Audio support since 6.6 IO protocol version.

struct _PRL_IO_AUDIO_ENCODING {
  PRL_UINT32 encodingType;
  PRL_UINT32 encodingQuality;
  PRL_UINT32 inout_bitRate;
  PRL_UINT32 inout_channelsNum;
  PRL_UINT32 inout_sampleRate;
  PRL_UINT32 inout_bitsPerChannel;
  PRL_UINT32 unused1;
  PRL_UINT32 unused2;
  PRL_UINT32 out_magicCookieSize;
  PRL_CHAR out_magicCookie[4];
};