FLV简介
FLV (Flash Video) 是由 Adobe 公司推出的一种封装格式,主要用于流媒体系统。
FLV 封装的媒体文件具有体积轻巧、封装播放简单等特点,很适合网络应用。
目前各浏览器普遍使用 Flash Player 作为网页播放器,使得安装有浏览器的计算机终端不需要另外安装播放器,
这也是 FLV 格式广为流行的原因之一。
FLV 文件主要由一个 Header 加上由多个 Tag 组成的 Body 构成。
一、FLV Header(UI8表示无符号8位,也就是一个字节;UB[5]表示一个字节中的5位)
二、FLV Body(Flv Body由一个一个Tag组成,每个Tag前都有一个PerviousTagSize字段,标记着前面一个Tag的大小。)
Tag有三种类型,Audio Tag(音频Tag),Video Tag(视频Tag),script Tag(又称Metadata Tag)
每个Tag由Tag Header和Tag Data组成,对于不同类型的Tag,Tag Header的格式都是相同的(都是11byte的长度),Tag Body的格式就不一样了。
综上所述FLV整体的结构如下图:
1、AudioTag Data
如果SoundFormat=10,那么音频数据就是AACAUDIODATA。
2、Video Tag Data
对于H.264数据来说,CodecID = 7。
当CodecID = 7时,视频数据就是AVCVIDEOPACKET格式。
3、Script Tag Data
该类型Tag又通常被称为MetadataTag,会放一些关于FLV视频和音频的元数据信息
如:duration、width、height等。通常该类型Tag会跟在FileHeader后面作为第一个Tag出现,而且只有一个。
第一个AMF包:
第一个字节一般为0x02,表示字符串,第2-3个字节表示字符串的长度,一般为0x000A,后面跟的就是字符串,一般为"onMetaData"。
第二AMF包:
第一个字节为0x08,表示数组,第2-5个字节表示数组元素个数,后面跟着就是数组的元素,格式为:元素名长度(UI16) + 元素名(UI8[n]) + 元素的值(double),最后以“009”结尾
原文链接:https://blog.csdn.net/weixin_42462202/article/details/88661883
此外本程序还可以分离FLV中的视频码流和音频码流。需要注意的是本程序并不能分离一些特定类型的音频(例如AAC)和视频。
#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;
}
原文链接:https://blog.csdn.net/leixiaohua1020/article/details/50535082
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