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ao_alsa: add options for controlling period/buffer size

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This commit is contained in:
wm4
2018-04-05 16:32:22 +02:00
committed by Jan Ekström
parent c647516278
commit 401bd57d44
2 changed files with 30 additions and 8 deletions
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14
DOCS/man/options.rst
View File

@@ -4147,6 +4147,20 @@ ALSA audio output options
or it will work only for files which use the layout implicit to your
ALSA device).
``--alsa-buffer-time=<microseconds>``
Set the requested buffer time in microseconds. A value of 0 skips requesting
anything from the ALSA API. This and the ``--alsa-periods`` option uses the
ALSA ``near`` functions to set the requested parameters. If doing so results
in an empty configuration set, setting these parameters is skipped.
Both options control the buffer size. A low buffer size can lead to higher
CPU usage and audio dropouts, while a high buffer size can lead to higher
latency in volume changes and other filtering.
``--alsa-periods=<number>``
Number of periods requested from the ALSA API. See ``--alsa-buffer-time``
for further remarks.
GPU renderer options
-----------------------

24
audio/out/ao_alsa.c
View File

@@ -30,6 +30,7 @@
#include <sys/time.h>
#include <stdlib.h>
#include <stdarg.h>
#include <limits.h>
#include <math.h>
#include <string.h>
@@ -59,6 +60,8 @@ struct ao_alsa_opts {
int resample;
int ni;
int ignore_chmap;
int buffer_time;
int frags;
};
#define OPT_BASE_STRUCT struct ao_alsa_opts
@@ -70,6 +73,8 @@ static const struct m_sub_options ao_alsa_conf = {
OPT_INTRANGE("alsa-mixer-index", mixer_index, 0, 0, 99),
OPT_FLAG("alsa-non-interleaved", ni, 0),
OPT_FLAG("alsa-ignore-chmap", ignore_chmap, 0),
OPT_INTRANGE("alsa-buffer-time", buffer_time, 0, 0, INT_MAX),
OPT_INTRANGE("alsa-periods", frags, 0, 0, INT_MAX),
{0}
},
.defaults = &(const struct ao_alsa_opts) {
@@ -77,6 +82,8 @@ static const struct m_sub_options ao_alsa_conf = {
.mixer_name = "Master",
.mixer_index = 0,
.ni = 0,
.buffer_time = 250000,
.frags = 16,
},
.size = sizeof(struct ao_alsa_opts),
};
@@ -99,9 +106,6 @@ struct priv {
struct ao_alsa_opts *opts;
};
#define BUFFER_TIME 250000 // 250ms
#define FRAGCOUNT 16
#define CHECK_ALSA_ERROR(message) \
do { \
if (err < 0) { \
@@ -648,6 +652,7 @@ alsa_error: ;
static int init_device(struct ao *ao, int mode)
{
struct priv *p = ao->priv;
struct ao_alsa_opts *opts = p->opts;
int ret = INIT_DEVICE_ERR_GENERIC;
char *tmp;
size_t tmp_s;
@@ -790,12 +795,15 @@ static int init_device(struct ao *ao, int mode)
snd_pcm_hw_params_copy(hwparams_backup, alsa_hwparams);
// Cargo-culted buffer settings; might still be useful for PulseAudio.
err = snd_pcm_hw_params_set_buffer_time_near
(p->alsa, alsa_hwparams, &(unsigned int){BUFFER_TIME}, NULL);
CHECK_ALSA_WARN("Unable to set buffer time near");
if (err >= 0) {
err = 0;
if (opts->buffer_time) {
err = snd_pcm_hw_params_set_buffer_time_near
(p->alsa, alsa_hwparams, &(unsigned int){opts->buffer_time}, NULL);
CHECK_ALSA_WARN("Unable to set buffer time near");
}
if (err >= 0 && opts->frags) {
err = snd_pcm_hw_params_set_periods_near
(p->alsa, alsa_hwparams, &(unsigned int){FRAGCOUNT}, NULL);
(p->alsa, alsa_hwparams, &(unsigned int){opts->frags}, NULL);
CHECK_ALSA_WARN("Unable to set periods");
}
if (err < 0)