VectorLinearResampler.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/Dsp.h"
 
namespace Audio
{
    struct FVectorLinearResampler
    {
        uint32 CurrentFrameFraction;
 
        // Returns the number of source frames necessary to generate the requested output
        // count at the given fixed point sample rate (1.0 rate is 65536)
        uint32 SourceFramesNeeded(uint32 OutputFramesNeeded, uint32 FixedPointSampleRate)
        {
            // the last run of the resampler will index [farthest_position >> 16] + 1, so we need
            // that +1 to make it a count from an index.
            uint32 FarthestPosition = CurrentFrameFraction + (OutputFramesNeeded - 1) * FixedPointSampleRate;
            return (FarthestPosition >> 16) + 2;
        }
 
        // Generate OutputFramesNeeded resampled output at the given fixed point sample rate (1.0 = 65536).
        // Returns the number of source frames to consume. The next run of the resample expects to get
        // SourceFrames + previous runs return value.
        //
        // stereo is deinterleaved, with the right channels being specified by Frames+StrideFloats.
        //
        SIGNALPROCESSING_API uint32 ResampleMono(uint32 OutputFramesNeeded, uint32 FixedPointSampleRate, float const* SourceFrames, float* OutputFrames);
        SIGNALPROCESSING_API uint32 ResampleStereo(uint32 OutputFramesNeeded, uint32 FixedPointSampleRate, float const* SourceFrames, uint32 SourceFramesStrideFloats, float* OutputFrames, uint32 OutputFramesStrideFloats);
    };
}