avformat/mov: fix frag_index.current out of sync

frag_index.current is used by cenc_filter, and is updated inside
mov_read_moof. It can out of sync regarding to mov_read_packet.

Partly fix ticket #9807.

Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>

1 files changed, 26 insertions, 1 deletions

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 6ee6ed0950..46731fe22c 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -7172,6 +7172,31 @@ static int cenc_decrypt(MOVContext *c, MOVStreamContext *sc, AVEncryptionInfo *s
     }
 }
 
+static MOVFragmentStreamInfo *get_frag_stream_info_from_pkt(MOVFragmentIndex *frag_index, AVPacket *pkt, int id)
+{
+    int current = frag_index->current;
+
+    if (!frag_index->nb_items)
+        return NULL;
+
+    // Check frag_index->current is the right one for pkt. It can out of sync.
+    if (current >= 0 && current < frag_index->nb_items) {
+        if (frag_index->item[current].moof_offset < pkt->pos &&
+            (current + 1 == frag_index->nb_items ||
+             frag_index->item[current + 1].moof_offset > pkt->pos))
+            return get_frag_stream_info(frag_index, current, id);
+    }
+
+
+    for (int i = 0; i < frag_index->nb_items; i++) {
+        if (frag_index->item[i].moof_offset > pkt->pos)
+            break;
+        current = i;
+    }
+    frag_index->current = current;
+    return get_frag_stream_info(frag_index, current, id);
+}
+
 static int cenc_filter(MOVContext *mov, AVStream* st, MOVStreamContext *sc, AVPacket *pkt, int current_index)
 {
     MOVFragmentStreamInfo *frag_stream_info;
@@ -7179,7 +7204,7 @@ static int cenc_filter(MOVContext *mov, AVStream* st, MOVStreamContext *sc, AVPa
     AVEncryptionInfo *encrypted_sample;
     int encrypted_index, ret;
 
-    frag_stream_info = get_frag_stream_info(&mov->frag_index, mov->frag_index.current, st->id);
+    frag_stream_info = get_frag_stream_info_from_pkt(&mov->frag_index, pkt, st->id);
     encrypted_index = current_index;
     encryption_index = NULL;
     if (frag_stream_info) {