Re: emu10k1 latency / capture period

[Takashi Iwai <tiwai@suse.de>]

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. 


Takashi


-------------------------------------------------------
This SF.Net email sponsored by Black Hat Briefings & Training.
Attend Black Hat Briefings & Training, Las Vegas July 24-29 - 
digital self defense, top technical experts, no vendor pitches, 
unmatched networking opportunities. Visit www.blackhat.com