From c32f455b7b9e8dd145077d634d9ba392a7e05cf3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Cerveau?= <scerveau@collabora.com>
Date: Mon, 19 Apr 2021 18:25:06 +0200
Subject: [PATCH] mxfdemux: fix keyframe detection in index

An index entry should be considered as a keyframe
if the flags allow a random access only.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2173>
---
 gst/mxf/mxfdemux.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/gst/mxf/mxfdemux.c b/gst/mxf/mxfdemux.c
index d34827c58b..5ed054ccd5 100644
--- a/gst/mxf/mxfdemux.c
+++ b/gst/mxf/mxfdemux.c
@@ -3796,8 +3796,13 @@ collect_index_table_segments (GstMXFDemux * demux)
           }
 
           index->offset = offset;
-          index->keyframe = ! !(segment->index_entries[i].flags & 0x80)
-              || (segment->index_entries[i].key_frame_offset == 0);
+          /* EG41-2004 Table 9: 0x80 = Random access */
+          /* random_access is more reliable to determine if the index is
+           * a key-frame than checking the keyframe_offset or the frame type flag.
+           * See https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2173#note_900580
+           * for more details.
+           */
+          index->keyframe = ! !(segment->index_entries[i].flags & 0x80);
           index->dts = pts_i;
         }
       }