qtdemux: do not ignore empty segments

Make sure empty segments are used and pushed with a gap event
to represent its data (or lack of it)

Each QtSegment is mapped into a GstSegment with the corresponding
media range. For empty QtSegments a gap event is pushed instead
of GstBuffers and it advances to the next QtSegment.

To make this work with seeks, need to keep track of the starting
'base' to make sure it remains consistently increasing when
pushing new segment events.
For example: if a seek makes qtdemux start from 5s, the first
segment will have a base=0. When the next segment is activated,
its base time will be QtSegment.time - qtdemux.segment_base so
that it doesn't include the first 5s that weren't played and
shouldn't be accounted on the running time

This purposedly will remove the fix made for
https://bugzilla.gnome.org/show_bug.cgi?id=700264, at this
point it was decided to respect the gaps, even if they cause
a delay on playback, because that's the way the file was crafted.

https://bugzilla.gnome.org/show_bug.cgi?id=345830

diff --git a/gst/isomp4/qtdemux.c b/gst/isomp4/qtdemux.c
index 40e5859..b0c5cd2 100644 (file)
--- a/gst/isomp4/qtdemux.c
+++ b/gst/isomp4/qtdemux.c
@@ -199,6 +199,8 @@ struct _QtDemuxSegment
   gdouble rate;
 };
 
+#define QTSEGMENT_IS_EMPTY(s) ((s)->media_start == GST_CLOCK_TIME_NONE)
+
 struct _QtDemuxStream
 {
   GstPad *pad;
@@ -1403,6 +1405,7 @@ gst_qtdemux_perform_seek (GstQTDemux * qtdemux, GstSegment * segment,
   }
   segment->position = desired_offset;
   segment->time = desired_offset;
+  qtdemux->segment_base = desired_offset;
 
   /* we stop at the end */
   if (segment->stop == -1)
@@ -1856,6 +1859,7 @@ gst_qtdemux_reset (GstQTDemux * qtdemux, gboolean hard)
   qtdemux->offset = 0;
   gst_adapter_clear (qtdemux->adapter);
   gst_segment_init (&qtdemux->segment, GST_FORMAT_TIME);
+  qtdemux->segment_base = 0;
 
   if (hard) {
     for (n = 0; n < qtdemux->n_streams; n++) {
@@ -3460,7 +3464,10 @@ gst_qtdemux_activate_segment (GstQTDemux * qtdemux, QtDemuxStream * stream,
     stop =
         MIN (segment->media_stop, stop - segment->time + segment->media_start);
 
-  if (qtdemux->segment.rate >= 0) {
+  if (G_UNLIKELY (QTSEGMENT_IS_EMPTY (segment))) {
+    start = segment->time + seg_time;
+    time = offset;
+  } else if (qtdemux->segment.rate >= 0) {
     start = MIN (segment->media_start + seg_time, stop);
     time = offset;
   } else {
@@ -3493,6 +3500,9 @@ gst_qtdemux_activate_segment (GstQTDemux * qtdemux, QtDemuxStream * stream,
   stream->segment.stop = stop;
   stream->segment.time = time;
   stream->segment.position = start;
+  stream->segment.base =
+      segment->time >
+      qtdemux->segment_base ? segment->time - qtdemux->segment_base : 0;
 
   /* now prepare and send the segment */
   if (stream->pad) {
@@ -3510,20 +3520,26 @@ gst_qtdemux_activate_segment (GstQTDemux * qtdemux, QtDemuxStream * stream,
 
   /* and move to the keyframe before the indicated media time of the
    * segment */
-  if (qtdemux->segment.rate >= 0) {
-    index = gst_qtdemux_find_index_linear (qtdemux, stream, start);
-    stream->to_sample = G_MAXUINT32;
-    GST_DEBUG_OBJECT (qtdemux, "moving data pointer to %" GST_TIME_FORMAT
-        ", index: %u, pts %" GST_TIME_FORMAT, GST_TIME_ARGS (start), index,
-        GST_TIME_ARGS (gst_util_uint64_scale (stream->samples[index].timestamp,
-                GST_SECOND, stream->timescale)));
+  if (G_LIKELY (!QTSEGMENT_IS_EMPTY (segment))) {
+    if (qtdemux->segment.rate >= 0) {
+      index = gst_qtdemux_find_index_linear (qtdemux, stream, start);
+      stream->to_sample = G_MAXUINT32;
+      GST_DEBUG_OBJECT (qtdemux, "moving data pointer to %" GST_TIME_FORMAT
+          ", index: %u, pts %" GST_TIME_FORMAT, GST_TIME_ARGS (start), index,
+          GST_TIME_ARGS (gst_util_uint64_scale (stream->
+                  samples[index].timestamp, GST_SECOND, stream->timescale)));
+    } else {
+      index = gst_qtdemux_find_index_linear (qtdemux, stream, stop);
+      stream->to_sample = index;
+      GST_DEBUG_OBJECT (qtdemux, "moving data pointer to %" GST_TIME_FORMAT
+          ", index: %u, pts %" GST_TIME_FORMAT, GST_TIME_ARGS (stop), index,
+          GST_TIME_ARGS (gst_util_uint64_scale (stream->
+                  samples[index].timestamp, GST_SECOND, stream->timescale)));
+    }
   } else {
-    index = gst_qtdemux_find_index_linear (qtdemux, stream, stop);
-    stream->to_sample = index;
-    GST_DEBUG_OBJECT (qtdemux, "moving data pointer to %" GST_TIME_FORMAT
-        ", index: %u, pts %" GST_TIME_FORMAT, GST_TIME_ARGS (stop), index,
-        GST_TIME_ARGS (gst_util_uint64_scale (stream->samples[index].timestamp,
-                GST_SECOND, stream->timescale)));
+    GST_DEBUG_OBJECT (qtdemux, "No need to look for keyframe, "
+        "this is an empty segment");
+    return TRUE;
   }
 
   /* gst_qtdemux_parse_sample () called from gst_qtdemux_find_index_linear ()
@@ -3585,8 +3601,8 @@ gst_qtdemux_activate_segment (GstQTDemux * qtdemux, QtDemuxStream * stream,
  */
 static gboolean
 gst_qtdemux_prepare_current_sample (GstQTDemux * qtdemux,
-    QtDemuxStream * stream, guint64 * offset, guint * size, guint64 * dts,
-    guint64 * pts, guint64 * duration, gboolean * keyframe)
+    QtDemuxStream * stream, gboolean * empty, guint64 * offset, guint * size,
+    guint64 * dts, guint64 * pts, guint64 * duration, gboolean * keyframe)
 {
   QtDemuxSample *sample;
   guint64 time_position;
@@ -3613,6 +3629,22 @@ gst_qtdemux_prepare_current_sample (GstQTDemux * qtdemux,
   if (G_UNLIKELY (stream->segment_index != seg_idx))
     gst_qtdemux_activate_segment (qtdemux, stream, seg_idx, time_position);
 
+  if (G_UNLIKELY (QTSEGMENT_IS_EMPTY (&stream->
+              segments[stream->segment_index]))) {
+    QtDemuxSegment *seg = &stream->segments[stream->segment_index];
+
+    GST_LOG_OBJECT (qtdemux, "Empty segment activated,"
+        " prepare empty sample");
+
+    *empty = TRUE;
+    *pts = *dts = time_position;
+    *duration = seg->duration - (time_position - seg->time);
+
+    return TRUE;
+  }
+
+  *empty = FALSE;
+
   GST_LOG_OBJECT (qtdemux, "segment active, index = %u of %u",
       stream->sample_index, stream->n_samples);
 
@@ -3655,6 +3687,14 @@ gst_qtdemux_advance_sample (GstQTDemux * qtdemux, QtDemuxStream * stream)
   QtDemuxSample *sample;
   QtDemuxSegment *segment;
 
+  /* get current segment */
+  segment = &stream->segments[stream->segment_index];
+
+  if (G_UNLIKELY (QTSEGMENT_IS_EMPTY (segment))) {
+    GST_DEBUG_OBJECT (qtdemux, "Empty segment, no samples to advance");
+    goto next_segment;
+  }
+
   if (G_UNLIKELY (stream->sample_index >= stream->to_sample)) {
     /* Mark the stream as EOS */
     GST_DEBUG_OBJECT (qtdemux,
@@ -3667,9 +3707,6 @@ gst_qtdemux_advance_sample (GstQTDemux * qtdemux, QtDemuxStream * stream)
   stream->sample_index++;
   stream->offset_in_sample = 0;
 
-  /* get current segment */
-  segment = &stream->segments[stream->segment_index];
-
   /* reached the last sample, we need the next segment */
   if (G_UNLIKELY (stream->sample_index >= stream->n_samples))
     goto next_segment;
@@ -4155,6 +4192,7 @@ gst_qtdemux_loop_state_movie (GstQTDemux * qtdemux)
   guint64 duration = 0;
   gboolean keyframe = FALSE;
   guint sample_size = 0;
+  gboolean empty = 0;
   guint size;
   gint index;
   gint i;
@@ -4218,16 +4256,23 @@ gst_qtdemux_loop_state_movie (GstQTDemux * qtdemux)
   }
 
   /* fetch info for the current sample of this stream */
-  if (G_UNLIKELY (!gst_qtdemux_prepare_current_sample (qtdemux, stream, &offset,
-              &sample_size, &dts, &pts, &duration, &keyframe)))
+  if (G_UNLIKELY (!gst_qtdemux_prepare_current_sample (qtdemux, stream, &empty,
+              &offset, &sample_size, &dts, &pts, &duration, &keyframe)))
     goto eos_stream;
 
   GST_DEBUG_OBJECT (qtdemux,
-      "pushing from stream %d, offset %" G_GUINT64_FORMAT
+      "pushing from stream %d, empty %d offset %" G_GUINT64_FORMAT
       ", size %d, dts=%" GST_TIME_FORMAT ", pts=%" GST_TIME_FORMAT
-      ", duration %" GST_TIME_FORMAT, index, offset, sample_size,
+      ", duration %" GST_TIME_FORMAT, index, empty, offset, sample_size,
       GST_TIME_ARGS (dts), GST_TIME_ARGS (pts), GST_TIME_ARGS (duration));
 
+  if (G_UNLIKELY (empty)) {
+    /* empty segment, push a gap and move to the next one */
+    gst_pad_push_event (stream->pad, gst_event_new_gap (pts, duration));
+    stream->segment.position = pts + duration;
+    goto next;
+  }
+
   /* hmm, empty sample, skip and move to next sample */
   if (G_UNLIKELY (sample_size <= 0))
     goto next;
@@ -6794,16 +6839,6 @@ qtdemux_parse_segments (GstQTDemux * qtdemux, QtDemuxStream * stream,
       media_time = QT_UINT32 (buffer + 20 + i * 12);
       duration = QT_UINT32 (buffer + 16 + i * 12);
 
-      /* -1 media time is an empty segment, just ignore it */
-      if (media_time == G_MAXUINT32) {
-        if (i == 0) {
-          /* first empty segment specifies sample offset (if movie timescale) */
-          stream->elst_offset =
-              gst_util_uint64_scale (duration, GST_SECOND, qtdemux->timescale);
-        }
-        continue;
-      }
-
       segment = &stream->segments[count++];
 
       /* time and duration expressed in global timescale */
@@ -6814,9 +6849,14 @@ qtdemux_parse_segments (GstQTDemux * qtdemux, QtDemuxStream * stream,
       segment->stop_time = stime;
       segment->duration = stime - segment->time;
       /* media_time expressed in stream timescale */
-      segment->media_start =
-          gst_util_uint64_scale (media_time, GST_SECOND, stream->timescale);
-      segment->media_stop = segment->media_start + segment->duration;
+      if (media_time != G_MAXUINT32) {
+        segment->media_start =
+            gst_util_uint64_scale (media_time, GST_SECOND, stream->timescale);
+        segment->media_stop = segment->media_start + segment->duration;
+      } else {
+        segment->media_start = GST_CLOCK_TIME_NONE;
+        segment->media_stop = GST_CLOCK_TIME_NONE;
+      }
       rate_int = GST_READ_UINT32_BE (buffer + 24 + i * 12);
 
       if (rate_int <= 1) {
@@ -6835,7 +6875,7 @@ qtdemux_parse_segments (GstQTDemux * qtdemux, QtDemuxStream * stream,
           GST_TIME_ARGS (segment->duration),
           GST_TIME_ARGS (segment->media_start), segment->rate, rate_int);
     }
-    GST_DEBUG_OBJECT (qtdemux, "found %d non-empty segments", count);
+    GST_DEBUG_OBJECT (qtdemux, "found %d segments", count);
     stream->n_segments = count;
   }
 done:

diff --git a/gst/isomp4/qtdemux.h b/gst/isomp4/qtdemux.h
index b56657a..9e29d11 100644 (file)
--- a/gst/isomp4/qtdemux.h
+++ b/gst/isomp4/qtdemux.h
@@ -121,6 +121,9 @@ struct _GstQTDemux {
   gint64 seek_offset;
   gint64 push_seek_start;
   gint64 push_seek_stop;
+  guint64 segment_base; /* The offset from which playback was started, needs to
+                         * be subtracted from GstSegment.base to get a correct
+                         * running time whenever a new QtSegment is activated */
 
 #if 0
   /* gst index support */