[alsa-devel] HDMI with more than 2ch ?

David Henningsson david.henningsson at canonical.com
Tue Jan 25 02:17:50 CET 2011

On 2011-01-24 10:16, Xavier Bestel wrote:
> Hi,
> I'm using HDMI output on an HD 2600, using KMS from kernel 2.6.37:
> http://www.alsa-project.org/db/?f=b3f67a0890f9878b7b3f345578e24eda0aaa59ac
> The problem is that only 2ch are supported (not 1, not 3 or more). I
> tested with speaker-test, it only works with -c 2.
> So how can I access the other PCM channels ? There are 8 of them
> available in the HDMI standard, I thought the card should be able to
> drive all of them.

According to your HDMI codec it only supports stereo output, not 
8-channel PCM. This is a limitation in your hardware, not in the HDMI 

That is, if you want more channels, you probably want to ac3-encode the 
audio data.

David Henningsson, Canonical Ltd.

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