Merge pull request #33 from gkasten/CL_avsync

pcm_get_htimestamp can now use CLOCK_MONOTONIC

2 files changed, 14 insertions, 0 deletions

diff --git a/include/tinyalsa/asoundlib.h b/include/tinyalsa/asoundlib.h
index 01a6303..ea8e23d 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_RUNNING	3
@@ -155,6 +156,8 @@ unsigned int pcm_frames_to_bytes(struct pcm *pcm, unsigned int frames);
 unsigned int pcm_bytes_to_frames(struct pcm *pcm, unsigned int bytes);
 
 /* 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 b081e87..1a5254b 100644
--- a/pcm.c
+++ b/pcm.c
@@ -724,6 +724,17 @@ 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;