[FFmpeg-cvslog] avcodec/utvideodec: fix gradient prediction when stride does not match width

[Paul B Mahol]

ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Fri Apr 21 21:44:28 2017 +0200| [49255370044cf4a58c81a88cb8206aee62086346] | committer: Paul B Mahol

avcodec/utvideodec: fix gradient prediction when stride does not match width

Fixes #6340.

Signed-off-by: Paul B Mahol <onemda at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=49255370044cf4a58c81a88cb8206aee62086346
---

 libavcodec/utvideodec.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/libavcodec/utvideodec.c b/libavcodec/utvideodec.c
index 25e32a6055..7979618f42 100644
--- a/libavcodec/utvideodec.c
+++ b/libavcodec/utvideodec.c
@@ -676,7 +676,11 @@ static void restore_gradient_planar_il(UtvideoContext *c, uint8_t *src, ptrdiff_
                 C = bsrc[i - 1];
                 bsrc[i] = (A - B + C + bsrc[i]) & 0xFF;
             }
-            for (i = 0; i < width; i++) {
+            A = bsrc[-stride];
+            B = bsrc[-(1 + stride + stride - width)];
+            C = bsrc[width - 1];
+            bsrc[stride] = (A - B + C + bsrc[stride]) & 0xFF;
+            for (i = 1; i < width; i++) {
                 A = bsrc[i - stride];
                 B = bsrc[i - (1 + stride)];
                 C = bsrc[i - 1 + stride];
@@ -774,7 +778,11 @@ static void restore_gradient_packed_il(uint8_t *src, int step, ptrdiff_t stride,
                 C = bsrc[i - step];
                 bsrc[i] = (A - B + C + bsrc[i]) & 0xFF;
             }
-            for (i = 0; i < width * step; i += step) {
+            A = bsrc[-stride];
+            B = bsrc[-(step + stride + stride - width * step)];
+            C = bsrc[width * step - step];
+            bsrc[stride] = (A - B + C + bsrc[stride]) & 0xFF;
+            for (i = step; i < width * step; i += step) {
                 A = bsrc[i - stride];
                 B = bsrc[i - (step + stride)];
                 C = bsrc[i - step + stride];