@@ -459,6 +459,11 @@ static int decode_p_frame(FourXContext *f, const uint8_t *buf, int length){

 static int decode_i_block(FourXContext *f, DCTELEM *block){

     int code, i, j, level, val;

+    if(get_bits_left(&f->gb) < 2){

+        av_log(f->avctx, AV_LOG_ERROR, "%d bits left before decode_i_block()\n", get_bits_left(&f->gb));

+        return -1;

+    }

+

     /* DC coef */

     val = get_vlc2(&f->pre_gb, f->pre_vlc.table, ACDC_VLC_BITS, 3);

     if (val>>4){