[pulseaudio-discuss] [PATCH 2/2] alsa: Add surround 2.1 profile

Tanu Kaskinen tanu.kaskinen at linux.intel.com
Tue Feb 11 00:39:27 PST 2014

On Mon, 2014-02-10 at 22:28 +0100, David Henningsson wrote:
> Are you ok if I push this one to master (just this one, not the chmap
> API one)?

What's the definition of the surround21 device in alsa? Is it "four
channels with channel map front-left, front-right, lfe, discarded"? If
it's that, would it be better to use aux0 as the last channel instead of
duplicating lfe? I'm thinking that the duplicated lfe may interfere with
remixing. For example, when recording a stereo stream from the 2.1 sink
monitor, does the lfe channel get downmixed twice?

If the last channel is discarded, it would be better to set the sink
channel map to just "front-left, front-right, lfe" and generate silence
for the fourth channel inside the alsa sink. I don't think that's
possible with the current infrastructure, however, and I'm not
suggesting that you should implement that, so this is just an idea for
future work.


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