[alsa-devel] [PATCH 0/4] [RFC] multi-channel HDMI audio support

Takashi Iwai tiwai at suse.de
Tue Nov 18 12:02:17 CET 2008

At Tue, 18 Nov 2008 16:57:13 +0800,
Wu Fengguang wrote:
> Hi all,
> This patchset attempts to support multi-channel HDMI audio.
> It contains two basic operations:
> - setup the CA(channel-allcation) byte in the audio infoframe
> - setup the converter channel to HDMI slot mapping
> Please check the last two patches for the detailed descriptions:
> 	[PATCH 1/4] hda: make standalone hdmi_fill_audio_infoframe()                               
> 	[PATCH 2/4] hda: make global snd_print_channel_allocation()                       
> 	[PATCH 3/4] hda: HDMI channel allocations for audio infoframe                               
> 	[PATCH 4/4] hda: HDMI channel mapping cleanups                                               
> The current implementation only does minimal works that can ensure the
> multi-channel audio playing out. However the wrong speakers may be choosed, and
> I really need more information/knowledge/instructions from you to get it right.

As mentioned in the reply to patch#3, the speaker positioning is
basically an unimplemented feature.  So, let's make it as simple as
possible right now.

There are two things we need to implement about speaker positioning:
- return PCM stream <-> speaker position map
- allow to choose different speaker model

The first one could be implemented likely using an extention to the
PCM with (a sort of) TLV entry at best.  Once the TLV format and ioctl
is defined, the rest of implementation would be relatively easy.

I still have no concrete idea how to implement the second item.  One
easy solution is to implement it as a control (e.g. mixer) element.
In this case, the implementation is pretty driver-specific, and no
change in the ALSA core side is needed.

BTW, the rest of patches look good to me.



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