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-rw-r--r--doc/mpd.conf.520
-rw-r--r--src/audioOutputs/audioOutput_alsa.c38
2 files changed, 43 insertions, 15 deletions
diff --git a/doc/mpd.conf.5 b/doc/mpd.conf.5
index 7ff364b8b..88c9a6d85 100644
--- a/doc/mpd.conf.5
+++ b/doc/mpd.conf.5
@@ -236,6 +236,26 @@ separate options. An example for oss: "dsp=/dev/dsp". An example for alsa09:
This specifies how many bytes to write to the audio device at once. Used only
by the ao output type. This parameter is to work around a bug in older
versions of libao on sound cards with very small buffers. The default is 1024.
+.SH OPTIONAL ALSA OUTPUT PARAMETERS
+.TP
+.B use_mmap <yes or no>
+Setting this allows you to use memory-mapped I/O. Certain hardware setups
+may benefit from this, but most do not.
+Most users do not need to set this.
+.TP
+.B buffer_time <time in microseconds>
+This sets the length of the hardware sample buffer in microseconds.
+Increasing it may help to reduce or eliminate skipping on certain setups.
+Most users do not need to change this.
+The default is 500000 microseconds (0.5 seconds).
+.TP
+.B period_time <time in microseconds>
+This sets the time between hardware sample transfers in microseconds.
+Increasing this can reduce CPU usage while lowering it can reduce underrun
+errors on bandwidth-limited devices. Some users have reported good results
+with this set to 50000, but not all devices support values this high.
+Most users do not need to change this.
+The default is 256000000 / sample_rate(kHz), or 5804us for CD-quality audio.
.SH REQUIRED SHOUT OUTPUT PARAMETERS
.TP
.B name <name>
diff --git a/src/audioOutputs/audioOutput_alsa.c b/src/audioOutputs/audioOutput_alsa.c
index 0842b9f83..bc727c556 100644
--- a/src/audioOutputs/audioOutput_alsa.c
+++ b/src/audioOutputs/audioOutput_alsa.c
@@ -46,6 +46,8 @@ typedef struct _AlsaData {
char * device;
snd_pcm_t * pcmHandle;
alsa_writei_t * writei;
+ unsigned int buffer_time;
+ unsigned int period_time;
int sampleSize;
int useMmap;
int canPause;
@@ -59,6 +61,8 @@ static AlsaData * newAlsaData() {
ret->pcmHandle = NULL;
ret->writei = snd_pcm_writei;
ret->useMmap = 0;
+ ret->buffer_time = MPD_ALSA_BUFFER_TIME;
+ ret->period_time = MPD_ALSA_PERIOD_TIME;
return ret;
}
@@ -70,17 +74,23 @@ static void freeAlsaData(AlsaData * ad) {
}
static int alsa_initDriver(AudioOutput * audioOutput, ConfigParam * param) {
- BlockParam * bp = NULL;
- AlsaData * ad;
-
- if(param) bp = getBlockParam(param, "device");
-
- ad = newAlsaData();
-
+ AlsaData * ad = newAlsaData();
+
+ if (param) {
+ BlockParam * bp = getBlockParam(param, "device");
+ ad->device = bp ? strdup(bp->value) : strdup("default");
+
+ if ((bp = getBlockParam(param, "use_mmap")) &&
+ (!strcasecmp(bp->value, "yes") ||
+ !strcasecmp(bp->value, "true")))
+ ad->useMmap = 1;
+ if ((bp = getBlockParam(param, "buffer_time")))
+ ad->buffer_time = atoi(bp->value);
+ if ((bp = getBlockParam(param, "period_time")))
+ ad->period_time = atoi(bp->value);
+ }
audioOutput->data = ad;
- ad->device = bp ? strdup(bp->value) : strdup("default");
-
return 0;
}
@@ -118,8 +128,6 @@ static int alsa_openDevice(AudioOutput * audioOutput)
unsigned int channels = audioFormat->channels;
snd_pcm_uframes_t alsa_buffer_size;
snd_pcm_uframes_t alsa_period_size;
- unsigned int alsa_buffer_time = MPD_ALSA_BUFFER_TIME;
- unsigned int alsa_period_time = MPD_ALSA_PERIOD_TIME;
int err;
char * cmd = NULL;
@@ -210,14 +218,14 @@ static int alsa_openDevice(AudioOutput * audioOutput)
cmd = "snd_pcm_hw_params_set_buffer_time_near";
err = snd_pcm_hw_params_set_buffer_time_near(ad->pcmHandle, hwparams,
- &alsa_buffer_time, 0);
+ &ad->buffer_time, 0);
if(err < 0) goto error;
- if (!alsa_period_time && sampleRate > 0)
- alsa_period_time = 1000000 * MPD_ALSA_SAMPLE_XFER / sampleRate;
+ if (!ad->period_time && sampleRate > 0)
+ ad->period_time = 1000000 * MPD_ALSA_SAMPLE_XFER / sampleRate;
cmd = "snd_pcm_hw_params_set_period_time_near";
err = snd_pcm_hw_params_set_period_time_near(ad->pcmHandle, hwparams,
- &alsa_period_time, 0);
+ &ad->period_time, 0);
if(err < 0) goto error;
cmd = "snd_pcm_hw_params";