avutil/frame: fix remove_side_data

remove_side_data is supposed to remove a single instance by design.
Since new_side_data() doesn't forbid add multiple instances of the
same type, remove_side_data should deal with that.
Signed-off-by: Marton Balint <cus@passwd.hu>

libavutil/frame.c

@@ -806,7 +806,7 @@ void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type)
 {
     int i;
 
-    for (i = 0; i < frame->nb_side_data; i++) {
+    for (i = frame->nb_side_data - 1; i >= 0; i--) {
         AVFrameSideData *sd = frame->side_data[i];
         if (sd->type == type) {
             free_side_data(&frame->side_data[i]);

libavutil/frame.h

@@ -920,8 +920,7 @@ AVFrameSideData *av_frame_get_side_data(const AVFrame *frame,
                                         enum AVFrameSideDataType type);
 
 /**
- * If side data of the supplied type exists in the frame, free it and remove it
- * from the frame.
+ * Remove and free all side data instances of the given type.
  */
 void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type);