DelayStereo.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/Delay.h"
#include "DSP/Filter.h"
 
namespace Audio
{
    // The different stereo delay modes
    namespace EStereoDelayMode
    {
        enum Type
        {
            Normal,
            Cross,
            PingPong,
 
            NumStereoDelayModes
        };
    }
 
    class FDelayStereo
    {
    public:
        SIGNALPROCESSING_API FDelayStereo();
        SIGNALPROCESSING_API ~FDelayStereo();
 
        // Initializes the stereo delay with given sample rate and default max delay length
        SIGNALPROCESSING_API void Init(const float InSampleRate, const int32 InNumChannels, const float InDelayLengthSec = 2.0f);
 
        // Resets the stereo delay state
        SIGNALPROCESSING_API void Reset();
 
        // Process a single frame of audio
        SIGNALPROCESSING_API void ProcessAudioFrame(const float* InFrame, float* OutFrame);
 
        // Process a buffer of audio
        SIGNALPROCESSING_API void ProcessAudio(const float* InBuffer, const int32 InNumSamples, float* OutBuffer);
 
        // Sets which delay stereo mode to use
        SIGNALPROCESSING_API void SetMode(const EStereoDelayMode::Type InMode);
 
        // Gets the current stereo dealy mode
        EStereoDelayMode::Type GetMode() const { return DelayMode; }
 
        // Sets the delay time in msec. 
        SIGNALPROCESSING_API void SetDelayTimeMsec(const float InDelayTimeMsec);
 
        // Sets the feedback amount
        SIGNALPROCESSING_API void SetFeedback(const float InFeedback);
 
        // Sets the delay ratio (scales difference between left and right stereo delays)
        SIGNALPROCESSING_API void SetDelayRatio(const float InDelayRatio);
 
        // Sets the amount of the effect to mix in the output
        SIGNALPROCESSING_API void SetWetLevel(const float InWetLevel);
 
        // Sets the amount of the effect to mix in the output
        SIGNALPROCESSING_API void SetDryLevel(const float InDryLevel);
 
        // Sets whether or not the filter is enabled
        SIGNALPROCESSING_API void SetFilterEnabled(bool bInEnabled);
 
        // Sets the filter settings
        SIGNALPROCESSING_API void SetFilterSettings(EBiquadFilter::Type InFilterType, const float InCutoffFrequency, const float InQ);
 
    protected:
        // Updates the delays based on recent parameters
        SIGNALPROCESSING_API void UpdateDelays();
 
        // Delay lines per channel
        TArray<FDelay> Delays;
 
        // Biquad filter per channel to feed the delay output through
        TArray<FBiquadFilter> BiquadFilters;
 
        // What mode the stereo delay is in
        EStereoDelayMode::Type DelayMode  = EStereoDelayMode::Normal;
 
        // Amount of delay time in msec 
        float DelayTimeMsec = 0.0f;
 
        // How much delay feedback to use
        float Feedback = 0.0f;
 
        // How much to shift the delays from each other
        float DelayRatio = 0.0f;
 
        // The amount of wet level on the output
        float WetLevel = 0.0f;
 
        // The amount of dry level on the output
        float DryLevel = 1.0f;
 
        // Filter data
        float FilterFreq = 20000.0f;
        float FilterQ = 2.0f;
        EBiquadFilter::Type FilterType = EBiquadFilter::Lowpass;
 
        // The number of channels to use (will sum mono)
        int32 NumChannels = 0;
 
        // If the delay has started processing yet
        bool bIsInit = true;
 
        bool bIsFilterEnabled = false;
    };
 
}