snd_pcm_uframes_t avail_min; /* min avail frames for wakeup */
snd_pcm_uframes_t xfer_align; /* obsolete: xfer size need to be a multiple */
snd_pcm_uframes_t start_threshold; /* min hw_avail frames for automatic start */
- snd_pcm_uframes_t stop_threshold; /* min avail frames for automatic stop */
- snd_pcm_uframes_t silence_threshold; /* min distance from noise for silence filling */
- snd_pcm_uframes_t silence_size; /* silence block size */
+ /*
+ * The following two thresholds alleviate playback buffer underruns; when
+ * hw_avail drops below the threshold, the respective action is triggered:
+ */
+ snd_pcm_uframes_t stop_threshold; /* - stop playback */
+ snd_pcm_uframes_t silence_threshold; /* - pre-fill buffer with silence */
+ snd_pcm_uframes_t silence_size; /* max size of silence pre-fill; when >= boundary,
+ * fill played area with silence immediately */
snd_pcm_uframes_t boundary; /* pointers wrap point */
unsigned int proto; /* protocol version */
unsigned int tstamp_type; /* timestamp type (req. proto >= 2.0.12) */
struct __snd_pcm_mmap_control64 {
__pad_before_uframe __pad1;
snd_pcm_uframes_t appl_ptr; /* RW: appl ptr (0...boundary-1) */
- __pad_before_uframe __pad2;
+ __pad_before_uframe __pad2; // This should be __pad_after_uframe, but binary
+ // backwards compatibility constraints prevent a fix.
__pad_before_uframe __pad3;
snd_pcm_uframes_t avail_min; /* RW: min available frames for wakeup */