280 lines
9.2 KiB
C++
280 lines
9.2 KiB
C++
/*该程序可以从H.264码流中分析得到它的基本单元NALU，并且可以简单解析NALU首部的字段。通过修改该程序可以实现不同的H.264码流处理功能*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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//0x00000001或0x000001是一个nalu的起始标志，遇到下一个此标志时为该nalu的结尾。
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//起始标志的后面第一个字节（type）里包含有nalu的类型，type & 0x1F即为该nalu的类型（nalu_type）。
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typedef enum {
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NALU_TYPE_SLICE = 1, //非IDR图像中不采用数据划分的片段，为P或B帧
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NALU_TYPE_DPA = 2, //非IDR图像中A类数据划分片段
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NALU_TYPE_DPB = 3, //非IDR图像中B类数据划分片段
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NALU_TYPE_DPC = 4, //非IDR图像中C类数据划分片段
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NALU_TYPE_IDR = 5, //IDR图像的片段，关键帧，I帧
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NALU_TYPE_SEI = 6, //补充增强信息
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NALU_TYPE_SPS = 7, //序列参数集（Sequence Parameter Set）
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NALU_TYPE_PPS = 8, //图像参数集PPS（Picture Parameter Set）
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NALU_TYPE_AUD = 9, //分割符
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NALU_TYPE_EOSEQ = 10, //序列结束符
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NALU_TYPE_EOSTREAM = 11, //流结束符
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NALU_TYPE_FILL = 12, //填充数据
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}NaluType;
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//类型说明参考：http://www.cnblogs.com/lidabo/p/4481601.html
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typedef enum {
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NALU_PRIORITY_DISPOSABLE = 0,
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NALU_PRIORITY_LOW = 1,
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NALU_PRIORITY_HIGH = 2,
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NALU_PRIORITY_HIGHEST = 3,
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}NaluPriority;
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typedef struct
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{
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int startcode_len; //! 起始码长度，3个字节或4个字节
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unsigned len; //! NALU长度，不包括起始码长度
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unsigned max_size; //! Nal Unit Buffer size
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int forbidden_bit; //! should be always FALSE
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//! 禁止位：网络发现NAL单元有比特错误时可设置该比特为1，以便接收方丢掉该单元。
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int nal_reference_idc; //! 表示NAL的优先级。0～3，取值越大，表示当前NAL越重要，需要优先受到保护。
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//! 如果当前NAL是属于参考帧的片，或是序列参数集，或是图像参数集这些重要的单位时，
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//! 本句法元素必需大于0。
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int nalu_type; //! NALU类型
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char *buf; //! contains the first byte followed by the EBSP
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} NALU_t;
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//如果NALU对应的Slice为一帧的开始就用0x00000001（四个字节），否则就用0x000001（三个字节）。
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int findStartCode3(unsigned char *buf)
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{
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if ( buf[0]!=0 || buf[1]!=0 || buf[2]!=1 ) {
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return 0; //0x000001
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} else {
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return 1;
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}
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}
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int findStartCode4(unsigned char *buf)
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{
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if ( buf[0]!=0 || buf[1]!=0 || buf[2]!=0 || buf[3]!=1 ) {
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return 0; //0x00000001
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} else {
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return 1;
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}
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}
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//如果NALU对应的Slice为一帧的开始就用0x00000001(即4个字节长度)，否则就用0x000001(即3个字节长度)。
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int findStartCode(const unsigned char *buf)
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{
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if (strlen((const char*)buf) >= 3) {
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if ( buf[0]==0 && buf[1]==0 && buf[2]==1) {
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return 3;
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}
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}
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if (strlen((const char*)buf) >= 4) {
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if ( buf[0]==0 && buf[1]==0 && buf[2]==0 && buf[3]==1) {
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return 4;
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}
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}
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return 0;
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}
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//获取NALU单元
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int getNalu(NALU_t *nalu, FILE *fp)
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{
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if (nalu == NULL) {
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return -1;
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}
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unsigned char *buf = (unsigned char *)malloc(nalu->max_size);
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if (buf == NULL) {
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return 0;
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} else {
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memset(buf, 0, nalu->max_size);
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}
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//默认起始码长度为3个字节
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nalu->startcode_len = 3;
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//读取前三个字节以判断NALU的起始标志
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//如果fread返回值不等于3，则表示已到文件结尾
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if (3 != fread(buf, 1, 3, fp)) {
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free(buf);
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return 0;
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}
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//获取起始码长度
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int info4 = 0; //4个字节长度的起始码，一帧的开始
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int info3 = 0; //3个字节长度的起始码
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int pos = 0; //当前位置
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//首先查找3字节的起始码
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info3 = findStartCode3(buf);
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if (info3 != 1) {
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//如果不是3字节长度的起始码，就再读取一个字节以判断是否为4字节长度的起始码
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if (1 != fread(buf+3, 1, 1, fp)) {
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free(buf);
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return 0;
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}
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info4 = findStartCode4(buf);
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if (info4 != 1) {
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free(buf);
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return -1;
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} else {
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pos = 4;
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nalu->startcode_len = 4;
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}
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} else {
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pos = 3;
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nalu->startcode_len = 3;
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}
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while (1) {
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//如果文件结束
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if (feof(fp)) {
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nalu->len = (pos-1) - nalu->startcode_len;
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memcpy(nalu->buf, &buf[nalu->startcode_len], nalu->len);
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nalu->forbidden_bit = nalu->buf[0] & 0x80; //1 bit
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nalu->nal_reference_idc = nalu->buf[0] & 0x60; //2 bit
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nalu->nalu_type = nalu->buf[0] & 0x1f; //5 bit
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free(buf);
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return pos-1;
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}
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//循环读取一个字符，为了查找下一个起始码的位置
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buf[pos++] = fgetc(fp);
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//首先查找4字节的起始码
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info4 = findStartCode4(&buf[pos-4]);
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if (info4 != 1) {
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//如果不是4字节的起始码，再判断是否是3字节的起始码
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info3 = findStartCode3(&buf[pos-3]);
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}
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//如果查找到了起始码就退出
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if (info3==1 || info4==1) {
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break;
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}
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}
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//程序能走到这一步表示查找到起始码
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//文件指针往回走3/4个字节，即起始码字节长度
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int rewind = (info4==1) ? -4 : -3;
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if (0 != fseek(fp, rewind, SEEK_CUR)) {
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free(buf);
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}
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//NALU长度不包括起始码长度
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//当前位置减去下一个起始码长度，再减去当前起始码长度
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nalu->len = (pos+rewind) - nalu->startcode_len;
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//NALU内容不包括起始码
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memcpy(nalu->buf, &buf[nalu->startcode_len], nalu->len);
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nalu->forbidden_bit = nalu->buf[0] & 0x80; //1000 0000，禁止位(1bit)
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nalu->nal_reference_idc = nalu->buf[0] & 0x60; //0110 0000，重要性指示位(2bit)
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nalu->nalu_type = nalu->buf[0] & 0x1f; //0001 1111，NALU类型(5bit)
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free(buf);
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//返回NALU长度(包括起始码长度)
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return pos+rewind;
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}
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int h264_parser(char *file)
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{
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if (file == NULL) {
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return 0;
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}
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//从文件中读取h264码流
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FILE *h264BitStream = fopen(file, "rb+");
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if (h264BitStream == NULL) {
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return 0;
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}
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NALU_t *nalu = (NALU_t *)malloc(sizeof(NALU_t));
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if (nalu == NULL) {
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return 0;
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} else {
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memset(nalu, 0, sizeof(NALU_t));
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}
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nalu->max_size = 100000;
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nalu->buf = (char *)malloc(100000);
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if (nalu->buf == NULL) {
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return 0;
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} else {
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memset(nalu->buf, 0, 100000);
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}
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printf("-----+-------- NALU Table ------+---------+\n");
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printf(" NUM | POS | IDC | TYPE | LEN |\n");
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printf("-----+---------+--------+-------+---------+\n");
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int data_offset=0;
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int nal_num=0; //NALU计数
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while(!feof(h264BitStream)) {
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//分析一个NALU，返回NALU长度(包括起始码长度)
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int dataLen = getNalu(nalu, h264BitStream);
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char sType[20] = {0};
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switch(nalu->nalu_type) {
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case NALU_TYPE_SLICE: sprintf(sType, "SLICE"); break;
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case NALU_TYPE_DPA: sprintf(sType, "DPA"); break;
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case NALU_TYPE_DPB: sprintf(sType, "DPB"); break;
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case NALU_TYPE_DPC: sprintf(sType, "DPC"); break;
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case NALU_TYPE_IDR: sprintf(sType, "IDR"); break;
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case NALU_TYPE_SEI: sprintf(sType, "SEI"); break;
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case NALU_TYPE_SPS: sprintf(sType, "SPS"); break;
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case NALU_TYPE_PPS: sprintf(sType, "PPS"); break;
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case NALU_TYPE_AUD: sprintf(sType, "AUD"); break;
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case NALU_TYPE_EOSEQ: sprintf(sType, "EOSEQ"); break;
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case NALU_TYPE_EOSTREAM: sprintf(sType, "EOSTREAM"); break;
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case NALU_TYPE_FILL: sprintf(sType, "FILL"); break;
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}
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char idc_str[20] = {0};
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switch(nalu->nal_reference_idc >> 5) {
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case NALU_PRIORITY_DISPOSABLE:sprintf(idc_str,"DISPOS"); break;
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case NALU_PRIORITY_LOW: sprintf(idc_str,"LOW"); break;
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case NALU_PRIORITY_HIGH: sprintf(idc_str,"HIGH"); break;
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case NALU_PRIORITY_HIGHEST: sprintf(idc_str,"HIGHEST");break;
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}
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FILE *out = stdout;
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fprintf(out,"%5d| %8d| %7s| %6s| %8d|\n",nal_num,data_offset,idc_str,sType,nalu->len);
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//NAL单元计数
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nal_num++;
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//数据偏移，也就是下一个NALU起始位置(起始码的位置)
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data_offset = data_offset + dataLen;
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}
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//释放内存
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if (nalu) {
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if (nalu->buf) {
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free(nalu->buf);
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nalu->buf = NULL;
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}
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free(nalu);
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}
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return 0;
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}
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int main(int argc, char *argv[])
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{
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if (argc == 2) {
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h264_parser(argv[1]);
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}
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return 0;
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}
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