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qtkitvideosrc: simplify timestamping algorithm
Aligning timestamps on duration boundaries, skipping frames and so forth are clearly things that fall outside the scope of a video source.
This commit is contained in:
Ole André Vadla Ravnås
parent
3ba76f825d
commit
b39609b405
1 changed files with 21 additions and 72 deletions
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@ -112,7 +112,6 @@ static GstPushSrcClass * parent_class;
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gint width, height;
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GstClockTime duration;
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guint64 offset;
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GstClockTime prev_ts;
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}
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- (id)init;
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@ -130,7 +129,7 @@ static GstPushSrcClass * parent_class;
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- (BOOL)query:(GstQuery *)query;
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- (GstStateChangeReturn)changeState:(GstStateChange)transition;
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- (GstFlowReturn)create:(GstBuffer **)buf;
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- (BOOL)timestampBuffer:(GstBuffer *)buf;
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- (void)timestampBuffer:(GstBuffer *)buf;
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- (void)captureOutput:(QTCaptureOutput *)captureOutput
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didOutputVideoFrame:(CVImageBufferRef)videoFrame
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withSampleBuffer:(QTSampleBuffer *)sampleBuffer
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@ -268,7 +267,6 @@ static GstPushSrcClass * parent_class;
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duration = gst_util_uint64_scale (GST_SECOND, DEVICE_FPS_D, DEVICE_FPS_N);
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offset = 0;
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prev_ts = GST_CLOCK_TIME_NONE;
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return YES;
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}
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@ -372,37 +370,33 @@ static GstPushSrcClass * parent_class;
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- (GstFlowReturn)create:(GstBuffer **)buf
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{
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*buf = NULL;
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CVPixelBufferRef frame;
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do {
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CVPixelBufferRef frame;
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[queueLock lockWhenCondition:HAS_FRAME_OR_STOP_REQUEST];
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if (stopRequest) {
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[queueLock unlock];
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return GST_FLOW_WRONG_STATE;
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}
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[queueLock lockWhenCondition:HAS_FRAME_OR_STOP_REQUEST];
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if (stopRequest) {
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[queueLock unlock];
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return GST_FLOW_WRONG_STATE;
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}
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frame = (CVPixelBufferRef) [queue lastObject];
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[queue removeLastObject];
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[queueLock unlockWithCondition:
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([queue count] == 0) ? NO_FRAMES : HAS_FRAME_OR_STOP_REQUEST];
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frame = (CVPixelBufferRef) [queue lastObject];
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[queue removeLastObject];
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[queueLock unlockWithCondition:
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([queue count] == 0) ? NO_FRAMES : HAS_FRAME_OR_STOP_REQUEST];
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*buf = gst_buffer_new_and_alloc (
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CVPixelBufferGetBytesPerRow (frame) * CVPixelBufferGetHeight (frame));
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CVPixelBufferLockBaseAddress (frame, 0);
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memcpy (GST_BUFFER_DATA (*buf), CVPixelBufferGetBaseAddress (frame),
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GST_BUFFER_SIZE (*buf));
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CVPixelBufferUnlockBaseAddress (frame, 0);
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CVBufferRelease (frame);
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if (*buf != NULL)
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gst_buffer_unref (*buf);
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*buf = gst_buffer_new_and_alloc (
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CVPixelBufferGetBytesPerRow (frame) * CVPixelBufferGetHeight (frame));
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CVPixelBufferLockBaseAddress (frame, 0);
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memcpy (GST_BUFFER_DATA (*buf), CVPixelBufferGetBaseAddress (frame),
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GST_BUFFER_SIZE (*buf));
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CVPixelBufferUnlockBaseAddress (frame, 0);
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CVBufferRelease (frame);
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} while (![self timestampBuffer:*buf]);
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[self timestampBuffer:*buf];
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return GST_FLOW_OK;
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}
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- (BOOL)timestampBuffer:(GstBuffer *)buf
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- (void)timestampBuffer:(GstBuffer *)buf
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{
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GstClock *clock;
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GstClockTime timestamp;
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@ -418,8 +412,6 @@ static GstPushSrcClass * parent_class;
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GST_OBJECT_UNLOCK (element);
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if (clock != NULL) {
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/* The time according to the current clock */
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timestamp = gst_clock_get_time (clock) - timestamp;
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if (timestamp > duration)
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timestamp -= duration;
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@ -428,55 +420,12 @@ static GstPushSrcClass * parent_class;
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gst_object_unref (clock);
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clock = NULL;
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/* Unless it's the first frame, align the current timestamp on a multiple
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* of duration since the previous */
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if (GST_CLOCK_TIME_IS_VALID (prev_ts)) {
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GstClockTime delta;
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guint delta_remainder, delta_offset;
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if (timestamp < prev_ts) {
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GST_DEBUG_OBJECT (element, "clock is ticking backwards");
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return NO;
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}
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/* Round to a duration boundary */
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delta = timestamp - prev_ts;
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delta_remainder = delta % duration;
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if (delta_remainder < duration / 3)
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timestamp -= delta_remainder;
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else
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timestamp += duration - delta_remainder;
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/* How many frames are we off then? */
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delta = timestamp - prev_ts;
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delta_offset = delta / duration;
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if (delta_offset == 1) /* perfect */
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GST_BUFFER_FLAG_UNSET (buf, GST_BUFFER_FLAG_DISCONT);
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else if (delta_offset > 1) {
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guint lost = delta_offset - 1;
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GST_DEBUG_OBJECT (element, "lost %d frame%s, setting discont flag",
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lost, (lost > 1) ? "s" : "");
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GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_DISCONT);
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} else if (delta_offset == 0) { /* overproduction, skip this frame */
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GST_DEBUG_OBJECT (element, "skipping frame");
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return NO;
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}
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offset += delta_offset;
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}
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prev_ts = timestamp;
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}
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GST_BUFFER_OFFSET (buf) = offset;
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GST_BUFFER_OFFSET (buf) = offset++;
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GST_BUFFER_OFFSET_END (buf) = GST_BUFFER_OFFSET (buf) + 1;
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GST_BUFFER_TIMESTAMP (buf) = timestamp;
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GST_BUFFER_DURATION (buf) = duration;
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return YES;
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}
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@end
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