cur_frame = avpkt->pts % s->frames_per_jpeg;
+ /* cur_frame is later used to calculate the buffer offset, so it mustn't be negative */
+ if (cur_frame < 0)
+ cur_frame += s->frames_per_jpeg;
+
/* Are we at the start of a block? */
if (!cur_frame) {
av_frame_unref(mjpeg_data);