转载: http://blog.csdn.net/leixiaohua1020/article/details/50534369
本文介绍的程序是视频码流处理程序。视频码流在视频播放器中的位置如下所示。
本文中的程序是一个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,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。
H.264原始码流(又称为“裸流”)是由一个一个的NALU组成的。他们的结构如下图所示。
其中每个NALU之间通过startcode(起始码)进行分隔,起始码分成两种:0x000001(3Byte)或者0x00000001(4Byte)。如果NALU对应的Slice为一帧的开始就用0x00000001,否则就用0x000001。
H.264码流解析的步骤就是首先从码流中搜索0x000001和0x00000001,分离出NALU;然后再分析NALU的各个字段。本文的程序即实现了上述的两个步骤。
关于nal_unit_type可以参考: http://www.cnblogs.com/pengdonglin137/p/5262114.html
#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 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 } NALU_t; FILE *h264bitstream = NULL; //!< the bit stream file int 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); //printf("Buf[0] = 0x%x\n", Buf[0]); 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 (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 file rewind = (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 code nalu->len = (pos+rewind)-nalu->startcodeprefix_len; memcpy (nalu->buf, &Buf[nalu->startcodeprefix_len], nalu->len);// //printf("nalu->buf[0] = 0x%x\n", nalu->buf[0]); 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); } /** * Analysis H.264 Bitstream * @param url Location of input H.264 bitstream file. */ int simplest_h264_parser(char *url){ NALU_t *n; 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++; } //Free if (n){ if (n->buf){ free(n->buf); n->buf=NULL; } free (n); } return 0; } int main(int argc, char *argv[]) { if (argc != 2 ) { printf("Usage: %s <h264 bitstream>\n", argv[0]); return -1; } if (simplest_h264_parser(argv[1]) == 0) { printf("Over.\n"); return 0; } else { printf("Error.\n"); return -1; } }
本程序的输入为一个H.264原始码流(裸流)的文件路径,输出为该码流的NALU统计数据,如下图所示。
pengdl@pengdl-HP:~/work/study/video/demo$ ./demo foreman_CIF_10.h264 -----+-------- NALU Table ------+---------+ NUM | POS | IDC | TYPE | LEN | -----+---------+--------+-------+---------+ 0| 0| LOW| SPS| 24| 1| 28| LOW| PPS| 4| 2| 36| LOW| IDR| 3700| 3| 3740| LOW| SLICE| 308| 4| 4052| LOW| SLICE| 459| 5| 4515| LOW| SLICE| 380| 6| 4899| LOW| SLICE| 611| 7| 5514| LOW| SLICE| 434| 8| 5952| LOW| SLICE| 456| 9| 6412| LOW| SLICE| 478| 10| 6894| LOW| SLICE| 496| 11| 7394| LOW| SLICE| 422| 12| 7820| LOW| SLICE| 831| 13| 8655| LOW| SLICE| 141| 14| 8800| LOW| SLICE| 275| 15| 9079| LOW| SLICE| 262| 16| 9345| LOW| SLICE| 403| 17| 9752| LOW| SLICE| 333| 18| 10089| LOW| SLICE| 298| 19| 10391| LOW| SLICE| 356| 20| 10751| LOW| SLICE| 322| 21| 11077| LOW| SLICE| 390| Over.
完。