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@suse.de 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.
- 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.
- 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@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
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