// Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies).

 // All rights reserved.

 // This component and the accompanying materials are made available

 // under the terms of "Eclipse Public License v1.0"

 // which accompanies this distribution, and is available

 // at the URL "http://www.eclipse.org/legal/epl-v10.html".

 //

 // Initial Contributors:

 // Nokia Corporation - initial contribution.

 //

 // Contributors:

 //

 // Description:

 //

 #include "parsers.h"

 //

 // Masks used for reading bits.

 //

 static const TInt KMP3Sync1Mask = 0xff;			// 11111111

 static const TInt KMP3Sync2Mask = 0xe0;			// 11100000

 static const TInt KMP3VersionMask = 0x18;		// 00011000

 static const TInt KMP3LayerMask = 0x06;			// 00000110

 static const TInt KMP3BitrateMask = 0xf0;		// 11110000

 static const TInt KMP3SampleRateMask = 0x0c;	// 00001100

 static const TInt KMP3PaddingMask = 0x02;		// 00000010

 static const TInt KBitsPerByte = 8;

 //

 // Macros for retrieving the values.

 //

 #define MP3_GET_SYNC1(d)				(d & KMP3Sync1Mask)

 #define MP3_GET_SYNC2(d)				((d & KMP3Sync2Mask) >> 5)

 #define MP3_GET_VERSION(d)				((d & KMP3VersionMask) >> 3)

 #define MP3_GET_LAYER(d)				((d & KMP3LayerMask) >> 1)

 #define MP3_GET_BITRATE(d)				((d & KMP3BitrateMask) >> 4)

 #define MP3_GET_SAMPLE_RATE(d)			((d & KMP3SampleRateMask) >> 2)

 #define MP3_GET_PADDING(d)				((d & KMP3PaddingMask) >> 1)

 //

 // Macros used for checking various bitfields.

 //

 #define IS_BAD_MP3_FRAME_SYNC1(s)		((s) != 0xff)

 #define IS_BAD_MP3_FRAME_SYNC2(s)		((s) != 0x07)	

 #define IS_BAD_MP3_VERSION(v)			((v) <  0x02)

 #define IS_BAD_MP3_LAYER(l)				((l) == 0x00) 

 #define IS_BAD_MP3_BITRATE(b)			((b) == 0x0f)	

 #define IS_BAD_MP3_SAMPLE_RATE(s)		((s) == 0x03)

 // 

 // Meanings of the 'Version' field.

 // --------------------------------

 // 00 - MPEG Version 2.5 (Unofficial standard. We don't support it.)

 // 01 - Reserved

 // 10 - MPEG Version 2

 // 11 - MPEG Version 1

 //

 static const TInt8 KMP3Version2 = 2;

 static const TInt8 KMP3Version1 = 3;

 // 

 // Meanings of the 'Layer' field.

 // ------------------------------

 // 00 - Reserved

 // 01 - Layer III

 // 10 - Layer II

 // 11 - Layer I

 //

 static const TUint16 KBad = 0;

 static const TUint16 KFree = 0;

 //

 // MPEG Version 1 bitrates. Measured in kilobits per second.

 //

 static const TUint16 KBitrateVersion1[4][16] =

 	{

 	{ KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad}, // Reserved layer

 	{KFree,   32,   40,   48,   56,   64,   80,   96,  112,  128,  160,  192,  224,  256,  320, KBad}, // Layer III

 	{KFree,   32,   48,   56,   64,   80,   96,  112,  128,  160,  192,  224,  256,  320,  384, KBad}, // Layer II

 	{KFree,   32,   64,   96,  128,  160,  192,  224,  256,  288,  320,  352,  384,  416,  448, KBad}  // Layer I

 	};

 //

 // MPEG Version 2 bitrates. Measured in kilobits per second.

 //

 static const TUint16 KBitrateVersion2[4][16] =

 	{

 	{ KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad, KBad}, // Reserved layer

 	{KFree,    8,   16,   24,   32,   40,   48,   56,   64,   80,   96,  112,  128,  144,  160, KBad}, // Layer III 

 	{KFree,    8,   16,   24,   32,   40,   48,   56,   64,   80,   96,  112,  128,  144,  160, KBad}, // Layer II

 	{KFree,   32,   48,   56,   64,   80,   96,  112,  128,  144,  160,  176,  192,  224,  256, KBad}  // Layer I

 	};

 //

 // Sample rates for the MPEG versions.

 //

 static const TUint16 KSampleRate[4][4] = 

 	{

 		{11025, 12000,  8000, KBad}, // Version 2.5

 		{ KBad,  KBad,  KBad, KBad}, // Reserved

 		{22050, 24000, 16000, KBad}, // Version 2

 		{44100, 48000, 32000, KBad}  // Version 1

 	};

 //

 // Sample rates per frame for the MPEG layers.

 //

 static const TUint16 KSamplesPerFrame[4][4] = 

 	{

 		{KBad, KBad, KBad, KBad}, // Reserved layer

 		{ 576, KBad,  576, 1152}, // Layer III

 		{1152, KBad, 1152, 1152}, // Layer II

 		{ 384, KBad,  384,  384}  // Layer I

 	};

 //

 // The various states the recognition process goes through.

 //

 typedef enum

 	{

 	ESearchFrame1,

 	ESearchFrame2

 	}

 TMP3State;

 //

 // This truth table maps the following flags to a confidence level.

 // -----------------------------------------------------------------

 // A: Frame2 found.

 // B: Frame1 found.

 // C: Extension recognised.

 //

 // A B C -> Confidence

 // ===================

 // 0 0 0 -> ENotRecognized

 // 0 0 1 -> EPossible

 // 0 1 0 -> ENotRecognized

 // 0 1 1 -> ECertain

 // 1 0 0 -> EPossible

 // 1 0 1 -> EProbable

 // 1 1 0 -> EProbable

 // 1 1 1 -> ECertain

 //

 // In the case where two consecutive mp3 frames

 // are found, ECertain is automatically returned.

 //

 static const TInt KMP3FlagsToConfidence[8] = 

 	{

 	KConfNotRecognised,

 	KConfPossible,

 	KConfNotRecognised,

 	KConfCertain,

 	KConfPossible,

 	KConfProbable,

 	KConfProbable,

 	KConfCertain

 	};

 #define KMP3ConfidenceMask	0x07	// 00000111

 #define KMP3Frame1Bit		KBit1

 #define KMP3Frame2Bit		KBit2

 //

 //

 //

 TMP3Parser::TMP3Parser(CReader& aReader, TFlags& aFlags)

  : 	iReader(aReader),

  	iFlags(aFlags)

 	{

 	}

 //

 // MP3 recogition function.

 //

 void TMP3Parser::DoRecognise(const TDesC& aExt, CReader& aReader, TMatch& aMatch)

 	{

 	TFlags flags;

 	// Try to match the extension.

 	if (aExt.MatchF(TPtrC(KExtMP3)) != KErrNotFound)

 		{

 		flags.SetExtensionFlag();

 		}

 	// Parse the data.

 	TMP3Parser parser(aReader, flags);

 	TRAP_IGNORE(parser.ParseL());

 	TInt confIndex = flags.GetBitField(KMP3ConfidenceMask);

 	aMatch.iConfidence = KMP3FlagsToConfidence[confIndex];

 	if (aMatch.iConfidence != KConfNotRecognised)

 		{

 		aMatch.iMime = KMimeMP3;

 		}

 	}

 //

 // Attempts to parse an mp3 file.

 // First of all it checks if there is an ID3 metadata header

 // present at the current reader position. Then it checks for up to

 // two consecutive mp3 audio frames.

 //

 void TMP3Parser::ParseL()

 	{

 	TInt length;

 	TMP3State state = ESearchFrame1;

 	FOREVER

 		{

 		TID3Parser::ReadAndSkipID3L(iReader);

 		TInt err = CheckForFrameHeaderL(length);

 		if (err == KErrNotFound)

 			{

 			return;

 			}

 		switch (state)

 			{

 			case ESearchFrame1:

 				iFlags.SetBit(KMP3Frame1Bit);

 				state = ESearchFrame2;

 				break;

 			case ESearchFrame2:

 				iFlags.SetBit(KMP3Frame2Bit);

 				return;

 			}

 		// Skip over the audio frame.

 		// This should be done after flags have been set.

 		iReader.SeekL(length - KMP3FrameHeaderSize);

 		}

 	}

 //

 // Checks for an MP3 frame header at the current reader position.

 // If one is not found KErrNotFound is returned and aFrameLength

 // remains unchanged. If one is found KErrNone is retured and

 // aFrameLength is set to the length of the frame.

 //

 TInt TMP3Parser::CheckForFrameHeaderL(TInt& aFrameLength)

 	{

 	TBuf8<KMP3FrameHeaderSize> data;

 	TUint8 versionIndex;

 	TUint8 layerIndex;

 	TUint8 bitrateIndex;

 	TUint8 sampleRateIndex;

 	TUint8 padding;

 	TUint8 sync;

 	data.SetLength(KMP3FrameHeaderSize);

 	iReader.ReadBytesL(data);

 	do

 		{

 		sync = MP3_GET_SYNC1(data[0]);

 		if (IS_BAD_MP3_FRAME_SYNC1(sync))

 			{

 			break;

 			}

 		sync = MP3_GET_SYNC2(data[1]);

 		if (IS_BAD_MP3_FRAME_SYNC2(sync))

 			{

 			break;

 			}

 		versionIndex = MP3_GET_VERSION(data[1]);

 		if (IS_BAD_MP3_VERSION(versionIndex))

 			{

 			break;

 			}

 		layerIndex = MP3_GET_LAYER(data[1]);

 		if (IS_BAD_MP3_LAYER(layerIndex))

 			{

 			break;

 			}

 		bitrateIndex = MP3_GET_BITRATE(data[2]);

 		if (IS_BAD_MP3_BITRATE(bitrateIndex))

 			{

 			break;

 			}

 		sampleRateIndex = MP3_GET_SAMPLE_RATE(data[2]);

 		if (IS_BAD_MP3_SAMPLE_RATE(sampleRateIndex))

 			{

 			break;

 			}

 		padding = MP3_GET_PADDING(data[2]);

 		// All the data is valid.

 		// Compute the audio data length.

 		TUint32 bitRate = KBad;

 		TUint16 sampleRate = KBad;

 		TUint16 samplesPerFrame = KBad;

 		if (versionIndex == KMP3Version1)

 			{

 			bitRate = KBitrateVersion1[layerIndex][bitrateIndex];

 			}

 		else if (versionIndex == KMP3Version2)

 			{

 			bitRate = KBitrateVersion2[layerIndex][bitrateIndex];

 			}

 		else 

 			{

 			// Version 2.5 is not supported.

 			break;

 			}

 		sampleRate = KSampleRate[versionIndex][sampleRateIndex];

 		samplesPerFrame = KSamplesPerFrame[layerIndex][versionIndex];

 		// Check we have valid values.

 		if ((bitRate == KBad) || (sampleRate == KBad) || (samplesPerFrame == KBad))

 			{

 			break;

 			}

 		bitRate *= 1000; // Convert to kilobits.

 		aFrameLength = (((samplesPerFrame / KBitsPerByte) * bitRate) / sampleRate) + padding;

 		return KErrNone;

 		}

 	while (EFalse);

 	// No valid frame header was found.

 	aFrameLength = 0;

 	iReader.SeekL(-KMP3FrameHeaderSize);

 	return KErrNotFound;

 	}