sl@0: // Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: // All rights reserved.
sl@0: // This component and the accompanying materials are made available
sl@0: // under the terms of "Eclipse Public License v1.0"
sl@0: // which accompanies this distribution, and is available
sl@0: // at the URL "http://www.eclipse.org/legal/epl-v10.html".
sl@0: //
sl@0: // Initial Contributors:
sl@0: // Nokia Corporation - initial contribution.
sl@0: //
sl@0: // Contributors:
sl@0: //
sl@0: // Description:
sl@0: //
sl@0: 
sl@0: #include "constants.h"
sl@0: #include "parsers.h"
sl@0: 
sl@0: // The length of the frame in written directly into the header.
sl@0: // It is 13 bits in length and spans 3 bytes.
sl@0: 
sl@0: #define AAC_SYNC1_MASK				0xff	// 11111111
sl@0: #define AAC_SYNC2_MASK				0xf0	// 11110000
sl@0: #define AAC_FRAME_LENGTH_MASK1		0x03	// 00000011
sl@0: #define AAC_FRAME_LENGTH_MASK2		0xff	// 11111111
sl@0: #define AAC_FRAME_LENGTH_MASK3		0xe0	// 11100000
sl@0: #define AAC_LAYER_MASK				0x06	// 00000110
sl@0: 
sl@0: #define AAC_GET_SYNC1(d)	(d)
sl@0: #define AAC_GET_SYNC2(d)	((d & AAC_SYNC2_MASK) >> 4)
sl@0: #define AAC_GET_LAYER(d)	(((d) & AAC_LAYER_MASK) >> 1)
sl@0: #define AAC_GET_FRAME_LENGTH(a, b, c) \
sl@0: 							(((a) & AAC_FRAME_LENGTH_MASK1) << 11) | \
sl@0: 							(((b) & AAC_FRAME_LENGTH_MASK2) << 03) | \
sl@0: 							(((c) & AAC_FRAME_LENGTH_MASK3) >> 05)
sl@0: 							
sl@0: 
sl@0: #define AAC_IS_BAD_SYNC1(s)			((s) != 0xff)
sl@0: #define AAC_IS_BAD_SYNC2(s)			((s) != 0x0f)
sl@0: #define AAC_IS_BAD_LAYER(l)			((l) != 0x00)
sl@0: #define AAC_IS_BAD_FRAME_LENGTH(l)	((l) < KAACFrameHeaderSize)
sl@0: 
sl@0: //
sl@0: // The various states the recognition process goes through.
sl@0: //
sl@0: typedef enum
sl@0: 	{
sl@0: 	ESearchFrame1,
sl@0: 	ESearchFrame2
sl@0: 	}
sl@0: TAACState;
sl@0: 
sl@0: //
sl@0: // This truth table maps the following flags to a confidence level.
sl@0: //
sl@0: // A: Extension identified.
sl@0: // B: Frame1 found.
sl@0: // C: Frame2 found.
sl@0: //
sl@0: // C B A -> Confidence
sl@0: // ===================
sl@0: // 0 0 0 -> ENotRecognised
sl@0: // 0 0 1 -> EPossible
sl@0: // 0 1 0 -> EProbable
sl@0: // 0 1 1 -> ECertain
sl@0: // 1 0 0 -> ENotRecognised (Can't have f2 without f1)
sl@0: // 1 0 1 -> ENotRecognised (Can't have f2 without f1)
sl@0: // 1 1 0 -> EProbable
sl@0: // 1 1 1 -> ECertain
sl@0: //
sl@0: static const TInt KAACFlagsToConfidence[8] =
sl@0: 	{
sl@0: 	KConfNotRecognised,
sl@0: 	KConfPossible,
sl@0: 	KConfProbable,
sl@0: 	KConfCertain,
sl@0: 	KConfNotRecognised,
sl@0: 	KConfNotRecognised,
sl@0: 	KConfProbable,
sl@0: 	KConfCertain
sl@0: 	};
sl@0: 	
sl@0: #define KAACConfidenceMask	0x07	// [0000 0111]
sl@0: #define KAACFrame1Bit		KBit1
sl@0: #define KAACFrame2Bit		KBit2
sl@0: 
sl@0: 
sl@0: 
sl@0: //
sl@0: // Constructs a TAACParser on the stack.
sl@0: //
sl@0: TAACParser::TAACParser(CReader& aReader, TFlags& aFlags)
sl@0:  :	iReader(aReader),
sl@0:  	iFlags(aFlags)
sl@0: 	{
sl@0: 	}
sl@0: 
sl@0: 
sl@0: //
sl@0: //
sl@0: //
sl@0: void TAACParser::DoRecognise(const TDesC& aFileExt, CReader& aReader, TMatch& aMatch)
sl@0: 	{
sl@0: 	TFlags flags;
sl@0: 	TBool extMatch;
sl@0: 	
sl@0: 	// See if the extension is recognised.
sl@0: 	extMatch = (aFileExt.MatchF(TPtrC(KExtAAC)) != KErrNotFound);
sl@0: 	
sl@0: 	// Try to match a known header.
sl@0: 	if (aReader.Match(TPtrC8(_S8("ADIF*"))))
sl@0: 		{
sl@0: 		aMatch.iConfidence = (extMatch ? KConfCertain : KConfProbable);
sl@0: 		aMatch.iMime = KMimeAAC;
sl@0: 		return;
sl@0: 		}
sl@0: 	
sl@0: 	// No known header so try to parse it.
sl@0: 	// Parsing uses flags to track what has been identified.
sl@0: 	if (extMatch)
sl@0: 		{
sl@0: 		flags.SetExtensionFlag();
sl@0: 		}
sl@0: 	
sl@0: 	TAACParser parser(aReader, flags);
sl@0: 	TRAP_IGNORE(parser.ParseL());
sl@0: 	
sl@0: 	TInt confIndex = flags.GetBitField(KAACConfidenceMask);
sl@0: 	aMatch.iConfidence = KAACFlagsToConfidence[confIndex];
sl@0: 	if (aMatch.iConfidence != KConfNotRecognised)
sl@0: 		{
sl@0: 		aMatch.iMime = KMimeAAC;
sl@0: 		}
sl@0: 	}
sl@0: 
sl@0: 
sl@0: //
sl@0: // Looks for valid AAC frame headers; at the current position
sl@0: // and immediately after (if one found).
sl@0: //
sl@0: void TAACParser::ParseL()
sl@0: 	{
sl@0: 	TInt frameLength;
sl@0: 	TAACState state = ESearchFrame1;
sl@0: 	
sl@0: 	// Check if it's an ADTS (raw) format AAC file.
sl@0: 	// There's no known metadata tag for AAC so the
sl@0: 	// first frame header should be at the start of the buffer.
sl@0: 	
sl@0: 	FOREVER
sl@0: 		{
sl@0: 		TID3Parser::ReadAndSkipID3L(iReader);
sl@0: 		
sl@0: 		TInt err = CheckForFrameHeaderL(frameLength);
sl@0: 		if (err == KErrNotFound)
sl@0: 			{
sl@0: 			return;
sl@0: 			}
sl@0: 			
sl@0: 		switch (state)
sl@0: 			{
sl@0: 			case ESearchFrame1:
sl@0: 				iFlags.SetBit(KAACFrame1Bit);
sl@0: 				state = ESearchFrame2;
sl@0: 				break;
sl@0: 					
sl@0: 			case ESearchFrame2:
sl@0: 				iFlags.SetBit(KAACFrame2Bit);
sl@0: 				return;
sl@0: 			}
sl@0: 		
sl@0: 		// Skip over the audio frame.
sl@0: 		// This should be done after flags have been set.
sl@0: 		iReader.SeekL(frameLength - KAACFrameHeaderSize);
sl@0: 		};
sl@0: 	}
sl@0: 
sl@0: 
sl@0: //
sl@0: // Looks for valid AAC frame header bit patterns.
sl@0: // If one is not found KErrNotFound is returned and aFrameLength
sl@0: // remains unchanged. If one is found KErrNone is retured and
sl@0: // aFrameLength is set to the length of the frame.
sl@0: //
sl@0: TInt TAACParser::CheckForFrameHeaderL(TInt& aFrameLength)
sl@0: 	{
sl@0: 	TBuf8<KAACFrameHeaderSize> header;
sl@0: 	
sl@0: 	header.SetLength(KAACFrameHeaderSize);
sl@0: 	iReader.ReadBytesL(header);
sl@0: 	
sl@0: 	do
sl@0: 		{
sl@0: 		if (AAC_IS_BAD_SYNC1(AAC_GET_SYNC1(header[0])))
sl@0: 			{
sl@0: 			break;
sl@0: 			}
sl@0: 			
sl@0: 		if (AAC_IS_BAD_SYNC2(AAC_GET_SYNC2(header[1])))
sl@0: 			{
sl@0: 			break;
sl@0: 			}
sl@0: 			
sl@0: 		if (AAC_IS_BAD_LAYER(AAC_GET_LAYER(header[1])))
sl@0: 			{
sl@0: 			break;
sl@0: 			}
sl@0: 			
sl@0: 		TInt frameLength = AAC_GET_FRAME_LENGTH(header[3], header[4], header[5]);
sl@0: 		if (AAC_IS_BAD_FRAME_LENGTH(frameLength))
sl@0: 			{
sl@0: 			break;
sl@0: 			}
sl@0: 		// All is ok.
sl@0: 		aFrameLength = frameLength;
sl@0: 		return KErrNone;
sl@0: 		}
sl@0: 	while (EFalse);
sl@0: 	
sl@0: 	// No frame header was found.
sl@0: 	aFrameLength = 0;
sl@0: 	iReader.SeekL(-KAACFrameHeaderSize);
sl@0: 	return KErrNotFound;
sl@0: 	}
sl@0: 	
sl@0: