1..h文件

#ifndef decode_rtp_to_h264_h
#define decode_rtp_to_h264_h



uint8_t* decode_rtp_to_h264(uint8_t *rtp_buf, int len, int* retLength);

#endif

2..m文件

#include <stdio.h>
#include <stdint.h>
#include <string.h>

#include "decode_rtp_to_h264.h"


typedef struct{
    /* byte 0 */
    uint8_t type:   5;  /* bit: 0~4 */
    uint8_t nri:    2;  /* bit: 5~6 */
    uint8_t f:      1;  /* bit: 7 */
} __attribute__ ((packed)) nalu_header_t; /* 1 bytes */

typedef struct{
    /* byte 0 */
    uint8_t type:   5;
    uint8_t r:      1;
    uint8_t e:      1;
    uint8_t s:      1;
} __attribute__ ((packed)) fu_header_t; /* 1 bytes */



static uint8_t h264_buf[1024*1024*10];
static int h264_pos = -1;
uint32_t reversebytes_uint32t(uint32_t value){

  return(value & 0x000000FFU) < ((value & 0x00FF0000U) >> 8 | (value & 0xFF000000U) >> 24);
}
static inline void h264_buf_write(void* data,int length){
    if (h264_pos>=0) {
        memcpy(h264_buf+h264_pos, data, length);
        h264_pos += length;
    }
}

uint8_t* decode_rtp_to_h264(uint8_t *rtp_buf, int len, int* retLength)
{
    int header_len = 12;
    int extension = rtp_buf[0] & (1<<4);
    
    if(extension) {
        uint32_t extLen = *((uint32_t*)(&rtp_buf[12]));
//        uint32_t frameId = *((uint32_t*)(&rtp_buf[16]));
        
        extLen = reversebytes_uint32t(extLen);
//        frameId = CFSwapInt32HostToBig(frameId);
        
        header_len += (extLen+1)*4;
    }
    
    static uint8_t ch0001[] = {0,0,0,1};
    
    nalu_header_t *nalu_header;
    fu_header_t   *fu_header;
    uint8_t h264_nal_header;
    
    nalu_header = (nalu_header_t *)&rtp_buf[header_len];//前12个字节是RTP 头
    
    if (nalu_header->type == 28) { /* FU-A */
        fu_header = (fu_header_t *)&rtp_buf[header_len + 1];
        if (fu_header->e == 1) { /* end of fu-a */ //分片结束
            h264_buf_write(&rtp_buf[header_len + 2],len - (header_len + 2));
            if (h264_pos>=0) {
                *retLength = h264_pos;
                h264_pos = -1;
//                printf("分片结束=======");
                return h264_buf;
            }
        } else if (fu_header->s == 1) { /* start of fu-a */ //分片开始
           
            h264_pos = 0;
            h264_buf_write(ch0001, 4);
            h264_nal_header = (fu_header->type & 0x1f)
            | (nalu_header->nri << 5)
            | (nalu_header->f << 7);
            h264_buf_write(&h264_nal_header,1);
//            printf("分片开始=======%d",h264_nal_header);
            h264_buf_write(&rtp_buf[header_len + 2], len - (header_len + 2));
        } else { /* middle of fu-a */
            h264_buf_write(&rtp_buf[header_len + 2], len - (header_len + 2));
//            printf("分片中=======");
        }
    } else { /* nalu */
        h264_pos = 0;
        h264_buf_write(ch0001, 4);
        h264_nal_header = (nalu_header->type & 0x1f)
        | (nalu_header->nri << 5)
        | (nalu_header->f << 7);
        h264_buf_write(&h264_nal_header,1);
//        printf("单包=======%d",h264_nal_header);
        h264_buf_write(&rtp_buf[header_len + 1], len - (header_len + 1));
        if (h264_pos>=0) {
            *retLength = h264_pos;
            h264_pos = -1;
            return h264_buf;
        }
    }
    
    return NULL;
}