block_last_index was too large (in mpeg1 decoding)

Originally committed as revision 301 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg12.c

@@ -948,7 +948,7 @@ static int mpeg1_decode_block(MpegEncContext *s,
         block[j] = level;
         i++;
     }
-    s->block_last_index[n] = i;
+    s->block_last_index[n] = i-1;
     return 0;
 }