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v4l2: improve timestamp code

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Sample the pipeline clock and device clock closer to eachother to reduce jitter.
Don't subtract the frame duration from the timestamp when we can use the device
timestamps.
Assume a delay of 1 frame in read-write mode.
This commit is contained in:
Wim Taymans 2012-04-25 09:41:46 +02:00
parent 46045316ce
commit a473750350
1 changed files with 32 additions and 29 deletions
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61
sys/v4l2/gstv4l2src.c
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@ -778,7 +778,7 @@ gst_v4l2src_fill (GstPushSrc * src, GstBuffer * buf)
GstV4l2Object *obj = v4l2src->v4l2object;
GstFlowReturn ret;
GstClock *clock;
GstClockTime timestamp, duration;
GstClockTime abs_time, base_time, timestamp, duration;
GstClockTime delay;
#if 0
@ -801,6 +801,28 @@ gst_v4l2src_fill (GstPushSrc * src, GstBuffer * buf)
timestamp = GST_BUFFER_TIMESTAMP (buf);
duration = obj->duration;
/* timestamps, LOCK to get clock and base time. */
/* FIXME: element clock and base_time is rarely changing */
GST_OBJECT_LOCK (v4l2src);
if ((clock = GST_ELEMENT_CLOCK (v4l2src))) {
/* we have a clock, get base time and ref clock */
base_time = GST_ELEMENT (v4l2src)->base_time;
gst_object_ref (clock);
} else {
/* no clock, can't set timestamps */
base_time = GST_CLOCK_TIME_NONE;
}
GST_OBJECT_UNLOCK (v4l2src);
/* sample pipeline clock */
if (clock) {
abs_time = gst_clock_get_time (clock);
gst_object_unref (clock);
} else {
abs_time = GST_CLOCK_TIME_NONE;
}
if (timestamp != GST_CLOCK_TIME_NONE) {
struct timespec now;
@ -830,46 +852,28 @@ gst_v4l2src_fill (GstPushSrc * src, GstBuffer * buf)
" delay %" GST_TIME_FORMAT, GST_TIME_ARGS (timestamp),
GST_TIME_ARGS (gstnow), GST_TIME_ARGS (delay));
} else {
delay = 0;
/* we assume 1 frame latency otherwise */
if (GST_CLOCK_TIME_IS_VALID (duration))
delay = duration;
else
delay = 0;
}
/* set buffer metadata */
GST_BUFFER_OFFSET (buf) = v4l2src->offset++;
GST_BUFFER_OFFSET_END (buf) = v4l2src->offset;
/* timestamps, LOCK to get clock and base time. */
/* FIXME: element clock and base_time is rarely changing */
GST_OBJECT_LOCK (v4l2src);
if ((clock = GST_ELEMENT_CLOCK (v4l2src))) {
/* we have a clock, get base time and ref clock */
timestamp = GST_ELEMENT (v4l2src)->base_time;
gst_object_ref (clock);
} else {
/* no clock, can't set timestamps */
timestamp = GST_CLOCK_TIME_NONE;
}
GST_OBJECT_UNLOCK (v4l2src);
duration = obj->duration;
if (G_LIKELY (clock)) {
if (G_LIKELY (abs_time != GST_CLOCK_TIME_NONE)) {
/* the time now is the time of the clock minus the base time */
timestamp = gst_clock_get_time (clock) - timestamp;
gst_object_unref (clock);
timestamp = abs_time - base_time;
/* adjust for delay in the device */
if (timestamp > delay)
timestamp -= delay;
else
timestamp = 0;
/* if we have a framerate adjust timestamp for frame latency */
if (GST_CLOCK_TIME_IS_VALID (duration)) {
if (timestamp > duration)
timestamp -= duration;
else
timestamp = 0;
}
} else {
timestamp = GST_CLOCK_TIME_NONE;
}
/* activate settings for next frame */
@ -886,7 +890,6 @@ gst_v4l2src_fill (GstPushSrc * src, GstBuffer * buf)
GST_INFO_OBJECT (src, "sync to %" GST_TIME_FORMAT " out ts %" GST_TIME_FORMAT,
GST_TIME_ARGS (v4l2src->ctrl_time), GST_TIME_ARGS (timestamp));
/* FIXME: use the timestamp from the buffer itself! */
GST_BUFFER_TIMESTAMP (buf) = timestamp;
GST_BUFFER_DURATION (buf) = duration;