Takashi Iwai wrote: > > At Tue, 06 Nov 2001 19:10:20 +0100, > Abramo wrote: > > > > 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). > > Yes, of course, I meant "not so quick and little" hack in kernel > code :) Hmm, perhaps i'm wrong, we can change the code without too > much rewrite.. Let me see.. > > Anyway, if we use ALSA timer on pcm, we'll need an additional API call > (or module parameter) for timer selection such as given in sequencer > API.
I'm strongly against a module parameter for that. We'd need an API call for tick source selection and a new ioctl, but I don't like very much the sequencer API way, I'd prefer something like: timer_fd = open(timer); pcm_fd = open(pcm); ioctl(pcm_fd, TICK_SOURCE, timer_fd); Of course all that is hidden under alsa-lib API. -- Abramo Bagnara mailto:[EMAIL PROTECTED] 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! _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
