CompressorProcessor.cpp

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/*  SPDX-License-Identifier: GPL-2.0-or-later */
/*!********************************************************************
 
  Audacity: A Digital Audio Editor
 
  CompressorProcessor.cpp
 
  Matthieu Hodgkinson
 
**********************************************************************/
 
#include "CompressorProcessor.h"
#include "MathApprox.h"
#include "SimpleCompressor/GainReductionComputer.h"
#include "SimpleCompressor/LookAheadGainReduction.h"
#include <algorithm>
#include <cassert>
 
float CompressorProcessor::GetMakeupGainDb(
   const DynamicRangeProcessorSettings& settings)
{
   return settings.outCompressionThreshDb - settings.inCompressionThreshDb;
}
 
float CompressorProcessor::GetMaxCompressionDb(
   const DynamicRangeProcessorSettings& settings)
{
   const auto tfEval = EvaluateTransferFunction(settings, 0);
   const auto netGain =
      settings.outCompressionThreshDb - settings.inCompressionThreshDb;
   return netGain - tfEval;
}
 
float CompressorProcessor::EvaluateTransferFunction(
   const DynamicRangeProcessorSettings& settings, float inputDb)
{
   return DanielRudrich::GainReductionComputer::getCharacteristicSample(
      inputDb, settings.kneeWidthDb, settings.inCompressionThreshDb,
      settings.compressionRatio, GetMakeupGainDb(settings));
}
 
CompressorProcessor::CompressorProcessor(
   const DynamicRangeProcessorSettings& settings)
    : mGainReductionComputer { std::make_unique<
         DanielRudrich::GainReductionComputer>() }
    , mLookAheadGainReduction { std::make_unique<
         DanielRudrich::LookAheadGainReduction>() }
    , mSettings { settings }
{
}
 
CompressorProcessor::~CompressorProcessor() = default;
 
void CompressorProcessor::ApplySettingsIfNeeded(
   const DynamicRangeProcessorSettings& settings)
{
   if (settings == mSettings)
      return;
 
   const auto lookaheadNeedsReinit =
      settings.lookaheadMs != mSettings.lookaheadMs;
   mSettings = settings;
 
   mGainReductionComputer->setThreshold(settings.inCompressionThreshDb);
   mGainReductionComputer->setKnee(settings.kneeWidthDb);
   mGainReductionComputer->setAttackTime(settings.attackMs / 1000);
   mGainReductionComputer->setReleaseTime(settings.releaseMs / 1000);
   mGainReductionComputer->setRatio(settings.compressionRatio);
   mGainReductionComputer->setMakeUpGain(GetMakeupGainDb(settings));
 
   if (lookaheadNeedsReinit)
   {
      mLookAheadGainReduction->setDelayTime(settings.lookaheadMs / 1000);
      Reinit();
   }
}
 
void CompressorProcessor::Init(int sampleRate, int numChannels, int blockSize)
{
   mSampleRate = sampleRate;
   mNumChannels = numChannels;
   mBlockSize = std::min(blockSize, maxBlockSize);
   Reinit();
}
 
const DynamicRangeProcessorSettings& CompressorProcessor::GetSettings() const
{
   return mSettings;
}
 
void CompressorProcessor::Process(
   const float* const* inBlock, float* const* outBlock, int blockLen)
{
   assert(Initialized());
   if (!Initialized())
      return;
 
   auto processed = 0;
   mLastFrameStats = {};
   std::vector<const float*> in(mNumChannels);
   std::vector<float*> out(mNumChannels);
   while (processed < blockLen)
   {
      for (auto i = 0; i < mNumChannels; ++i)
      {
         in[i] = inBlock[i] + processed;
         out[i] = outBlock[i] + processed;
      }
      const auto toProcess = std::min(blockLen - processed, mBlockSize);
      UpdateEnvelope(in.data(), toProcess);
      CopyWithDelay(in.data(), toProcess);
 
      float delayedInputAbsMax = 0;
      int delayedInputAbsMaxIndex = 0;
      ApplyEnvelope(
         out.data(), toProcess, delayedInputAbsMax, delayedInputAbsMaxIndex);
 
      const auto blockMaxDb = log2ToDb * FastLog2(delayedInputAbsMax);
      if (mLastFrameStats.maxInputSampleDb < blockMaxDb)
      {
         mLastFrameStats.maxInputSampleDb = blockMaxDb;
         mLastFrameStats.dbGainOfMaxInputSample =
            mEnvelope[delayedInputAbsMaxIndex];
      }
 
      processed += toProcess;
   }
}
 
const std::vector<std::vector<float>>&
CompressorProcessor::GetDelayedInput() const
{
   return mDelayedInput;
}
 
const CompressorProcessor::FrameStats&
CompressorProcessor::GetLastFrameStats() const
{
   return mLastFrameStats;
}
 
float CompressorProcessor::EvaluateTransferFunction(float inputDb) const
{
   return mGainReductionComputer->getCharacteristicSample(inputDb);
}
 
void CompressorProcessor::UpdateEnvelope(const float* const* in, int blockLen)
{
   // Fill mEnvelope with max of all in channels;
   for (auto i = 0; i < blockLen; ++i)
   {
      auto max = 0.f;
      for (auto j = 0; j < mNumChannels; ++j)
      {
         const auto x = std::abs(in[j][i]);
         if (x > max)
            max = x;
      }
      mEnvelope[i] = max;
   }
 
   // TODO: uses std::log10 ; use log2 optimization instead.
   mGainReductionComputer->computeGainInDecibelsFromSidechainSignal(
      mEnvelope.data(), mEnvelope.data(), blockLen);
 
   if (mSettings.lookaheadMs <= 0)
      return;
 
   mLookAheadGainReduction->pushSamples(mEnvelope.data(), blockLen);
   mLookAheadGainReduction->process();
   mLookAheadGainReduction->readSamples(mEnvelope.data(), blockLen);
}
 
void CompressorProcessor::CopyWithDelay(const float* const* in, int blockLen)
{
   const auto d = mLookAheadGainReduction->getDelayInSamples();
   for (auto i = 0; i < mNumChannels; ++i)
      std::copy(in[i], in[i] + blockLen, mDelayedInput[i].data() + d);
}
 
void CompressorProcessor::ApplyEnvelope(
   float* const* out, int blockLen, float& delayedInputAbsMax,
   int& delayedInputAbsMaxIndex)
{
   const auto makeupGainDb = mGainReductionComputer->getMakeUpGain();
   const auto d = mLookAheadGainReduction->getDelayInSamples();
   std::array<float, 2> chanAbsMax { 0.f, 0.f };
   std::array<int, 2> chanAbsMaxIndex { 0, 0 };
   for (auto i = 0; i < mNumChannels; ++i)
   {
      const auto in = mDelayedInput[i].data();
      for (auto j = 0; j < blockLen; ++j)
      {
         if (std::abs(in[j]) > chanAbsMax[i])
         {
            chanAbsMax[i] = std::abs(in[j]);
            chanAbsMaxIndex[i] = j;
         }
         out[i][j] =
            in[j] * std::pow(10.f, 0.05f * (mEnvelope[j] + makeupGainDb));
      }
      std::move(in + blockLen, in + blockLen + d, in);
   }
   const auto i = chanAbsMax[0] > chanAbsMax[1] ? 0 : 1;
   delayedInputAbsMax = chanAbsMax[i];
   delayedInputAbsMaxIndex = chanAbsMaxIndex[i];
}
 
void CompressorProcessor::Reinit()
{
   if (!Initialized())
      // Not there yet.
      return;
   mGainReductionComputer->prepare(mSampleRate);
   // In this order: setDelayTime, then prepare:
   mLookAheadGainReduction->setDelayTime(mSettings.lookaheadMs / 1000);
   mLookAheadGainReduction->prepare(mSampleRate, mBlockSize);
   const auto maxDelay =
      std::max(compressorMaxLookaheadMs, limiterMaxLookaheadMs) * mSampleRate /
      1000;
   const auto d = mLookAheadGainReduction->getDelayInSamples();
   assert(d <= maxDelay);
   mDelayedInput.resize(mNumChannels);
   std::for_each(mDelayedInput.begin(), mDelayedInput.end(), [&](auto& v) {
      v.reserve(maxDelay + mBlockSize);
      v.resize(d + mBlockSize);
      std::fill(v.begin(), v.end(), 0.f);
   });
   std::fill(mEnvelope.begin(), mEnvelope.end(), 0.f);
}
 
bool CompressorProcessor::Initialized() const
{
   return mSampleRate != 0 && mNumChannels != 0 && mBlockSize != 0;
}