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Current libsamplerate source
author Chris Cannam
date Tue, 18 Oct 2016 13:24:45 +0100
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Chris@41 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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Chris@41 3
Chris@41 4 <HEAD>
Chris@41 5 <TITLE>
Chris@41 6 Secret Rabbit Code (aka libsamplerate)
Chris@41 7 </TITLE>
Chris@41 8 <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)">
Chris@41 9 <META NAME="Version" CONTENT="libsamplerate-0.1.8">
Chris@41 10 <META NAME="Description" CONTENT="The Secret Rabbit Code Home Page">
Chris@41 11 <META NAME="Keywords" CONTENT="libsamplerate sound resample audio dsp Linux">
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Chris@41 23 <TABLE ALIGN="center" WIDTH="98%">
Chris@41 24 <TR>
Chris@41 25 <TD VALIGN="top">
Chris@41 26 <BR>
Chris@41 27 <DIV CLASS="nav">
Chris@41 28 <BR>
Chris@41 29 <A HREF="index.html">Home</A><BR>
Chris@41 30 <BR>
Chris@41 31 <A HREF="api_simple.html">Simple API</A><BR>
Chris@41 32 <A HREF="api_full.html">Full API</A><BR>
Chris@41 33 <A HREF="api_callback.html">Callback API</A><BR>
Chris@41 34 <A HREF="api_misc.html">Miscellaneous</A><BR>
Chris@41 35 <A HREF="api_misc.html#ErrorReporting">Error Handling</A><BR>
Chris@41 36 <BR>
Chris@41 37 <DIV CLASS="block">
Chris@41 38 Author :<BR>Erik de Castro Lopo
Chris@41 39 <!-- pepper -->
Chris@41 40 <BR><BR>
Chris@41 41 <!-- pepper -->
Chris@41 42
Chris@41 43 </DIV>
Chris@41 44 <IMG SRC=
Chris@41 45 "/cgi-bin/Count.cgi?ft=6|frgb=55;55;55|tr=0|md=6|dd=B|st=1|sh=1|df=src_api.dat"
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Chris@41 48
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Chris@41 50 <!-- pepper -->
Chris@41 51 <!-- ######################################################################## -->
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Chris@41 53 <TD VALIGN="top">
Chris@41 54 <DIV CLASS="block">
Chris@41 55
Chris@41 56 <H1><B>Simple API</B></H1>
Chris@41 57
Chris@41 58 <P>
Chris@41 59 <B>Important Note:</B>
Chris@41 60 The simple API is not designed to work on small chunks of a larger piece of
Chris@41 61 audio.
Chris@41 62 If you attempt to use it this way you are doing it wrong and will not get the
Chris@41 63 results you want.
Chris@41 64 For processing audio data in chunks you <b>must</b> use the
Chris@41 65 <a href="api_full.html">full api</a>
Chris@41 66 or the
Chris@41 67 <a href="api_callback.html">callback based api</a>.
Chris@41 68 </P>
Chris@41 69
Chris@41 70 <br/><br/>
Chris@41 71
Chris@41 72 <P>
Chris@41 73 The simple API consists of a single function :
Chris@41 74 </P>
Chris@41 75 <PRE>
Chris@41 76 int src_simple (SRC_DATA *data, int converter_type, int channels) ;
Chris@41 77 </PRE>
Chris@41 78 <P>
Chris@41 79 The use of this function rather than the more fully featured API requires the caller
Chris@41 80 to know the total length of the input data before hand and that all input and output
Chris@41 81 data can be held in the system's memory at once.
Chris@41 82 It also assumes that there is a single constant ratio between input and output sample
Chris@41 83 rates.
Chris@41 84 <!--
Chris@41 85 If these conditions cannot be met, the full featured API should be used instead.
Chris@41 86 In addition, this documentation is complemented by this
Chris@41 87 <A HREF="ex_simple.html">example code</A>. -->
Chris@41 88 </P>
Chris@41 89
Chris@41 90 <P>
Chris@41 91 Dealing with the easy stuff first, the <B>converter_type</B> parameter should be
Chris@41 92 one of the values defined in <B>samplerate.h</B> and documented
Chris@41 93 <A HREF="api_misc.html#Converters">here</A> while the <b>channels</b> parameter
Chris@41 94 specifies the number of interleaved channels that the sample rate converter
Chris@41 95 is being asked to process (number of input channels and output channels is always
Chris@41 96 equal).
Chris@41 97 There is no hard upper limit on the number of channels; it is limited purely
Chris@41 98 by the amount of memory available.
Chris@41 99 </P>
Chris@41 100
Chris@41 101
Chris@41 102 <P>
Chris@41 103 The first parameter to <B>src_simple</B> is a pointer to an <B>SRC_DATA</B> struct
Chris@41 104 (more info <A HREF="api_misc.html#SRC_DATA">here</A>) defined as follows:
Chris@41 105 </P>
Chris@41 106 <PRE>
Chris@41 107 typedef struct
Chris@41 108 { float *data_in, *data_out ;
Chris@41 109
Chris@41 110 long input_frames, output_frames ;
Chris@41 111 long input_frames_used, output_frames_gen ;
Chris@41 112
Chris@41 113 int end_of_input ;
Chris@41 114
Chris@41 115 double src_ratio ;
Chris@41 116 } SRC_DATA ;
Chris@41 117 </PRE>
Chris@41 118 <P>
Chris@41 119 The fields of this struct which must be filled in by the caller are:
Chris@41 120 </P>
Chris@41 121 <PRE>
Chris@41 122 data_in : A pointer to the input data samples.
Chris@41 123 input_frames : The number of frames of data pointed to by data_in.
Chris@41 124 data_out : A pointer to the output data samples.
Chris@41 125 output_frames : Maximum number of frames pointer to by data_out.
Chris@41 126 src_ratio : Equal to output_sample_rate / input_sample_rate.
Chris@41 127 </PRE>
Chris@41 128 <P>
Chris@41 129 When the <B>src_simple</B> function returns <B>output_frames_gen</B> will be
Chris@41 130 set to the number of output frames generated and <B>input_frames_used</B> will
Chris@41 131 be set to the number of input frames used to generate the provided number of
Chris@41 132 output frames.
Chris@41 133 </P>
Chris@41 134 <P>
Chris@41 135 The <B>src_simple</B> function returns a non-zero value when an error occurs.
Chris@41 136 See <A HREF="api_misc.html#ErrorReporting">here</A> for how to convert the error value into
Chris@41 137 a text string.
Chris@41 138 </P>
Chris@41 139
Chris@41 140 </DIV>
Chris@41 141 </TD></TR>
Chris@41 142 </TABLE>
Chris@41 143
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Chris@41 146