[Ekiga-list] Alsa Weirdness

yannick sevmek at free.fr
Fri Dec 8 17:45:47 UTC 2006

Le jeudi 07 décembre 2006 à 19:19 +0000, Mario Rossi a écrit :
> Reading ALSA documentation about dmix
> http://alsa.opensrc.org/DmixPlugin
> At the very bottom, there is this interesting info about dmix.
> Basically the suggestion is... to use JACK (???). Does anybody know
> whether it exists a dmix equivalent in JACK with better results?
> "
> Can dmix be used within a single program to effectively mix different
> "voices"? Does its latency permit scheduling with (at least)
> single-frame accuracy (e.g., I start VoiceA? and wish to setup and
> schedule VoiceB? to be "added to the mix" at a certain point)? If
> someone knows how to do this, some guidance or a nudge in the right
> direction would be greatly appreciated.
> ---
> Answer: Latency depends on period and buffer size. AFAIK dmix is not
> designed as sample-accurate (because it is usually not needed on
> general purpose audio system and will make the design quite complex).
> If you need sample-accurate and fully syncronized mixer/router, you
> should consider using the Jack http://jackaudio.org/. Large number of
> Linux audio applications, where sample-accurate mixing is needed,
> support Jack.
> On the other hand, overall latency of the audio system will still
> mostly depend on period size. As small as your period size can be, as
> low latecy you will get.
> Of course, low latency needs good task scheduler in kernel. If you
> start getting xruns on low latency audio setup, you should use some
> low-latency/realtime kernel patches. I reccomend Ingo Molnar's
> realtime preempt http://people.redhat.com/mingo/realtime-preempt/ or
> Con Colivas patch set http://members.optusnet.com.au/ckolivas/kernel/.
> "


I've tried some time ago to use Ekiga with JACK, but without succes.
Here is how I proceded :


I hope this will help...


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