[alsa-devel] wrong channel mappings for HDMI audio

Dan Christensen jdc at uwo.ca
Sat Nov 13 01:26:11 CET 2010

Anssi Hannula <anssi.hannula at iki.fi> writes:

> This is a known issue, the NVIDIA MCP79/7A HDMI hardware has incorrect
> channel mapping.
> I reported this several months ago as "Wrong channel order with
> multichannel HDMI on MCP7A":
> http://www.spinics.net/lists/alsa-devel/msg35948.html
> (there are some earlier reports from 2009 as well)

Great, thanks for confirming it's not just me.

> I'm using this workaround at the moment:
>  pcm.!hdmi {
>      type             route
>      slave.pcm "cards.HDA-Intel.pcm.hdmi.0:CARD=NVidia,AES0=0x4,AES1=0x82,AES2=0x0,AES3=0x2"
>      ttable.0.0 1
>      ttable.1.1 1
>      ttable.2.4 1
>      ttable.3.5 1
>      ttable.4.2 1
>      ttable.5.3 1
>      ttable.6.6 1
>      ttable.7.7 1
>  }

I can confirm that this fixes things for me.

> (not a perfect workaround as I'm hardcoding AESx instead of using the
> ones provided as arguments, but at least you get the idea)

I don't understand this comment, but hopefully if I just put the above
in my asound.conf, all should be fine, right?

> As for the preferred solution to this problem, as far as I understand,
> that would be for the driver to have some ioctl that would provide
> alsa-lib information about the unusual channel mapping, and alsa-lib
> could then remap the channels using a channel remapping plugin.

Alternatively, can the fix just be hardcoded for this audio card?


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