how and where share my codes

Thanks Didier Barvaux, that solved my question.

I only modify a little for my college study,maybe it is not necessary to share.

Tell me what are your modifications. I'll tell you if it is of interest for all.

It is about RTP detection.

That looks interesting ! What did you changed ? Is it the library itself or did you improve the code in the RTP callback?

I modify the code in the RTP callback,it shows as follows:
uint8_t count = 0;
uint32_t ssrc[4] = {0};
static bool rtp_detect_cb(const unsigned char *const ip,
                          const unsigned char *const udp,
                          const unsigned char *const payload,
                          const unsigned int payload_size,
                          void *const rtp_private)
{
 const uint16_t max_well_known_port = 1024;
 const uint16_t sip_port = 5060;
 uint16_t udp_sport;
 uint16_t udp_dport;
 uint16_t udp_len;
 uint8_t rtp_pt;
 uint32_t currentSsrc ;
 bool is_rtp = false;

 assert(ip != NULL);
 assert(udp != NULL);
 assert(payload != NULL);
 assert(rtp_private == NULL);

 /* retrieve UDP source and destination ports and UDP length */
 memcpy(&udp_sport, udp, sizeof(uint16_t));
 memcpy(&udp_dport, udp + 2, sizeof(uint16_t));
 memcpy(&udp_len, udp + 4, sizeof(uint16_t));

 /* RTP streams do not use well known ports */
 if(ntohs(udp_sport) <= max_well_known_port ||
    ntohs(udp_dport) <= max_well_known_port)
 {
  goto not_rtp;
 }

 /* SIP (UDP/5060) is not RTP */
 if(ntohs(udp_sport) == sip_port && ntohs(udp_dport) == sip_port)
 {
  goto not_rtp;
 }

 /* the UDP destination port of RTP packet is even (the RTCP destination
  * port are RTP destination port + 1, so it is odd) */
 if((ntohs(udp_dport) % 2) != 0)
 {
  goto not_rtp;
 }

 /* UDP Length shall not be too large */
 if(ntohs(udp_len) > 200)
 {
  goto not_rtp;
 }

 /* UDP payload shall at least contain the smallest RTP header */
 if(payload_size < 12)
 {
  goto not_rtp;
 }

 /* RTP version bits shall be 2 */
 if(((payload[0] >> 6) & 0x3) != 0x2)
 {
  goto not_rtp;
 }

 /* RTP payload type shall be GSM (0x03), ITU-T G.723 (0x04),
  * ITU-T G.729 (0x12), dynamic RTP type 97 (0x61),
  * telephony-event (0x65), Speex (0x72),
  * or dynamic RTP type 125 (0x7d) */
 rtp_pt = payload[1] & 0x7f;
 if(rtp_pt != 0x03 && rtp_pt != 0x04 && rtp_pt != 0x12 && rtp_pt != 0x61 &&
    rtp_pt != 0x65 && rtp_pt != 0x72 && rtp_pt != 0x7d)
 {
  goto not_rtp;
 }

    memcpy(&currentSsrc, payload + 8, sizeof(uint32_t));
    if(ssrc[0] != ntohl(currentSsrc) || ssrc[1] != ntohl(currentSsrc)||ssrc[2] != ntohl(currentSsrc) || ssrc[3] != ntohl(currentSsrc))
    {
        ssrc[count++ & 0x03] = ntohl(currentSsrc);
        goto not_rtp;
    }
 /* we think that the UDP packet is a RTP packet */
 is_rtp = true;

not_rtp:
 return is_rtp;
}