| 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') |