different nperiods for capture and playback when opening a device in duplex mode ?

different nperiods for capture and playback when opening a device in duplex mode ?

[Joern Nettingsmeier]

hello alsa people !

i have a problem with jack on a sblive giving dropouts.
i found this might be due to too few periods per buffergla.
unfortunately, the sblive only seems to support two periods for
capturing, and jack sets both play and capture to the same number of
periods.

is it possible with alsa to use different settings for capture and
playback, either periods or buffer size or both ?
if yes, i might try and add that to jack, but since this is my first
undertaking with alsa programming, i thought i'd ask first :)

i got this idea from glame, which uses 2 and 4 periods and also
different sizes and runs dropout-free. it does not however open the card
full-duplex, but uses two threads that operate in halfduplex mode
instead.

i'd also appreciate pointers to programs that do this already, so that i
might refer to the sources for "inspiration" :)

best,

jörn


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Re: different nperiods for capture and playback when opening a device in duplex mode ?

[Paul Davis]

>is it possible with alsa to use different settings for capture and
>playback, either periods or buffer size or both ?
>if yes, i might try and add that to jack, but since this is my first
>undertaking with alsa programming, i thought i'd ask first :)
>
>i got this idea from glame, which uses 2 and 4 periods and also
>different sizes and runs dropout-free. it does not however open the card
>full-duplex, but uses two threads that operate in halfduplex mode
>instead.

ALSA doesn't support "full duplex" to start with. You always have to
open two separate handles for this. Hence, the problem is 100% inside
of JACK's ALSA driver/client. It is written to use the same number of
periods in both directions. It would be possible to change this but it
would not be easy.

Your problems with JACK are caused by a different problem as far as I
can tell (so far), and GLAME's design won't help. More on the jack-dev
list later today (i hope).

--p


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