For example, we can set period_size 32 to one device. But the device consumes 40 frames each time. Can we said it support period_size 32? I found many devices have this situation. On Fri, Aug 3, 2018 at 4:30 PM Takashi Iwai <tiwai@xxxxxxx> wrote: > On Fri, 03 Aug 2018 10:09:30 +0200, > Yu-hsuan Hsu wrote: > > > > Thank for your answer! > > > > The other question is if we set period_size to N, but the frames it > > consumes once is 5N. > > Then the assumption is wrong. How the hardware can issue an IRQ at N > consumption while it processes for 5N in once? > > > Takashi > > > Can it said it supports period_size N? How do we check > > whether the period_size can be set correctly? > > > > On Fri, Aug 3, 2018 at 3:31 PM Takashi Iwai <tiwai@xxxxxxx> wrote: > > > > > On Fri, 03 Aug 2018 08:28:37 +0200, > > > Yu-hsuan Hsu wrote: > > > > > > > > Hi all, > > > > > > > > I have a question about the period we set in hw_params. I found > different > > > > boards may have different explanations about it. I have two guesses > about > > > > its meaning. > > > > > > > > 1. The period_size is the size of each hardware's consumption. If we > set > > > > period size to N, the pcm will consume N frames each time. > > > > > > > > 2. The period_size is the size to control when hardware call > interrupt. > > > If > > > > we set period size to N, the pcm consume frames in its step. When the > > > > number of frames it consumes more than N, it will call interrupt. > > > > > > 2 is the correct answer. > > > > > > > > > HTH, > > > > > > Takashi > > > > > > > We can use snd_pcm_avail function to check the real available frames > in > > > > the device. If guess 1 is correct, the size of consumption should be > > > fixed. > > > > Else, setting period_size is nothing to do with hardware's > > > > consumption. I've checked some boards and found that each board has > > > > different behavior (Most of them meet guess 2). I'm confuse which > one is > > > > correct. Thanks! > > > > _______________________________________________ > > > > Alsa-devel mailing list > > > > Alsa-devel@xxxxxxxxxxxxxxxx > > > > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel > > > > > > > > > [2 <text/html; UTF-8 (quoted-printable)>] > > > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
