H264文件解析出nalu数据，送给ffmpeg解码，opencv显示

本博客主要是H264的视频码流有ffmpeg 解码后，有opencv先，这里贴出全部代码，你只需自己建个工程，配置一下ffmpeg库和opencv3.0库就好了。(这里采用自己打开h264文件，解析出来每个nalu数据，把每一个nalu数据送给ffmpeg库，解码出yuv,然后把yuv转成BGR格式，用opencv显示出来）

头文件 H264.h

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <string.h>
#include <winsock2.h>
typedef struct
{
int startcodeprefix_len;      //! 4 for parameter sets and first slice in picture, 3 for everything else (suggested)
unsigned len;                 //! Length of the NAL unit (Excluding the start code, which does not belong to the NALU)
unsigned max_size;            //! Nal Unit Buffer size
int forbidden_bit;            //! should be always FALSE
int nal_reference_idc;        //! NALU_PRIORITY_xxxx
int nal_unit_type;            //! NALU_TYPE_xxxx
char *buf;                    //! contains the first byte followed by the EBSP
unsigned short lost_packets;  //! true, if packet loss is detected
} NALU_t;
int GetNalu();
void FreeNALU(NALU_t *n);
NALU_t *AllocNALU(int buffersize);
void OpenBitstreamFile(char *fn);
int GetAnnexbNALU(NALU_t *nalu);
void dump(NALU_t *nal);
int DumpChar(char * filename, char * buf, int len);
FILE * getFile();

H264.cpp

// rtspSend.cpp : Defines the entry point for the console application.
//

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <memory.h>
#include "h264.h"
static char* dumpRoot = ".\\dump\\";
static char file2open[1024];
#define  UDP_MAX_SIZE 1400

FILE *bits = NULL;                //!< the bit stream file
static int FindStartCode2(unsigned char *Buf);//查找开始字符0x000001
static int FindStartCode3(unsigned char *Buf);//查找开始字符0x00000001

//
static int info2=0, info3=0;
// RTP_FIXED_HEADER *rtp_hdr;

// NALU_HEADER      *nalu_hdr;
// FU_INDICATOR *fu_ind;
// FU_HEADER        *fu_hdr;

FILE * getFile()
{
return bits;
}

//为NALU_t结构体分配内存空间
NALU_t *AllocNALU(int buffersize)
{
NALU_t *nal =NULL;

if ((nal = (NALU_t*)calloc (1, sizeof (NALU_t))) == NULL)
{
printf("AllocNALU: n");
exit(0);
}

nal->max_size=buffersize;

if ((nal->buf = (char*)calloc (buffersize, sizeof (char))) == NULL)
{
free (nal);
printf ("AllocNALU: nal->buf");
exit(0);
}

return nal;
}

//释放
void FreeNALU(NALU_t *n)
{
if (n)
{
if (n->buf)
{
free(n->buf);
n->buf=NULL;
}
free (n);
}
}

void OpenBitstreamFile (char *fn)
{
if (NULL == (bits=fopen(fn, "rb")))
{
printf("open file error\n");
exit(0);
}
}

//这个函数输入为一个NAL结构体，主要功能为得到一个完整的NALU并保存在NALU_t的buf中，
//获取他的长度，填充F,IDC,TYPE位。
//并且返回两个开始字符之间间隔的字节数，即包含有前缀的NALU的长度
int GetAnnexbNALU (NALU_t *nalu)
{
int pos = 0;
int StartCodeFound, rewind;
unsigned char *Buf;

if ((Buf = (unsigned char*)calloc (nalu->max_size , sizeof(char))) == NULL)
printf ("GetAnnexbNALU: Could not allocate Buf memory\n");

nalu->startcodeprefix_len=3;//初始化码流序列的开始字符为3个字节

if (3 != fread (Buf, 1, 3, bits))//从码流中读3个字节
{
free(Buf);
return 0;
}
info2 = FindStartCode2 (Buf);//判断是否为0x000001
if(info2 != 1)
{
//如果不是，再读一个字节
if(1 != fread(Buf+3, 1, 1, bits))//读一个字节
{
free(Buf);
return 0;
}
info3 = FindStartCode3 (Buf);//判断是否为0x00000001
if (info3 != 1)//如果不是，返回-1
{
free(Buf);
return -1;
}
else
{
//如果是0x00000001,得到开始前缀为4个字节
pos = 4;
nalu->startcodeprefix_len = 4;
}
}
else
{
//如果是0x000001,得到开始前缀为3个字节
nalu->startcodeprefix_len = 3;
pos = 3;
}
//查找下一个开始字符的标志位
StartCodeFound = 0;
info2 = 0;
info3 = 0;

while (!StartCodeFound)
{
if (feof (bits))//判断是否到了文件尾
{
nalu->len = (pos-1)-nalu->startcodeprefix_len;
memcpy (nalu->buf, &Buf[nalu->startcodeprefix_len], nalu->len);
nalu->forbidden_bit = nalu->buf[0] & 0x80; //1 bit
nalu->nal_reference_idc = nalu->buf[0] & 0x60; // 2 bit
nalu->nal_unit_type = (nalu->buf[0]) & 0x1f;// 5 bit
free(Buf);
return pos-1;
}
Buf[pos++] = fgetc (bits);//读一个字节到BUF中
info3 = FindStartCode3(&Buf[pos-4]);//判断是否为0x00000001
if(info3 != 1)
info2 = FindStartCode2(&Buf[pos-3]);//判断是否为0x000001
StartCodeFound = (info2 == 1 || info3 == 1);
}

// Here, we have found another start code (and read length of startcode bytes more than we should
// have.  Hence, go back in the file
rewind = (info3 == 1)? -4 : -3;

if (0 != fseek (bits, rewind, SEEK_CUR))//把文件指针指向前一个NALU的末尾
{
free(Buf);
printf("GetAnnexbNALU: Cannot fseek in the bit stream file");
}

// Here the Start code, the complete NALU, and the next start code is in the Buf.
// The size of Buf is pos, pos+rewind are the number of bytes excluding the next
// start code, and (pos+rewind)-startcodeprefix_len is the size of the NALU excluding the start code

nalu->len = (pos+rewind)-nalu->startcodeprefix_len;
memcpy (nalu->buf, &Buf[nalu->startcodeprefix_len], nalu->len);//拷贝一个完整NALU，不拷贝起始前缀0x000001或0x00000001
nalu->forbidden_bit = nalu->buf[0] & 0x80;      //1 bit
nalu->nal_reference_idc = nalu->buf[0] & 0x60;  //2 bit
nalu->nal_unit_type = (nalu->buf[0]) & 0x1f;    //5 bit
free(Buf);

return (pos+rewind);//返回两个开始字符之间间隔的字节数，即包含有前缀的NALU的长度
}

static int FindStartCode2 (unsigned char *Buf)
{
if(Buf[0]!=0 || Buf[1]!=0 || Buf[2] !=1)
return 0; //判断是否为0x000001,如果是返回1
else
return 1;
}

static int FindStartCode3 (unsigned char *Buf)
{
if(Buf[0]!=0 || Buf[1]!=0 || Buf[2] !=0 || Buf[3] !=1)
return 0;//判断是否为0x00000001,如果是返回1
else
return 1;
}

int rtpnum = 0;

//输出NALU长度和TYPE
void dump(NALU_t *nal)
{
if (!nal)
return;
printf("%3d, len: %6d  ",rtpnum++, nal->len);
printf("nal_unit_type: %x\n", nal->nal_unit_type);
}

int DumpChar(char * filename, char * buf, int len)
{
FILE* file;
int w, h;
unsigned char * temp = (unsigned char *)buf;
sprintf(file2open, "%s%s", dumpRoot, filename);
int mHeight = 0;
int mWidth = 100;
int mYu = 0;
mHeight = len / 100;
mYu = len % 100;
file = fopen(file2open, "w+");
for (h = 0; h < mHeight; h++)
{
for (w = 0; w < mWidth - 1; w++)
{
fprintf_s(file, "%3x,", temp[h * mWidth + w]);
}
fprintf_s(file, "%3x\n", temp[h * mWidth + w]);
}

for (w = 0; w < mYu - 1; w++)
{
fprintf_s(file, "%3x,", temp[h * mWidth + w]);
}
fprintf_s(file, "%3x\n", temp[h * mWidth + w]);
fclose(file);
return 0;
}

main.cpp

#include "H264.h"
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/avutil.h"
};
#include "opencv2/opencv.hpp"

AVCodec         *pCodec = NULL;
AVCodecContext  *pCodecCtx = NULL;
SwsContext      *img_convert_ctx = NULL;
AVFrame         *pFrame = NULL;
AVFrame         *pFrameBGR = NULL;

int H264_Init(void)
{
/* register all the codecs */
avcodec_register_all();

/* find the h264 video decoder */
pCodec = avcodec_find_decoder(CODEC_ID_H264);
if (!pCodec) {
fprintf(stderr, "codec not found\n");
}
pCodecCtx = avcodec_alloc_context3(pCodec);

//初始化参数，下面的参数应该由具体的业务决定
//pCodecCtx->time_base.num = 1;
//pCodecCtx->frame_number = 1; //每包一个视频帧
//pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
//pCodecCtx->bit_rate = 0;
//pCodecCtx->time_base.den = 30;//帧率
//pCodecCtx->width = 960;//视频宽
//pCodecCtx->height = 544;//视频高

/* open the coderc */
if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
fprintf(stderr, "could not open codec\n");
}
// Allocate video frame
pFrame = avcodec_alloc_frame();
if (pFrame == NULL)
return -1;
// Allocate an AVFrame structure
pFrameBGR = avcodec_alloc_frame();
if (pFrameBGR == NULL)
return -1;
return 0;

}

static int dumpCount = 0;
static int first = 0;
static uint8_t *out_buffer = NULL;
int H264_2_RGB(char *inputbuf, int frame_size, unsigned char *outputbuf, unsigned int*outsize)
{

int             decode_size;
int             numBytes;
int             av_result;
uint8_t         *buffer = NULL;

printf("Video decoding\n");
int ret, got_picture;
AVPacket packet;
av_init_packet(&packet);
packet.size = frame_size;
packet.data = (uint8_t *)inputbuf;

ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, &packet);
if (ret < 0)
{
printf("Decode Error. ret = %d（解码错误）\n", ret);
return -1;
}

if (first == 0)
{
out_buffer = (uint8_t *)av_malloc(avpicture_get_size(AV_PIX_FMT_BGR24, pCodecCtx->width, pCodecCtx->height));
avpicture_fill((AVPicture *)pFrameBGR, out_buffer, AV_PIX_FMT_BGR24, pCodecCtx->width, pCodecCtx->height);

first = 1;
}

struct SwsContext *img_convert_ctx;
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_BGR24, SWS_BICUBIC, NULL, NULL, NULL);

sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameBGR->data, pFrameBGR->linesize);

memcpy(outputbuf, pFrameBGR->data[0], pCodecCtx->width * pCodecCtx->height * 3);
*outsize = pCodecCtx->width * pCodecCtx->height * 3;

return 0;
}

void H264_Release(void)
{
avcodec_close(pCodecCtx);
av_free(pCodecCtx);
av_free(pFrame);
av_free(pFrameBGR);
}
int main(int argc, char* argv[])
{
OpenBitstreamFile("./x264.h264");
NALU_t *nal;
char fName[300];
int Frame = 0;
nal = AllocNALU(8000000);//为结构体nalu_t及其成员buf分配空间。返回值为指向nalu_t存储空间的指针

H264_Init();

unsigned char *outputbuf = (unsigned char *)calloc(1000 * 1000, sizeof(char));
unsigned int outsize = 0;

unsigned char *m_pData = (unsigned char *)calloc(1000 * 1000, sizeof(char));

int sizeHeBing = 0;
while (!feof(getFile()))
{
GetAnnexbNALU(nal);//每执行一次，文件的指针指向本次找到的NALU的末尾，
//下一个位置即为下个NALU的起始码0x000001
dump(nal);//输出NALU长度和TYPE

sprintf(fName, "dump[Len=%d][%d].txt", nal->len, Frame);

memset(m_pData, 0, 4);
m_pData[3] = 1;
memcpy(m_pData + 4, nal->buf, nal->len);
sizeHeBing = nal->len + 4;
Frame++;

int ret = H264_2_RGB((char *)m_pData, sizeHeBing, outputbuf, &outsize);
if(ret != 0)
continue;

cv::Mat  image = cv::Mat(pCodecCtx->height, pCodecCtx->width, CV_8UC3);

memcpy(image.data, outputbuf, pCodecCtx->height * pCodecCtx->width * 3);

cv::imshow("xxx", image);

cv::waitKey(40);

//DumpChar(fName, nal->buf, nal->len);

//Sleep(33);
}

FreeNALU(nal);
return 0;
}