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matroskademux: implement keyframe search also without cluster prev size

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If we have cluster prev size (GStreamer muxer will write it by default),
we can go back to the previous cluster efficiently, but if we don't then
just search backwards until we find a cluster ebml identifier, like we
do when searching for clusters in the bisection loop.
This commit is contained in:
Tim-Philipp Müller 2018-08-15 12:53:34 +01:00
parent 2d6efbbae2
commit 9d6621a30d
1 changed files with 22 additions and 15 deletions
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37
gst/matroska/matroska-demux.c
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@ -2250,11 +2250,6 @@ gst_matroska_demux_scan_back_for_keyframe_cluster (GstMatroskaDemux * demux,
GST_DEBUG_OBJECT (demux, "Cluster starts with delta frame, backtracking");
if (cluster.prev_size == 0 || cluster.prev_size > off) {
GST_LOG_OBJECT (demux, "Cluster has no or invalid prev size, stopping");
break;
}
/* Don't scan back more than this much in time from the cluster we
* originally landed on. This is mostly a sanity check in case a file
* always has keyframes in the middle of clusters and never at the
@ -2271,7 +2266,24 @@ gst_matroska_demux_scan_back_for_keyframe_cluster (GstMatroskaDemux * demux,
}
}
off -= cluster.prev_size;
/* If we have cluster prev_size we can skip back efficiently. If not,
* we'll just do a brute force search for a cluster identifier */
if (cluster.prev_size > 0 && off >= cluster.prev_size) {
off -= cluster.prev_size;
} else {
GstFlowReturn flow;
GST_LOG_OBJECT (demux, "Cluster has no or invalid prev size, searching "
"for previous cluster instead then");
flow = gst_matroska_demux_search_cluster (demux, &off, FALSE);
if (flow != GST_FLOW_OK) {
GST_DEBUG_OBJECT (demux, "cluster search yielded flow %s, stopping",
gst_flow_get_name (flow));
break;
}
}
if (off <= first_cluster_offset) {
GST_LOG_OBJECT (demux, "Reached first cluster, stopping");
*cluster_offset = first_cluster_offset;
@ -2507,15 +2519,10 @@ retry:
* that starts with a keyframe - and if not backtrack until we find one that
* does. */
if (demux->have_nonintraonly_v_streams && demux->max_backtrack_distance > 0) {
if (demux->seen_cluster_prevsize) {
if (gst_matroska_demux_scan_back_for_keyframe_cluster (demux,
&cluster_offset, &cluster_time)) {
GST_INFO_OBJECT (demux, "Adjusted cluster to %" GST_TIME_FORMAT " @ "
"%" G_GUINT64_FORMAT, GST_TIME_ARGS (cluster_time), cluster_offset);
}
} else {
GST_FIXME_OBJECT (demux, "implement scanning back to prev cluster "
"without cluster prev size field");
if (gst_matroska_demux_scan_back_for_keyframe_cluster (demux,
&cluster_offset, &cluster_time)) {
GST_INFO_OBJECT (demux, "Adjusted cluster to %" GST_TIME_FORMAT " @ "
"%" G_GUINT64_FORMAT, GST_TIME_ARGS (cluster_time), cluster_offset);
}
}