snd_pcm_runtime.buffer_size question

snd_pcm_runtime.buffer_size question

[Tim Blechmann]

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hi all,
i am currently fighting with the snd_pcm_runtime.buffer_size. how is the
value defined?

i would expect:
channels * periods * period_size * sample_bits/8
(in my case 64*5*128*3)

however in the code, i am working on, it seems to be:
periods * period_size
(in my case 5*128)

am i missing something obvious?

thanks, tim

-- 
tim@klingt.org
http://tim.klingt.org

Just what the hell is the experimental tradition?
  Morton Feldman



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Re: snd_pcm_runtime.buffer_size question

[Takashi Iwai]

At Wed, 11 Feb 2009 18:21:11 +0100,
Tim Blechmann wrote:
> 
> hi all,
> i am currently fighting with the snd_pcm_runtime.buffer_size. how is the
> value defined?
> 
> i would expect:
> channels * periods * period_size * sample_bits/8
> (in my case 64*5*128*3)
> 
> however in the code, i am working on, it seems to be:
> periods * period_size
> (in my case 5*128)
> 
> am i missing something obvious?

There is a difference between buffer_size and buffer_bytes.
The former is in "frame" unit while the latter is in bytes.
In ALSA, 1 frame corresponds to (channels*sample_bits/8) bytes.


Takashi