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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_CUBIC_H
     18 #define ANDROID_AUDIO_RESAMPLER_CUBIC_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 class AudioResamplerCubic : public AudioResampler {
     30 public:
     31     AudioResamplerCubic(int inChannelCount, int32_t sampleRate) :
     32         AudioResampler(inChannelCount, sampleRate, MED_QUALITY) {
     33     }
     34     virtual void resample(int32_t* out, size_t outFrameCount,
     35             AudioBufferProvider* provider);
     36 private:
     37     // number of bits used in interpolation multiply - 14 bits avoids overflow
     38     static const int kNumInterpBits = 14;
     39 
     40     // bits to shift the phase fraction down to avoid overflow
     41     static const int kPreInterpShift = kNumPhaseBits - kNumInterpBits;
     42     typedef struct {
     43         int32_t a, b, c, y0, y1, y2, y3;
     44     } state;
     45     void init();
     46     void resampleMono16(int32_t* out, size_t outFrameCount,
     47             AudioBufferProvider* provider);
     48     void resampleStereo16(int32_t* out, size_t outFrameCount,
     49             AudioBufferProvider* provider);
     50     static inline int32_t interp(state* p, int32_t x) {
     51         return (((((p->a * x >> 14) + p->b) * x >> 14) + p->c) * x >> 14) + p->y1;
     52     }
     53     static inline void advance(state* p, int16_t in) {
     54         p->y0 = p->y1;
     55         p->y1 = p->y2;
     56         p->y2 = p->y3;
     57         p->y3 = in;
     58         p->a = (3 * (p->y1 - p->y2) - p->y0 + p->y3) >> 1;
     59         p->b = (p->y2 << 1) + p->y0 - (((5 * p->y1 + p->y3)) >> 1);
     60         p->c = (p->y2 - p->y0) >> 1;
     61     }
     62     state left, right;
     63 };
     64 
     65 // ----------------------------------------------------------------------------
     66 }; // namespace android
     67 
     68 #endif /*ANDROID_AUDIO_RESAMPLER_CUBIC_H*/
     69