[linux-dvb] API ioctls for Bypass and RAW Audio

Dr. Werner Fink werner at suse.de
Wed Oct 19 18:56:16 CEST 2005


Hi,

just finished two steps in the firmware for the FF DVB cards of TT.
The first is the possiblity of AC3 for Live channels and the other
if the playback of RAW Audio like Mpeg Audio, PCM, AC3, and DTS.

Therefore I'd like to ask about some ioctls which aren't
very well documented in the dvb-kernel.

I guess that for switching the firmware into bypass for the next
Audio PID of a Live channel the ioctl:

     AUDIO_SET_BYPASS_MODE

is usable, isn't it?

Which ioctl should be used for playpack RAW Audio?  I've found
two ioctl's:

     AUDIO_SET_STREAMTYPE

and

     AUDIO_SET_ATTRIBUTES

...  currently the first one is NOP in av7110.c and the second
is not implemented.  For the second I've found in audio.h of
the API for the user space:

  typedef uint16_t audio_attributes_t;
  /*   bits: descr. */
  /*   15-13 audio coding mode (0=ac3, 2=mpeg1, 3=mpeg2ext, 4=LPCM, 6=DTS, */
  /*   12    multichannel extension */
  /*   11-10 audio type (0=not spec, 1=language included) */
  /*    9- 8 audio application mode (0=not spec, 1=karaoke, 2=surround) */
  /*    7- 6 Quantization / DRC (mpeg audio: 1=DRC exists)(lpcm: 0=16bit,  */
  /*    5- 4 Sample frequency fs (0=48kHz, 1=96kHz) */
  /*    2- 0 number of audio channels (n+1 channels) */

it seems that for the bit field 5-4 the value 2 for 44.1kHz and
the value 3 for 32kHz are missed.

For what the ioctls AUDIO_SET_STREAMTYPE and AUDIO_SET_ATTRIBUTES
should by used.


       Werner

-- 
AC3 loop through sound card http://bitstreamout.sourceforge.net/
Howto http://www.vdr-portal.de/board/thread.php?threadid=1958
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