vp8: force reallocation in update_thread_context after frame size change

Signed-off-by: Janne Grunau <janne-libav@jannau.net>
(cherry picked from commit 5653579381)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/vp8.c

@@ -33,6 +33,19 @@
 #   include "arm/vp8.h"
 #endif
 
+static void free_buffers(VP8Context *s)
+{
+    av_freep(&s->macroblocks_base);
+    av_freep(&s->filter_strength);
+    av_freep(&s->intra4x4_pred_mode_top);
+    av_freep(&s->top_nnz);
+    av_freep(&s->edge_emu_buffer);
+    av_freep(&s->top_border);
+    av_freep(&s->segmentation_map);
+
+    s->macroblocks = NULL;
+}
+
 static void vp8_decode_flush(AVCodecContext *avctx)
 {
     VP8Context *s = avctx->priv_data;
@@ -45,15 +58,7 @@ static void vp8_decode_flush(AVCodecContext *avctx)
     }
     memset(s->framep, 0, sizeof(s->framep));
 
-    av_freep(&s->macroblocks_base);
-    av_freep(&s->filter_strength);
-    av_freep(&s->intra4x4_pred_mode_top);
-    av_freep(&s->top_nnz);
-    av_freep(&s->edge_emu_buffer);
-    av_freep(&s->top_border);
-    av_freep(&s->segmentation_map);
-
-    s->macroblocks        = NULL;
+    free_buffers(s);
 }
 
 static int update_dimensions(VP8Context *s, int width, int height)
@@ -1750,6 +1755,11 @@ static int vp8_decode_update_thread_context(AVCodecContext *dst, const AVCodecCo
 {
     VP8Context *s = dst->priv_data, *s_src = src->priv_data;
 
+    if (s->macroblocks_base &&
+        (s_src->mb_width != s->mb_width || s_src->mb_height != s->mb_height)) {
+        free_buffers(s);
+    }
+
     s->prob[0] = s_src->prob[!s_src->update_probabilities];
     s->segmentation = s_src->segmentation;
     s->lf_delta = s_src->lf_delta;