void ff_rtp_send_data(AVFormatContext *s1, const uint8_t *buf1, int len, int m)
{
    RTPMuxContext *s = s1->priv_data;

    av_dlog(s1, "rtp_send_data size=%d\n", len);

    /* build the RTP header */
    avio_w8(s1->pb, RTP_VERSION << 6);
    avio_w8(s1->pb, (s->payload_type & 0x7f) | ((m & 0x01) << 7));
    avio_wb16(s1->pb, s->seq);
    avio_wb32(s1->pb, s->timestamp);
    avio_wb32(s1->pb, s->ssrc);

    avio_write(s1->pb, buf1, len);
    avio_flush(s1->pb);

    s->seq = (s->seq + 1) & 0xffff;
    s->octet_count += len;
    s->packet_count++;
}