声明：此篇示例源码非原创，原作者雷霄骅。雷霄骅，中国传媒大学通信与信息系统专业博士生，在此向雷霄骅雷神致敬。
代码原文地址：视音频数据处理入门：H.264视频码流解析

一、前言

示例源码是一个H.264码流解析程序。该程序可以从H.264码流中分析得到它的基本单元NALU，分离出NALU，然后再分析NALU的各个字段。

关于NALU的相关内容可参考文章【H.264】H.264详解（一）—— 一文看懂H.264协议

二、示例源码

【1】目录结构

project/
├── Makefile
├── h264parser.c
├── sintel.h264

【2】Makefile源码

app:h264parser.cgcc -o app h264parser.c
clean:rm -f app

【3】h264parser.c源码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>typedef enum {NALU_TYPE_SLICE    = 1,NALU_TYPE_DPA      = 2,NALU_TYPE_DPB      = 3,NALU_TYPE_DPC      = 4,NALU_TYPE_IDR      = 5,NALU_TYPE_SEI      = 6,NALU_TYPE_SPS      = 7,NALU_TYPE_PPS      = 8,NALU_TYPE_AUD      = 9,NALU_TYPE_EOSEQ    = 10,NALU_TYPE_EOSTREAM = 11,NALU_TYPE_FILL     = 12,
} NaluType;typedef enum {NALU_PRIORITY_DISPOSABLE = 0,NALU_PRIRITY_LOW         = 1,NALU_PRIORITY_HIGH       = 2,NALU_PRIORITY_HIGHEST    = 3
} NaluPriority;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 sizeint forbidden_bit;            //! should be always FALSEint nal_reference_idc;        //! NALU_PRIORITY_xxxxint nal_unit_type;            //! NALU_TYPE_xxxx    char *buf;                    //! contains the first byte followed by the EBSP
} NALU_t;FILE *h264bitstream = NULL;                //!< the bit stream fileint info2=0, info3=0;static int FindStartCode2 (unsigned char *Buf){if(Buf[0]!=0 || Buf[1]!=0 || Buf[2] !=1) return 0; //0x000001?else return 1;
}static int FindStartCode3 (unsigned char *Buf){if(Buf[0]!=0 || Buf[1]!=0 || Buf[2] !=0 || Buf[3] !=1) return 0;//0x00000001?else return 1;
}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;if (3 != fread (Buf, 1, 3, h264bitstream)){free(Buf);return 0;}info2 = FindStartCode2 (Buf);if(info2 != 1) {if(1 != fread(Buf+3, 1, 1, h264bitstream)){free(Buf);return 0;}info3 = FindStartCode3 (Buf);if (info3 != 1){ free(Buf);return -1;}else {pos = 4;nalu->startcodeprefix_len = 4;}}else{nalu->startcodeprefix_len = 3;pos = 3;}StartCodeFound = 0;info2 = 0;info3 = 0;while (!StartCodeFound){if (feof (h264bitstream)){nalu->len = (pos-1)-nalu->startcodeprefix_len;memcpy (nalu->buf, &Buf[nalu->startcodeprefix_len], nalu->len);     nalu->forbidden_bit = nalu->buf[0] & 0x80; //1 bitnalu->nal_reference_idc = nalu->buf[0] & 0x60; // 2 bitnalu->nal_unit_type = (nalu->buf[0]) & 0x1f;// 5 bitfree(Buf);return pos-1;}Buf[pos++] = fgetc (h264bitstream);info3 = FindStartCode3(&Buf[pos-4]);if(info3 != 1)info2 = FindStartCode2(&Buf[pos-3]);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 filerewind = (info3 == 1)? -4 : -3;if (0 != fseek (h264bitstream, rewind, SEEK_CUR)){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 codenalu->len = (pos+rewind)-nalu->startcodeprefix_len;memcpy (nalu->buf, &Buf[nalu->startcodeprefix_len], nalu->len);//nalu->forbidden_bit = nalu->buf[0] & 0x80; //1 bitnalu->nal_reference_idc = nalu->buf[0] & 0x60; // 2 bitnalu->nal_unit_type = (nalu->buf[0]) & 0x1f;// 5 bitfree(Buf);return (pos+rewind);
}/*** Analysis H.264 Bitstream* @param url    Location of input H.264 bitstream file.*/
int simplest_h264_parser(char *url){NALU_t *n = NULL;int buffersize=100000;//FILE *myout=fopen("output_log.txt","wb+");FILE *myout=stdout;h264bitstream=fopen(url, "rb+");if (h264bitstream==NULL){printf("Open file error\n");return 0;}n = (NALU_t*)calloc (1, sizeof(NALU_t));if (n == NULL){printf("Alloc NALU Error\n");return 0;}n->max_size=buffersize;n->buf = (char*)calloc (buffersize, sizeof(char));if (n->buf == NULL){free (n);printf ("AllocNALU: n->buf");return 0;}int data_offset=0;int nal_num=0;printf("-----+-------- NALU Table ------+---------+\n");printf(" NUM |   POS   |   IDC  |  TYPE |   LEN   |\n");printf("-----+---------+--------+-------+---------+\n");while(!feof(h264bitstream)){int data_lenth;data_lenth=GetAnnexbNALU(n);char type_str[20]={0};switch(n->nal_unit_type){case NALU_TYPE_SLICE:sprintf(type_str,"SLICE");break;case NALU_TYPE_DPA:sprintf(type_str,"DPA");break;case NALU_TYPE_DPB:sprintf(type_str,"DPB");break;case NALU_TYPE_DPC:sprintf(type_str,"DPC");break;case NALU_TYPE_IDR:sprintf(type_str,"IDR");break;case NALU_TYPE_SEI:sprintf(type_str,"SEI");break;case NALU_TYPE_SPS:sprintf(type_str,"SPS");break;case NALU_TYPE_PPS:sprintf(type_str,"PPS");break;case NALU_TYPE_AUD:sprintf(type_str,"AUD");break;case NALU_TYPE_EOSEQ:sprintf(type_str,"EOSEQ");break;case NALU_TYPE_EOSTREAM:sprintf(type_str,"EOSTREAM");break;case NALU_TYPE_FILL:sprintf(type_str,"FILL");break;}char idc_str[20]={0};switch(n->nal_reference_idc>>5){case NALU_PRIORITY_DISPOSABLE:sprintf(idc_str,"DISPOS");break;case NALU_PRIRITY_LOW:sprintf(idc_str,"LOW");break;case NALU_PRIORITY_HIGH:sprintf(idc_str,"HIGH");break;case NALU_PRIORITY_HIGHEST:sprintf(idc_str,"HIGHEST");break;}fprintf(myout,"%5d| %8d| %7s| %6s| %8d|\n",nal_num,data_offset,idc_str,type_str,n->len);data_offset=data_offset+data_lenth;nal_num++;}//Freeif (n){if (n->buf){free(n->buf);n->buf=NULL;}free (n);}return 0;
}int main(int argc, char* argv[]){simplest_h264_parser("sintel.h264");return 0;
}

【4】编译运行

【5】源码下载地址

H.264详解（二）- H264视频码流解析示例源码