Re: [Alsa-devel] Re: [linux-audio-dev] minimum tick time

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Subject: Re: [Alsa-devel] Re: [linux-audio-dev] minimum tick time
From: Abramo Bagnara (abramo_AT_alsa-project.org)
Date: Tue Nov 06 2001 - 20:10:20 EET


Takashi Iwai wrote:
>
> Hi Maarten,
>
> At Tue, 6 Nov 2001 17:12:01 +0100,
> Maarten de Boer wrote:
> >
> > Hello,
> >
> > I am trying to get low latency with alsa.
> > I have kernel 2.4.13 with the preemptive patch and the
> > alsa-driver/utils/patches/rtc-2.4.9.dif patch applied.
> > In the kernel configuration, I turned on RTC and
> > Preemptive.
> >
> > I run the alsa-lib/test/latency.c test in poll mode,
> > but the problem is the tick time, which is at 100 Hz:
> >
> > snd_pcm_hw_params_get_tick_time(params, NULL) = 10000
> >
> > What am I doing wrong?
>
> The timer invoked by pcm is only system timer, so resolution is fixed
> as HZ. IMO, it would be nice to make it available to use other timer
> sources, but this will lead to major rewrite..

This would not imply a "major" rewrite: the API and the kernel code has
been thought for that.
You need simply to have different snd_pcm_tick_set functions (see
pcm_lib.c).

-- 
Abramo Bagnara                       mailto:abramo_AT_alsa-project.org

Opera Unica Phone: +39.546.656023 Via Emilia Interna, 140 48014 Castel Bolognese (RA) - Italy

ALSA project http://www.alsa-project.org It sounds good!


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