ZLKMedia/3rdpart/media-server/librtp/payload/rtp-ps-unpack.c

/// RFC2250 2. Encapsulation of MPEG System and Transport Streams (p3)

#include "rtp-packet.h"
#include "rtp-payload-helper.h"
#include "rtp-payload-internal.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>

// Pack start code
static const uint8_t s_mpeg2_packet_start[] =  {0x00, 0x00, 0x01, 0xBA};

static int rtp_decode_ps(void* p, const void* packet, int bytes)
{
    struct rtp_packet_t pkt;
    struct rtp_payload_helper_t *helper;

    helper = (struct rtp_payload_helper_t *)p;
    if (!helper || 0 != rtp_packet_deserialize(&pkt, packet, bytes))
        return -EINVAL;

//    if(-1 == helper->flags)
//    {
//        if(pkt.payloadlen < sizeof(s_mpeg2_packet_start) + 2 || 0 != memcmp(s_mpeg2_packet_start, pkt.payload, sizeof(s_mpeg2_packet_start)))
//           return 0; // packet discard, wait for first packet
//    }

    // 2.1 RTP header usage(p4)
    // M bit: Set to 1 whenever the timestamp is discontinuous. (such as
    // might happen when a sender switches from one data
    // source to another).This allows the receiver and any
    // intervening RTP mixers or translators that are synchronizing
    // to the flow to ignore the difference between this timestamp
    // and any previous timestamp in their clock phase detectors.
//    if (pkt.rtp.m)
//    {
//        //TODO: test
//        // new frame start
//        helper->size = 0; // discard previous packets
//        helper->lost = 0;
//        helper->flags |= RTP_PAYLOAD_FLAG_PACKET_LOST; // notify source changed
//        helper->seq = (uint16_t)pkt.rtp.seq;
//        helper->timestamp = pkt.rtp.timestamp;
//    }
//    else
    {
        rtp_payload_check(helper, &pkt);
    }
    
    // ignore RTP M bit
    if (pkt.payloadlen > sizeof(s_mpeg2_packet_start)  && 0 == memcmp(s_mpeg2_packet_start, pkt.payload, sizeof(s_mpeg2_packet_start)))
        rtp_payload_onframe(helper); // new frame/access start

    rtp_payload_write(helper, &pkt);
    return helper->lost ? 0 : 1; // packet handled
}

struct rtp_payload_decode_t *rtp_ps_decode(void)
{
    static struct rtp_payload_decode_t decode = {
        rtp_payload_helper_create,
        rtp_payload_helper_destroy,
        rtp_decode_ps,
    };

    return &decode;
}