initial commit

backend/lib/ffmpeg-meter.mjs

@@ -0,0 +1,100 @@
+import { spawn } from 'child_process'
+import createDebug from 'debug'
+import { EventEmitter } from 'events'
+import process from 'process'
+
+const debug = createDebug('meter')
+
+export class AlsaMeter extends EventEmitter {
+  constructor (opts = {}) {
+    super()
+    if (!opts.input) this.input = { host: 'alsa', device: 'default' }
+    else if (typeof opts.input === 'string') this.input = { host: 'alsa', input: opts.input }
+    else this.input = opts.input
+    // setInterval(() => console.log(this._lastMessage), 1000)
+  }
+
+  open () {
+    if (!this._opening) this._opening = this._open()
+    return this._opening
+  }
+
+  async _open () {
+    const cmd = 'ffmpeg'
+    let args = [
+      '-nostats',
+      '-f',
+      this.input.host,
+      '-i',
+      this.input.device,
+      '-filter_complex',
+      'ebur128=peak=true',
+      '-f',
+      'null',
+      '-'
+    ]
+    debug('spawn: ' + `${cmd} ${args.map(a => `"${a}"`).join(' ')}`)
+    this.proc = spawn(cmd, args)
+
+    // const onclose = (ev) => {
+    //   this._closed = true
+    //   this.proc.kill()
+    // }
+    // process.on('exit', onclose.bind('exit'))
+    // process.on('SIGINT', onclose.bind('SIGINT'))
+    // process.on('SIGTERM', onclose.bind('SIGTERM'))
+
+    this.proc.stderr.on('data', msg => {
+      this.parseMessage(msg)
+    })
+
+    return new Promise((resolve, reject) => {
+      this.proc.stderr.once('data', msg => {
+        this._open = true
+        resolve()
+      })
+    })
+  }
+
+  parseMessage (msg) {
+    let str = msg.toString('utf-8')
+    let match = str.match(/\[.*\](.*)/)
+    if (!match || match.length !== 2) return null
+    str = match[1].trim()
+    let parts = str.split(/([a-zA-Z]+:)/).filter(f => f)
+    let last = null
+    let map = parts.reduce((agg, token, i) => {
+      token = token.trim()
+      if (last) {
+        agg[last] = token
+        last = null
+      } else {
+        last = token.replace(/[:\s]/g, '')
+      }
+      return agg
+    }, {})
+
+    let res = {}
+    if (map.LRA) res.LRA = parseFloat(map.LRA.replace('LU', ''))
+    if (map.t) res.t = parseFloat(map.t)
+    if (map.TARGET) res.TARGET = parseFloat(map.TARGET.replace('LUFS', ''))
+    if (map.I) res.I = parseFloat(map.I.replace('LUFS', ''))
+    if (map.M) res.M = parseFloat(map.M)
+    if (map.S) res.S = parseFloat(map.S)
+    for (let key of ['FTPK', 'TPK']) {
+      if (map[key]) {
+        let parts = map[key].split(/\s+/)
+        if (parts.length >= 2) {
+          res[key] = [parseFloat(parts[0]), parseFloat(parts[1])]
+        } else {
+          res[key] = null
+        }
+      }
+    }
+    if (Object.keys(res).length) {
+      // debug(Object.entries(res).map(([k, v]) => `${k}: ${v}`).join(' | '))
+      this._lastMessage = res
+      this.emit('meter', res)
+    }
+  }
+}