They can be different if the last keyframe failed to decode correctly.
Fixes possible invalid reads in such a case.
Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC:libav-stable@libav.org
} else {
/* delta frame */
uint8_t *previous = s->prev->data[i];
- if (!previous) {
+ if (!previous ||
+ s->prev->width != s->width || s->prev->height != s->height) {
av_log(avctx, AV_LOG_ERROR, "Missing reference frame.\n");
result = AVERROR_INVALIDDATA;
goto err;