MultiMono.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "HAL/Platform.h"
#include "Containers/ArrayView.h"
#include "Containers/StaticArray.h"
 
// Collection of multi-mono DSP algorithms. Although technically most of these are just setup to call the mono versions, there is enough
// boilerplate to warrant a single lib.
 
// Example Multi-mono-layout: [L][L][L][L][L][R][R][R][R][R], i.e. an entire channels worth of frames consecutively in memory, next
// to the next channel and so on.
 
namespace Audio
{
    constexpr int32 MaxStackMultiMonoChannels = 128; // Some relatively high number. These are just pointers on stack.
 
    // Stack array of pointers alias.
    template<typename T> using TStackArrayOfPointers = TArray<T*,TInlineAllocator<MaxStackMultiMonoChannels>>;
 
    // Helper to create array of pointers from multi-mono.
    // Warning Array of pointers will be larger than you need, but filled to InNumChannels
    template<typename T> TStackArrayOfPointers<T> MakeMultiMonoPointersFromView(TArrayView<T> InMultiMono, const int32 InNumFrames, const int32 InNumChannels)
    {
        checkSlow(InNumChannels <= MaxStackMultiMonoChannels);
        checkSlow(InNumChannels > 0);
        checkSlow(InMultiMono.GetData());
        checkSlow(InMultiMono.Num() % InNumFrames == 0 && InMultiMono.Num() >= InNumFrames);
        TStackArrayOfPointers<T> ArrayOfPointers;
        ArrayOfPointers.SetNum(InNumChannels);
        for (int32 i = 0; i < InNumChannels; ++i)
        {
            ArrayOfPointers[i] = InMultiMono.GetData() + (InNumFrames * i);
        }
        return ArrayOfPointers; // RTO so this should just inline
    }
    
    SIGNALPROCESSING_API void MultiMonoMixUpOrDown(
        TArrayView<const float> InSrc, const TArrayView<float> InDst, const int32 NumFrames, TArrayView<const float> MixGains,
            const int32 NumSrcChannels, const int32 NumDstChannels);
 
    SIGNALPROCESSING_API void MultiMonoMixUpOrDown(
        TArrayView<const float*> InSrc, TArrayView<float*> InDst, const int32 NumFrames,TArrayView<const float> MixGains);
    
}