// RFC3640 RTP Payload Format for Transport of MPEG-4 Elementary Streams

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

static int rtp_decode_mpeg4_generic(void *p, const void *packet, int bytes)
{
    int i, size;
    int au_size;
    int au_numbers;
    int au_header_length;
    const uint8_t *ptr, *pau, *pend;
    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) || pkt.payloadlen < 4)
        return -EINVAL;

    rtp_payload_check(helper, &pkt);

    // save payload
    ptr = (const uint8_t *)pkt.payload;
    pend = ptr + pkt.payloadlen;

    // AU-headers-length
    au_header_length = (ptr[0] << 8) + ptr[1];
    au_header_length = (au_header_length + 7) / 8; // bit -> byte

    if (ptr + au_header_length /*AU-size*/ > pend || au_header_length < 2) {
        assert(0);
        // helper->size = 0;
        helper->lost = 1;
        // helper->flags |= RTP_PAYLOAD_FLAG_PACKET_LOST;
        return -1; // invalid packet
    }

    // 3.3.6. High Bit-rate AAC
    // SDP fmtp: sizeLength=13; indexLength=3; indexDeltaLength=3;
    au_size = 2; // only AU-size
    au_numbers = au_header_length / au_size;
    assert(0 == au_header_length % au_size);
    ptr += 2;                     // skip AU headers length section 2-bytes
    pau = ptr + au_header_length; // point to Access Unit

    for (i = 0; i < au_numbers; i++) {
        size = (ptr[0] << 8) | (ptr[1] & 0xF8);
        size = size >> 3; // bit -> byte
        if (pau + size > pend) {
            // fragment ?
            assert(1 == au_numbers);
            pkt.payload = pau;
            pkt.payloadlen = size;
            rtp_payload_write(helper, &pkt);
            return 1;
        }

        // TODO: add ADTS/ASC ???
        pkt.payload = pau;
        pkt.payloadlen = size;
        rtp_payload_write(helper, &pkt);

        ptr += au_size;
        pau += size;

        if (au_numbers > 1 || pkt.rtp.m) {
            if (helper->size != size) {
                // helper->size = 0;
                helper->lost = 1;
                // helper->flags |= RTP_PAYLOAD_FLAG_PACKET_LOST;
            }
            rtp_payload_onframe(helper);
        }
    }

    return helper->lost ? 0 : 1; // packet handled
}

struct rtp_payload_decode_t *rtp_mpeg4_generic_decode()
{
    static struct rtp_payload_decode_t unpacker = {
        rtp_payload_helper_create,
        rtp_payload_helper_destroy,
        rtp_decode_mpeg4_generic,
    };

    return &unpacker;
}