[alsa-devel] A question about period
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.
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!
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
Thank for your answer!
The other question is if we set period_size to N, but the frames it consumes once is 5N. 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
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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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@suse.de 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@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
[2 <text/html; UTF-8 (quoted-printable)>]
On Fri, 03 Aug 2018 12:04:34 +0200, Yu-hsuan Hsu wrote:
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.
The question remains: how can the hardware issue an IRQ of period size 32 while it can consume 40 frames at each time?
As you asked in the first post, the period size is the size where the hardware notifies the update. Your description above doesn't match with the definition...
Takashi
On Fri, Aug 3, 2018 at 4:30 PM Takashi Iwai tiwai@suse.de 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@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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Sorry for my unclear question. The device usually provide the range of period_size to us, such as 16 to 1024 (We can get it from snd_pcm_hw_params_get_period_size_min and max). It means we can choose period_size 16 for this hardware device. However, the device only consumes 40 frames at each time. It only issue IRQ after it consumes 40 frames. My question is, whether it can support period_size 16 as it said? Or it need to change the range of period_size it provides.
Thank you for your patience and assistance.
yuhsuan
On Fri, Aug 3, 2018 at 6:14 PM Takashi Iwai tiwai@suse.de wrote:
On Fri, 03 Aug 2018 12:04:34 +0200, Yu-hsuan Hsu wrote:
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.
The question remains: how can the hardware issue an IRQ of period size 32 while it can consume 40 frames at each time?
As you asked in the first post, the period size is the size where the hardware notifies the update. Your description above doesn't match with the definition...
Takashi
On Fri, Aug 3, 2018 at 4:30 PM Takashi Iwai tiwai@suse.de 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@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
[2 <text/html; UTF-8 (quoted-printable)>]
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On Fri, 03 Aug 2018 19:24:05 +0200, Yu-hsuan Hsu wrote:
Sorry for my unclear question. The device usually provide the range of period_size to us, such as 16 to 1024 (We can get it from snd_pcm_hw_params_get_period_size_min and max). It means we can choose period_size 16 for this hardware device. However, the device only consumes 40 frames at each time. It only issue IRQ after it consumes 40 frames. My question is, whether it can support period_size 16 as it said? Or it need to change the range of period_size it provides.
In that case, allowing period_size = 16 is obviously wrong. The practical minimum of period size is 40. This must be set up via either snd_pcm_hardware or some hw_constraints.
Takashi
Thank you for your patience and assistance.
yuhsuan
On Fri, Aug 3, 2018 at 6:14 PM Takashi Iwai tiwai@suse.de wrote:
On Fri, 03 Aug 2018 12:04:34 +0200, Yu-hsuan Hsu wrote:
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.
The question remains: how can the hardware issue an IRQ of period size 32 while it can consume 40 frames at each time?
As you asked in the first post, the period size is the size where the hardware notifies the update. Your description above doesn't match with the definition...
Takashi
On Fri, Aug 3, 2018 at 4:30 PM Takashi Iwai tiwai@suse.de 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@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. > > 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@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel >
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Got it! Thank you very much. There are many drivers has this problem.
yuhsuan
On Sat, Aug 4, 2018 at 2:31 AM Takashi Iwai tiwai@suse.de wrote:
On Fri, 03 Aug 2018 19:24:05 +0200, Yu-hsuan Hsu wrote:
Sorry for my unclear question. The device usually provide the range of period_size to us, such as 16 to 1024 (We can get it from snd_pcm_hw_params_get_period_size_min and max). It means we can choose period_size 16 for this hardware device. However, the device only
consumes
40 frames at each time. It only issue IRQ after it consumes 40 frames. My question is, whether it can support period_size 16 as it said? Or it need to change the range of period_size it provides.
In that case, allowing period_size = 16 is obviously wrong. The practical minimum of period size is 40. This must be set up via either snd_pcm_hardware or some hw_constraints.
Takashi
Thank you for your patience and assistance.
yuhsuan
On Fri, Aug 3, 2018 at 6:14 PM Takashi Iwai tiwai@suse.de wrote:
On Fri, 03 Aug 2018 12:04:34 +0200, Yu-hsuan Hsu wrote:
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.
The question remains: how can the hardware issue an IRQ of period size 32 while it can consume 40 frames at each time?
As you asked in the first post, the period size is the size where the hardware notifies the update. Your description above doesn't match with the definition...
Takashi
On Fri, Aug 3, 2018 at 4:30 PM Takashi Iwai tiwai@suse.de 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@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. > > > > 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@alsa-project.org > > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel > > > [2 <text/html; UTF-8 (quoted-printable)>]
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participants (2)
-
Takashi Iwai -
Yu-hsuan Hsu