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Tweak ALSA nperiod setting, fallback to nearest

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This is mainly for RME RayDAT that has a fixed buffersize of 16k:

  dev_name : hw:HDSPMxc2f6c5,0
  channels : 36
  min_rate : 32000
  max_rate : 192000
  min_bufz : 16384
  max_bufz : 16384
  min_nper : 4
  max_nper : 512

However nperiod configuration determines the effective latency
regardless.

This is similar to https://github.com/jackaudio/jack1/blob/master/drivers/alsa/alsa_driver.c#L476-L486
This commit is contained in:
Robin Gareus 2020-04-29 23:55:51 +02:00
parent 6eb48e40a0
commit 3a6a9cfa6c
No known key found for this signature in database
GPG key ID: A090BCE02CF57F04
4 changed files with 26 additions and 38 deletions
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16
libs/backends/alsa/alsa_audiobackend.cc
View file

@ -270,25 +270,23 @@ std::vector<uint32_t>
AlsaAudioBackend::available_period_sizes (const std::string& driver, const std::string& device) const
{
std::vector<uint32_t> ps;
ps.push_back (2);
ALSADeviceInfo* nfo = NULL;
if (device == get_standard_device_name(DeviceNone)) {
return ps;
}
if (device == _output_audio_device && _output_audio_device_info.valid) {
nfo = &_output_audio_device_info;
} else {
ps.push_back (2);
return ps;
}
if (nfo->min_nper == 2) {
ps.push_back (2);
if (nfo->max_nper >= 3) {
if (nfo->max_nper > 2) {
ps.push_back (3);
}
if (nfo->max_nper > 3) {
ps.push_back (nfo->min_nper);
}
} else {
ps.push_back (nfo->min_nper);
ps.push_back (3);
}
return ps;

41
libs/backends/alsa/zita-alsa-pcmi.cc
View file

@ -486,11 +486,7 @@ void Alsa_pcmi::initialise (const char *play_name, const char *capt_name, const
}
if (snd_pcm_hw_params_get_periods (_play_hwpar, &nfrag, &dir) || (nfrag != _play_nfrag) || dir)
{
if (_debug & DEBUG_INIT) fprintf (stderr, "Alsa_pcmi: can't get requested number of periods for playback.\n");
if ((_debug & FRAG_NEAR) == 0) {
_state = -5;
return;
}
if (_debug & DEBUG_INIT) fprintf (stderr, "Alsa_pcmi warning: requested %u periods for playback, using %u.\n", _play_nfrag, nfrag);
}
snd_pcm_hw_params_get_format (_play_hwpar, &_play_format);
@ -776,29 +772,24 @@ int Alsa_pcmi::set_hwpar (snd_pcm_t *handle, snd_pcm_hw_params_t *hwpar, const
sname, _fsize);
return -4;
}
if ((_debug & FRAG_NEAR)) {
unsigned int nf = nfrag;
snd_pcm_hw_params_set_periods_min (handle, hwpar, &nf, NULL);
if (nf > nfrag) {
nfrag = nf;
}
if (snd_pcm_hw_params_set_periods_near (handle, hwpar, &nfrag, NULL) < 0) {
if (_debug & DEBUG_INIT) fprintf (stderr, "Alsa_pcmi: can't set %s periods to %u.\n",
sname, nfrag);
return -5;
}
} else {
if (snd_pcm_hw_params_set_periods (handle, hwpar, nfrag, 0) < 0)
{
if (_debug & DEBUG_INIT) fprintf (stderr, "Alsa_pcmi: can't set %s periods to %u.\n",
sname, nfrag);
return -5;
}
unsigned int nf = nfrag;
snd_pcm_hw_params_set_periods_min (handle, hwpar, &nf, NULL);
if (nf < nfrag) {
nf = nfrag;
}
if (snd_pcm_hw_params_set_buffer_size (handle, hwpar, _fsize * nfrag) < 0)
if (snd_pcm_hw_params_set_periods_near (handle, hwpar, &nf, NULL) < 0) {
if (_debug & DEBUG_INIT) fprintf (stderr, "Alsa_pcmi: can't set %s periods to %u (requested %u).\n",
sname, nf, nfrag);
return -5;
}
if (_debug & DEBUG_INIT) fprintf (stderr, "Alsa_pcmi: use %d periods for %s ((requested %u).\n", nf, sname, nfrag);
if (snd_pcm_hw_params_set_buffer_size (handle, hwpar, _fsize * nf) < 0)
{
if (_debug & DEBUG_INIT) fprintf (stderr, "Alsa_pcmi: can't set %s buffer length to %lu.\n",
sname, _fsize * nfrag);
sname, _fsize * nf);
return -4;
}
if (snd_pcm_hw_params (handle, hwpar) < 0)

3
libs/backends/alsa/zita-alsa-pcmi.h
View file

@ -60,8 +60,7 @@ public:
DEBUG_DATA = 8,
DEBUG_ALL = 15,
FORCE_16B = 256,
FORCE_2CH = 512,
FRAG_NEAR = 1024
FORCE_2CH = 512
};
void printinfo (void);