[FFmpeg-cvslog] mpegvideo: Fix undefined negative shifts in ff_init_block_index

[Luca Barbato]

ffmpeg | branch: master | Luca Barbato <lu_zero at gentoo.org> | Wed Mar  2 18:52:23 2016 -0500| [7d4a1ff344cbf969ac648642a0fd8484fd5b8637] | committer: Vittorio Giovara

mpegvideo: Fix undefined negative shifts in ff_init_block_index

Found-by: gcc5-ubsan.

Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=7d4a1ff344cbf969ac648642a0fd8484fd5b8637
---

 libavcodec/mpegvideo.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index e0787a6..5974e18 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -1754,9 +1754,9 @@ void ff_init_block_index(MpegEncContext *s){ //FIXME maybe rename
     s->block_index[5]= s->mb_stride*(s->mb_y + s->mb_height + 2) + s->b8_stride*s->mb_height*2 + s->mb_x - 1;
     //block_index is not used by mpeg2, so it is not affected by chroma_format
 
-    s->dest[0] = s->current_picture.f->data[0] + ((s->mb_x - 1) <<  mb_size);
-    s->dest[1] = s->current_picture.f->data[1] + ((s->mb_x - 1) << (mb_size - s->chroma_x_shift));
-    s->dest[2] = s->current_picture.f->data[2] + ((s->mb_x - 1) << (mb_size - s->chroma_x_shift));
+    s->dest[0] = s->current_picture.f->data[0] + (s->mb_x - 1) * (1 << mb_size);
+    s->dest[1] = s->current_picture.f->data[1] + (s->mb_x - 1) * (1 << (mb_size - s->chroma_x_shift));
+    s->dest[2] = s->current_picture.f->data[2] + (s->mb_x - 1) * (1 << (mb_size - s->chroma_x_shift));
 
     if(!(s->pict_type==AV_PICTURE_TYPE_B && s->avctx->draw_horiz_band && s->picture_structure==PICT_FRAME))
     {