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make period count configurable

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the period count is just as important for playback latency as the period
size, so it makes no sense to have only one of them configurable.

as a drive-by, fix up the handling of periods in info() & dumpinfo().
This commit is contained in:
Oswald Buddenhagen
2022-08-06 17:44:15 +02:00
parent de2fc3c992
commit 17d171c1a5
2 changed files with 18 additions and 9 deletions
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20
alsaaudio.c
View File

@@ -110,6 +110,7 @@ typedef struct {
unsigned int channels;
unsigned int rate;
snd_pcm_format_t format;
unsigned int periods;
snd_pcm_uframes_t periodsize;
int framesize;
@@ -384,11 +385,10 @@ static int alsapcm_setup(alsapcm_t *self)
self->channels);
dir = 0;
unsigned int periods = 4;
snd_pcm_hw_params_set_rate_near(self->handle, hwparams, &self->rate, &dir);
snd_pcm_hw_params_set_period_size_near(self->handle, hwparams,
&self->periodsize, &dir);
snd_pcm_hw_params_set_periods_near(self->handle, hwparams, &periods, &dir);
snd_pcm_hw_params_set_periods_near(self->handle, hwparams, &self->periods, &dir);
/* Write it to the device */
res = snd_pcm_hw_params(self->handle, hwparams);
@@ -401,6 +401,7 @@ static int alsapcm_setup(alsapcm_t *self)
snd_pcm_hw_params_get_channels(hwparams, &self->channels);
snd_pcm_hw_params_get_rate(hwparams, &self->rate, &dir);
snd_pcm_hw_params_get_period_size(hwparams, &self->periodsize, &dir);
snd_pcm_hw_params_get_periods(hwparams, &self->periods, &dir);
self->framesize = self->channels * snd_pcm_hw_params_get_sbits(hwparams)/8;
@@ -422,13 +423,15 @@ alsapcm_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
int rate = 44100;
int channels = 2;
int format = SND_PCM_FORMAT_S16_LE;
int periods = 4;
int periodsize = 32;
char *kw[] = { "type", "mode", "device", "cardindex", "card", "rate", "channels", "format", "periodsize", NULL };
char *kw[] = { "type", "mode", "device", "cardindex", "card",
"rate", "channels", "format", "periodsize", "periods", NULL };
if (!PyArg_ParseTupleAndKeywords(args, kwds, "|Oisiziiii", kw,
&pcmtypeobj, &pcmmode, &device,
&cardidx, &card, &rate, &channels, &format, &periodsize))
if (!PyArg_ParseTupleAndKeywords(args, kwds, "|Oisiziiiii", kw,
&pcmtypeobj, &pcmmode, &device, &cardidx, &card,
&rate, &channels, &format, &periodsize, &periods))
return NULL;
if (cardidx >= 0) {
@@ -475,6 +478,7 @@ alsapcm_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
self->channels = channels;
self->rate = rate;
self->format = format;
self->periods = periods;
self->periodsize = periodsize;
res = snd_pcm_open(&(self->handle), device, self->pcmtype,
@@ -586,7 +590,7 @@ alsapcm_dumpinfo(alsapcm_t *self, PyObject *args)
printf("buffer size = %d frames\n", (int)frames);
snd_pcm_hw_params_get_periods(hwparams, &val, &dir);
printf("periods per buffer = %d frames\n", val);
printf("periods per buffer = %d\n", val);
snd_pcm_hw_params_get_rate_numden(hwparams, &val, &val2);
printf("exact rate = %d/%d bps\n", val, val2);
@@ -760,7 +764,7 @@ alsapcm_info(alsapcm_t *self, PyObject *args)
snd_pcm_hw_params_get_periods(hwparams, &val, &dir);
value=PyLong_FromUnsignedLong((unsigned long) val);
PyDict_SetItemString(info,"get_periods", value);
PyDict_SetItemString(info,"periods", value);
Py_DECREF(value);
snd_pcm_hw_params_get_rate_numden(hwparams, &val, &val2);

7
doc/libalsaaudio.rst
View File

@@ -96,7 +96,7 @@ PCM objects in :mod:`alsaaudio` can play or capture (record) PCM
sound through speakers or a microphone. The PCM constructor takes the
following arguments:
.. class:: PCM(type=PCM_PLAYBACK, mode=PCM_NORMAL, rate=44100, channels=2, format=PCM_FORMAT_S16_LE, periodsize=32, device='default', cardindex=-1)
.. class:: PCM(type=PCM_PLAYBACK, mode=PCM_NORMAL, rate=44100, channels=2, format=PCM_FORMAT_S16_LE, periodsize=32, periods=4, device='default', cardindex=-1)
This class is used to represent a PCM device (either for playback and
recording). The arguments are:
@@ -146,6 +146,7 @@ following arguments:
Make sure you understand :ref:`the meaning of periods <term-period>`.
The default value is 32, which is below the actual minimum of most devices,
and will therefore likely be larger in practice.
* *periods* - the number of periods in the buffer. The default value is 4.
* *device* - the name of the PCM device that should be used (for example
a value from the output of :func:`pcms`). The default value is
``'default'``.
@@ -158,6 +159,10 @@ following arguments:
This will construct a PCM object with the given settings.
*Changed in 0.10:*
- Added the optional named parameter `periods`.
*Changed in 0.9:*
- Added the optional named parameters `rate`, `channels`, `format` and `periodsize`.