On Friday, November 25, 2011 16:52:00 Mauro Carvalho Chehab wrote:
> Em 25-11-2011 13:22, Hans Verkuil escreveu:
> > Using V4L for the video part is easy. But where it becomes a bit more
> > complicated is
> > with the audio device. I assume again that it receives a compressed audio
> > stream
> > (is that correct?), and alsa doesn't handle that yet. I believe Samsung ran
> > into the
> > same issue. For raw audio an alsa output is the logical choice, but for
> > compressed
> > audio it is not so clear.
>
> Sure that alsa doesn't handle compressed audio? a quick grep for MPEG under
> drivers/sound
> shows several things related to MPEG audio support:
>
> $ git grep -i mpeg sound|wc -l
> 92
>
> $ git grep -i mpeg sound
>
> ...
> sound/core/pcm.c: FORMAT(MPEG),
> sound/core/pcm.c: case AFMT_MPEG:
> sound/core/pcm.c: return "MPEG";
> sound/core/pcm_misc.c: [SNDRV_PCM_FORMAT_MPEG] = {
> sound/drivers/vx/vx_cmd.h:#define MASK_VALID_PIPE_MPEG_PARAM 0x000040
> sound/drivers/vx/vx_cmd.h:#define MASK_SET_PIPE_MPEG_PARAM 0x000002
> sound/drivers/vx/vx_cmd.h:#define P_PREPARE_FOR_MPEG3_MASK
> 0x02
> sound/drivers/vx/vx_core.c: if (chip->audio_info & VX_AUDIO_INFO_MPEG1)
> sound/drivers/vx/vx_core.c: snd_iprintf(buffer, " mpeg1");
> sound/drivers/vx/vx_core.c: if (chip->audio_info & VX_AUDIO_INFO_MPEG2)
> sound/drivers/vx/vx_core.c: snd_iprintf(buffer, " mpeg2");
> ...
>
>
> So, I think that alsa accepts compressed audio.
Nice. I was told once that they didn't support it, but I'm clearly wrong.
Both MPEG and AC3 audio is supported.
Regards,
Hans
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