libavcodec/fmvc.c:152: error: Uninitialized Value
  The value read from opcode was never initialized.

libavcodec/fmvc.c:152:17: 
150.             if (opcode >= 0x40) {
151.                 bytestream2_skip(gb, 1);
152.                 pos = - ((opcode >> 2) & 7) - 1 - 8 * bytestream2_get_byte(gb);
                     ^
153.                 len =    (opcode >> 5)      - 1;
154. 
