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

Dr. Werner Fink werner at suse.de
Thu Oct 20 19:09:33 CEST 2005


Hi,

is there really no one out here which want to be able to
use RAW Audio streams? That means replaying Audio without
the needs of a PES remuxer?  The hardware can do it, the
firmware will support it ... but the DVB API 3 and
DVB API 4 seems not be designed for this approach.

How to extend the DVB API 3 for RAW Audio replay?
Do I need a new ioctl or should I extend
AUDIO_SELECT_SOURCE by something like AUDIO_SOURCE_MEMORY_RAW
or use the AUDIO_SET_STREAMTYPE and define a type
class AUDIO_CAP_RAW_XXX.

On Wed, Oct 19, 2005 at 06:56:16PM +0200, Dr. Werner Fink wrote:
> 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

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