Fix T87967: M2T video seeking is broken

Bug caused by integer overflow in ffmpeg_generic_seek_workaround().
Function max_ii() was used to limit int_64tvalue.

After fixing the issue there was another issue, where near-infinite loop
was caused by requested_pos being very large and stream being cut in a
way, that it was missing keyframe at beginning.
This was fixed by checking if we are reading beyond file content.

Reviewed By: zeddb

Differential Revision: https://developer.blender.org/D11888

1 files changed, 7 insertions, 6 deletions

diff --git a/source/blender/imbuf/intern/anim_movie.c b/source/blender/imbuf/intern/anim_movie.c
index 2998c4781b6..dbca16ca82b 100644
--- a/source/blender/imbuf/intern/anim_movie.c
+++ b/source/blender/imbuf/intern/anim_movie.c
@@ -1213,7 +1213,7 @@ static int ffmpeg_generic_seek_workaround(struct anim *anim,
   /* Step backward frame by frame until we find the key frame we are looking for. */
   while (current_pts != 0) {
     current_pts = *requested_pts - (int64_t)round(offset * steps_per_frame);
-    current_pts = max_ii(current_pts, 0);
+    current_pts = MAX2(current_pts, 0);
 
     /* Seek to timestamp. */
     if (av_seek_frame(anim->pFormatCtx, anim->videoStream, current_pts, AVSEEK_FLAG_BACKWARD) <
@@ -1243,11 +1243,12 @@ static int ffmpeg_generic_seek_workaround(struct anim *anim,
         /* We found the I-frame we were looking for! */
         break;
       }
-      if (cur_pts == prev_pts) {
-        /* We got the same key frame packet twice.
-         * This probably means that we have hit the beginning of the stream. */
-        break;
-      }
+    }
+
+    if (cur_pts == prev_pts) {
+      /* We got the same key frame packet twice.
+       * This probably means that we have hit the beginning of the stream. */
+      break;
     }
 
     prev_pts = cur_pts;