1 // Copyright (c) 2003-2009 Nokia Corporation and/or its subsidiary(-ies).

     2 // All rights reserved.

     3 // This component and the accompanying materials are made available

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

     5 // which accompanies this distribution, and is available

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

     7 //

     8 // Initial Contributors:

     9 // Nokia Corporation - initial contribution.

    10 //

    11 // Contributors:

    12 //

    13 // Description:

    14 //

    15 

    16 #include "MMFAudioSPcm16ToALawCodec.h"

    17 

    18 /***

    19 *

    20 * Convert

    21 *

    22 */

    23 EXPORT_C void TMMFAudioSPcm16ToAlawCodec::Convert(TUint8* aSrc, TUint8* aDst, TInt aSamples)

    24 	{

    25 	TInt16* pcm = (TInt16*)aSrc;

    26 	TInt16* pcmLimit = pcm + aSamples; 

    27 

    28 	while (pcm < pcmLimit)

    29 		{

    30 		*aDst++ = PcmSampleToAlaw(*pcm++);

    31 		}

    32 

    33 	}

    34 

    35 //[ conversion look up table pcm16 to alaw ]

    36 const TInt8 TMMFAudioSPcm16ToAlawCodec::KExpLut[] = 

    37 	{

    38 	1,1,2,2,3,3,3,3,

    39 	4,4,4,4,4,4,4,4,

    40 	5,5,5,5,5,5,5,5,

    41 	5,5,5,5,5,5,5,5,

    42 	6,6,6,6,6,6,6,6,

    43 	6,6,6,6,6,6,6,6,

    44 	6,6,6,6,6,6,6,6,

    45 	6,6,6,6,6,6,6,6,

    46 	7,7,7,7,7,7,7,7,

    47 	7,7,7,7,7,7,7,7,

    48 	7,7,7,7,7,7,7,7,

    49 	7,7,7,7,7,7,7,7,

    50 	7,7,7,7,7,7,7,7,

    51 	7,7,7,7,7,7,7,7,

    52 	7,7,7,7,7,7,7,7,

    53 	7,7,7,7,7,7,7,7

    54 	};

    55 

    56 /***

    57 *

    58 * PcmSampleToAlaw

    59 * @param aLaw

    60 * @return TUint8

    61 *

    62 */

    63 TUint8 TMMFAudioSPcm16ToAlawCodec::PcmSampleToAlaw(TInt aPcm)

    64 	{

    65     TInt sign;

    66 	TInt exponent;

    67 	TInt mantissa;

    68 	TUint8 alawbyte;

    69 

    70     sign = ((~aPcm) >> 8) & KMaskSign8bit;		

    71     if (sign == 0)

    72 		aPcm = -aPcm;	

    73     if (aPcm > KMda16PcmToAlawClip) 

    74 		aPcm = KMda16PcmToAlawClip;

    75 

    76     if (aPcm >= 256)

    77 		{

    78 		exponent = KExpLut[( aPcm >> 8 ) & 0x7F];

    79 		mantissa = ( aPcm >> ( exponent + 3 ) ) & 0x0F;

    80 		alawbyte = STATIC_CAST( TUint8, (( exponent << 4 ) | mantissa));

    81 		}

    82     else

    83 		alawbyte = STATIC_CAST( TUint8, aPcm >> 4);

    84 

    85     alawbyte ^= (sign ^ 0x55);

    86 

    87     return alawbyte;

    88 	}

    89