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, int count, 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, int count, void *payload, int length) 68 { 69 int8_t *ulaws = (int8_t *)payload; 70 if (length > count) { 71 length = count; 72 } 73 for (int i = 0; i < length; ++i) { 74 int ulaw = ~ulaws[i]; 75 int exponent = (ulaw >> 4) & 0x07; 76 int mantissa = ulaw & 0x0F; 77 int sample = (((mantissa << 3) + 132) << exponent) - 132; 78 samples[i] = (ulaw < 0 ? -sample : sample); 79 } 80 return length; 81 } 82 83 //------------------------------------------------------------------------------ 84 85 class AlawCodec : public AudioCodec 86 { 87 public: 88 int set(int sampleRate, const char *fmtp) { 89 mSampleCount = sampleRate / 50; 90 return mSampleCount; 91 } 92 int encode(void *payload, int16_t *samples); 93 int decode(int16_t *samples, int count, void *payload, int length); 94 private: 95 int mSampleCount; 96 }; 97 98 int AlawCodec::encode(void *payload, int16_t *samples) 99 { 100 int8_t *alaws = (int8_t *)payload; 101 for (int i = 0; i < mSampleCount; ++i) { 102 int sample = samples[i]; 103 int sign = (sample >> 8) & 0x80; 104 if (sample < 0) { 105 sample = -sample; 106 } 107 if (sample > 32767) { 108 sample = 32767; 109 } 110 int exponent = gExponents[sample >> 8]; 111 int mantissa = (sample >> (exponent == 0 ? 4 : exponent + 3)) & 0x0F; 112 alaws[i] = (sign | (exponent << 4) | mantissa) ^ 0xD5; 113 } 114 return mSampleCount; 115 } 116 117 int AlawCodec::decode(int16_t *samples, int count, void *payload, int length) 118 { 119 int8_t *alaws = (int8_t *)payload; 120 if (length > count) { 121 length = count; 122 } 123 for (int i = 0; i < length; ++i) { 124 int alaw = alaws[i] ^ 0x55; 125 int exponent = (alaw >> 4) & 0x07; 126 int mantissa = alaw & 0x0F; 127 int sample = (exponent == 0 ? (mantissa << 4) + 8 : 128 ((mantissa << 3) + 132) << exponent); 129 samples[i] = (alaw < 0 ? sample : -sample); 130 } 131 return length; 132 } 133 134 } // namespace 135 136 AudioCodec *newUlawCodec() 137 { 138 return new UlawCodec; 139 } 140 141 AudioCodec *newAlawCodec() 142 { 143 return new AlawCodec; 144 } 145
