[pulseaudio-discuss] HDMI sink is stereo-only

[Colin Guthrie]

'Twas brillig, and Xavier Bestel at 23/01/11 07:19 did gyre and gimble:
> Hi,
> 
> sorry to poke you about that, but that problem isn't a PA one, it's
> either ALSA or Radeon, but none of them even answered. So I figured you
> guys have had a lot of experience dealing with ALSA drivers troubles and
> could tell me where to look for solutions (or at least correct
> diagnostic).
> 
> I have a Radeon HD2600, linked though a DVI-to-HDMI cable to a Yamaha
> RX-1600 amp. ALSA doesn't accept something else than stereo files, e.g:
> 
> [root at awak:~]$ speaker-test -Dhw:1,3 -c6 -twav
> 
> speaker-test 1.0.23
> 
> Playback device is hw:1,3
> Stream parameters are 48000Hz, S16_LE, 6 channels
> WAV file(s)
> Channels count (6) not available for playbacks: Argument invalide
> Setting of hwparams failed: Argument invalide
> 
> always fails for -cx with x != 2. Which is weird because HDMI should
> support 8 PCM channels AFAIK. My amp is configured for 5.1.
> 
> Do you guys know of any way of debugging this and find where is the
> problem (snd_hda_intel, snd_hda_codec, snd_hda_codec_hdmi, or even the
> amp) ?

IIUC, HDMI is a digital output and as such only accepts either stereo
PCM or pre-encoded streams that you pass through directly without any
mixing or interference.

At the moment, only git master PA support passthrough, but you should be
able to do it via ALSA quite happily if the application supports it.

You can however set things up with a special ALSA plugin that allows you
to encode 6 channel audio into the special format and push it into the
HDMI. I blogged about this recently, so those instructions may work well
for you:

http://colin.guthr.ie/2010/12/bobby-digital-in-5-1-surround/

HTHs

Col

-- 

Colin Guthrie
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http://colin.guthr.ie/

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