@@ -58,7 +58,8 @@ static int vp5_parse_header(VP56Context *s, const uint8_t *buf, int buf_size,

         vp56_rac_gets(c, 8);  /* number of displayed macroblock rows */

         vp56_rac_gets(c, 8);  /* number of displayed macroblock cols */

         vp56_rac_gets(c, 2);

-        if (16*cols != s->avctx->coded_width ||

+        if (!s->macroblocks || /* first frame */

+            16*cols != s->avctx->coded_width ||

             16*rows != s->avctx->coded_height) {

             avcodec_set_dimensions(s->avctx, 16*cols, 16*rows);

             return 2;

@@ -657,8 +657,6 @@ av_cold void vp56_init(AVCodecContext *avctx, int flip, int has_alpha)

     dsputil_init(&s->dsp, avctx);

     ff_init_scantable(s->dsp.idct_permutation, &s->scantable,ff_zigzag_direct);

-    avcodec_set_dimensions(avctx, 0, 0);

-

     for (i=0; i<4; i++)

         s->framep[i] = &s->frames[i];

     s->framep[VP56_FRAME_UNUSED] = s->framep[VP56_FRAME_GOLDEN];

@@ -75,7 +75,8 @@ static int vp6_parse_header(VP56Context *s, const uint8_t *buf, int buf_size,

         /* buf[4] is number of displayed macroblock rows */

         /* buf[5] is number of displayed macroblock cols */

-        if (16*cols != s->avctx->coded_width ||

+        if (!s->macroblocks || /* first frame */

+            16*cols != s->avctx->coded_width ||

             16*rows != s->avctx->coded_height) {

             avcodec_set_dimensions(s->avctx, 16*cols, 16*rows);

             if (s->avctx->extradata_size == 1) {