qtdemux: preserve stop of segment when doing seeks in push mode

When handling seeks in push mode, qtdemux converts the seek to bytes
and pushes upstream. It needs to keep track of the seek and the
subsequent segment to be able to map them back to the requested
seek time and properly preserve the segment stop of the seek.

This is done by using the start offset in bytes of the seek,
that should be the same of the segment from upstream. And this
is also backwards compatible with what qtdemux already was using.

https://bugzilla.gnome.org/show_bug.cgi?id=707530

gst/isomp4/qtdemux.c

@@ -1256,17 +1256,17 @@ gst_qtdemux_do_push_seek (GstQTDemux * qtdemux, GstPad * pad, GstEvent * event)
   GstFormat format;
   GstSeekFlags flags;
   GstSeekType cur_type, stop_type;
-  gint64 cur, stop;
+  gint64 cur, stop, key_cur;
   gboolean res;
   gint64 byte_cur;
+  gint64 original_stop;
+  guint32 seqnum;
 
   GST_DEBUG_OBJECT (qtdemux, "doing push-based seek");
 
   gst_event_parse_seek (event, &rate, &format, &flags,
       &cur_type, &cur, &stop_type, &stop);
-
+  seqnum = gst_event_get_seqnum (event);
-  /* FIXME, always play to the end */
-  stop = -1;
 
   /* only forward streaming and seeking is possible */
   if (rate <= 0)
@@ -1277,10 +1277,16 @@ gst_qtdemux_do_push_seek (GstQTDemux * qtdemux, GstPad * pad, GstEvent * event)
           stop_type, &stop))
     goto no_format;
 
+  /* Upstrea seek in bytes will have undefined stop, but qtdemux stores
+   * the original stop position to use when upstream pushes the new segment
+   * for this seek */
+  original_stop = stop;
+  stop = -1;
+
   /* find reasonable corresponding BYTE position,
    * also try to mind about keyframes, since we can not go back a bit for them
    * later on */
-  gst_qtdemux_adjust_seek (qtdemux, cur, NULL, &byte_cur);
+  gst_qtdemux_adjust_seek (qtdemux, cur, &key_cur, &byte_cur);
 
   if (byte_cur == -1)
     goto abort_seek;
@@ -1289,19 +1295,20 @@ gst_qtdemux_do_push_seek (GstQTDemux * qtdemux, GstPad * pad, GstEvent * event)
       "start %" G_GINT64_FORMAT ", stop %" G_GINT64_FORMAT, rate, byte_cur,
       stop);
 
-  if (!(flags & GST_SEEK_FLAG_KEY_UNIT)) {
-    GST_DEBUG_OBJECT (qtdemux,
-        "Requested seek time: %" GST_TIME_FORMAT ", calculated seek offset: %"
-        G_GUINT64_FORMAT, GST_TIME_ARGS (cur), byte_cur);
   GST_OBJECT_LOCK (qtdemux);
-    qtdemux->requested_seek_time = cur;
   qtdemux->seek_offset = byte_cur;
-    GST_OBJECT_UNLOCK (qtdemux);
+  if (!(flags & GST_SEEK_FLAG_KEY_UNIT)) {
+    qtdemux->push_seek_start = cur;
+  } else {
+    qtdemux->push_seek_start = key_cur;
   }
+  qtdemux->push_seek_stop = original_stop;
+  GST_OBJECT_UNLOCK (qtdemux);
 
   /* BYTE seek event */
   event = gst_event_new_seek (rate, GST_FORMAT_BYTES, flags, cur_type, byte_cur,
       stop_type, stop);
+  gst_event_set_seqnum (event, seqnum);
   res = gst_pad_push_event (qtdemux->sinkpad, event);
 
   return res;
@@ -1813,8 +1820,6 @@ gst_qtdemux_reset (GstQTDemux * qtdemux, gboolean hard)
       gst_object_unref (qtdemux->pending_newsegment);
     qtdemux->pending_newsegment = NULL;
     qtdemux->upstream_newsegment = TRUE;
-    qtdemux->requested_seek_time = GST_CLOCK_TIME_NONE;
-    qtdemux->seek_offset = 0;
     qtdemux->upstream_seekable = FALSE;
     qtdemux->upstream_size = 0;
 
@@ -1897,30 +1902,38 @@ gst_qtdemux_handle_sink_event (GstPad * sinkpad, GstObject * parent,
         }
       }
 
+      /* check if this matches a time seek we received previously
+       * FIXME for backwards compatibility reasons we use the
+       * seek_offset here to compare. In the future we might want to
+       * change this to use the seqnum as it uniquely should identify
+       * the segment that corresponds to the seek. */
+      GST_DEBUG_OBJECT (demux, "Stored seek offset: %" G_GINT64_FORMAT
+          ", received segment offset %" G_GINT64_FORMAT,
+          demux->seek_offset, segment.start);
+      if (segment.format == GST_FORMAT_BYTES
+          && demux->seek_offset == segment.start) {
+        GST_OBJECT_LOCK (demux);
+        offset = segment.start;
+
+        segment.format = GST_FORMAT_TIME;
+        segment.start = demux->push_seek_start;
+        segment.stop = demux->push_seek_stop;
+        GST_DEBUG_OBJECT (demux, "Replaced segment with stored seek "
+            "segment %" GST_TIME_FORMAT " - %" GST_TIME_FORMAT,
+            GST_TIME_ARGS (segment.start), GST_TIME_ARGS (segment.stop));
+        GST_OBJECT_UNLOCK (demux);
+      }
+
       /* we only expect a BYTE segment, e.g. following a seek */
       if (segment.format == GST_FORMAT_BYTES) {
         if (GST_CLOCK_TIME_IS_VALID (segment.start)) {
-          gint64 requested_seek_time;
-          guint64 seek_offset;
-
           offset = segment.start;
 
-          GST_OBJECT_LOCK (demux);
-          requested_seek_time = demux->requested_seek_time;
-          seek_offset = demux->seek_offset;
-          demux->requested_seek_time = -1;
-          demux->seek_offset = -1;
-          GST_OBJECT_UNLOCK (demux);
-
-          if (offset == seek_offset) {
-            segment.start = requested_seek_time;
-          } else {
           gst_qtdemux_find_sample (demux, segment.start, TRUE, FALSE, NULL,
               NULL, (gint64 *) & segment.start);
           if ((gint64) segment.start < 0)
             segment.start = 0;
         }
-        }
         if (GST_CLOCK_TIME_IS_VALID (segment.stop)) {
           gst_qtdemux_find_sample (demux, segment.stop, FALSE, FALSE, NULL,
               NULL, (gint64 *) & segment.stop);

gst/isomp4/qtdemux.h

@@ -105,6 +105,9 @@ struct _GstQTDemux {
   GstSegment segment;
   GstEvent *pending_newsegment;
   gboolean upstream_newsegment;
+  gint64 seek_offset;
+  gint64 push_seek_start;
+  gint64 push_seek_stop;
 
 #if 0
   /* gst index support */
@@ -112,9 +115,6 @@ struct _GstQTDemux {
   gint index_id;
 #endif
 
-  gint64 requested_seek_time;
-  guint64 seek_offset;
-
   gboolean upstream_seekable;
   gint64 upstream_size;