[FFmpeg-devel] [PATCH] libavfilter:vf_thumbnail.c: Fix bug in buffer handling for RGB width

[Chris Kennedy]

This is a pretty obvious bug we caught in the thumbnail filter that is very
subtle and hardly ever shows issues except for certain videos.  Yet it can
be seen how it is blatantly going out of bounds by basing the width
increment off of i*3 that resulted in odd crashes in rare cases.


Thanks,
Chris
-- 
---
Chris Kennedy
Video Engineer
CrunchyRoll - http://www.crunchyroll.com
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diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c
index 1883154..a1272a0 100644
--- a/libavfilter/vf_thumbnail.c
+++ b/libavfilter/vf_thumbnail.c
@@ -142,7 +142,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)

     // update current frame RGB histogram
     for (j = 0; j < inlink->h; j++) {
-        for (i = 0; i < inlink->w; i++) {
+        // last third of image, walk every 3 bytes/pixels reading RGB
+        for (i = 0; i < inlink->w/3; i++) {
             hist[0*256 + p[i*3    ]]++;
             hist[1*256 + p[i*3 + 1]]++;
             hist[2*256 + p[i*3 + 2]]++;