FLV音频帧信息

最新推荐文章于 2021-07-21 20:43:09 发布

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最新推荐文章于 2021-07-21 20:43:09 发布

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分类专栏：流媒体文章标签： flv ios 2010

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本文详细解析了FLV文件头、音频信息、视频标签等关键部分的结构，并展示了如何通过C++读取并展示这些信息，提供了一个深入理解FLV文件内部结构的指南。

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# include < iostream >
# include < fstream >
using namespace std ;

typedef struct _FLVHead
{
     unsigned char flv [ 3 ] ;
     unsigned char version ;
     unsigned char FlagsVideo : 1 ;
     unsigned char Flags : 1 ;
     unsigned char FlagsAudio : 1 ;
     unsigned char Flags1 : 5 ;
     unsigned int DataOffset ;
} FLVHead ;

typedef struct _AudioInfo
{
     unsigned char SoundType : 1 ;
     unsigned char SoundSize : 1 ;
     unsigned char SoundRate : 2 ;
     unsigned char SoundFormat : 4 ;
} AudioInfo ;

typedef struct _FLVTag
{
     unsigned int SizeOfLastTag ;
     unsigned int Type : 8 ;
     unsigned int DataSize : 24 ;
     unsigned int TimeStamp : 24 ;
     unsigned int ExtenTimeStamp : 8 ;
     unsigned int StreamID : 24 ;
     unsigned int AVData : 8 ;
} FLVTag ;

const char * SoundFormat [ ] = {
"Linear PCM, platform endian" ,
"ADPCM" ,
"MP3" ,
"Linear PCM, little endian" ,
"Nellymoser 16-kHz mono" ,
"Nellymoser 8-kHz mono" ,
"Nellymoser" ,
"G.711 A-law logarithmic PCM" ,
"G.711 mu-law logarithmic PCM" ,
"reserved" ,
"AAC" ,
"MP3 8-Khz" ,
"Device-specific sound" ,
} ;
const char * SoundRate [ ] = {
"5.5-kHz" ,
"11-kHz" ,
"22-kHz" ,
"44-kHz" ,
} ;
const char * SoundSize [ ] =
{
"snd8Bit" ,
"snd16Bit" ,
} ;
const char * SoundType [ ] =
{
"sndMono" ,
"sndStereo" ,
} ;
unsigned int ReverseInt24 ( unsigned int B )
{
     unsigned char * A = ( unsigned char * ) & B ;
     return A [ 0 ] < < 16 |
         A [ 1 ] < < 8 |
         A [ 2 ] ;
}
unsigned int ReverseInt32 ( unsigned int B )
{
     unsigned char * A = ( unsigned char * ) & B ;
     return A [ 0 ] < < 24 |
         A [ 1 ] < < 16 |
         A [ 2 ] < < 8 |
         A [ 3 ] ;
}
void ShowAudioInfo ( const AudioInfo * paudioInfo )
{
     cout < < " SoundFormat : " < < SoundFormat [ paudioInfo - > SoundFormat ] < < endl ;
     cout < < " SoundRate : " < < SoundRate [ paudioInfo - > SoundRate ] < < endl ;
     cout < < " SoundSize : " < < SoundSize [ paudioInfo - > SoundSize ] < < endl ;
     cout < < " SoundType : " < < SoundType [ paudioInfo - > SoundType ] < < endl ;
}
void ShowTagInfo ( const FLVTag * pflvTag , const unsigned char * buf )
{
     if ( pflvTag - > Type = = 8 )
     {
         cout < < "Audio Tag" < < endl ;
        ShowAudioInfo ( ( AudioInfo * ) buf + 15 ) ;
     }
     else if ( pflvTag - > Type = = 18 )
     {
         cout < < "Script Tag" < < endl ;
     }
     else if ( pflvTag - > Type = = 9 )
     {
         cout < < "Video Tag" < < endl ;
     }
}

int main ( )
{
     unsigned char buf [ 1024 ] ;
     char flvname [ 255 ] = "101.flv" ;

     ifstream flvfile ;
    flvfile . open ( flvname , ifstream : : binary | ifstream : : in ) ;
     cout < < flvname < < endl ;
     if ( flvfile . is_open ( ) )
     {
         long seekpos = 0 ;
        flvfile . seekg ( 0 , ios : : end ) ;
         long length = flvfile . tellg ( ) ;
        flvfile . seekg ( 0 , ios : : beg ) ;
        flvfile . read ( ( char * ) buf , 20 ) ;
        FLVHead     * pflvhead = ( FLVHead * ) buf ;
         unsigned int seekoffset = pflvhead - > DataOffset ;
         while ( ! flvfile . eof ( ) )
         {
            flvfile . seekg ( seekoffset , ios : : beg ) ;
         flvfile . read ( ( char * ) buf , 1024 ) ;
            FLVTag * pflvTag = ( FLVTag * ) buf ;
            pflvTag - > SizeOfLastTag = ReverseInt32 ( pflvTag - > SizeOfLastTag ) ;
            pflvTag - > DataSize = ReverseInt24 ( pflvTag - > DataSize ) ;
            pflvTag - > TimeStamp = ReverseInt24 ( pflvTag - > TimeStamp ) ;
             cout < < "StreamID: " < < std : : dec < < pflvTag - > StreamID < < endl ;
             cout < < "AVData : " < < std : : dec < < pflvTag - > AVData < < endl ;
            pflvTag - > StreamID = ReverseInt24 ( pflvTag - > StreamID ) ;
             cout < < "Offset : 0x" < < std : : hex < < seekoffset < < endl ;
             cout < < "Size : " < < std : : dec < < pflvTag - > DataSize < < endl ;
            ShowTagInfo ( pflvTag , buf ) ;
            seekoffset + = pflvTag - > DataSize + 15 ;
             //system("pause");

         }
     }
     return 0 ;

}

转自 http://www.diybl.com/course/3_program/c++/cppjs/20100308/196935.html