[LAU] ALSA_OUT hack

torbenh torbenh at gmx.de
Wed Nov 10 10:08:00 UTC 2010


On Tue, Nov 09, 2010 at 11:43:09PM -0800, Ken Restivo wrote:
> Question about the alsa_out tool in the JACK github.
> 
> How critical is the libresample portion of the code? What would happen if I removed it?
> 
> i.e. if I were sending, say, one stereo pair to one amp, and another stereo pair to a different amp, and didn't care about the word clocks being in sync, do I really need that libresample stuff sucking up valuable CPU?  Or could I whack it? What would be the difficulties created by doing that? Again, this'd be only for output channels and I wouldn't need the word clocks to be in sync.

you are confusing things here.
its not about wordclocks being in sync. if your wordclocks are in sync.
you dont need alsa_out.

but most likely your wordclocks are not in sync. this means your
soundcards run at different drifing samplerates, and one soundcard will
consume a different amount of samples per jack cycle. but jack is
feeding period samples each cycle.

first try using -q option set to 0 because that will use linear resampling.
reducing the value of the -s option (default 256) will also improve cpu usage. 
but might yield worse performance of the algorithm. it depends a bit on
the soundcards you are using.


-- 
torben Hohn


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