RV30 decoder passes possible frame sizes in extradata and selects

an appropriate frame size from them in slice, make my decoder do
that as well.

This fixes issue 779



git-svn-id: file:///var/local/repositories/ffmpeg/trunk@16529 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/rv30.c

@@ -38,6 +38,7 @@ static int rv30_parse_slice_header(RV34DecContext *r, GetBitContext *gb, SliceIn
     int mb_bits;
     int w = r->s.width, h = r->s.height;
     int mb_size;
+    int rpr;
 
     memset(si, 0, sizeof(SliceInfo));
     if(get_bits(gb, 3))
@@ -49,9 +50,14 @@ static int rv30_parse_slice_header(RV34DecContext *r, GetBitContext *gb, SliceIn
     si->quant = get_bits(gb, 5);
     skip_bits1(gb);
     si->pts = get_bits(gb, 13);
-    skip_bits(gb, r->rpr);
+    rpr = get_bits(gb, r->rpr);
+    if(!rpr){
         si->width  = w;
         si->height = h;
+    }else{
+        si->width  = r->s.avctx->extradata[6 + rpr*2] << 2;
+        si->height = r->s.avctx->extradata[7 + rpr*2] << 2;
+    }
     mb_size = ((w + 15) >> 4) * ((h + 15) >> 4);
     mb_bits = ff_rv34_get_start_offset(gb, mb_size);
     si->start = get_bits(gb, mb_bits);
@@ -248,6 +254,10 @@ static av_cold int rv30_decode_init(AVCodecContext *avctx)
     }
     r->rpr = (avctx->extradata[1] & 7) >> 1;
     r->rpr = FFMIN(r->rpr + 1, 3);
+    if(avctx->extradata_size - 8 < (r->rpr - 1) * 2){
+        av_log(avctx, AV_LOG_ERROR, "Insufficient extradata - need at least %d bytes, got %d\n",
+               6 + r->rpr * 2, avctx->extradata_size);
+    }
     r->parse_slice_header = rv30_parse_slice_header;
     r->decode_intra_types = rv30_decode_intra_types;
     r->decode_mb_info     = rv30_decode_mb_info;