libavcodec/fmvc.c:222: error: Uninitialized Value
  The value read from opcode was never initialized.

libavcodec/fmvc.c:222:13: 
220.         bytestream2_skip(gb, 1);
221.         if (opcode < 0x10) {
222.             pos = -(opcode >> 2) - 1 - 4 * bytestream2_get_byte(gb);
                 ^
223. 
224.             bytestream2_init(&gbc, pb->buffer_start, pb->buffer_end - pb->buffer_start);
