mpegvideo: treat delayed pictures as used

This requires to move the avcodec_default_free_buffers() call to
ff_MPV_common_end() since otherwise delayed pictures would get freed
during a size change.

libavcodec/h264.h

@@ -95,12 +95,6 @@
 #define IS_REF0(a)         ((a) & MB_TYPE_REF0)
 #define IS_8x8DCT(a)       ((a) & MB_TYPE_8x8DCT)
 
-/**
- * Value of Picture.reference when Picture is not a reference picture, but
- * is held for delayed output.
- */
-#define DELAYED_PIC_REF 4
-
 #define QP_MAX_NUM (51 + 2 * 6)           // The maximum supported qp
 
 /* NAL unit types */

libavcodec/mpegvideo.c

@@ -1008,9 +1008,6 @@ static int free_context_frame(MpegEncContext *s)
     for (i = 0; i < 3; i++)
         av_freep(&s->visualization_buffer[i]);
 
-    if (!(s->avctx->active_thread_type & FF_THREAD_FRAME))
-        avcodec_default_free_buffers(s->avctx);
-
     return 0;
 }
 
@@ -1126,6 +1123,9 @@ void ff_MPV_common_end(MpegEncContext *s)
 
     free_context_frame(s);
 
+    if (!(s->avctx->active_thread_type & FF_THREAD_FRAME))
+        avcodec_default_free_buffers(s->avctx);
+
     s->context_initialized      = 0;
     s->last_picture_ptr         =
     s->next_picture_ptr         =
@@ -1244,7 +1244,7 @@ static inline int pic_is_unused(MpegEncContext *s, Picture *pic)
 {
     if (pic->f.data[0] == NULL)
         return 1;
-    if (pic->needs_realloc)
+    if (pic->needs_realloc && !(pic->f.reference & DELAYED_PIC_REF))
         if (!pic->owner2 || pic->owner2 == s)
             return 1;
     return 0;

libavcodec/mpegvideo.h

@@ -79,6 +79,12 @@ enum OutputFormat {
 #define EXT_START_CODE          0x000001b5
 #define USER_START_CODE         0x000001b2
 
+/**
+ * Value of Picture.reference when Picture is not a reference picture, but
+ * is held for delayed output.
+ */
+#define DELAYED_PIC_REF 4
+
 struct MpegEncContext;
 
 /**