[pulseaudio-discuss] Avoiding 2ch upmixing to all speakers

Colin Guthrie gmane at colin.guthr.ie
Mon Nov 8 12:58:56 PST 2010

'Twas brillig, and Tanu Kaskinen at 08/11/10 17:47 did gyre and gimble:
> On Thu, 2010-11-04 at 22:47 +0000, Dom H wrote:
>> I have a 4.1 system and pulse does a good job of mixing the missing
>> centre into the fronts for 5.1 audio tracks, I'm recently switched
>> from a digital out system with my external receiver doing all the
>> decoding and mixing, to my HTPC doing the job and outputting analogue
>> to my amp. I'm trying to get pulse to mimic the exact behaviour of my
>> external decoder, have a few questions though;
>> 1. Can I stop 2ch audio being mixed to all 4 speakers but retain the
>> centre mixing into the mains for 5.1 tracks?
> I don't think so.

I think one way to get half-way towards this solution would be to use a
module-remap-sink with a 2 channel setup and the remix=no argument. When
you want to play 2ch sounds, you will have to explicitly select the 2ch
virtual device which may not be that convenient.

>> Have the pulse devs considered replicating how most hardware decoders
>> handling speaker configuration? As an example, on my Denon receiver,
>> each speaker can be configured as Large, Small or None. Large speakers
>> receive regular full range output, small speakers have their low
>> frequency mixed to the subwoofer output and output sent to a 'None'
>> speaker is mixed elsewhere (eg centre into fronts) Seems like quite an
>> elegant solution, would certainly solve all the issues I'm seeing
>> listed above.
> I haven't heard that anyone is planning to improve the remixing code.
> Patches would surely be accepted, though, so it's only a question of who
> has the time and motivation to do the work.
> For the issue number one, adding a configuration option for stereo
> duplication shouldn't be very hard. Any takers?

I think in the past we discussed how to configure mixing in this way but
I can't remember what we came up with. I think the general options were
relating to how mono and stereo sounds were upmixed but further than
that too much configuration was kinda thought to be unnecessary
(generally speaking - someone will always find a need of course!)



Colin Guthrie

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