[pulseaudio-discuss] Help with CMI8768 Please

[Jim Duda]

On 09/13/2009 01:49 PM, Lennart Poettering wrote:
> On Sat, 12.09.09 10:54, Jim Duda (jim at duda.tzo.com) wrote:
>
>> load-module module-alsa-sink device=a52encode rate=48000 channels=6
>> sink_name=alsa_surround
>
> PA should be able to detect a properly set up a52 alsa module
> automatically. Debian does it right afaik.
>

I get this when I start pulse 0.0.15 from fedora 11

I: alsa-util.c: Error opening PCM device surround40:0: No such file or directory
I: (alsa-lib)pcm.c: Unknown PCM a52:0
I: alsa-util.c: Error opening PCM device a52:0: No such file or directory
I: (alsa-lib)pcm_hw.c: open /dev/snd/pcmC0D1c failed
I: alsa-util.c: Error opening PCM device surround41:0: No such file or directory
I: (alsa-lib)pcm_hw.c: open /dev/snd/pcmC0D1c failed
I: alsa-util.c: Error opening PCM device surround50:0: No such file or directory

I would like to try and debug this.  Can you tell me which pulse source file
looks for a52?

> port, however when a52 is used it is encoded in a AC-3 compressed
> stream while when using "spdif" it is encoded in uncompressed PCM.
>

Okay, great, this is what I want.  I'm assuming that directly attaching to
the a52 "plug" using asound.conf results in the same as auto detection.
Auto detection is just better.

>
> Please note that a52 is little tested. Fedora does not ship this ALSA
> pugin for patent reasons and hence I never actually tested it. Also,
> first decoding AC3 to PCM in mplayer and then encoding it again to AC3
> in PA certainly won't help audio quality. I fear as long as PA can
> only deal with PCM properly it's best to bypass it if you want to do
> AC3 digital output.

Okay, this makes sense to me.  When using mplayer or xine to play mpeg
files with AC3, I will use the ac3_raw device, bypassing pulse.

I will only use the "a52" path when playing pcm audio to my surround system.

I'm certainly willing to do some a52 testing for you.

Your support is fantastic Lennart!!  Much appreciated.

Jim