lavf/mov.c: Use the first sidx for tracks without sidx.

According to spec ISO_IEC_15444_12 "For any media stream for which no segment index is present, referred to as non‐indexed stream, the media stream associated with the first Segment Index box in the segment serves as a reference stream in a sense that it also describes the subsegments for any non‐indexed media stream."
Signed-off-by: Sasi Inguva <isasi@google.com>
Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/isom.h

@@ -179,6 +179,7 @@ typedef struct MOVStreamContext {
     int32_t *display_matrix;
     uint32_t format;
 
+    int has_sidx;  // If there is an sidx entry for this stream.
     struct {
         int use_subsamples;
         uint8_t* auxiliary_info;

libavformat/mov.c

@@ -4202,7 +4202,8 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     uint8_t version;
     unsigned i, track_id;
     AVStream *st = NULL;
-    MOVStreamContext *sc;
+    AVStream *ref_st;
+    MOVStreamContext *sc, *ref_sc;
     MOVFragmentIndex *index = NULL;
     MOVFragmentIndex **tmp;
     AVRational timescale;
@@ -4284,9 +4285,26 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     c->fragment_index_data = tmp;
     c->fragment_index_data[c->fragment_index_count++] = index;
+    sc->has_sidx = 1;
+
+    if (offset == avio_size(pb)) {
+        for (i = 0; i < c->fc->nb_streams; i++) {
+            if (c->fc->streams[i]->id == c->fragment_index_data[0]->track_id) {
+                ref_st = c->fc->streams[i];
+                ref_sc = ref_st->priv_data;
+                break;
+            }
+        }
+        for (i = 0; i < c->fc->nb_streams; i++) {
+            st = c->fc->streams[i];
+            sc = st->priv_data;
+            if (!sc->has_sidx) {
+                st->duration = sc->track_end = av_rescale(ref_st->duration, sc->time_scale, ref_sc->time_scale);
+            }
+        }
 
-    if (offset == avio_size(pb))
         c->fragment_index_complete = 1;
+    }
 
     return 0;
 }
@@ -5847,13 +5865,14 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
 static int mov_seek_fragment(AVFormatContext *s, AVStream *st, int64_t timestamp)
 {
     MOVContext *mov = s->priv_data;
+    MOVStreamContext *sc = st->priv_data;
     int i, j;
 
     if (!mov->fragment_index_complete)
         return 0;
 
     for (i = 0; i < mov->fragment_index_count; i++) {
-        if (mov->fragment_index_data[i]->track_id == st->id) {
+        if (mov->fragment_index_data[i]->track_id == st->id || !sc->has_sidx) {
             MOVFragmentIndex *index = mov->fragment_index_data[i];
             for (j = index->item_count - 1; j >= 0; j--) {
                 if (index->items[j].time <= timestamp) {