VLC *dc_vlc;
static inline int decode_dc(MJpegDecodeContext *s, int dc_index){    VLC *dc_vlc;    int code, diff;    dc_vlc = &s->vlcs[0][dc_index];    code = get_vlc(&s->gb, dc_vlc);    if (code < 0)        return 0xffff;    if (code == 0) {        diff = 0;    } else {        diff = get_bits(&s->gb, code);        if ((diff & (1 << (code - 1))) == 0)             diff = (-1 << code) | (diff + 1);    }    return diff;}