| pcm_mode | 
     PCM byte encoding used.  See constants below. | 
     Read / Write | 
     OGGVORBIS_PCM_S16_LE | 
    
    
     | rate | 
     PCM Sampling rate.  Measured in Hz. | 
     Write only | 
     44100 | 
    
    
     | bitrate | 
     
      Vorbis Average Bitrate Encoding / Variable Bitrate Encoding.  
      Measured in bps (ABR) or Quality level (VBR: 0.0 to 1.0).  
      128000 ABR is rough equal to 0.4 VBR.
      | 
     Write only | 
     128000 | 
    
    
     | channels | 
     Number of PCM channels.  1 == Mono, 2 == Stereo. | 
     Write only | 
     2 | 
    
    
     | serialno | 
     
      Serial Number of stream within file.  Must be unique within file.
      Because of the potential to select a duplicate serial number within
      a chained file, make efforts to manually assign unique numbers when
      encoding.
      | 
     Write only | 
     Random | 
    
    
     | comments | 
     
      Associative array of file comments.  
      Will be translated to strtoupper($name) . "=$value".
      Note: This context option is not available in oggvorbis-0.1
      | 
     Write only | 
     array('ENCODER' => 'PHP/OggVorbis, http://pear.php.net/oggvorbis') |