avcodec/ffv1dec: Fix AC_GOLOMB_RICE min size check

Found-by: mkver

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/ffv1dec.c

@@ -884,9 +884,13 @@ static int decode_frame(AVCodecContext *avctx, AVFrame *rframe,
             return AVERROR_INVALIDDATA;
     } else {
         int w = avctx->width;
-        for (int i = 0; w > (1<<ff_log2_run[i]); i++)
+        int s = 1 + w / (1<<23);
+
+        w /= s;
+
+        for (i = 0; w > (1<<ff_log2_run[i]); i++)
             w -= ff_log2_run[i];
-        if (buf_size < (avctx->height + i + 6)/ 8)
+        if (buf_size < (avctx->height + i + 6) / 8 * s)
             return AVERROR_INVALIDDATA;
     }