Subject: Re: [linux-audio-dev] buffering, latency, cut-outs
From: Jake Donham (jake_AT_crankshaft.bitmechanic.com)
Date: to tammi 13 2000 - 15:15:47 EST
> >The code is not multi-threaded; we're using GTK+'s polling mechanism
> >to watch the /dev/dsp file descriptor. I guess this means that GTK+
> >could delay things arbitrarily if it doesn't come back and poll the
> >file descriptors often enough.
>
> Yep, you'd better believe it can. And does. Even for MIDI data, this
> approach has too much jitter. You really need a dedicated thread if
> you want good response times.
OK, that makes sense. But then it seems to me that I need mutexes on
all the objects which the GUI might change, and then the audio thread
can once again become delayed by the GUI thread (but perhaps not as
badly). Is that true? (I have a fair amount of experience with threads
in Java but none in C.)
> OTOH, its pretty amazing that you can get dropouts with this much
> buffering! What kind of system is this happening on ?
Yes, it's surprising to me too. I can observe it on a P3-450 with
256Mb (with a fair amount of stuff running--it's my work dev box so it
has X, xemacs, netscape, mysql, apache, vmware, etc.) But 16K of
buffer is like 350 microseconds and that seems unusually bad.
Thanks,
Jake
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