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[audio] Correct alsa period size calculation

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and rename the variable since it's not the size of the frame (may be
from the very early days of ALSA development, and I suspect the
terminology changed a bit).

The calculation was including the bits per sample, which makes no sense
as the period size determines the number of samples in a submission
chunk (and thus latency). For now, set it to around 5.5ms (will probably
need a cvar).
This commit is contained in:
Bill Currie 2021-06-22 11:33:22 +09:00
parent 097d44e270
commit 421421e038
1 changed files with 14 additions and 8 deletions
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22
libs/audio/targets/snd_alsa.c
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@ -201,7 +201,7 @@ SNDDMA_Init (void)
snd_pcm_hw_params_t **_hw = &hw;
snd_pcm_sw_params_t *sw;
snd_pcm_sw_params_t **_sw = &sw;
snd_pcm_uframes_t frag_size;
snd_pcm_uframes_t period_size;
if (!load_libasound ())
return false;
@ -339,7 +339,6 @@ retry_open:
err = qfsnd_pcm_hw_params_set_rate_near (pcm, hw,
&rate, 0);
if (0 <= err) {
frag_size = 8 * bps * (rate / 11025);
break;
}
}
@ -360,16 +359,20 @@ retry_open:
qfsnd_strerror (err));
goto error;
}
frag_size = 8 * bps * (rate / 11025);
break;
}
err = qfsnd_pcm_hw_params_set_period_size_near (pcm, hw, &frag_size, 0);
// works out to about 5.5ms (5.3 for 48k, 5.8 for 44k1) but consistent for
// different sample rates
period_size = 64 * (rate / 11025);
err = qfsnd_pcm_hw_params_set_period_size_near (pcm, hw, &period_size, 0);
if (0 > err) {
Sys_Printf ("ALSA: unable to set period size near %i. %s\n",
(int) frag_size, qfsnd_strerror (err));
(int) period_size, qfsnd_strerror (err));
goto error;
}
int dir;
qfsnd_pcm_hw_params_get_period_size (hw, &period_size, &dir);
err = qfsnd_pcm_hw_params (pcm, hw);
if (0 > err) {
Sys_Printf ("ALSA: unable to install hw params: %s\n",
@ -432,11 +435,14 @@ retry_open:
sn.frames = buffer_size;
sn.speed = rate;
SNDDMA_GetDMAPos (); //XXX sets sn.buffer
Sys_Printf ("%5d channels\n", sn.channels);
Sys_Printf ("%5d samples\n", sn.frames);
Sys_Printf ("%5d channels %sinterleaved\n", sn.channels,
sn.xfer ? "non-" : "");
Sys_Printf ("%5d samples (%.1fms)\n", sn.frames,
1000.0 * sn.frames / sn.speed);
Sys_Printf ("%5d samplepos\n", sn.framepos);
Sys_Printf ("%5d samplebits\n", sn.samplebits);
Sys_Printf ("%5d submission_chunk\n", sn.submission_chunk);
Sys_Printf ("%5d submission_chunk (%.1fms)\n", sn.submission_chunk,
1000.0 * sn.submission_chunk / sn.speed);
Sys_Printf ("%5d speed\n", sn.speed);
Sys_Printf ("0x%lx dma buffer\n", (long) sn.buffer);