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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
//=============================================================================
#ifndef MPAHEADER_H
#define MPAHEADER_H
#ifdef _WIN32
#pragma once
#endif
#pragma once
#define MPA_HEADER_SIZE 4 // MPEG-Audio Header Size 32bit
#define MAXTIMESREAD 5
class CMPAFile;
class CMPAHeader
{
public:
CMPAHeader( CMPAFile* pMPAFile, uint32 dwExpectedOffset = 0, bool bSubsequentFrame = false, bool bReverse = false );
~CMPAHeader();
bool SkipEmptyFrames();
// bitrate is in bit per second, to calculate in bytes => (/ 8)
uint32 GetBytesPerSecond() const { return m_dwBitrate / 8; };
// calc number of seconds from number of frames
uint32 GetLengthSecond(uint32 dwNumFrames) const { return dwNumFrames * m_dwSamplesPerFrame / m_dwSamplesPerSec; };
uint32 GetBytesPerSecond( uint32 dwNumFrames, uint32 dwNumBytes ) const { return dwNumBytes / GetLengthSecond( dwNumFrames ); };
bool IsMono() const { return (m_ChannelMode == SingleChannel)?true:false; };
// true if MPEG2/2.5 otherwise false
bool IsLSF() const { return m_bLSF; };
private:
static const uint32 m_dwMaxRange;
static const uint32 m_dwTolerance;
static const uint32 m_dwSamplingRates[4][3];
static const uint32 m_dwPaddingSizes[3];
static const uint32 m_dwBitrates[2][3][15];
static const uint32 m_dwSamplesPerFrames[2][3];
static const uint32 m_dwCoefficients[2][3];
// necessary for CRC check (not yet implemented)
static const uint32 m_dwSideinfoSizes[2][3][2];
static const uint16 wCRC16Table[256];
bool m_bLSF; // true means lower sampling frequencies (=MPEG2/MPEG2.5)
CMPAFile* m_pMPAFile;
public:
static const char * m_szLayers[];
static const char * m_szMPEGVersions[];
static const char * m_szChannelModes[];
static const char * m_szEmphasis[];
enum MPAVersion
{
MPEG25 = 0,
MPEGReserved,
MPEG2,
MPEG1
}m_Version;
enum MPALayer
{
Layer1 = 0,
Layer2,
Layer3,
LayerReserved
}m_Layer;
enum Emphasis
{
EmphNone = 0,
Emph5015,
EmphReserved,
EmphCCITJ17
}m_Emphasis;
enum ChannelMode
{
Stereo,
JointStereo,
DualChannel,
SingleChannel
}m_ChannelMode;
uint32 m_dwSamplesPerSec;
uint32 m_dwSamplesPerFrame;
uint32 m_dwBitrate; // in bit per second (1 kb = 1000 bit, not 1024)
uint32 m_dwSyncOffset;
uint32 m_dwComputedFrameSize, m_dwRealFrameSize;
uint32 m_dwPaddingSize;
// flags
bool m_bCopyright, m_bPrivate, m_bOriginal;
bool m_bCRC;
uint8 m_ModeExt;
private:
enum HeaderError
{
noError,
noSync,
freeBitrate,
headerCorrupt
};
HeaderError DecodeHeader( uint32 dwHeader, bool bSimpleDecode = false );
inline HeaderError IsSync( uint32 dwOffset, bool bExtended );
};
#endif // MPAHEADER_H
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