視音訊資料處理入門：FLV封裝格式解析
阿新 • • 發佈：2019-02-19
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視音訊資料處理入門系列文章：
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前兩篇文章介紹了音訊碼流處理程式和視訊碼流處理程式，本文介紹將他們打包到一起後的資料——封裝格式資料的處理程式。封裝格式資料在視訊播放器中的位置如下所示。
原理
FLV封裝格式是由一個FLV Header檔案頭和一個一個的Tag組成的。Tag中包含了音訊資料以及視訊資料。FLV的結構如下圖所示。
程式碼
整個程式位於simplest_flv_parser()函式中，如下所示。/** * 最簡單的視音訊資料處理示例 * Simplest MediaData Test * * 雷霄驊 Lei Xiaohua * [email protected] * 中國傳媒大學/數字電視技術 * Communication University of China / Digital TV Technology * http://blog.csdn.net/leixiaohua1020 * * 本專案包含如下幾種視音訊測試示例： * (1)畫素資料處理程式。包含RGB和YUV畫素格式處理的函式。 * (2)音訊取樣資料處理程式。包含PCM音訊取樣格式處理的函式。 * (3)H.264碼流分析程式。可以分離並解析NALU。 * (4)AAC碼流分析程式。可以分離並解析ADTS幀。 * (5)FLV封裝格式分析程式。可以將FLV中的MP3音訊碼流分離出來。 * (6)UDP-RTP協議分析程式。可以將分析UDP/RTP/MPEG-TS資料包。 * * This project contains following samples to handling multimedia data: * (1) Video pixel data handling program. It contains several examples to handle RGB and YUV data. * (2) Audio sample data handling program. It contains several examples to handle PCM data. * (3) H.264 stream analysis program. It can parse H.264 bitstream and analysis NALU of stream. * (4) AAC stream analysis program. It can parse AAC bitstream and analysis ADTS frame of stream. * (5) FLV format analysis program. It can analysis FLV file and extract MP3 audio stream. * (6) UDP-RTP protocol analysis program. It can analysis UDP/RTP/MPEG-TS Packet. * */ #include <stdio.h> #include <stdlib.h> #include <string.h> //Important! #pragma pack(1) #define TAG_TYPE_SCRIPT 18 #define TAG_TYPE_AUDIO 8 #define TAG_TYPE_VIDEO 9 typedef unsigned char byte; typedef unsigned int uint; typedef struct { byte Signature[3]; byte Version; byte Flags; uint DataOffset; } FLV_HEADER; typedef struct { byte TagType; byte DataSize[3]; byte Timestamp[3]; uint Reserved; } TAG_HEADER; //reverse_bytes - turn a BigEndian byte array into a LittleEndian integer uint reverse_bytes(byte *p, char c) { int r = 0; int i; for (i=0; i<c; i++) r |= ( *(p+i) << (((c-1)*8)-8*i)); return r; } /** * Analysis FLV file * @param url Location of input FLV file. */ int simplest_flv_parser(char *url){ //whether output audio/video stream int output_a=1; int output_v=1; //------------- FILE *ifh=NULL,*vfh=NULL, *afh = NULL; //FILE *myout=fopen("output_log.txt","wb+"); FILE *myout=stdout; FLV_HEADER flv; TAG_HEADER tagheader; uint previoustagsize, previoustagsize_z=0; uint ts=0, ts_new=0; ifh = fopen(url, "rb+"); if ( ifh== NULL) { printf("Failed to open files!"); return -1; } //FLV file header fread((char *)&flv,1,sizeof(FLV_HEADER),ifh); fprintf(myout,"============== FLV Header ==============\n"); fprintf(myout,"Signature: 0x %c %c %c\n",flv.Signature[0],flv.Signature[1],flv.Signature[2]); fprintf(myout,"Version: 0x %X\n",flv.Version); fprintf(myout,"Flags : 0x %X\n",flv.Flags); fprintf(myout,"HeaderSize: 0x %X\n",reverse_bytes((byte *)&flv.DataOffset, sizeof(flv.DataOffset))); fprintf(myout,"========================================\n"); //move the file pointer to the end of the header fseek(ifh, reverse_bytes((byte *)&flv.DataOffset, sizeof(flv.DataOffset)), SEEK_SET); //process each tag do { previoustagsize = _getw(ifh); fread((void *)&tagheader,sizeof(TAG_HEADER),1,ifh); //int temp_datasize1=reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize)); int tagheader_datasize=tagheader.DataSize[0]*65536+tagheader.DataSize[1]*256+tagheader.DataSize[2]; int tagheader_timestamp=tagheader.Timestamp[0]*65536+tagheader.Timestamp[1]*256+tagheader.Timestamp[2]; char tagtype_str[10]; switch(tagheader.TagType){ case TAG_TYPE_AUDIO:sprintf(tagtype_str,"AUDIO");break; case TAG_TYPE_VIDEO:sprintf(tagtype_str,"VIDEO");break; case TAG_TYPE_SCRIPT:sprintf(tagtype_str,"SCRIPT");break; default:sprintf(tagtype_str,"UNKNOWN");break; } fprintf(myout,"[%6s] %6d %6d |",tagtype_str,tagheader_datasize,tagheader_timestamp); //if we are not past the end of file, process the tag if (feof(ifh)) { break; } //process tag by type switch (tagheader.TagType) { case TAG_TYPE_AUDIO:{ char audiotag_str[100]={0}; strcat(audiotag_str,"| "); char tagdata_first_byte; tagdata_first_byte=fgetc(ifh); int x=tagdata_first_byte&0xF0; x=x>>4; switch (x) { case 0:strcat(audiotag_str,"Linear PCM, platform endian");break; case 1:strcat(audiotag_str,"ADPCM");break; case 2:strcat(audiotag_str,"MP3");break; case 3:strcat(audiotag_str,"Linear PCM, little endian");break; case 4:strcat(audiotag_str,"Nellymoser 16-kHz mono");break; case 5:strcat(audiotag_str,"Nellymoser 8-kHz mono");break; case 6:strcat(audiotag_str,"Nellymoser");break; case 7:strcat(audiotag_str,"G.711 A-law logarithmic PCM");break; case 8:strcat(audiotag_str,"G.711 mu-law logarithmic PCM");break; case 9:strcat(audiotag_str,"reserved");break; case 10:strcat(audiotag_str,"AAC");break; case 11:strcat(audiotag_str,"Speex");break; case 14:strcat(audiotag_str,"MP3 8-Khz");break; case 15:strcat(audiotag_str,"Device-specific sound");break; default:strcat(audiotag_str,"UNKNOWN");break; } strcat(audiotag_str,"| "); x=tagdata_first_byte&0x0C; x=x>>2; switch (x) { case 0:strcat(audiotag_str,"5.5-kHz");break; case 1:strcat(audiotag_str,"1-kHz");break; case 2:strcat(audiotag_str,"22-kHz");break; case 3:strcat(audiotag_str,"44-kHz");break; default:strcat(audiotag_str,"UNKNOWN");break; } strcat(audiotag_str,"| "); x=tagdata_first_byte&0x02; x=x>>1; switch (x) { case 0:strcat(audiotag_str,"8Bit");break; case 1:strcat(audiotag_str,"16Bit");break; default:strcat(audiotag_str,"UNKNOWN");break; } strcat(audiotag_str,"| "); x=tagdata_first_byte&0x01; switch (x) { case 0:strcat(audiotag_str,"Mono");break; case 1:strcat(audiotag_str,"Stereo");break; default:strcat(audiotag_str,"UNKNOWN");break; } fprintf(myout,"%s",audiotag_str); //if the output file hasn't been opened, open it. if(output_a!=0&&afh == NULL){ afh = fopen("output.mp3", "wb"); } //TagData - First Byte Data int data_size=reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize))-1; if(output_a!=0){ //TagData+1 for (int i=0; i<data_size; i++) fputc(fgetc(ifh),afh); }else{ for (int i=0; i<data_size; i++) fgetc(ifh); } break; } case TAG_TYPE_VIDEO:{ char videotag_str[100]={0}; strcat(videotag_str,"| "); char tagdata_first_byte; tagdata_first_byte=fgetc(ifh); int x=tagdata_first_byte&0xF0; x=x>>4; switch (x) { case 1:strcat(videotag_str,"key frame ");break; case 2:strcat(videotag_str,"inter frame");break; case 3:strcat(videotag_str,"disposable inter frame");break; case 4:strcat(videotag_str,"generated keyframe");break; case 5:strcat(videotag_str,"video info/command frame");break; default:strcat(videotag_str,"UNKNOWN");break; } strcat(videotag_str,"| "); x=tagdata_first_byte&0x0F; switch (x) { case 1:strcat(videotag_str,"JPEG (currently unused)");break; case 2:strcat(videotag_str,"Sorenson H.263");break; case 3:strcat(videotag_str,"Screen video");break; case 4:strcat(videotag_str,"On2 VP6");break; case 5:strcat(videotag_str,"On2 VP6 with alpha channel");break; case 6:strcat(videotag_str,"Screen video version 2");break; case 7:strcat(videotag_str,"AVC");break; default:strcat(videotag_str,"UNKNOWN");break; } fprintf(myout,"%s",videotag_str); fseek(ifh, -1, SEEK_CUR); //if the output file hasn't been opened, open it. if (vfh == NULL&&output_v!=0) { //write the flv header (reuse the original file's hdr) and first previoustagsize vfh = fopen("output.flv", "wb"); fwrite((char *)&flv,1, sizeof(flv),vfh); fwrite((char *)&previoustagsize_z,1,sizeof(previoustagsize_z),vfh); } #if 0 //Change Timestamp //Get Timestamp ts = reverse_bytes((byte *)&tagheader.Timestamp, sizeof(tagheader.Timestamp)); ts=ts*2; //Writeback Timestamp ts_new = reverse_bytes((byte *)&ts, sizeof(ts)); memcpy(&tagheader.Timestamp, ((char *)&ts_new) + 1, sizeof(tagheader.Timestamp)); #endif //TagData + Previous Tag Size int data_size=reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize))+4; if(output_v!=0){ //TagHeader fwrite((char *)&tagheader,1, sizeof(tagheader),vfh); //TagData for (int i=0; i<data_size; i++) fputc(fgetc(ifh),vfh); }else{ for (int i=0; i<data_size; i++) fgetc(ifh); } //rewind 4 bytes, because we need to read the previoustagsize again for the loop's sake fseek(ifh, -4, SEEK_CUR); break; } default: //skip the data of this tag fseek(ifh, reverse_bytes((byte *)&tagheader.DataSize, sizeof(tagheader.DataSize)), SEEK_CUR); } fprintf(myout,"\n"); } while (!feof(ifh)); _fcloseall(); return 0; }
上文中的函式呼叫方法如下所示。
simplest_flv_parser("cuc_ieschool.flv");結果
本程式的輸入為一個FLV的檔案路徑，輸出為FLV的統計資料，如下圖所示。
此外本程式還可以分離FLV中的視訊碼流和音訊碼流。需要注意的是本程式並不能分離一些特定型別的音訊（例如AAC）和視訊，這一工作有待以後有時間再完成。
下載
Simplest mediadata test
專案主頁開源中國：http://git.oschina.net/leixiaohua1020/simplest_mediadata_test
CSDN下載地址：http://download.csdn.net/detail/leixiaohua1020/9422409
本專案包含如下幾種視音訊資料解析示例：
(1)畫素資料處理程式。包含RGB和YUV畫素格式處理的函式。
(2)音訊取樣資料處理程式。包含PCM音訊取樣格式處理的函式。
(3)H.264碼流分析程式。可以分離並解析NALU。
(4)AAC碼流分析程式。可以分離並解析ADTS幀。
(5)FLV封裝格式分析程式。可以將FLV中的MP3音訊碼流分離出來。
(6)UDP-RTP協議分析程式。可以將分析UDP/RTP/MPEG-TS資料包。
雷霄驊 (Lei Xiaohua)
[email protected]
http://blog.csdn.net/leixiaohua1020