Voice support for discord-haskell.

Supplementary library to discord-haskell. See the project README on GitHub for more information. https://github.com/yutotakano/discord-haskell-voice

discord-haskell-voice

Welcome to discord-haskell-voice! This library provides you with a high-level interface for interacting with Discord's Voice API, building on top of the discord-haskell library by Karl.

For a quick intuitive introduction to what this library enables you to do, see the following snippet of code:

rickroll :: Channel -> DiscordHandler ()
rickroll c@(ChannelVoice {}) = do
    void $ runVoice $ do
        join (channelGuild c) (channelId c)
        playYouTube "https://www.youtube.com/watch?v=dQw4w9WgXcQ"

The library actively uses and supports conduit, which enables you to write something like the following as well!

rickrollHalfVolume :: Channel -> DiscordHandler ()
rickrollHalfVolume c@(ChannelVoice {}) = do
    void $ runVoice $ do
        join (channelGuild c) (channelId c)
        let halfAmplitude = awaitForever $ \current ->
                yield $ round $ fromIntegral current * 0.5
        playYouTube' "rickroll" $ packInt16C .| halfAmplitude .| unpackInt16C
        liftIO $ print "finished playing!"

Requirements

• The library uses saltine for encryption and decryption of audio packets. This requires libsodium to be installed on your system. See their README for information.
• The library requires Opus libraries to be installed on your system. The libopus-dev package available on package repositories should be sufficient on most *nix systems. The opus brew package suffices on Mac. Windows is unexplored yet (WSL works).
• If you are to use any variants of playFile, playYouTube, you will need FFmpeg installed. To specify a custom executable name, see the -With function variants.
• If you are to use any variants of playYouTube, you will additionally need youtube-dl installed. This is used to get the stream URL to pass to FFmpeg. To specify a custom executable name (such as yt-dlp), use playYouTubeWith.

Features

What is supported:

• Can join/leave Discord voice channels. It is possible to join multiple of them simultaneously (one per sever) and stream different contents to each.
• It is also possible to join many voice channels (across many servers) and play the same content, radio/subscriber-style.
• You can play arbitrary PCM audio, arbitrary audio (with FFmpeg), and arbitrary internet audio (with youtube-dl).
• You can transform audio arbitrarily using Conduit.
• As it streams content, the library /should/ use constant memory (unverified).
• OPUS encoding and specific implementation details such as handshakes and encryption are done opaquely, and a nice abstraction layer is provided.

What is not supported:

• Decrypting audio packets sent from Discord (other people's voices), and decoding them to PCM.

See examples/BasicMusicBot.hs for a bot that uses many advanced features of the library, including dynamically adjusting the stream audio using a TVar (and allowing users to change the TVar using a /volume command).

Installation

This library is available on Hackage, at https://hackage.haskell.org/package/discord-haskell-voice.

Cabal

To use it in your Cabal-based project, add discord-haskell-voice as a dependency in your .cabal file:

# --- myproject.cabal <truncated>
 build-depends:
      base >=4.7 && <5
    , discord-haskell ==1.14.0
    , discord-haskell-voice ==2.3.1

Stack

To use it in your Stack-based project, add discord-haskell-voice in both your package.yaml and stack.yaml files (since this library is not available in Stackage for the same reason discord-haskell is not on Stackage)

# --- stack.yaml <truncated>
extra-deps:
- discord-haskell-1.14.0
- discord-haskell-voice-2.3.1

# --- package.yaml <truncated>
dependencies:
- base >= 4.7 && < 5
- discord-haskell == 1.14.0
- discord-haskell-voice == 2.3.1

Documentation

See the Haddock documentation on the Hackage page, at https://hackage.haskell.org/package/discord-haskell-voice/docs/Discord-Voice.html.

Future Plans

• Use stm-conduit and stm for a safer Chan?
• Look into SubprocessException seemingly never been thrown (e.g. when SIGINT is signalled to the libarry while FFmpeg is running)
• Consider, document, and improve the distinction of errors (VoiceError) vs exceptions, and note down why any choices are made.