I do the following: knowing the sample rate and the current position of the HW pointer (via snd_pcm_avail_update - why there is no function which would tell me directly that - the current position in the buffer?) I can calculate when the required position _will_ happen. So I can just schedule the timer or sleep until that time. When it arrives I can check again snd_pcm_avail_update to see whether my calculation way correct and adjust the sleep period.
I do not understand why ALSA drivers (or at least some plug-ins) could not do the same? There is also another problem: I understand that snd_pcm_avail_update does not really read current count from the card, but uses a value stored in memory. So it will only be updated when the card generates an interrupt. Is there any way to force snd_pcm_avail_update or to use another function which will for sure query the HW and not use the cached value? If the card does not have a capability to report it, this could be extrapolated from the last time sample counter was updated and the current time. On Mon, 30 Sep 2002, Wolfgang Hesseler wrote: > Paul Davis <[EMAIL PROTECTED]> wrote > > the only way around this is to use an alternate, higher-frequency > > interrupt source, such as the RTC (real time clock), but this > > is invariably power-of-2 also, and worse, doesn't run in sync > > with audio or video. if you could find a suitable source, you just > > check the current frames/space available every interrupt, and move on > > from there. i don't know of any suitable interrupt sources. One can recompile the kernel with HZ=2000 to get at least 1 ms timer resolution. And then use the method above, synchronizing by reading snd_pcm_avail_update and noting when it changes. Best regards, -- Tomasz Motylewski ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
