G711Codec.cpp revision d85beac45c12a65076a1c157681de9a5b03bdec7 
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
19namespace {
20
21const 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
34class UlawCodec : public AudioCodec
35{
36public:
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);
43private:
44    int mSampleCount;
45};
46
47int 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
67int 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
82class AlawCodec : public AudioCodec
83{
84public:
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);
91private:
92    int mSampleCount;
93};
94
95int 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
114int 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
130AudioCodec *newUlawCodec()
131{
132    return new UlawCodec;
133}
134
135AudioCodec *newAlawCodec()
136{
137    return new AlawCodec;
138}
139