[alsa-devel] Required/preferred multichannel order for ALSA
lrg at ti.com
Fri Apr 27 11:21:37 CEST 2012
On Thu, 2012-04-26 at 16:33 -0500, Ricardo Neri wrote:
> Hi Takashi, list,
> I am implementing multichannel support for HDMI on Texas Instruments'
> OMAP4. I would like to know if ALSA mandates a specific channel order or
> has a preferred one.
> I tried to find some guidance in alsa-lib or in the alsa driver. All I
> could find is the order described in speaker-test:
> FL/FR/RL/RR/C/LFE/SL/SR. This order seems to be in use due to historical
> reasons . It was also mentioned that an API to set/get the channel
> mapping was going to be implemented ; I tried to find it without
> success. As  and  are very old posts, I was wondering if the
> situation has changed.
> My question arises from the fact that HDMI audio uses the channel
> ordering defined in CEA-861 section 6.6.2, which is different from what
> speaker-test expects. This also different from the order that SMPTE 320M
> specifies. OMAP4 is able to alter the channel mapping, so I could match
> what ALSA expects if such required/preferred order exists.
> Thanks in advance for your comments.
A lot of hardware now can remap channels to suit the use case so it
would probably be good to have an ALSA API to get/set the mappings.
This seems like it would be a good subject for the BoF.
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