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-rw-r--r--include/tinyalsa/asoundlib.h3
-rw-r--r--pcm.c11
2 files changed, 14 insertions, 0 deletions
diff --git a/include/tinyalsa/asoundlib.h b/include/tinyalsa/asoundlib.h
index 3d20b94..5c08577 100644
--- a/include/tinyalsa/asoundlib.h
+++ b/include/tinyalsa/asoundlib.h
@@ -55,6 +55,7 @@ struct pcm;
* second call to pcm_write will attempt to
* restart the stream.
*/
+#define PCM_MONOTONIC 0x00000008 /* see pcm_get_htimestamp */
/* PCM runtime states */
#define PCM_STATE_OPEN 0
@@ -166,6 +167,8 @@ unsigned int pcm_bytes_to_frames(struct pcm *pcm, unsigned int bytes);
unsigned int pcm_get_latency(struct pcm *pcm);
/* Returns available frames in pcm buffer and corresponding time stamp.
+ * The clock is CLOCK_MONOTONIC if flag PCM_MONOTONIC was specified in pcm_open,
+ * otherwise the clock is CLOCK_REALTIME.
* For an input stream, frames available are frames ready for the
* application to read.
* For an output stream, frames available are the number of empty frames available
diff --git a/pcm.c b/pcm.c
index ca3eb3e..8195c7c 100644
--- a/pcm.c
+++ b/pcm.c
@@ -719,6 +719,17 @@ struct pcm *pcm_open(unsigned int card, unsigned int device,
goto fail;
}
+#ifdef SNDRV_PCM_IOCTL_TTSTAMP
+ if (pcm->flags & PCM_MONOTONIC) {
+ int arg = SNDRV_PCM_TSTAMP_TYPE_MONOTONIC;
+ rc = ioctl(pcm->fd, SNDRV_PCM_IOCTL_TTSTAMP, &arg);
+ if (rc < 0) {
+ oops(pcm, rc, "cannot set timestamp type");
+ goto fail;
+ }
+ }
+#endif
+
pcm->underruns = 0;
return pcm;