### Install OpusDotNet Package

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Instructions for installing the OpusDotNet library using NuGet or the .NET CLI.

```bash
Install-Package OpusDotNet
```

```bash
dotnet add package OpusDotNet
```

--------------------------------

### Install OpusDotNet NuGet Package

Source: https://github.com/mrphil2105/opusdotnet/blob/master/README.md

This command installs the OpusDotNet library using the NuGet Package Manager. OpusDotNet is a wrapper for libopus, facilitating audio encoding and decoding.

```powershell
Install-Package OpusDotNet
```

--------------------------------

### Configure Opus Application Mode

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Demonstrates how to initialize the OpusEncoder with different Application modes (VoIP, Audio, RestrictedLowDelay) to optimize for speech, music, or low-latency requirements.

```csharp
using OpusDotNet;

using (var voipEncoder = new OpusEncoder(Application.VoIP, 48000, 1)) { }
using (var audioEncoder = new OpusEncoder(Application.Audio, 48000, 2)) { }
using (var lowDelayEncoder = new OpusEncoder(Application.RestrictedLowDelay, 48000, 1)) { }
```

--------------------------------

### Encode PCM Audio with OpusEncoder

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Demonstrates how to initialize an OpusEncoder and convert raw 16-bit PCM audio into compressed Opus format with custom encoding parameters.

```csharp
using OpusDotNet;

using (var encoder = new OpusEncoder(Application.VoIP, 48000, 2))
{
    encoder.VBR = true;
    encoder.Complexity = 10;
    encoder.FEC = true;
    encoder.ExpectedPacketLoss = 10;
    encoder.DTX = true;

    int frameSizeMs = 20;
    int pcmLength = frameSizeMs * 48000 / 1000 * 2 * 2;
    byte[] pcmBytes = new byte[pcmLength];

    int targetBitrate = 128000;
    int opusBufferLength = targetBitrate * frameSizeMs / 8 / 1000;
    byte[] opusBytes = new byte[opusBufferLength];

    int encodedLength = encoder.Encode(pcmBytes, pcmLength, opusBytes, opusBufferLength);
    Console.WriteLine($"Encoded {pcmLength} PCM bytes to {encodedLength} Opus bytes");
}
```

--------------------------------

### Configure Audio Parameters and Buffer Sizes

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Provides reference arrays for supported sample rates and frame sizes in OpusDotNet. Includes a helper function to calculate the required PCM buffer size based on sample rate, channels, and frame duration.

```csharp
int[] validSampleRates = { 8000, 12000, 16000, 24000, 48000 };
double[] validFrameSizes = { 2.5, 5, 10, 20, 40, 60 };

int CalculatePcmBufferSize(int sampleRate, int channels, double frameSizeMs)
{
    return (int)(frameSizeMs * sampleRate / 1000 * channels * 2);
}
```

--------------------------------

### Decode Opus Audio with OpusDecoder

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Shows how to initialize an OpusDecoder to convert compressed Opus packets back into raw 16-bit PCM audio data.

```csharp
using OpusDotNet;

using (var decoder = new OpusDecoder(48000, 2))
{
    byte[] opusPacket = /* your compressed Opus data */;
    int opusLength = opusPacket.Length;

    int frameSizeMs = 20;
    int pcmBufferLength = frameSizeMs * 48000 / 1000 * 2 * 2;
    byte[] pcmBytes = new byte[pcmBufferLength];

    int decodedLength = decoder.Decode(opusPacket, opusLength, pcmBytes, pcmBufferLength);
    Console.WriteLine($"Decoded {opusLength} Opus bytes to {decodedLength} PCM bytes");
}
```

--------------------------------

### C# Audio Encoding and Decoding with OpusDotNet

Source: https://github.com/mrphil2105/opusdotnet/blob/master/README.md

Demonstrates basic audio encoding and decoding using OpusDotNet in C#. It initializes an OpusEncoder and OpusDecoder, encodes silence into Opus format, and then decodes it back to PCM. This is useful for VoIP applications.

```csharp
using (var encoder = new OpusEncoder(Application.Audio, 48000, 2))
{
    encoder.Bitrate = 128000; // 128 kbps
    encoder.VBR = true; // Variable bitrate
}
using (var decoder = new OpusDecoder(48000, 2))
{
    // 40 ms of silence at 48 KHz (2 channels).
    byte[] inputPCMBytes = new byte[40 * 48000 / 1000 * 2 * 2];
    byte[] opusBytes = encoder.Encode(inputPCMBytes, inputPCMBytes.Length, out int encodedLength);
    byte[] outputPCMBytes = decoder.Decode(opusBytes, encodedLength, out int decodedLength);
}
```

--------------------------------

### OpusDecoder Usage

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Illustrates how to use the OpusDecoder class to decode Opus-compressed audio back into raw PCM format. It includes setting up the decoder and processing received Opus packets.

```APIDOC
## OpusDecoder Usage

### Description
This section demonstrates the usage of the `OpusDecoder` class for decoding Opus-compressed audio data back into raw 16-bit PCM format. It covers initializing the decoder and performing the decoding operation on received Opus packets.

### Method
N/A (Class Usage)

### Endpoint
N/A (Class Usage)

### Parameters
N/A (Class Usage)

### Request Example
```csharp
using OpusDotNet;

// Create a decoder for 48 kHz stereo output
using (var decoder = new OpusDecoder(48000, 2))
{
    // Received Opus packet from network or file
    byte[] opusPacket = /* your compressed Opus data */;
    int opusLength = opusPacket.Length;

    // Allocate PCM output buffer for 20ms at 48 kHz stereo
    int frameSizeMs = 20;
    int pcmBufferLength = frameSizeMs * 48000 / 1000 * 2 * 2; // 3840 bytes
    byte[] pcmBytes = new byte[pcmBufferLength];

    // Decode the audio
    int decodedLength = decoder.Decode(opusPacket, opusLength, pcmBytes, pcmBufferLength);

    // Use pcmBytes[0..decodedLength] for playback
    Console.WriteLine($"Decoded {opusLength} Opus bytes to {decodedLength} PCM bytes");
}
```

### Response
N/A (Class Usage)

### Response Example
N/A (Class Usage)
```

--------------------------------

### OpusEncoder Usage

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Demonstrates how to use the OpusEncoder class to encode raw PCM audio data into Opus format. It covers initialization, configuration of encoding parameters, and the encoding process.

```APIDOC
## OpusEncoder Usage

### Description
This section shows how to initialize and use the `OpusEncoder` class to convert raw 16-bit PCM audio into the compressed Opus format. It includes examples of setting various encoding parameters like sample rate, channels, bitrate, VBR, FEC, DTX, and the actual encoding process.

### Method
N/A (Class Usage)

### Endpoint
N/A (Class Usage)

### Parameters
N/A (Class Usage)

### Request Example
```csharp
using OpusDotNet;

// Create an encoder for VoIP audio at 48 kHz stereo
using (var encoder = new OpusEncoder(Application.VoIP, 48000, 2))
{
    // Configure encoder settings
    encoder.VBR = true;           // Enable variable bitrate
    encoder.Complexity = 10;      // Maximum quality (0-10)
    encoder.FEC = true;           // Enable forward error correction
    encoder.ExpectedPacketLoss = 10; // Expect 10% packet loss
    encoder.DTX = true;           // Enable discontinuous transmission

    // 20 ms of audio at 48 kHz stereo (20 * 48000 / 1000 * 2 channels * 2 bytes per sample)
    int frameSizeMs = 20;
    int pcmLength = frameSizeMs * 48000 / 1000 * 2 * 2; // 3840 bytes
    byte[] pcmBytes = new byte[pcmLength];

    // Fill pcmBytes with your audio data...

    // Output buffer - size determines bitrate (e.g., 128 kbps for 20ms = 320 bytes)
    int targetBitrate = 128000; // 128 kbps
    int opusBufferLength = targetBitrate * frameSizeMs / 8 / 1000;
    byte[] opusBytes = new byte[opusBufferLength];

    // Encode the audio
    int encodedLength = encoder.Encode(pcmBytes, pcmLength, opusBytes, opusBufferLength);

    // Use opusBytes[0..encodedLength] for transmission or storage
    Console.WriteLine($"Encoded {pcmLength} PCM bytes to {encodedLength} Opus bytes");
}
```

### Response
N/A (Class Usage)

### Response Example
N/A (Class Usage)
```

--------------------------------

### Implement Real-time Audio Encoding and Decoding with OpusDotNet

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

This class encapsulates the Opus encoder and decoder to process audio frames. It includes methods for calculating frame sizes, encoding PCM data, decoding Opus packets, and handling packet loss via FEC.

```csharp
using System;
using OpusDotNet;

public class OpusAudioProcessor : IDisposable
{
    private readonly OpusEncoder _encoder;
    private readonly OpusDecoder _decoder;
    private readonly int _frameSizeMs;
    private readonly int _sampleRate;
    private readonly int _channels;

    public OpusAudioProcessor(int sampleRate = 48000, int channels = 2, int frameSizeMs = 20)
    {
        _sampleRate = sampleRate;
        _channels = channels;
        _frameSizeMs = frameSizeMs;

        _encoder = new OpusEncoder(Application.VoIP, sampleRate, channels)
        {
            VBR = true,
            Complexity = 5,
            FEC = true,
            ExpectedPacketLoss = 5
        };

        _decoder = new OpusDecoder(sampleRate, channels);
    }

    public int GetPcmFrameSize()
    {
        return _frameSizeMs * _sampleRate / 1000 * _channels * 2;
    }

    public (byte[] opusData, int length) Encode(byte[] pcmData, int targetBitrate = 64000)
    {
        int pcmLength = GetPcmFrameSize();
        if (pcmData.Length < pcmLength)
        {
            throw new ArgumentException($"PCM data must be at least {pcmLength} bytes");
        }

        int opusBufferSize = targetBitrate * _frameSizeMs / 8 / 1000;
        byte[] opusBytes = new byte[opusBufferSize];

        try
        {
            int encodedLength = _encoder.Encode(pcmData, pcmLength, opusBytes, opusBufferSize);
            return (opusBytes, encodedLength);
        }
        catch (OpusException ex)
        {
            Console.WriteLine($"Encoding error: {ex.Error} - {ex.Message}");
            throw;
        }
    }

    public (byte[] pcmData, int length) Decode(byte[] opusData, int opusLength)
    {
        int pcmBufferSize = GetPcmFrameSize();
        byte[] pcmBytes = new byte[pcmBufferSize];

        try
        {
            int decodedLength = _decoder.Decode(opusData, opusLength, pcmBytes, pcmBufferSize);
            return (pcmBytes, decodedLength);
        }
        catch (OpusException ex)
        {
            Console.WriteLine($"Decoding error: {ex.Error} - {ex.Message}");
            throw;
        }
    }

    public (byte[] pcmData, int length) HandlePacketLoss()
    {
        int pcmBufferSize = GetPcmFrameSize();
        byte[] pcmBytes = new byte[pcmBufferSize];
        int recoveredLength = _decoder.Decode(null, -1, pcmBytes, pcmBufferSize);
        return (pcmBytes, recoveredLength);
    }

    public void Dispose()
    {
        _encoder?.Dispose();
        _decoder?.Dispose();
    }
}
```

--------------------------------

### Force Encoder Channels

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Explains how to override automatic channel selection by setting the ForceChannels property to Mono or Stereo.

```csharp
using OpusDotNet;

using (var encoder = new OpusEncoder(Application.Audio, 48000, 2)) {
    encoder.ForceChannels = ForceChannels.Mono;
}
```

--------------------------------

### Handle OpusException in C#

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Demonstrates how to catch and handle specific Opus codec errors using the OpusException class. It includes a switch statement to map OpusError enums to user-friendly messages.

```csharp
try
{
    using (var encoder = new OpusEncoder(Application.VoIP, 48000, 2))
    {
        byte[] invalidPcm = new byte[100];
        byte[] opus = new byte[256];
        encoder.Encode(invalidPcm, 100, opus, 256);
    }
}
catch (OpusException ex)
{
    switch (ex.Error)
    {
        case OpusError.BadArg: Console.WriteLine("Invalid arguments provided"); break;
        case OpusError.BufferTooSmall: Console.WriteLine("Output buffer is too small"); break;
        case OpusError.InvalidPacket: Console.WriteLine("Corrupted audio data"); break;
        case OpusError.InternalError: Console.WriteLine("Internal Opus error"); break;
        case OpusError.InvalidState: Console.WriteLine("Encoder/decoder state is invalid"); break;
        case OpusError.AllocFail: Console.WriteLine("Memory allocation failed"); break;
        default: Console.WriteLine($"Opus error: {ex.Message}"); break;
    }
}
```

--------------------------------

### Set Encoder Bandwidth

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Shows how to adjust the MaxBandwidth property of the OpusEncoder to balance between audio fidelity and compression efficiency.

```csharp
using OpusDotNet;

using (var encoder = new OpusEncoder(Application.VoIP, 48000, 1)) {
    encoder.MaxBandwidth = Bandwidth.WideBand;
    encoder.MaxBandwidth = Bandwidth.FullBand;
}
```

--------------------------------

### Forward Error Correction (FEC) Handling

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Explains how to implement Forward Error Correction (FEC) using OpusDotNet to mitigate audio quality degradation caused by packet loss in network transmissions.

```APIDOC
## Forward Error Correction (FEC) Handling

### Description
This section details how to handle Forward Error Correction (FEC) with the `OpusDecoder` to recover audio data when packets are lost during transmission. It shows how to simulate packet loss and utilize the decoder's FEC capabilities.

### Method
N/A (Class Usage)

### Endpoint
N/A (Class Usage)

### Parameters
N/A (Class Usage)

### Request Example
```csharp
using OpusDotNet;

using (var decoder = new OpusDecoder(48000, 2))
{
    int frameSizeMs = 20;
    int pcmBufferLength = frameSizeMs * 48000 / 1000 * 2 * 2;
    byte[] pcmBytes = new byte[pcmBufferLength];

    // Simulate receiving packets (some may be lost)
    byte[][] receivedPackets = /* array of Opus packets, null entries indicate loss */;

    for (int i = 0; i < receivedPackets.Length; i++)
    {
        if (receivedPackets[i] == null)
        {
            // Packet lost - attempt FEC recovery
            // Pass null and -1 to indicate packet loss
            int recoveredLength = decoder.Decode(null, -1, pcmBytes, pcmBufferLength);
            Console.WriteLine($"Recovered {recoveredLength} bytes using FEC");
        }
        else
        {
            // Normal decode
            int decodedLength = decoder.Decode(receivedPackets[i], receivedPackets[i].Length, pcmBytes, pcmBufferLength);
            Console.WriteLine($"Decoded {decodedLength} bytes");
        }
    }
}
```

### Response
N/A (Class Usage)

### Response Example
N/A (Class Usage)
```

--------------------------------

### Handle Packet Loss with FEC

Source: https://context7.com/mrphil2105/opusdotnet/llms.txt

Explains how to utilize Forward Error Correction (FEC) within the OpusDecoder to recover audio data when network packet loss occurs.

```csharp
using OpusDotNet;

using (var decoder = new OpusDecoder(48000, 2))
{
    int frameSizeMs = 20;
    int pcmBufferLength = frameSizeMs * 48000 / 1000 * 2 * 2;
    byte[] pcmBytes = new byte[pcmBufferLength];

    byte[][] receivedPackets = /* array of Opus packets, null entries indicate loss */;

    for (int i = 0; i < receivedPackets.Length; i++)
    {
        if (receivedPackets[i] == null)
        {
            int recoveredLength = decoder.Decode(null, -1, pcmBytes, pcmBufferLength);
            Console.WriteLine($"Recovered {recoveredLength} bytes using FEC");
        }
        else
        {
            int decodedLength = decoder.Decode(receivedPackets[i], receivedPackets[i].Length, pcmBytes, pcmBufferLength);
            Console.WriteLine($"Decoded {decodedLength} bytes");
        }
    }
}
```

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