From mboxrd@z Thu Jan  1 00:00:00 1970
From: Louise Hoffman <louise.hoffman@gmail.com>
Subject: Re:
	=?windows-1252?q?Warning/error_from_ALSA=92s_pcm=5Fm?=
	=?windows-1252?q?in=2Ec_example=2E_Possible_problem=3F?=
Date: Sun, 31 Jan 2010 21:53:33 +0100
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>> The correct way is to use snd_pcm_get_params() to get buffer_size and
> period_size
>
> *snd_pcm_set_params() has limitation
>
> The most common sound card (e.g. HDA ) has the following constraints
> on period bytes and buffer bytes
>
> =A0 =A0 snd_pcm_hw_constraint_step(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_=
BYTES,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A012=
8);
> =A0 =A0 snd_pcm_hw_constraint_step(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_=
BYTES,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 128);

I am probably not good enough to understand these changes =3D( Pretty
hard core stuff =3D)


> you cannot get exactly 0.5 second period time when rate is multiple of 3 (
> e.g. 48000 Hz )

Does this mean, that I shouldn't give snd_pcm_writei() the number of
all the frames in the buffer, but only

sample_rate * latency =3D frames

?

So if I e.g. have:
sample_rate =3D 44100
latency =3D 0.5 [s]
all_frames =3D 100000

The number of frames that I should give to snd_pcm_writei() would be

sample_rate * latency =3D frames
44100*0.5 =3D 22050

and the number of iterations the for-loop should be?:

(int) 100000/22050 =3D 4; with frames=3D22050

and one extra, but only with

100000 mod 22050 =3D 11800

frames?