[alsa-devel] Only stereo output possible with ATI Tahiti XT HDMI Audio [Radeon HD 7970 Series] [1002:aaa0]

Olivier Langlois olivier at trillion01.com
Thu May 16 15:30:21 CEST 2013

On Wed, 2013-05-15 at 09:46 -0400, Olivier Langlois wrote:

> In the meantime, I have tried to setup an alternative with my given
> wcaps:
> lano1106 at whippet2 ~ :( $ cat /etc/asound.conf
> pcm.mypcm {
>    type plug
>    slave {
>      pcm "hdmi:{AES0 0x6 AES1 0x82 AES2 0x0 AES3 0x2}"
>    }
> }
> pcm.a52encode {
>     type a52
>     slavepcm mypcm
> }
> pcm.!default pcm.a52encode
> lano1106 at whippet2 ~ $ speaker-test -c6
> speaker-test 1.0.27
> Playback device is default
> Stream parameters are 48000Hz, S16_LE, 6 channels
> Using 16 octaves of pink noise
> Access type not available for playback: Invalid argument
> Setting of hwparams failed: Invalid argument
> Apparently, SND_PCM_ACCESS_RW_INTERLEAVED is not supported with my
> setup.
I am grateful that noone has replied as it has allowed me to dig alsa
and appreciate further its design.

For completeness and help the next user stumbling on the same problem, I
am autoreplying to myself

Trivia quiz: What kind of access mode does the a52 plugin accept?
A: It depends...INTERLEAVED if libavcodec is old or NONINTERLEAVED if
you have a recent ffmpeg setup, in anycase, a plug shield you from

pcm.a52encode {
    type a52
    card 0

pcm.a52accessadapter {
    type plug
    slave {
      pcm a52encode

pcm.!default pcm.a52accessadapter

Concerning ATI Tahiti 7.1 HDMI output. Looking into patch_hdmi.c and by
seeing the special secret magic handshake to enable 7.1 output for a nvidia
device made me thinking about a slight hope to do something similar for
my card. I'll report back if I find the ATI magic incantation to reach
7.1 nirvana.

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