ring-mqtt/lib/streaming/streaming-session.js

// This code is largely copied from ring-client-api, but converted from Typescript
// to straight Javascript and some code not required for ring-mqtt removed.
// Much thanks to @dgreif for the original code which is the basis for this work.

import { FfmpegProcess, reservePorts, RtpSplitter, } from '@homebridge/camera-utils'
import { firstValueFrom, ReplaySubject, Subject } from 'rxjs'
import pathToFfmpeg from 'ffmpeg-for-homebridge'
import { concatMap, take } from 'rxjs/operators'
import { Subscribed } from './subscribed.js'

function getCleanSdp(sdp) {
    return sdp
        .split('\nm=')
        .slice(1)
        .map((section) => 'm=' + section)
        .join('\n')
}

export class StreamingSession extends Subscribed {
    constructor(camera, connection) {
        super()
        this.camera = camera
        this.connection = connection
        this.onCallEnded = new ReplaySubject(1)
        this.onUsingOpus = new ReplaySubject(1)
        this.onVideoRtp = new Subject()
        this.onAudioRtp = new Subject()
        this.audioSplitter = new RtpSplitter()
        this.videoSplitter = new RtpSplitter()
        this.hasEnded = false
        this.bindToConnection(connection)
    }

    bindToConnection(connection) {
        this.addSubscriptions(
            connection.onAudioRtp.subscribe(this.onAudioRtp), 
            connection.onVideoRtp.subscribe(this.onVideoRtp), 
            connection.onCallAnswered.subscribe((sdp) => {
                this.onUsingOpus.next(sdp.toLocaleLowerCase().includes(' opus/'))
            }), 
            connection.onCallEnded.subscribe(() => this.callEnded()))
    }

    async reservePort(bufferPorts = 0) {
        const ports = await reservePorts({ count: bufferPorts + 1 })
        return ports[0]
    }

    get isUsingOpus() {
        return firstValueFrom(this.onUsingOpus)
    }

    async startTranscoding(ffmpegOptions) {
        if (this.hasEnded) {
            return
        }
        const videoPort = await this.reservePort(1)
        const audioPort = await this.reservePort(1)
        
        const ringSdp = await Promise.race([
            firstValueFrom(this.connection.onCallAnswered),
            firstValueFrom(this.onCallEnded),
        ])

        if (!ringSdp) {
            // Call ended before answered'
            return
        }
        const usingOpus = await this.isUsingOpus
        
        const ffmpegInputArguments = [
            '-hide_banner',
            '-protocol_whitelist',
            'pipe,udp,rtp,file,crypto',
            // Ring will answer with either opus or pcmu
            ...(usingOpus ? ['-acodec', 'libopus'] : []),
            '-f',
            'sdp',
            ...(ffmpegOptions.input || []),
            '-i',
            'pipe:'
        ]
        
        const inputSdp = getCleanSdp(ringSdp)
            .replace(/m=audio \d+/, `m=audio ${audioPort}`)
            .replace(/m=video \d+/, `m=video ${videoPort}`)

        const ff = new FfmpegProcess({
            ffmpegArgs: ffmpegInputArguments.concat(
                ...(ffmpegOptions.audio || ['-acodec', 'aac']), 
                ...(ffmpegOptions.video || ['-vcodec', 'copy']),
                ...(ffmpegOptions.output || [])),
            ffmpegPath: pathToFfmpeg,
            exitCallback: () => this.callEnded()
        })

        this.addSubscriptions(this.onAudioRtp.pipe(concatMap((rtp) => {
            return this.audioSplitter.send(rtp.serialize(), { port: audioPort })
        })).subscribe())

        this.addSubscriptions(this.onVideoRtp.pipe(concatMap((rtp) => {
            return this.videoSplitter.send(rtp.serialize(), { port: videoPort })
        })).subscribe())

        this.onCallEnded.pipe(take(1)).subscribe(() => ff.stop())

        ff.writeStdin(inputSdp)
        
        // Request a key frame now that ffmpeg is ready to receive
        this.requestKeyFrame()
    }

    callEnded() {
        if (this.hasEnded) {
            return
        }
        this.hasEnded = true
        this.unsubscribe()
        this.onCallEnded.next()
        this.connection.stop()
        this.audioSplitter.close()
        this.videoSplitter.close()
    }

    stop() {
        this.callEnded()
    }

    requestKeyFrame() {
        this.connection.requestKeyFrame()
    }
}