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https://github.com/cookiengineer/audacity
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188 lines
5.7 KiB
HTML
188 lines
5.7 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML>
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<HEAD>
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<TITLE>
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Secret Rabbit Code (aka libsamplerate)
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</TITLE>
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<META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)">
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<META NAME="Version" CONTENT="libsamplerate-0.1.7">
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<META NAME="Description" CONTENT="The Secret Rabbit Code Home Page">
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<META NAME="Keywords" CONTENT="libsamplerate sound resample audio dsp Linux">
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<LINK REL=StyleSheet HREF="SRC.css" TYPE="text/css" MEDIA="all">
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</HEAD>
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<BODY TEXT="#FFFFFF" BGCOLOR="#000000" LINK="#FB1465" VLINK="#FB1465" ALINK="#FB1465">
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<!-- pepper -->
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<CENTER>
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<IMG SRC="SRC.png" HEIGHT=100 WIDTH=760 ALT="SRC.png">
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</CENTER>
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<BR>
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<TABLE ALIGN="center" WIDTH="98%">
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<TR>
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<TD VALIGN="top">
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<BR>
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<DIV CLASS="nav">
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<BR>
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<A HREF="index.html">Home</A><BR>
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<BR>
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<A HREF="api_simple.html">Simple API</A><BR>
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<A HREF="api_full.html">Full API</A><BR>
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<A HREF="api_callback.html">Callback API</A><BR>
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<A HREF="api_misc.html">Miscellaneous</A><BR>
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<A HREF="api_misc.html#ErrorReporting">Error Handling</A><BR>
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<BR>
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<DIV CLASS="block">
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Author :<BR>Erik de Castro Lopo
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<BR><BR>
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</DIV>
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<IMG SRC=
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"/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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HEIGHT=30 WIDTH=100 ALT="counter.gif">
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</DIV>
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</TD>
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<!-- ######################################################################## -->
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<TD VALIGN="top">
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<DIV CLASS="block">
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<H1><B>Full API</B></H1>
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<P>
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The full API consists of the following functions :
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</P>
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<PRE>
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SRC_STATE* <A HREF="#Init">src_new</A> (int converter_type, int channels, int *error) ;
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SRC_STATE* <A HREF="#CleanUp">src_delete</A> (SRC_STATE *state) ;
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int <A HREF="#Process">src_process</A> (SRC_STATE *state, SRC_DATA *data) ;
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int <A HREF="#Reset">src_reset</A> (SRC_STATE *state) ;
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int <A HREF="#SetRatio">src_set_ratio</A> (SRC_STATE *state, double new_ratio) ;
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</PRE>
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<A NAME="Init"></A>
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<H3><BR>Initialisation</H3>
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<PRE>
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SRC_STATE* src_new (int converter_type, int channels, int *error) ;
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</PRE>
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<P>
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The <B>src_new</B> function returns an anonymous pointer to a sample rate
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converter object, src_state.
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If an error occurs the function returns a NULL pointer and fills in the
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error value pointed to by the <B>error</B> pointer supplied by the caller.
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The converter must be one of the supplied converter types documented
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<A HREF="api_misc.html#Converters">here</A>.
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</P>
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<A NAME="CleanUp"></A>
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<H3><BR>Cleanup</H3>
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<PRE>
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SRC_STATE* src_delete (SRC_STATE *state) ;
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</PRE>
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<P>
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The <B>src_delete</B> function frees up all memory allocated for the given sample
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rate converter object and returns a NULL pointer.
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The caller is responsible for freeing any memory passed to the sample rate converter
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via the pointer to the <B>SRC_DATA</B> struct.
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</P>
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<A NAME="Process"></A>
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<H3><BR>Process</H3>
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<PRE>
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int src_process (SRC_STATE *state, SRC_DATA *data) ;
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</PRE>
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<P>
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The <B>src_process</B> function processes the data provided by the caller
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in an <B>SRC_DATA</B> struct using the sample rate converter object specified
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by the <B>SRC_STATE</B> pointer.
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When operating on streaming data, this function can be called over and over again,
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with each new call providing new input data and returning new output data.
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</P>
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<P>
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The <B>SRC_DATA</B> struct passed as the second parameter to the <B>src_process</B>
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function has the following fields:
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</P>
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<PRE>
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typedef struct
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{ float *data_in, *data_out ;
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long input_frames, output_frames ;
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long input_frames_used, output_frames_gen ;
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int end_of_input ;
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double src_ratio ;
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} SRC_DATA ;
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</PRE>
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<P>
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The fields of this struct which must be filled in by the caller are:
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</P>
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<PRE>
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data_in : A pointer to the input data samples.
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input_frames : The number of frames of data pointed to by data_in.
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data_out : A pointer to the output data samples.
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output_frames : Maximum number of frames pointer to by data_out.
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src_ratio : Equal to output_sample_rate / input_sample_rate.
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end_of_input : Equal to 0 if more input data is available and 1
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otherwise.
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</PRE>
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<P>
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Note that the data_in and data_out arrays may not overlap. If they do, the
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library will return an error code.
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</P>
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<P>
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When the <B>src_process</B> function returns <B>output_frames_gen</B> will be
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set to the number of output frames generated and <B>input_frames_used</B> will
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be set to the number of input frames consumed to generate the provided number of
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output frames.
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</P>
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<P>
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The <B>src_process</B> function returns non-zero if an error occurs.
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The non-zero error return value can be decoded into a text string using the function
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documented <A HREF="api_misc.html#ErrorReporting">here</A>.
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</P>
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<A NAME="Reset"></A>
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<H3><BR>Reset</H3>
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<PRE>
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int src_reset (SRC_STATE *state) ;
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</PRE>
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<P>
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The <B>src_reset</B> function resets the internal state of the sample rate
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converter object to the same state it had immediately after its creation using
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<B>src_new</B>.
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This should be called whenever a sample rate converter is to be used on two
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separate, unrelated pieces of audio.
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</P>
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<A NAME="SetRatio"></A>
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<H3><BR>Set Ratio</H3>
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<PRE>
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int src_set_ratio (SRC_STATE *state, double new_ratio) ;
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</PRE>
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<P>
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The <B>src_set_ratio</B> function allows the modification of the conversion
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ratio between calls to <B>src_process</B>.
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This allows a step response in the conversion ratio.
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It returns non-zero on error and the error return value can be decoded into
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a text string using the function documented
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<A HREF="api_misc.html#ErrorReporting">here</A>.</P>
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