OpusEncoder.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/Encoders/IAudioEncoder.h"
 
#if !PLATFORM_TVOS
 
class FOpusEncoderPrivateState;
class FOggEncapsulator;
 
// Possible frame sizes to use for the encoder.
enum class EOpusFrameSizes : uint8
{
    Min, // 2.5 milliseconds
    Small, // 5 milliseconds
    MediumLow, // 10 milliseconds
    MediumHigh, // 20 milliseconds
    High, // 40 milliseconds
    Max, // 60 milliseconds
};
 
enum class EOpusMode : uint8
{
    File, // Use this when encoding a .opus file. Pushes the Opus frames into Ogg packets.
    AudioStream, // Use this for general music and non-speech streaming applications.
    VoiceStream // Use this for Voice-specific applications.
};
 
class FOpusEncoder : public Audio::IAudioEncoder
{
public:
    FOpusEncoder(const FSoundQualityInfo& InInfo, int32 AverageBufferCallbackSize, EOpusFrameSizes InFrameSize = EOpusFrameSizes::MediumLow, EOpusMode InMode = EOpusMode::File);
    ~FOpusEncoder();
 
    virtual int32 GetCompressedPacketSize() const override;
 
protected:
    virtual int64 SamplesRequiredPerEncode() const override;
    virtual bool StartFile(const FSoundQualityInfo& InQualityInfo, TArray<uint8>& OutFileStart) override;
    virtual bool EncodeChunk(const TArray<float>& InAudio, TArray<uint8>& OutBytes) override;
    virtual bool EndFile(TArray<uint8>& OutBytes) override;
 
private:
    FOpusEncoder();
 
    int32 GetNumSamplesForEncode(EOpusFrameSizes InFrameSize) const;
    int32 GetNumSamplesForPreskip();
 
    int32 LastValidFrameSize;
    int32 NumChannels;
    int32 SampleRate;
    int32 UncompressedFrameSize;
 
    // Private state so that we don't have a public dependency on opus libraries.
    // Uniquely owned by this instance. Only a raw pointer because the destructor is not accessible.
    FOpusEncoderPrivateState* PrivateOpusState;
 
    // Private state. Only used if we are generating a .opus file, which are ogg encapsulations of an opus stream.
    FOggEncapsulator* PrivateOggEncapsulator;
 
    // Used for .opus files only:
    uint32 GranulePos;
    uint32 PacketIndex;
};
 
#endif // !PLATFORM_TVOS