s->first_rtcp_ntp_time = AV_NOPTS_VALUE;
static int rtp_read_header(AVFormatContext *s1,                           AVFormatParameters *ap){    RTPContext *s = s1->priv_data;    s->payload_type = -1;    s->last_rtcp_ntp_time = AV_NOPTS_VALUE;    return 0;}