Subject: [linux-audio-dev] Re: more bad low latency results
From: Maarten de Boer (maarten.deboer_AT_iua.upf.es)
Date: Thu Nov 15 2001 - 21:12:36 EET
On Thu, 15 Nov 2001 13:50:39 -0500
Paul Davis <pbd_AT_op.net> wrote:
> >> Hmm sounds like h/w problem, then..
> >> It's interesting to know where the data is contaminated, whether on
> >> the driver level or transfer between capture and playback on
> >> user-space, or what else..
> >
> >I would say on driver level: I write the data to disk right after the
> >snd_pcm_readi call.
>
> i hope i'm forgetting something. you're not writing to disk from the
> same thread as called snd_pcm_readi are you? that's guaranteed to
> eliminate low latency performance ...
As a matter of fact I am, but in this case I am not measuring latency.
What happens is that the sound thru of the alsa-lib/test/latency sounds
bad. I want to know where this happens, so I write the input to disk
right after snd_pcm_readi. With a big fragment size. And obviously, the
problem existed before I started writing to disk; if not, I would not
have written to disk :-)
Maarten
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