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