[FFmpeg-devel] [PATCH] avcodec/dxva2_mpeg2.c: don't try to get surface index for absent frame

[Anton Fedchin]

From: Anton Fedchin <afedchin at ruswizards.com>

after 153b36f there is a possibility to crash when trying to get index of
a surface which points to nirvana. it may occurs when a mpeg2 stream starts
with non i-frame.
---
 libavcodec/dxva2_mpeg2.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/dxva2_mpeg2.c b/libavcodec/dxva2_mpeg2.c
index 8cc21bf199..c862e6e5e4 100644
--- a/libavcodec/dxva2_mpeg2.c
+++ b/libavcodec/dxva2_mpeg2.c
@@ -48,11 +48,11 @@ static void fill_picture_parameters(AVCodecContext *avctx,
     memset(pp, 0, sizeof(*pp));
     pp->wDecodedPictureIndex         = ff_dxva2_get_surface_index(avctx, ctx, current_picture->f);
     pp->wDeblockedPictureIndex       = 0;
-    if (s->pict_type != AV_PICTURE_TYPE_I)
+    if (s->pict_type != AV_PICTURE_TYPE_I && s->last_picture_ptr)
         pp->wForwardRefPictureIndex  = ff_dxva2_get_surface_index(avctx, ctx, s->last_picture.f);
     else
         pp->wForwardRefPictureIndex  = 0xffff;
-    if (s->pict_type == AV_PICTURE_TYPE_B)
+    if (s->pict_type == AV_PICTURE_TYPE_B && s->next_picture_ptr)
         pp->wBackwardRefPictureIndex = ff_dxva2_get_surface_index(avctx, ctx, s->next_picture.f);
     else
         pp->wBackwardRefPictureIndex = 0xffff;
-- 
2.17.1.windows.2