xiph
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vorbis
镜像来自 https://git.xiph.org/vorbis.git


			
				
					
						
						
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<title>vorbisfile - Example Code</title>
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<td><p class=tiny>Vorbisfile documentation</p></td>
<td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td>
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<h1>Example Code: seeking</h1>

<p>
The following is a run-through of the seeking example program supplied
with vorbisfile - <a href="seeking_test_c.html">seeking_test.c</a>.  
This program tests the vorbisfile <a href="ov_time_seek.html">ov_time_seek</a> function by seeking to random points within the file.

<p>
First, relevant headers, including vorbis-specific "codec.h" and "vorbisfile.h" have to be included.

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#include &lt;stdlib.h>
#include &lt;stdio.h>
#include "vorbis/codec.h"
#include "vorbis/vorbisfile.h"
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<p>Inside main(), we declare our primary OggVorbis_File structure.  We also declare other helpful variables to track our progress within the file.
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int main(){
  OggVorbis_File ov;
  int i;
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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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#ifdef _WIN32 /* We need to set stdin to binary mode under Windows */
  _setmode( _fileno( stdin ), _O_BINARY );
#endif
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<p><a href="ov_open_callbacks.html">ov_open()</a> must be
called to initialize the <a href="OggVorbis_File.html">OggVorbis_File</a> structure with default values.  
<a href="ov_open_callbacks.html">ov_open_callbacks()</a> also checks to ensure that we're reading Vorbis format and not something else.

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  if(ov_open_callbacks(stdin,&ov,NULL,-1, OV_CALLBACKS_NOCLOSE)<0){
    printf("Could not open input as an OggVorbis file.\n\n");
    exit(1);
  }

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<p>
First we check to make sure the stream is seekable using <a href="ov_seekable.html">ov_seekable</a>.

<p>Then we seek to 100 random spots in the bitstream using <a href="ov_time_seek.html">ov_time_seek</a> with randomly generated values.

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  /* print details about each logical bitstream in the input */
  if(ov_seekable(&ov)){
    double length=ov_time_total(&ov,-1);
    printf("testing seeking to random places in %g seconds....\n",length);
    for(i=0;i<100;i++){
      double val=(double)rand()/RAND_MAX*length;
      ov_time_seek(&ov,val);
      printf("\r\t%d [%gs]...     ",i,val);
      fflush(stdout);
    }
    
    printf("\r                                   \nOK.\n\n");
  }else{
    printf("Standard input was not seekable.\n");
  }
  
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<p>
When we're done seeking, we need to call <a href="ov_clear.html">ov_clear()</a> to release the bitstream.

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  ov_clear(&ov);
  return 0;
}
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<p>
The full source for seeking_test.c can be found with the vorbis
distribution in <a href="seeking_test_c.html">seeking_test.c</a>.

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<td><p class=tiny>copyright &copy; 2007 Xiph.org</p></td>
<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a><br><a href="mailto:team@vorbis.org">team@vorbis.org</a></p></td>
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<td><p class=tiny>Vorbisfile documentation</p></td>
<td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td>
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