Voice

Native Dependencies

Follow the installation guide to install the required native dependencies.

Example Usage

Note

In the following examples streams and VoiceClient instances are not disposed because they should be stored somewhere and disposed later.

Sending Voice

[SlashCommand("play", "Plays music", Contexts = [InteractionContextType.Guild])]
public async Task PlayAsync(string track)
{
    // Check if the specified track is a well formed uri
    if (!Uri.IsWellFormedUriString(track, UriKind.Absolute))
    {
        await RespondAsync(InteractionCallback.Message("Invalid track!"));
        return;
    }

    var guild = Context.Guild!;

    // Get the user voice state
    if (!guild.VoiceStates.TryGetValue(Context.User.Id, out var voiceState))
    {
        await RespondAsync(InteractionCallback.Message("You are not connected to any voice channel!"));
        return;
    }

    var client = Context.Client;

    // You should check if the bot is already connected to the voice channel.
    // If so, you should use an existing 'VoiceClient' instance instead of creating a new one.
    // You also need to add a synchronization here. 'JoinVoiceChannelAsync' should not be used concurrently for the same guild
    var voiceClient = await client.JoinVoiceChannelAsync(
        guild.Id,
        voiceState.ChannelId.GetValueOrDefault());

    // Connect
    await voiceClient.StartAsync();

    // Enter speaking state, to be able to send voice
    await voiceClient.EnterSpeakingStateAsync(SpeakingFlags.Microphone);

    // Respond to the interaction
    await RespondAsync(InteractionCallback.Message($"Playing {Path.GetFileName(track)}!"));

    // Create a stream that sends voice to Discord
    var outStream = voiceClient.CreateOutputStream();

    // We create this stream to automatically convert the PCM data returned by FFmpeg to Opus data.
    // The Opus data is then written to 'outStream' that sends the data to Discord
    OpusEncodeStream stream = new(outStream, PcmFormat.Short, VoiceChannels.Stereo, OpusApplication.Audio);

    ProcessStartInfo startInfo = new("ffmpeg")
    {
        RedirectStandardOutput = true,
    };
    var arguments = startInfo.ArgumentList;

    // Set reconnect attempts in case of a lost connection to 1
    arguments.Add("-reconnect");
    arguments.Add("1");

    // Set reconnect attempts in case of a lost connection for streamed media to 1
    arguments.Add("-reconnect_streamed");
    arguments.Add("1");

    // Set the maximum delay between reconnection attempts to 5 seconds
    arguments.Add("-reconnect_delay_max");
    arguments.Add("5");

    // Specify the input
    arguments.Add("-i");
    arguments.Add(track);

    // Set the logging level to quiet mode
    arguments.Add("-loglevel");
    arguments.Add("-8");

    // Set the number of audio channels to 2 (stereo)
    arguments.Add("-ac");
    arguments.Add("2");

    // Set the output format to 16-bit signed little-endian
    arguments.Add("-f");
    arguments.Add("s16le");

    // Set the audio sampling rate to 48 kHz
    arguments.Add("-ar");
    arguments.Add("48000");

    // Direct the output to stdout
    arguments.Add("pipe:1");

    // Start the FFmpeg process
    var ffmpeg = Process.Start(startInfo)!;

    // Copy the FFmpeg stdout to 'stream', which encodes the voice using Opus and passes it to 'outStream'
    await ffmpeg.StandardOutput.BaseStream.CopyToAsync(stream);

    // Flush 'stream' to make sure all the data has been sent and to indicate to Discord that we have finished sending
    await stream.FlushAsync();
}

Receiving Voice

[SlashCommand("echo", "Creates echo", Contexts = [InteractionContextType.Guild])]
public async Task<string> EchoAsync()
{
    var guild = Context.Guild!;
    var userId = Context.User.Id;

    // Get the user voice state
    if (!guild.VoiceStates.TryGetValue(userId, out var voiceState))
        return "You are not connected to any voice channel!";

    var client = Context.Client;

    // You should check if the bot is already connected to the voice channel.
    // If so, you should use an existing 'VoiceClient' instance instead of creating a new one.
    // You also need to add a synchronization here. 'JoinVoiceChannelAsync' should not be used concurrently for the same guild
    var voiceClient = await client.JoinVoiceChannelAsync(
        guild.Id,
        voiceState.ChannelId.GetValueOrDefault(),
        new() { RedirectInputStreams = true /* Required to receive voice */ });

    // Connect
    await voiceClient.StartAsync();

    // Enter speaking state, to be able to send voice
    await voiceClient.EnterSpeakingStateAsync(SpeakingFlags.Microphone);

    // Create a stream that sends voice to Discord
    var outStream = voiceClient.CreateOutputStream(normalizeSpeed: false);

    voiceClient.VoiceReceive += args =>
    {
        // Pass current user voice directly to the output to create echo
        if (args.UserId == userId)
            return outStream.WriteAsync(args.Frame);
        return default;
    };

    // Return the response
    return "Echo!";
}