[alsa-devel] Wrong channel order with multichannel HDMI on NVIDIA MCP7A

Takashi Iwai tiwai at suse.de
Tue Aug 3 22:54:07 CEST 2010

At Tue, 3 Aug 2010 23:32:45 +0300,
Anssi Hannula wrote:
> pl bossart kirjoitti tiistai, 3. elokuuta 2010 23:15:28:
> > > Well, this is one of my looong-standing TODOs.
> > > Originally I wanted to implement a new API to get/set the
> > > channel-mapping, mainly for HDMI.
> > > But, I've been recently too busy for other tasks (I can spend little
> > > time for ALSA), thus it's pending forever.
> > 
> > You would only need an API to get the channel mapping. The HDMI sink
> > will report its speaker configuration through a CEA code (section 7.4
> > of the spec), and if we parsed the EDID info we could present the
> > relevant channel order to user-space apps.
> I'm not sure I see how that will help with the problem of this thread, though, 
> i.e. NVIDIA MCP7A hdmi codec apparently assuming audio being fed in windows 
> channel order instead of alsa channel order.

If we get the channel order, the channels could be remapped either by
the app itself or an alsa-lib plugin.  The channel-map API itself is
just a bridge for that...


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