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      1 /*
      2  * Copyright (C) 2007 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 #ifndef ANDROID_AUDIO_RESAMPLER_SINC_H
     18 #define ANDROID_AUDIO_RESAMPLER_SINC_H
     19 
     20 #include <stdint.h>
     21 #include <sys/types.h>
     22 #include <cutils/log.h>
     23 
     24 #include "AudioResampler.h"
     25 
     26 namespace android {
     27 
     28 // ----------------------------------------------------------------------------
     29 
     30 class AudioResamplerSinc : public AudioResampler {
     31 public:
     32     AudioResamplerSinc(int bitDepth, int inChannelCount, int32_t sampleRate);
     33 
     34     ~AudioResamplerSinc();
     35 
     36     virtual void resample(int32_t* out, size_t outFrameCount,
     37             AudioBufferProvider* provider);
     38 private:
     39     void init();
     40 
     41     template<int CHANNELS>
     42     void resample(int32_t* out, size_t outFrameCount,
     43             AudioBufferProvider* provider);
     44 
     45     template<int CHANNELS>
     46     inline void filterCoefficient(
     47             int32_t& l, int32_t& r, uint32_t phase, int16_t const *samples);
     48 
     49     template<int CHANNELS>
     50     inline void interpolate(
     51             int32_t& l, int32_t& r,
     52             int32_t const* coefs, int16_t lerp, int16_t const* samples);
     53 
     54     template<int CHANNELS>
     55     inline void read(int16_t*& impulse, uint32_t& phaseFraction,
     56             int16_t const* in, size_t inputIndex);
     57 
     58     int16_t *mState;
     59     int16_t *mImpulse;
     60     int16_t *mRingFull;
     61 
     62     int32_t const * mFirCoefs;
     63     static const int32_t mFirCoefsDown[];
     64     static const int32_t mFirCoefsUp[];
     65 
     66     // ----------------------------------------------------------------------------
     67     static const int32_t RESAMPLE_FIR_NUM_COEF       = 8;
     68     static const int32_t RESAMPLE_FIR_LERP_INT_BITS  = 4;
     69 
     70     // we have 16 coefs samples per zero-crossing
     71     static const int coefsBits = RESAMPLE_FIR_LERP_INT_BITS;        // 4
     72     static const int cShift = kNumPhaseBits - coefsBits;            // 26
     73     static const uint32_t cMask  = ((1<<coefsBits)-1) << cShift;    // 0xf<<26 = 3c00 0000
     74 
     75     // and we use 15 bits to interpolate between these samples
     76     // this cannot change because the mul below rely on it.
     77     static const int pLerpBits = 15;
     78     static const int pShift = kNumPhaseBits - coefsBits - pLerpBits;    // 11
     79     static const uint32_t pMask  = ((1<<pLerpBits)-1) << pShift;    // 0x7fff << 11
     80 
     81     // number of zero-crossing on each side
     82     static const unsigned int halfNumCoefs = RESAMPLE_FIR_NUM_COEF;
     83 };
     84 
     85 // ----------------------------------------------------------------------------
     86 }; // namespace android
     87 
     88 #endif /*ANDROID_AUDIO_RESAMPLER_SINC_H*/
     89