extern inline int av_log2(unsigned int v)
static inline int av_log2(unsigned int v)
extern inline int av_log2(unsigned int v){    int n;    n = 0;    if (v & 0xffff0000) {        v >>= 16;        n += 16;    }    if (v & 0xff00) {        v >>= 8;        n += 8;    }    if (v & 0xf0) {        v >>= 4;        n += 4;    }    if (v & 0xc) {        v >>= 2;        n += 2;    }    if (v & 0x2) {        n++;    }    return n;}