94 lines
2.8 KiB
C
94 lines
2.8 KiB
C
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/*
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* Copyright (C) 2007 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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#ifndef ANDROID_AUDIO_RESAMPLER_H
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#define ANDROID_AUDIO_RESAMPLER_H
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#include <stdint.h>
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#include <sys/types.h>
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#include "AudioBufferProvider.h"
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namespace android {
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// ----------------------------------------------------------------------------
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class AudioResampler {
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public:
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// Determines quality of SRC.
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// LOW_QUALITY: linear interpolator (1st order)
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// MED_QUALITY: cubic interpolator (3rd order)
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// HIGH_QUALITY: fixed multi-tap FIR (e.g. 48KHz->44.1KHz)
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// NOTE: high quality SRC will only be supported for
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// certain fixed rate conversions. Sample rate cannot be
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// changed dynamically.
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enum src_quality {
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DEFAULT=0,
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LOW_QUALITY=1,
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MED_QUALITY=2,
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HIGH_QUALITY=3
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};
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static AudioResampler* create(int bitDepth, int inChannelCount,
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int32_t sampleRate, int quality=DEFAULT);
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virtual ~AudioResampler();
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virtual void init() = 0;
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virtual void setSampleRate(int32_t inSampleRate);
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virtual void setVolume(int16_t left, int16_t right);
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virtual void resample(int32_t* out, size_t outFrameCount,
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AudioBufferProvider* provider) = 0;
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protected:
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// number of bits for phase fraction - 30 bits allows nearly 2x downsampling
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static const int kNumPhaseBits = 30;
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// phase mask for fraction
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static const uint32_t kPhaseMask = (1LU<<kNumPhaseBits)-1;
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// multiplier to calculate fixed point phase increment
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static const double kPhaseMultiplier = 1L << kNumPhaseBits;
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enum format {MONO_16_BIT, STEREO_16_BIT};
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AudioResampler(int bitDepth, int inChannelCount, int32_t sampleRate);
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// prevent copying
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AudioResampler(const AudioResampler&);
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AudioResampler& operator=(const AudioResampler&);
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int32_t mBitDepth;
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int32_t mChannelCount;
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int32_t mSampleRate;
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int32_t mInSampleRate;
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AudioBufferProvider::Buffer mBuffer;
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union {
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int16_t mVolume[2];
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uint32_t mVolumeRL;
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};
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int16_t mTargetVolume[2];
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format mFormat;
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size_t mInputIndex;
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int32_t mPhaseIncrement;
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uint32_t mPhaseFraction;
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};
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// ----------------------------------------------------------------------------
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}
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; // namespace android
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#endif // ANDROID_AUDIO_RESAMPLER_H
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