176 lines
5.4 KiB
HTML
176 lines
5.4 KiB
HTML
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<html>
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<head>
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<title>vorbisfile - Example Code</title>
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<link rel=stylesheet href="style.css" type="text/css">
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</head>
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<body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
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<table border=0 width=100%>
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<tr>
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<td><p class=tiny>Vorbisfile documentation</p></td>
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<td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
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</tr>
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</table>
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<h1>Chaining Example Code</h1>
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<p>
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The following is a run-through of the chaining example program supplied
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with vorbisfile - <a href="chaining_example_c.html">chaining_example.c</a>.
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This program demonstrates how to work with a chained bitstream.
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<p>
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First, relevant headers, including vorbis-specific "codec.h" and "vorbisfile.h" have to be included.
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<br><br>
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<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td>
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<pre><b>
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#include "vorbis/codec.h"
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#include "vorbis/vorbisfile.h"
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#include "../lib/misc.h"
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</b></pre>
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</td>
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</tr>
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</table>
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<p>Inside main(), we declare our primary OggVorbis_File structure. We also declare a other helpful variables to track our progress within the file.
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<br><br>
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<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td>
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<pre><b>
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int main(){
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OggVorbis_File ov;
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int i;
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</b></pre>
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</td>
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</tr>
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</table>
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<p>This example takes its input on stdin which is in 'text' mode by default under Windows; this will corrupt the input data unless set to binary mode. This applies only to Windows.
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<br><br>
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<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td>
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<pre><b>
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#ifdef _WIN32 /* We need to set stdin to binary mode under Windows */
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_setmode( _fileno( stdin ), _O_BINARY );
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#endif
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</b></pre>
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</td>
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</tr>
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</table>
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<p>We call <a href="ov_open_callbacks.html">ov_open_callbacks()</a> to
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initialize the <a href="OggVorbis_File.html">OggVorbis_File</a>
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structure. <a href="ov_open_callbacks.html">ov_open_callbacks()</a>
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also checks to ensure that we're reading Vorbis format and not
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something else. The OV_CALLBACKS_NOCLOSE callbacks instruct
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libvorbisfile not to close stdin later during cleanup.<p>
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<br><br>
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<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td>
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<pre><b>
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if(ov_open_callbacks(stdin,&ov,NULL,-1,OV_CALLBACKS_NOCLOSE)<0){
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printf("Could not open input as an OggVorbis file.\n\n");
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exit(1);
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}
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</b></pre>
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</td>
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</tr>
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</table>
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<p>
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First we check to make sure the stream is seekable using <a href="ov_seekable.html">ov_seekable</a>.
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<p>Then we're going to find the number of logical bitstreams in the physical bitstream using <a href="ov_streams.html">ov_streams</a>.
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<p>We use <a href="ov_time_total.html">ov_time_total</a> to determine the total length of the physical bitstream. We specify that we want the entire bitstream by using the argument <tt>-1</tt>.
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<br><br>
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<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td>
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<pre><b>
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if(ov_seekable(&ov)){
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printf("Input bitstream contained %ld logical bitstream section(s).\n",
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ov_streams(&ov));
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printf("Total bitstream playing time: %ld seconds\n\n",
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(long)ov_time_total(&ov,-1));
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}else{
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printf("Standard input was not seekable.\n"
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"First logical bitstream information:\n\n");
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}
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</b></pre>
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</td>
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</tr>
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</table>
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<p>Now we're going to iterate through each logical bitstream and print information about that bitstream.
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<p>We use <a href="ov_info.html">ov_info</a> to pull out the <a href="../libvorbis/vorbis_info.html">vorbis_info</a> struct for each logical bitstream. This struct contains bitstream-specific info.
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<p><a href="ov_serialnumber.html">ov_serialnumber</a> retrieves the unique serial number for the logical bistream. <a href="ov_raw_total.html">ov_raw_total</a> gives the total compressed bytes for the logical bitstream, and <a href="ov_time_total.html">ov_time_total</a> gives the total time in the logical bitstream.
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<br><br>
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<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td>
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<pre><b>
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for(i=0;i<ov_streams(&ov);i++){
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vorbis_info *vi=ov_info(&ov,i);
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printf("\tlogical bitstream section %d information:\n",i+1);
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printf("\t\t%ldHz %d channels bitrate %ldkbps serial number=%ld\n",
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vi->rate,vi->channels,ov_bitrate(&ov,i)/1000,
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ov_serialnumber(&ov,i));
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printf("\t\tcompressed length: %ld bytes ",(long)(ov_raw_total(&ov,i)));
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printf(" play time: %lds\n",(long)ov_time_total(&ov,i));
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}
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</b></pre>
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</td>
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</tr>
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</table>
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<p>
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When we're done with the entire physical bitstream, we need to call <a href="ov_clear.html">ov_clear()</a> to release the bitstream.
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<br><br>
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<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td>
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<pre><b>
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ov_clear(&ov);
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return 0;
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}
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</b></pre>
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</td>
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</tr>
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</table>
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<p>
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The full source for chaining_example.c can be found with the vorbis
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distribution in <a href="chaining_example_c.html">chaining_example.c</a>.
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<br><br>
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<hr noshade>
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<table border=0 width=100%>
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<tr valign=top>
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<td><p class=tiny>copyright © 2000-2010 Xiph.Org</p></td>
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<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td>
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</tr><tr>
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<td><p class=tiny>Vorbisfile documentation</p></td>
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<td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
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</tr>
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</table>
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</body>
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</html>
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