Re: emu10k1 latency / capture period

[Takashi Iwai <tiwai@suse.de>]

At Tue, 22 Jun 2004 13:29:36 +0200 (CEST),
Jaroslav wrote:
> 
> On Tue, 22 Jun 2004, Takashi Iwai wrote:
> 
> > At Mon, 21 Jun 2004 16:20:38 -0400,
> > Lee Revell wrote:
> > > 
> > > The capture will be driven by the playback interrupts (I think
> > > EFX_BUFFER(HALF)FULL).  This would look very similar to the 
> > > interrupt handler example #2 in your ALSA driver guide, which 
> > > uses timer interrupts to drive the capture/playback, except 
> > > that for playback, in addition to calling snd_pcm_period_elapsed()
> > > on the playback substream, we also maintain a pointer to the 
> > > corresponding *capture* substream, and call snd_pcm_period_elapsed() 
> > > on it, manually tracking the frames processed in the same way the timer
> > > interrupt example does.
> > 
> > Even if we ignore the capture interrupts and use an additional
> > interrupt source (e.g. an extra playback stream), the size of capture
> > buffer still must follow the restriction.  That is, the minimal
> > capture buffer size is still 384 x 2 bytes, although the period size
> > can be set independently to smaller than 384 bytes. 
> 
> You can do lowlatency even with huge ring buffer, if you have a good
> interrupt / scheduling timer, but it requires changes in application.

Yes.  At least, JACK should work well.


Takashi


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