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:
set(int sampleRate,const char * fmtp)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
encode(void * payload,int16_t * samples)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
decode(int16_t * samples,int count,void * payload,int length)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:
set(int sampleRate,const char * fmtp)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
encode(void * payload,int16_t * samples)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
decode(int16_t * samples,int count,void * payload,int length)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
newUlawCodec()136 AudioCodec *newUlawCodec()
137 {
138 return new UlawCodec;
139 }
140
newAlawCodec()141 AudioCodec *newAlawCodec()
142 {
143 return new AlawCodec;
144 }
145