AVInputFormat *avif= s->iformat;
static int av_seek_frame_byte(AVFormatContext *s, int stream_index, int64_t pos, int flags){    AVInputFormat *avif= s->iformat;    int64_t pos_min, pos_max;#if 0    AVStream *st;    if (stream_index < 0)        return -1;    st= s->streams[stream_index];#endif    pos_min = s->data_offset;    pos_max = url_filesize(url_fileno(&s->pb)) - 1;    if     (pos < pos_min) pos= pos_min;    else if(pos > pos_max) pos= pos_max;    url_fseek(&s->pb, pos, SEEK_SET);#if 0    av_update_cur_dts(s, st, ts);#endif    return 0;}