[FFmpeg-devel] [PATCH] avformat/mov: prevent duplication of first fragment's ctts_data

[Daniel Glöckner]

MP4 files with fragments might have the first moof box that is mentioned
in a fragment index before the first mdat box. Since it is then already
parsed by mov_read_header, we have to make sure that mov_switch_root
will not parse it again when seeking by setting the headers_read flag in
the index. Parsing it a second time would cause the ctts_data array to
receive a second copy of the information from the trun box, leading to
wrong PTS values for the second and following fragments in presence of
B-frames.

Fixes ticket 6560.

Signed-off-by: Daniel Glöckner <daniel-gl at gmx.net>
---
 libavformat/mov.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 63f84be..c2da1b6 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -6345,6 +6345,13 @@ static int mov_read_header(AVFormatContext *s)
     }
     ff_configure_buffers_for_index(s, AV_TIME_BASE);
 
+    for (i = 0; i < mov->fragment_index_count; i++) {
+        MOVFragmentIndex *idx = mov->fragment_index_data[i];
+        for (j = 0; j < idx->item_count; j++)
+            if (idx->items[j].moof_offset <= mov->fragment.moof_offset)
+                idx->items[j].headers_read = 1;
+    }
+
     return 0;
 }
 
-- 
2.7.0