[alsa-devel] Required/preferred multichannel order for ALSA

Ricardo Neri ricardo.neri at ti.com
Thu Apr 26 23:33:57 CEST 2012

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 [1]. It was also mentioned that an API to set/get the channel 
mapping was going to be implemented [2]; I tried to find it without 
success. As [1] and [2] 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.



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