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1 // Copyright (c) 2003-2009 Nokia Corporation and/or its subsidiary(-ies). |
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2 // All rights reserved. |
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3 // This component and the accompanying materials are made available |
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4 // under the terms of "Eclipse Public License v1.0" |
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5 // which accompanies this distribution, and is available |
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6 // at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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7 // |
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8 // Initial Contributors: |
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9 // Nokia Corporation - initial contribution. |
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10 // |
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11 // Contributors: |
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12 // |
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13 // Description: |
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14 // MMFAudioImaAdpcmToS16PcmCodec.cpp |
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15 // |
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16 // |
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17 |
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18 #include "MMFAudioImaAdpcmToS16PcmCodec.h" |
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19 |
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20 /** |
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21 * |
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22 * Convert |
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23 * @param aSrc |
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24 * @param aDst |
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25 * @param aSamples |
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26 * |
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27 */ |
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28 EXPORT_C void TMMFAudioImaAdpcmToS16PcmCodec::Convert(TUint8* aSrc, TUint8* aDst, TInt aSamples) |
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29 { |
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30 TInt delta; // Current adpcm output value |
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31 TInt step; // Stepsize |
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32 TInt valpred; // Predicted value |
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33 TInt vpdiff; // Current change to valpred |
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34 TInt index; // Current step change index |
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35 |
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36 //[Read first sample and index from block header |
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37 // we do not need to store the information across calls |
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38 //since we process the entire block here] |
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39 valpred = (*aSrc++) & KAndMask8bit; |
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40 valpred |= STATIC_CAST(TInt16, ((*aSrc++) << 8)); |
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41 index = *aSrc++; |
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42 TUint8* dst=aDst; |
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43 |
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44 aSrc++; //skip reserved header byte |
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45 |
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46 //Write first sample to dest |
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47 *aDst++ = STATIC_CAST( TUint8, valpred); |
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48 *aDst++ = STATIC_CAST( TUint8, valpred >> 8); |
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49 dst += 2; |
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50 aSamples --; |
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51 |
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52 TBool theBufferStep = ETrue; |
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53 TInt bufferValue = 0; |
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54 for ( ; aSamples > 0 ; aSamples-- ) |
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55 { |
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56 // Step 1 - get the delta value |
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57 if ( theBufferStep) |
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58 { |
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59 bufferValue = *aSrc++; |
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60 delta = bufferValue & 0xf; |
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61 } |
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62 else |
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63 { |
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64 delta = (bufferValue >> 4) & 0xf; |
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65 } |
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66 |
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67 theBufferStep = !theBufferStep; |
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68 |
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69 ASSERT(index >= 0); |
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70 step = KStepSizeTable[index]; |
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71 |
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72 vpdiff = step>>3; |
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73 if ( delta & 4 ) |
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74 vpdiff += step; |
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75 if ( delta & 2 ) |
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76 vpdiff += step>>1; |
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77 if ( delta & 1 ) |
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78 vpdiff += step>>2; |
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79 |
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80 if ( delta & 8 ) |
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81 valpred -= vpdiff; |
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82 else |
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83 valpred += vpdiff; |
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84 |
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85 if ( valpred > (KClamp - 1) ) |
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86 valpred = (KClamp - 1); |
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87 else if ( valpred < -KClamp ) |
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88 valpred = -KClamp; |
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89 |
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90 index += KIndexTable[delta]; |
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91 if ( index < 0 ) |
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92 index = 0; |
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93 if ( index > KMaxImaAdpcmTableEntries ) |
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94 index = KMaxImaAdpcmTableEntries; |
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95 |
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96 *dst++ = STATIC_CAST( TUint8, valpred&KAndMask8bit); |
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97 *dst++ = STATIC_CAST( TUint8, (valpred>>8) ); |
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98 } |
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99 } |
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100 |
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101 |
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102 |
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103 // IMA-ADPCM step variation table |
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104 const TInt TMMFAudioImaAdpcmToS16PcmCodec::KIndexTable[] = |
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105 { |
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106 -1, -1, -1, -1, 2, 4, 6, 8, |
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107 -1, -1, -1, -1, 2, 4, 6, 8 |
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108 }; |
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109 |
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110 const TInt TMMFAudioImaAdpcmToS16PcmCodec::KStepSizeTable[89] = |
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111 { |
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112 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, |
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113 19, 21, 23, 25, 28, 31, 34, 37, 41, 45, |
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114 50, 55, 60, 66, 73, 80, 88, 97, 107, 118, |
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115 130, 143, 157, 173, 190, 209, 230, 253, 279, 307, |
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116 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, |
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117 876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, |
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118 2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358, |
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119 5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899, |
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120 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767 |
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121 }; |