avcodec/mpegvideo: dont overwrite emu_edge buffer

Fixes vsynth3 fate failures on mips
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpegvideo.c

@@ -450,7 +450,8 @@ static int frame_size_alloc(MpegEncContext *s, int linesize)
     // VC1 computes luma and chroma simultaneously and needs 19X19 + 9x9
     // at uvlinesize. It supports only YUV420 so 24x24 is enough
     // linesize * interlaced * MBsize
-    FF_ALLOCZ_OR_GOTO(s->avctx, s->edge_emu_buffer, alloc_size * 4 * 24,
+    // we also use this buffer for encoding in encode_mb_internal() needig an additional 32 lines
+    FF_ALLOCZ_OR_GOTO(s->avctx, s->edge_emu_buffer, alloc_size * 4 * 68,
                       fail);
 
     FF_ALLOCZ_OR_GOTO(s->avctx, s->me.scratchpad, alloc_size * 4 * 16 * 2,

libavcodec/mpegvideo_enc.c

@@ -2024,7 +2024,7 @@ static av_always_inline void encode_mb_internal(MpegEncContext *s,
              (mb_y * mb_block_height * wrap_c) + mb_x * mb_block_width;
 
     if((mb_x * 16 + 16 > s->width || mb_y * 16 + 16 > s->height) && s->codec_id != AV_CODEC_ID_AMV){
-        uint8_t *ebuf = s->edge_emu_buffer + 32;
+        uint8_t *ebuf = s->edge_emu_buffer + 36 * wrap_y;
         int cw = (s->width  + s->chroma_x_shift) >> s->chroma_x_shift;
         int ch = (s->height + s->chroma_y_shift) >> s->chroma_y_shift;
         s->vdsp.emulated_edge_mc(ebuf, ptr_y,