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_H 18 #define ANDROID_AUDIO_RESAMPLER_H 19 20 #include <stdint.h> 21 #include <sys/types.h> 22 #include <cutils/compiler.h> 23 24 #include <media/AudioBufferProvider.h> 25 26 namespace android { 27 // ---------------------------------------------------------------------------- 28 29 class ANDROID_API AudioResampler { 30 public: 31 // Determines quality of SRC. 32 // LOW_QUALITY: linear interpolator (1st order) 33 // MED_QUALITY: cubic interpolator (3rd order) 34 // HIGH_QUALITY: fixed multi-tap FIR (e.g. 48KHz->44.1KHz) 35 // NOTE: high quality SRC will only be supported for 36 // certain fixed rate conversions. Sample rate cannot be 37 // changed dynamically. 38 enum src_quality { 39 DEFAULT_QUALITY=0, 40 LOW_QUALITY=1, 41 MED_QUALITY=2, 42 HIGH_QUALITY=3, 43 VERY_HIGH_QUALITY=4, 44 }; 45 46 static AudioResampler* create(int bitDepth, int inChannelCount, 47 int32_t sampleRate, src_quality quality=DEFAULT_QUALITY); 48 49 virtual ~AudioResampler(); 50 51 virtual void init() = 0; 52 virtual void setSampleRate(int32_t inSampleRate); 53 virtual void setVolume(int16_t left, int16_t right); 54 virtual void setLocalTimeFreq(uint64_t freq); 55 56 // set the PTS of the next buffer output by the resampler 57 virtual void setPTS(int64_t pts); 58 59 // Resample int16_t samples from provider and accumulate into 'out'. 60 // A mono provider delivers a sequence of samples. 61 // A stereo provider delivers a sequence of interleaved pairs of samples. 62 // Multi-channel providers are not supported. 63 // In either case, 'out' holds interleaved pairs of fixed-point signed Q19.12. 64 // That is, for a mono provider, there is an implicit up-channeling. 65 // Since this method accumulates, the caller is responsible for clearing 'out' initially. 66 // FIXME assumes provider is always successful; it should return the actual frame count. 67 virtual void resample(int32_t* out, size_t outFrameCount, 68 AudioBufferProvider* provider) = 0; 69 70 virtual void reset(); getUnreleasedFrames()71 virtual size_t getUnreleasedFrames() const { return mInputIndex; } 72 73 // called from destructor, so must not be virtual getQuality()74 src_quality getQuality() const { return mQuality; } 75 76 protected: 77 // number of bits for phase fraction - 30 bits allows nearly 2x downsampling 78 static const int kNumPhaseBits = 30; 79 80 // phase mask for fraction 81 static const uint32_t kPhaseMask = (1LU<<kNumPhaseBits)-1; 82 83 // multiplier to calculate fixed point phase increment 84 static const double kPhaseMultiplier = 1L << kNumPhaseBits; 85 86 AudioResampler(int bitDepth, int inChannelCount, int32_t sampleRate, src_quality quality); 87 88 // prevent copying 89 AudioResampler(const AudioResampler&); 90 AudioResampler& operator=(const AudioResampler&); 91 92 int64_t calculateOutputPTS(int outputFrameIndex); 93 94 const int32_t mBitDepth; 95 const int32_t mChannelCount; 96 const int32_t mSampleRate; 97 int32_t mInSampleRate; 98 AudioBufferProvider::Buffer mBuffer; 99 union { 100 int16_t mVolume[2]; 101 uint32_t mVolumeRL; 102 }; 103 int16_t mTargetVolume[2]; 104 size_t mInputIndex; 105 int32_t mPhaseIncrement; 106 uint32_t mPhaseFraction; 107 uint64_t mLocalTimeFreq; 108 int64_t mPTS; 109 110 private: 111 const src_quality mQuality; 112 113 // Return 'true' if the quality level is supported without explicit request 114 static bool qualityIsSupported(src_quality quality); 115 116 // For pthread_once() 117 static void init_routine(); 118 119 // Return the estimated CPU load for specific resampler in MHz. 120 // The absolute number is irrelevant, it's the relative values that matter. 121 static uint32_t qualityMHz(src_quality quality); 122 }; 123 124 // ---------------------------------------------------------------------------- 125 } 126 ; // namespace android 127 128 #endif // ANDROID_AUDIO_RESAMPLER_H 129