Stream Hooks

Stream hooks are middlewares which has the ability to modify the streaming behavior. There are two types of stream hooks in Discord Player:

onBeforeCreateStream

Discord Player by default uses registered extractors to stream audio. If you need to override what needs to be streamed, you can use this hook.

const fs = require('fs');
 
// other code
const queue = player.nodes.create(..., {
    ...,
    async onBeforeCreateStream(track, source, _queue) {
        if (track.title === 'some title') {
            return fs.createReadStream('./playThisInstead.mp3');
        }
    }
});

<GuildQueue>.onBeforeCreateStream is called before actually downloading the stream. It is a different concept from extractors, where you are just downloading streams. source here will be a track source. Streams from onBeforeCreateStream are then piped to FFmpeg and sent to onAfterCreateStream hook.

onAfterCreateStream

This hook can be used to post-process pcm stream. This is the final step before creating audio resource. Example:

const queue = player.nodes.create(..., {
    ...,
    async onAfterCreateStream(pcmStream, queue) {
        // return opus encoded stream
        const encoder = new OpusEncoder();
        return {
            stream: encoder.encode(pcmStream),
            type: StreamType.Opus
        };
    }
});