Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 1 | #ifndef __BITSTREAM_H_ |
| 2 | #define __BITSTREAM_H_ |
| 3 | |
| 4 | #define KPackedFrameLen 10 |
| 5 | #define KUnpackedFrameLen 22 |
| 6 | |
| 7 | // Below values are taken from the APS design document |
| 8 | const TUint8 KG729FullPayloadBits[] = { 8, 10, 8, 1, 13, 4, 7, 5, 13, 4, 7 }; |
| 9 | const TUint KNumFullFrameParams = 11; |
| 10 | const TUint8 KG729SIDPayloadBits[] = { 1, 5, 4, 5 }; |
| 11 | const TUint KNumSIDFrameParams = 4; |
| 12 | |
| 13 | /*! |
| 14 | @class TBitStream |
| 15 | |
| 16 | @discussion Provides compression from 16-bit-word-aligned G.729 audio frames |
| 17 | (used in S60 G.729 DSP codec) to 8-bit stream, and vice versa. |
| 18 | */ |
| 19 | class TBitStream |
| 20 | { |
| 21 | public: |
| 22 | /*! |
| 23 | @function TBitStream |
| 24 | |
| 25 | @discussion Constructor |
| 26 | */ |
| 27 | TBitStream():iDes(iData,KUnpackedFrameLen){} |
| 28 | /*! |
| 29 | @function CompressG729Frame |
| 30 | |
| 31 | @discussion Compress either a 22-byte G.729 full rate frame to 10 bytes |
| 32 | or a 8-byte G.729 Annex.B SID frame to 2 bytes. |
| 33 | @param aSrc Reference to the uncompressed source frame data |
| 34 | @param aIsSIDFrame True if the source is a SID frame |
| 35 | @result a reference to the compressed frame |
| 36 | */ |
| 37 | const TDesC8& CompressG729Frame( const TDesC8& aSrc, TBool aIsSIDFrame = EFalse ); |
| 38 | |
| 39 | /*! |
| 40 | @function ExpandG729Frame |
| 41 | |
| 42 | @discussion Expand a 10-byte G.729 full rate frame to 22 bytes |
| 43 | or a 2-byte G.729 Annex.B SID frame to 8(22) bytes. |
| 44 | @param aSrc Reference to the compressed source frame data |
| 45 | @param aIsSIDFrame True if the source is a SID frame |
| 46 | @result a reference to a descriptor representing the uncompressed frame. |
| 47 | Note that SID frames are zero-padded to 22 bytes as well. |
| 48 | */ |
| 49 | const TDesC8& ExpandG729Frame( const TDesC8& aSrc, TBool aIsSIDFrame = EFalse ); |
| 50 | |
| 51 | private: |
| 52 | void Compress( TUint8 aValue, TUint8 aNumOfBits ); |
| 53 | void Expand( const TUint8* aSrc, TInt aDstIdx, TUint8 aNumOfBits ); |
| 54 | |
| 55 | private: |
| 56 | TUint8 iData[KUnpackedFrameLen]; |
| 57 | TPtr8 iDes; |
| 58 | TInt iIdx; |
| 59 | TInt iBitOffset; |
| 60 | }; |
| 61 | |
| 62 | |
| 63 | const TDesC8& TBitStream::CompressG729Frame( const TDesC8& aSrc, TBool aIsSIDFrame ) |
| 64 | { |
| 65 | // reset data |
| 66 | iDes.FillZ(iDes.MaxLength()); |
| 67 | iIdx = iBitOffset = 0; |
| 68 | |
| 69 | TInt numParams = (aIsSIDFrame) ? KNumSIDFrameParams : KNumFullFrameParams; |
| 70 | const TUint8* p = const_cast<TUint8*>(aSrc.Ptr()); |
| 71 | |
| 72 | for(TInt i = 0, pIdx = 0; i < numParams; i++, pIdx += 2) |
| 73 | { |
| 74 | TUint8 paramBits = (aIsSIDFrame) ? KG729SIDPayloadBits[i] : KG729FullPayloadBits[i]; |
| 75 | if(paramBits > 8) |
| 76 | { |
| 77 | Compress(p[pIdx+1], paramBits - 8); // msb |
| 78 | paramBits = 8; |
| 79 | } |
| 80 | Compress(p[pIdx], paramBits); // lsb |
| 81 | } |
| 82 | |
| 83 | if( iBitOffset ) |
| 84 | iIdx++; |
| 85 | |
| 86 | iDes.SetLength(iIdx); |
| 87 | return iDes; |
| 88 | } |
| 89 | |
| 90 | |
| 91 | const TDesC8& TBitStream::ExpandG729Frame( const TDesC8& aSrc, TBool aIsSIDFrame ) |
| 92 | { |
| 93 | // reset data |
| 94 | iDes.FillZ(iDes.MaxLength()); |
| 95 | iIdx = iBitOffset = 0; |
| 96 | |
| 97 | TInt numParams = (aIsSIDFrame) ? KNumSIDFrameParams : KNumFullFrameParams; |
| 98 | const TUint8* p = const_cast<TUint8*>(aSrc.Ptr()); |
| 99 | |
| 100 | for(TInt i = 0, dIdx = 0; i < numParams; i++, dIdx += 2) |
| 101 | { |
| 102 | TUint8 paramBits = (aIsSIDFrame) ? KG729SIDPayloadBits[i] : KG729FullPayloadBits[i]; |
| 103 | if(paramBits > 8) |
| 104 | { |
| 105 | Expand(p, dIdx+1, paramBits - 8); // msb |
| 106 | paramBits = 8; |
| 107 | } |
| 108 | Expand(p, dIdx, paramBits); // lsb |
| 109 | } |
| 110 | |
| 111 | iDes.SetLength(KUnpackedFrameLen); |
| 112 | return iDes; |
| 113 | } |
| 114 | |
| 115 | |
| 116 | void TBitStream::Compress( TUint8 aValue, TUint8 aNumOfBits ) |
| 117 | { |
| 118 | // clear bits that will be discarded |
| 119 | aValue &= (0xff >> (8 - aNumOfBits)); |
| 120 | |
| 121 | // calculate required bitwise left shift |
| 122 | TInt shl = 8 - (iBitOffset + aNumOfBits); |
| 123 | |
| 124 | if (shl == 0) // no shift required |
| 125 | { |
| 126 | iData[iIdx++] |= aValue; |
| 127 | iBitOffset = 0; |
| 128 | } |
| 129 | else if (shl > 0) // bits fit into current byte |
| 130 | { |
| 131 | iData[iIdx] |= (aValue << shl); |
| 132 | iBitOffset += aNumOfBits; |
| 133 | } |
| 134 | else |
| 135 | { |
| 136 | iBitOffset = -shl; |
| 137 | iData[iIdx] |= (aValue >> iBitOffset); // right shift |
| 138 | iData[++iIdx] |= (aValue << (8-iBitOffset)); // push remaining bits to next byte |
| 139 | } |
| 140 | } |
| 141 | |
| 142 | |
| 143 | void TBitStream::Expand( const TUint8* aSrc, TInt aDstIdx, TUint8 aNumOfBits ) |
| 144 | { |
| 145 | TUint8 aValue = aSrc[iIdx] & (0xff >> iBitOffset); |
| 146 | |
| 147 | // calculate required bitwise right shift |
| 148 | TInt shr = 8 - (iBitOffset + aNumOfBits); |
| 149 | |
| 150 | if (shr == 0) // no shift required |
| 151 | { |
| 152 | iData[aDstIdx] = aValue; |
| 153 | iIdx++; |
| 154 | iBitOffset = 0; |
| 155 | } |
| 156 | else if (shr > 0) // right shift |
| 157 | { |
| 158 | iData[aDstIdx] = (aValue >> shr); |
| 159 | iBitOffset += aNumOfBits; |
| 160 | } |
| 161 | else // shift left and take remaining bits from the next src byte |
| 162 | { |
| 163 | iBitOffset = -shr; |
| 164 | iData[aDstIdx] = aValue << iBitOffset; |
| 165 | iData[aDstIdx] |= aSrc[++iIdx] >> (8 - iBitOffset); |
| 166 | } |
| 167 | } |
| 168 | |
| 169 | #endif // __BITSTREAM_H_ |
| 170 | |
| 171 | // eof |