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/*
* Copyrightm (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "AudioCodec.h"
namespace {
const int8_t gExponents[128] = {
0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
};
//------------------------------------------------------------------------------
class UlawCodec : public AudioCodec
{
public:
int set(int sampleRate, const char *fmtp) {
mSampleCount = sampleRate / 50;
return mSampleCount;
}
int encode(void *payload, int16_t *samples);
int decode(int16_t *samples, void *payload, int length);
private:
int mSampleCount;
};
int UlawCodec::encode(void *payload, int16_t *samples)
{
int8_t *ulaws = (int8_t *)payload;
for (int i = 0; i < mSampleCount; ++i) {
int sample = samples[i];
int sign = (sample >> 8) & 0x80;
if (sample < 0) {
sample = -sample;
}
sample += 132;
if (sample > 32767) {
sample = 32767;
}
int exponent = gExponents[sample >> 8];
int mantissa = (sample >> (exponent + 3)) & 0x0F;
ulaws[i] = ~(sign | (exponent << 4) | mantissa);
}
return mSampleCount;
}
int UlawCodec::decode(int16_t *samples, void *payload, int length)
{
int8_t *ulaws = (int8_t *)payload;
for (int i = 0; i < length; ++i) {
int ulaw = ~ulaws[i];
int exponent = (ulaw >> 4) & 0x07;
int mantissa = ulaw & 0x0F;
int sample = (((mantissa << 3) + 132) << exponent) - 132;
samples[i] = (ulaw < 0 ? -sample : sample);
}
return length;
}
//------------------------------------------------------------------------------
class AlawCodec : public AudioCodec
{
public:
int set(int sampleRate, const char *fmtp) {
mSampleCount = sampleRate / 50;
return mSampleCount;
}
int encode(void *payload, int16_t *samples);
int decode(int16_t *samples, void *payload, int length);
private:
int mSampleCount;
};
int AlawCodec::encode(void *payload, int16_t *samples)
{
int8_t *alaws = (int8_t *)payload;
for (int i = 0; i < mSampleCount; ++i) {
int sample = samples[i];
int sign = (sample >> 8) & 0x80;
if (sample < 0) {
sample = -sample;
}
if (sample > 32767) {
sample = 32767;
}
int exponent = gExponents[sample >> 8];
int mantissa = (sample >> (exponent == 0 ? 4 : exponent + 3)) & 0x0F;
alaws[i] = (sign | (exponent << 4) | mantissa) ^ 0xD5;
}
return mSampleCount;
}
int AlawCodec::decode(int16_t *samples, void *payload, int length)
{
int8_t *alaws = (int8_t *)payload;
for (int i = 0; i < length; ++i) {
int alaw = alaws[i] ^ 0x55;
int exponent = (alaw >> 4) & 0x07;
int mantissa = alaw & 0x0F;
int sample = (exponent == 0 ? (mantissa << 4) + 8 :
((mantissa << 3) + 132) << exponent);
samples[i] = (alaw < 0 ? sample : -sample);
}
return length;
}
} // namespace
AudioCodec *newUlawCodec()
{
return new UlawCodec;
}
AudioCodec *newAlawCodec()
{
return new AlawCodec;
}
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