avcodec/rv30: fix switching back to the original resolution

Fixes part of Ticket1388
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/rv30.c

@@ -67,6 +67,9 @@ static int rv30_parse_slice_header(RV34DecContext *r, GetBitContext *gb, SliceIn
 
         w = r->s.avctx->extradata[6 + rpr*2] << 2;
         h = r->s.avctx->extradata[7 + rpr*2] << 2;
+    } else {
+        w = r->orig_width;
+        h = r->orig_height;
     }
     si->width  = w;
     si->height = h;
@@ -259,6 +262,9 @@ static av_cold int rv30_decode_init(AVCodecContext *avctx)
     RV34DecContext *r = avctx->priv_data;
     int ret;
 
+    r->orig_width  = avctx->coded_width;
+    r->orig_height = avctx->coded_height;
+
     if (avctx->extradata_size < 2) {
         av_log(avctx, AV_LOG_ERROR, "Extradata is too small.\n");
         return AVERROR(EINVAL);

libavcodec/rv34.h

@@ -109,6 +109,8 @@ typedef struct RV34DecContext{
     int weight1, weight2;    ///< B frame distance fractions (0.14) used in motion compensation
     int mv_weight1, mv_weight2;
 
+    int orig_width, orig_height;
+
     uint16_t *cbp_luma;      ///< CBP values for luma subblocks
     uint8_t  *cbp_chroma;    ///< CBP values for chroma subblocks
     uint16_t *deblock_coefs; ///< deblock coefficients for each macroblock