CompressorProcessor.h

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/*  SPDX-License-Identifier: GPL-2.0-or-later */
/*!********************************************************************
 
  Audacity: A Digital Audio Editor
 
  CompressorProcessor.h
 
  Matthieu Hodgkinson
 
**********************************************************************/
#pragma once
 
#include "DynamicRangeProcessorTypes.h"
#include <array>
#include <limits>
#include <memory>
#include <vector>
 
namespace DanielRudrich
{
class GainReductionComputer;
class LookAheadGainReduction;
} // namespace DanielRudrich
 
class DYNAMIC_RANGE_PROCESSOR_API CompressorProcessor
{
public:
   struct FrameStats
   {
      float maxInputSampleDb = -std::numeric_limits<float>::infinity();
      float dbGainOfMaxInputSample = 0;
   };
 
   static float
   GetMaxCompressionDb(const DynamicRangeProcessorSettings& settings);
   static float GetMakeupGainDb(const DynamicRangeProcessorSettings& settings);
   static float EvaluateTransferFunction(
      const DynamicRangeProcessorSettings& settings, float inputDb);
 
   CompressorProcessor(
      const DynamicRangeProcessorSettings& settings = {
         // No reason to initialize with compressor settings other than
         // convenience.
         CompressorSettings {} });
   CompressorProcessor(const CompressorProcessor& other) = delete;
   ~CompressorProcessor();
 
   void ApplySettingsIfNeeded(const DynamicRangeProcessorSettings& settings);
   void Init(int sampleRate, int numChannels, int blockSize);
   void Reinit();
   const DynamicRangeProcessorSettings& GetSettings() const;
   void
   Process(const float* const* inBlock, float* const* outBlock, int blockLen);
   const std::vector<std::vector<float>>& GetDelayedInput() const;
   const FrameStats& GetLastFrameStats() const;
   float EvaluateTransferFunction(float inputDb) const;
 
private:
   void UpdateEnvelope(const float* const* inBlock, int blockLen);
   void CopyWithDelay(const float* const* inBlock, int blockLen);
   void ApplyEnvelope(
      float* const* outBlock, int blockLen, float& delayedInputMax,
      int& delayedInputMaxIndex);
   bool Initialized() const;
 
   static constexpr auto maxBlockSize = 512;
 
   const std::unique_ptr<DanielRudrich::GainReductionComputer>
      mGainReductionComputer;
   const std::unique_ptr<DanielRudrich::LookAheadGainReduction>
      mLookAheadGainReduction;
   DynamicRangeProcessorSettings mSettings;
   int mSampleRate = 0;
   int mNumChannels = 0;
   int mBlockSize = 0;
   std::array<float, maxBlockSize> mEnvelope;
   std::vector<std::vector<float>>
      mDelayedInput; // Can't conveniently use an array here, because neither
                     // delay time nor sample rate are known at compile time.
                     // Re-allocation during playback is only done if the user
                     // changes the look-ahead settings, in which case glitches
                     // are hardly avoidable anyway.
   FrameStats mLastFrameStats;
};