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pcm: add control for ASLA thresholds to pcm_open

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Add the ability to explicitly set start, stop and silence thresholds during
tinyalsa's pcm_open.  Setting any of these values to 0 in your pcm_config
structure will cause the system to use its old defaults.
This commit is contained in:
John Grossman
2011-07-21 10:59:55 -07:00
committed by Simon Wilson
parent ee99f213b2
commit 3bb114a645
2 changed files with 25 additions and 3 deletions
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include/tinyalsa/asoundlib.h
+12
View File
@@ -59,6 +59,18 @@ struct pcm_config {
unsigned int period_size;
unsigned int period_count;
enum pcm_format format;
/* Values to use for the ALSA start, stop and silence thresholds. Setting
* any one of these values to 0 will cause the default tinyalsa values to be
* used instead. Tinyalsa defaults are as follows.
*
* start_threshold : period_count * period_size
* stop_threshold : period_count * period_size
* silence_threshold : 0
*/
unsigned int start_threshold;
unsigned int stop_threshold;
unsigned int silence_threshold;
};
/* Mixer control types */
pcm.c
+13 -3
View File
@@ -427,11 +427,21 @@ struct pcm *pcm_open(unsigned int card, unsigned int device,
sparams.tstamp_mode = SNDRV_PCM_TSTAMP_ENABLE;
sparams.period_step = 1;
sparams.avail_min = 1;
sparams.start_threshold = config->period_count * config->period_size;
sparams.stop_threshold = config->period_count * config->period_size;
if (!config->start_threshold)
sparams.start_threshold = config->period_count * config->period_size;
else
sparams.start_threshold = config->start_threshold;
if (!config->stop_threshold)
sparams.stop_threshold = config->period_count * config->period_size;
else
sparams.stop_threshold = config->stop_threshold;
sparams.xfer_align = config->period_size / 2; /* needed for old kernels */
sparams.silence_size = 0;
sparams.silence_threshold = 0;
sparams.silence_threshold = config->silence_threshold;
if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_SW_PARAMS, &sparams)) {
oops(pcm, errno, "cannot set sw params");