1 /* 2 * Copyrightm (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "AudioCodec.h" 18 19 namespace { 20 21 const int8_t gExponents[128] = { 22 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 23 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 24 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 25 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 26 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 27 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 28 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 29 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 30 }; 31 32 //------------------------------------------------------------------------------ 33 34 class UlawCodec : public AudioCodec 35 { 36 public: 37 int set(int sampleRate, const char *fmtp) { 38 mSampleCount = sampleRate / 50; 39 return mSampleCount; 40 } 41 int encode(void *payload, int16_t *samples); 42 int decode(int16_t *samples, void *payload, int length); 43 private: 44 int mSampleCount; 45 }; 46 47 int UlawCodec::encode(void *payload, int16_t *samples) 48 { 49 int8_t *ulaws = (int8_t *)payload; 50 for (int i = 0; i < mSampleCount; ++i) { 51 int sample = samples[i]; 52 int sign = (sample >> 8) & 0x80; 53 if (sample < 0) { 54 sample = -sample; 55 } 56 sample += 132; 57 if (sample > 32767) { 58 sample = 32767; 59 } 60 int exponent = gExponents[sample >> 8]; 61 int mantissa = (sample >> (exponent + 3)) & 0x0F; 62 ulaws[i] = ~(sign | (exponent << 4) | mantissa); 63 } 64 return mSampleCount; 65 } 66 67 int UlawCodec::decode(int16_t *samples, void *payload, int length) 68 { 69 int8_t *ulaws = (int8_t *)payload; 70 for (int i = 0; i < length; ++i) { 71 int ulaw = ~ulaws[i]; 72 int exponent = (ulaw >> 4) & 0x07; 73 int mantissa = ulaw & 0x0F; 74 int sample = (((mantissa << 3) + 132) << exponent) - 132; 75 samples[i] = (ulaw < 0 ? -sample : sample); 76 } 77 return length; 78 } 79 80 //------------------------------------------------------------------------------ 81 82 class AlawCodec : public AudioCodec 83 { 84 public: 85 int set(int sampleRate, const char *fmtp) { 86 mSampleCount = sampleRate / 50; 87 return mSampleCount; 88 } 89 int encode(void *payload, int16_t *samples); 90 int decode(int16_t *samples, void *payload, int length); 91 private: 92 int mSampleCount; 93 }; 94 95 int AlawCodec::encode(void *payload, int16_t *samples) 96 { 97 int8_t *alaws = (int8_t *)payload; 98 for (int i = 0; i < mSampleCount; ++i) { 99 int sample = samples[i]; 100 int sign = (sample >> 8) & 0x80; 101 if (sample < 0) { 102 sample = -sample; 103 } 104 if (sample > 32767) { 105 sample = 32767; 106 } 107 int exponent = gExponents[sample >> 8]; 108 int mantissa = (sample >> (exponent == 0 ? 4 : exponent + 3)) & 0x0F; 109 alaws[i] = (sign | (exponent << 4) | mantissa) ^ 0xD5; 110 } 111 return mSampleCount; 112 } 113 114 int AlawCodec::decode(int16_t *samples, void *payload, int length) 115 { 116 int8_t *alaws = (int8_t *)payload; 117 for (int i = 0; i < length; ++i) { 118 int alaw = alaws[i] ^ 0x55; 119 int exponent = (alaw >> 4) & 0x07; 120 int mantissa = alaw & 0x0F; 121 int sample = (exponent == 0 ? (mantissa << 4) + 8 : 122 ((mantissa << 3) + 132) << exponent); 123 samples[i] = (alaw < 0 ? sample : -sample); 124 } 125 return length; 126 } 127 128 } // namespace 129 130 AudioCodec *newUlawCodec() 131 { 132 return new UlawCodec; 133 } 134 135 AudioCodec *newAlawCodec() 136 { 137 return new AlawCodec; 138 } 139
