Any function that is specified erroneously is silently dropped. Up to 32 functions are kept, the rest are dropped. If the specification is empty the encoder defaults to "tukey(0.5)".
Chris@1: When more than one function is specified, then for every subframe the encoder will try each of them separately and choose the window that results in the smallest compressed subframe.
Chris@1: Note that each function specified causes the encoder to occupy a floating point array in which to store the window.
Chris@1:
Default Value:
"tukey(0.5)"
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
specification
See above.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
specification != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: Set to false to use only the specified quantized linear predictor coefficient precision, or true to search neighboring precision values and use the best one.
Chris@1:
Default Value:
false
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
See above.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: Set to false to let the encoder estimate the best model order based on the residual signal energy, or true to force the encoder to evaluate all order models and select the best.
Chris@1:
Default Value:
false
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
See above.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: The partition order determines the context size in the residual. The context size will be approximately blocksize / (2 ^ order).
Chris@1: Set both min and max values to 0 to force a single context, whose Rice parameter is based on the residual signal variance. Otherwise, set a min and max order, and the encoder will search all orders, using the mean of each context for its Rice parameter, and use the best.
Chris@1:
Default Value:
0
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
See above.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: The partition order determines the context size in the residual. The context size will be approximately blocksize / (2 ^ order).
Chris@1: Set both min and max values to 0 to force a single context, whose Rice parameter is based on the residual signal variance. Otherwise, set a min and max order, and the encoder will search all orders, using the mean of each context for its Rice parameter, and use the best.
Chris@1:
Default Value:
0
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
See above.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: Set an estimate of the total samples that will be encoded. This is merely an estimate and may be set to 0 if unknown. This value will be written to the STREAMINFO block before encoding, and can remove the need for the caller to rewrite the value later if the value is known before encoding.
Chris@1:
Default Value:
0
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
value
See above.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true.
Chris@1: Set the metadata blocks to be emitted to the stream before encoding. A value of NULL, 0 implies no metadata; otherwise, supply an array of pointers to metadata blocks. The array is non-const since the encoder may need to change the is_last flag inside them, and in some cases update seek point offsets. Otherwise, the encoder will not modify or free the blocks. It is up to the caller to free the metadata blocks after encoding finishes.
Chris@1:
Note:
The encoder stores only copies of the pointers in the metadata array; the metadata blocks themselves must survive at least until after FLAC__stream_encoder_finish() returns. Do not free the blocks until then.
Chris@1: The STREAMINFO block is always written and no STREAMINFO block may occur in the supplied array.
Chris@1: By default the encoder does not create a SEEKTABLE. If one is supplied in the metadata array, but the client has specified that it does not support seeking, then the SEEKTABLE will be written verbatim. However by itself this is not very useful as the client will not know the stream offsets for the seekpoints ahead of time. In order to get a proper seektable the client must support seeking. See next note.
Chris@1: SEEKTABLE blocks are handled specially. Since you will not know the values for the seek point stream offsets, you should pass in a SEEKTABLE 'template', that is, a SEEKTABLE object with the required sample numbers (or placeholder points), with 0 for the frame_samples and stream_offset fields for each point. If the client has specified that it supports seeking by providing a seek callback to FLAC__stream_encoder_init_stream() or both seek AND read callback to FLAC__stream_encoder_init_ogg_stream() (or by using FLAC__stream_encoder_init*_file() or FLAC__stream_encoder_init*_FILE()), then while it is encoding the encoder will fill the stream offsets in for you and when encoding is finished, it will seek back and write the real values into the SEEKTABLE block in the stream. There are helper routines for manipulating seektable template blocks; see metadata.h: FLAC__metadata_object_seektable_template_*(). If the client does not support seeking, the SEEKTABLE will have inaccurate offsets which will slow down or remove the ability to seek in the FLAC stream.
Chris@1: The encoder instance will modify the first SEEKTABLE block as it transforms the template to a valid seektable while encoding, but it is still up to the caller to free all metadata blocks after encoding.
Chris@1: A VORBIS_COMMENT block may be supplied. The vendor string in it will be ignored. libFLAC will use it's own vendor string. libFLAC will not modify the passed-in VORBIS_COMMENT's vendor string, it will simply write it's own into the stream. If no VORBIS_COMMENT block is present in the metadata array, libFLAC will write an empty one, containing only the vendor string.
Chris@1: The Ogg FLAC mapping requires that the VORBIS_COMMENT block be the second metadata block of the stream. The encoder already supplies the STREAMINFO block automatically. If metadata does not contain a VORBIS_COMMENT block, the encoder will supply that too. Otherwise, if metadata does contain a VORBIS_COMMENT block and it is not the first, the init function will reorder metadata by moving the VORBIS_COMMENT block to the front; the relative ordering of the other blocks will remain as they were.
Chris@1: The Ogg FLAC mapping limits the number of metadata blocks per stream to 65535. If num_blocks exceeds this the function will return false.
Chris@1:
Default Value:
NULL, 0
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to set.
Chris@1:
metadata
See above.
Chris@1:
num_blocks
See above.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__bool
false if the encoder is already initialized, else true. false if the encoder is already initialized, or if num_blocks > 65535 if encoding to Ogg FLAC, else true.
Chris@1: Get the current encoder state as a C string. This version automatically resolves FLAC__STREAM_ENCODER_VERIFY_DECODER_ERROR by getting the verify decoder's state.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
A encoder instance to query.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
const
char * The encoder state as a C string. Do not modify the contents.
Chris@1: Get relevant values about the nature of a verify decoder error. Useful when the stream encoder state is FLAC__STREAM_ENCODER_VERIFY_DECODER_ERROR. The arguments should be addresses in which the stats will be returned, or NULL if value is not desired.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An encoder instance to query.
Chris@1:
absolute_sample
The absolute sample number of the mismatch.
Chris@1:
frame_number
The number of the frame in which the mismatch occurred.
Chris@1:
channel
The channel in which the mismatch occurred.
Chris@1:
sample
The number of the sample (relative to the frame) in which the mismatch occurred.
Chris@1: Get the previously set estimate of the total samples to be encoded. The encoder merely mimics back the value given to FLAC__stream_encoder_set_total_samples_estimate() since it has no other way of knowing how many samples the client will encode.
Chris@1: Initialize the encoder instance to encode native FLAC streams.
Chris@1: This flavor of initialization sets up the encoder to encode to a native FLAC stream. I/O is performed via callbacks to the client. For encoding to a plain file via filename or open FILE*, FLAC__stream_encoder_init_file() and FLAC__stream_encoder_init_FILE() provide a simpler interface.
Chris@1: The call to FLAC__stream_encoder_init_stream() currently will also immediately call the write callback several times, once with the fLaC signature, and once for each encoded metadata block.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An uninitialized encoder instance.
Chris@1:
write_callback
See FLAC__StreamEncoderWriteCallback. This pointer must not be NULL.
Chris@1:
seek_callback
See FLAC__StreamEncoderSeekCallback. This pointer may be NULL if seeking is not supported. The encoder uses seeking to go back and write some some stream statistics to the STREAMINFO block; this is recommended but not necessary to create a valid FLAC stream. If seek_callback is not NULL then a tell_callback must also be supplied. Alternatively, a dummy seek callback that just returns FLAC__STREAM_ENCODER_SEEK_STATUS_UNSUPPORTED may also be supplied, all though this is slightly less efficient for the encoder.
Chris@1:
tell_callback
See FLAC__StreamEncoderTellCallback. This pointer may be NULL if seeking is not supported. If seek_callback is NULL then this argument will be ignored. If seek_callback is not NULL then a tell_callback must also be supplied. Alternatively, a dummy tell callback that just returns FLAC__STREAM_ENCODER_TELL_STATUS_UNSUPPORTED may also be supplied, all though this is slightly less efficient for the encoder.
Chris@1:
metadata_callback
See FLAC__StreamEncoderMetadataCallback. This pointer may be NULL if the callback is not desired. If the client provides a seek callback, this function is not necessary as the encoder will automatically seek back and update the STREAMINFO block. It may also be NULL if the client does not support seeking, since it will have no way of going back to update the STREAMINFO. However the client can still supply a callback if it would like to know the details from the STREAMINFO.
Chris@1:
client_data
This value will be supplied to callbacks in their client_data argument.
Chris@1:
Chris@1:
Chris@1:
Assertions:
encoder != NULL
Chris@1:
Chris@1:
Return values:
Chris@1:
Chris@1:
FLAC__StreamEncoderInitStatus
FLAC__STREAM_ENCODER_INIT_STATUS_OK if initialization was successful; see FLAC__StreamEncoderInitStatus for the meanings of other return values.
Chris@1: Initialize the encoder instance to encode Ogg FLAC streams.
Chris@1: This flavor of initialization sets up the encoder to encode to a FLAC stream in an Ogg container. I/O is performed via callbacks to the client. For encoding to a plain file via filename or open FILE*, FLAC__stream_encoder_init_ogg_file() and FLAC__stream_encoder_init_ogg_FILE() provide a simpler interface.
Chris@1: The call to FLAC__stream_encoder_init_ogg_stream() currently will also immediately call the write callback several times to write the metadata packets.
Chris@1:
Parameters:
Chris@1:
Chris@1:
encoder
An uninitialized encoder instance.
Chris@1:
read_callback
See FLAC__StreamEncoderReadCallback. This pointer must not be NULL if seek_callback is non-NULL since they are both needed to be able to write data back to the Ogg FLAC stream in the post-encode phase.
Chris@1:
write_callback
See FLAC__StreamEncoderWriteCallback. This pointer must not be NULL.
Chris@1:
seek_callback
See FLAC__StreamEncoderSeekCallback. This pointer may be NULL if seeking is not supported. The encoder uses seeking to go back and write some some stream statistics to the STREAMINFO block; this is recommended but not necessary to create a valid FLAC stream. If seek_callback is not NULL then a tell_callback must also be supplied. Alternatively, a dummy seek callback that just returns FLAC__STREAM_ENCODER_SEEK_STATUS_UNSUPPORTED may also be supplied, all though this is slightly less efficient for the encoder.
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tell_callback
See FLAC__StreamEncoderTellCallback. This pointer may be NULL if seeking is not supported. If seek_callback is NULL then this argument will be ignored. If seek_callback is not NULL then a tell_callback must also be supplied. Alternatively, a dummy tell callback that just returns FLAC__STREAM_ENCODER_TELL_STATUS_UNSUPPORTED may also be supplied, all though this is slightly less efficient for the encoder.
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metadata_callback
See FLAC__StreamEncoderMetadataCallback. This pointer may be NULL if the callback is not desired. If the client provides a seek callback, this function is not necessary as the encoder will automatically seek back and update the STREAMINFO block. It may also be NULL if the client does not support seeking, since it will have no way of going back to update the STREAMINFO. However the client can still supply a callback if it would like to know the details from the STREAMINFO.
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client_data
This value will be supplied to callbacks in their client_data argument.
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Assertions:
encoder != NULL
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Return values:
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FLAC__StreamEncoderInitStatus
FLAC__STREAM_ENCODER_INIT_STATUS_OK if initialization was successful; see FLAC__StreamEncoderInitStatus for the meanings of other return values.
Chris@1: Initialize the encoder instance to encode native FLAC files.
Chris@1: This flavor of initialization sets up the encoder to encode to a plain native FLAC file. For non-stdio streams, you must use FLAC__stream_encoder_init_stream() and provide callbacks for the I/O.
An open file. The file should have been opened with mode "w+b" and rewound. The file becomes owned by the encoder and should not be manipulated by the client while encoding. Unless file is stdout, it will be closed when FLAC__stream_encoder_finish() is called. Note however that a proper SEEKTABLE cannot be created when encoding to stdout since it is not seekable.
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progress_callback
See FLAC__StreamEncoderProgressCallback. This pointer may be NULL if the callback is not desired.
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client_data
This value will be supplied to callbacks in their client_data argument.
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Assertions:
encoder != NULL
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file != NULL
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Return values:
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FLAC__StreamEncoderInitStatus
FLAC__STREAM_ENCODER_INIT_STATUS_OK if initialization was successful; see FLAC__StreamEncoderInitStatus for the meanings of other return values.
Chris@1: Initialize the encoder instance to encode Ogg FLAC files.
Chris@1: This flavor of initialization sets up the encoder to encode to a plain Ogg FLAC file. For non-stdio streams, you must use FLAC__stream_encoder_init_ogg_stream() and provide callbacks for the I/O.
An open file. The file should have been opened with mode "w+b" and rewound. The file becomes owned by the encoder and should not be manipulated by the client while encoding. Unless file is stdout, it will be closed when FLAC__stream_encoder_finish() is called. Note however that a proper SEEKTABLE cannot be created when encoding to stdout since it is not seekable.
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progress_callback
See FLAC__StreamEncoderProgressCallback. This pointer may be NULL if the callback is not desired.
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client_data
This value will be supplied to callbacks in their client_data argument.
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Assertions:
encoder != NULL
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file != NULL
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Return values:
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FLAC__StreamEncoderInitStatus
FLAC__STREAM_ENCODER_INIT_STATUS_OK if initialization was successful; see FLAC__StreamEncoderInitStatus for the meanings of other return values.
Chris@1: Initialize the encoder instance to encode native FLAC files.
Chris@1: This flavor of initialization sets up the encoder to encode to a plain FLAC file. If POSIX fopen() semantics are not sufficient (for example, with Unicode filenames on Windows), you must use FLAC__stream_encoder_init_FILE(), or FLAC__stream_encoder_init_stream() and provide callbacks for the I/O.
The name of the file to encode to. The file will be opened with fopen(). Use NULL to encode to stdout. Note however that a proper SEEKTABLE cannot be created when encoding to stdout since it is not seekable.
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progress_callback
See FLAC__StreamEncoderProgressCallback. This pointer may be NULL if the callback is not desired.
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client_data
This value will be supplied to callbacks in their client_data argument.
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Assertions:
encoder != NULL
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Return values:
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FLAC__StreamEncoderInitStatus
FLAC__STREAM_ENCODER_INIT_STATUS_OK if initialization was successful; see FLAC__StreamEncoderInitStatus for the meanings of other return values.
Chris@1: Initialize the encoder instance to encode Ogg FLAC files.
Chris@1: This flavor of initialization sets up the encoder to encode to a plain Ogg FLAC file. If POSIX fopen() semantics are not sufficient (for example, with Unicode filenames on Windows), you must use FLAC__stream_encoder_init_ogg_FILE(), or FLAC__stream_encoder_init_ogg_stream() and provide callbacks for the I/O.
The name of the file to encode to. The file will be opened with fopen(). Use NULL to encode to stdout. Note however that a proper SEEKTABLE cannot be created when encoding to stdout since it is not seekable.
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progress_callback
See FLAC__StreamEncoderProgressCallback. This pointer may be NULL if the callback is not desired.
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client_data
This value will be supplied to callbacks in their client_data argument.
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Assertions:
encoder != NULL
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Return values:
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FLAC__StreamEncoderInitStatus
FLAC__STREAM_ENCODER_INIT_STATUS_OK if initialization was successful; see FLAC__StreamEncoderInitStatus for the meanings of other return values.
Chris@1: Finish the encoding process. Flushes the encoding buffer, releases resources, resets the encoder settings to their defaults, and returns the encoder state to FLAC__STREAM_ENCODER_UNINITIALIZED. Note that this can generate one or more write callbacks before returning, and will generate a metadata callback.
Chris@1: Note that in the course of processing the last frame, errors can occur, so the caller should be sure to check the return value to ensure the file was encoded properly.
Chris@1: In the event of a prematurely-terminated encode, it is not strictly necessary to call this immediately before FLAC__stream_encoder_delete() but it is good practice to match every FLAC__stream_encoder_init_*() with a FLAC__stream_encoder_finish().
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Parameters:
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encoder
An uninitialized encoder instance.
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Assertions:
encoder != NULL
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Return values:
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FLAC__bool
false if an error occurred processing the last frame; or if verify mode is set (see FLAC__stream_encoder_set_verify()), there was a verify mismatch; else true. If false, caller should check the state with FLAC__stream_encoder_get_state() for more information about the error.
Chris@1: Submit data for encoding. This version allows you to supply the input data via an array of pointers, each pointer pointing to an array of samples samples representing one channel. The samples need not be block-aligned, but each channel should have the same number of samples. Each sample should be a signed integer, right-justified to the resolution set by FLAC__stream_encoder_set_bits_per_sample(). For example, if the resolution is 16 bits per sample, the samples should all be in the range [-32768,32767].
Chris@1: For applications where channel order is important, channels must follow the order as described in the frame header.
Chris@1: Submit data for encoding. This version allows you to supply the input data where the channels are interleaved into a single array (i.e. channel0_sample0, channel1_sample0, ... , channelN_sample0, channel0_sample1, ...). The samples need not be block-aligned but they must be sample-aligned, i.e. the first value should be channel0_sample0 and the last value channelN_sampleM. Each sample should be a signed integer, right-justified to the resolution set by FLAC__stream_encoder_set_bits_per_sample(). For example, if the resolution is 16 bits per sample, the samples should all be in the range [-32768,32767].
Chris@1: For applications where channel order is important, channels must follow the order as described in the frame header.
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Parameters:
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encoder
An initialized encoder instance in the OK state.
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buffer
An array of channel-interleaved data (see above).
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samples
The number of samples in one channel, the same as for FLAC__stream_encoder_process(). For example, if encoding two channels, 1000samples corresponds to a buffer of 2000 values.