recording: use MediaRecorder and ffmpeg plus more improvements

- glitch free audio recording! (maybe)
- improved preroll management and disk streaming
- merged in audio-timeline package
- new streaming based on pre-sliced clips on disk
- export to 32bit wav (instead of 16bit)
- finish recording before closing window

closes #172
closes #153

README.md

@@ -103,12 +103,11 @@ https://www.youtube.com/watch?v=2oVcNaDpPz0
 
 - [loop-grid](https://github.com/mmckegg/loop-grid)
 - [audio-slot](https://github.com/mmckegg/audio-slot)
-- [audio-timeline](https://github.com/mmckegg/audio-timeline)
 - [wave-recorder](https://github.com/mmckegg/wave-recorder)
 - [web-midi](https://github.com/mmckegg/web-midi)
 - [bopper](https://github.com/wavejs/bopper)
 - [micro-css](https://github.com/mmckegg/micro-css)
-- [mercury](https://github.com/raynos/mercury)
+- [mutant](https://github.com/mmckegg/mutant)
 - [observ-fs](https://github.com/mmckegg/observ-fs)
 - [observ-midi](https://github.com/mmckegg/observ-midi)
 - [electron](https://github.com/atom/electron)

bin/build-ffmpeg.sh

@@ -0,0 +1,3 @@
+./configure --enable-static --disable-shared --disable-all --enable-ffmpeg --enable-avcodec --enable-avformat --enable-avutil --enable-swresample --enable-swscale --enable-avfilter --disable-network --disable-d3d11va --disable-dxva2 --disable-vaapi --disable-vda --disable-vdpau --enable-decoder=opus --enable-demuxer=matroska --enable-protocol=file --enable-protocol=pipe --disable-bzlib --disable-iconv --disable-libxcb --disable-lzma --disable-sdl --disable-securetransport --disable-xlib --disable-zlib --enable-filter=aresample --enable-encoder=pcm_f32le --enable-muxer=wav --enable-muxer=segment --enable-libopus && make
+
+# build for windows: https://github.com/rdp/ffmpeg-windows-build-helpers

index.js

@@ -31,6 +31,18 @@ MidiStream.watchPortNames(function (ports) {
   midiPorts.set(ports)
 })
 
+var closing = false
+window.onbeforeunload = function (e) {
+  // ensure recording is saved on close
+  if (!closing && window.currentProject && window.currentProject.actions.prepareToClose) {
+    window.currentProject.actions.prepareToClose(function () {
+      closing = true
+      electron.remote.getCurrentWindow().close()
+    })
+    return false
+  }
+}
+
 // create root context
 var audioContext = new global.AudioContext()
 var nodes = require('./nodes')

lib/record-to-disk.js

@@ -0,0 +1,107 @@
+var ReadableBlobStream = require('readable-blob-stream')
+var spawn = require('child_process').spawn
+var fs = require('fs')
+var join = require('path').join
+var getExt = require('path').extname
+var getBaseName = require('path').basename
+var getDirName = require('path').dirname
+var ffmpeg = join(__dirname, '..', 'bin', 'ffmpeg-' + process.platform)
+
+if (process.platform === 'win32') {
+  ffmpeg += '.exe'
+}
+
+module.exports = recordToDisk
+
+function recordToDisk (path, mediaStream) {
+  var chunkDuration = 0.5 // seconds
+  var mediaRecorder = new window.MediaRecorder(mediaStream, { mimeType: 'audio/webm' })
+  var onFinish = null
+  mediaRecorder.chunkCount = 0
+  mediaRecorder.start(chunkDuration * 1000)
+
+  var output = WaveWriter(path, function () {
+    if (onFinish) {
+      onFinish.apply(this, arguments)
+    }
+  })
+
+  mediaRecorder.ondataavailable = function (e) {
+    mediaRecorder.chunkCount += 1
+    var stream = ReadableBlobStream(e.data)
+    stream.pipe(output, {end: false})
+  }
+
+  return function stopRecording (cb) {
+    onFinish = cb
+    mediaRecorder.requestData()
+    mediaRecorder.stop()
+
+    setTimeout(function () {
+      output.end()
+    }, 200)
+  }
+}
+
+function WaveWriter (outputFile, onDone) {
+  var ext = getExt(outputFile)
+  var base = getBaseName(outputFile, ext)
+  var dir = getDirName(outputFile)
+  var segmentLength = 30
+
+  var outputInfo = {
+    sampleRate: 48000,
+    recordedAt: Date.now(),
+    duration: 0,
+    channels: 2,
+    segments: []
+  }
+
+  writeOutputInfo()
+
+  var child = spawn(ffmpeg, [
+    '-i', '-',
+    '-acodec', 'pcm_f32le',
+    '-f', 'segment',
+    '-segment_list', 'pipe:1',
+    '-segment_list_type', 'csv',
+    '-segment_time', segmentLength,
+    join(dir, base + '-%05d.wav')
+  ])
+
+  // child.stderr.on('data', function (c) {
+  //   console.log(c.toString())
+  // })
+
+  child.stdout.on('data', function (data) {
+    if (outputInfo.segments.length) {
+      // ensure correct segment length time
+      outputInfo.segments[outputInfo.segments.length - 1].duration = segmentLength
+    }
+    var parts = data.toString().trim().split(',')
+    var duration = parseFloat(parts[2]) - parseFloat(parts[1])
+    outputInfo.segments.push({src: './' + parts[0], duration: duration})
+    outputInfo.duration = outputInfo.segments.reduce((r, s) => r + s.duration, 0)
+    writeOutputInfo()
+  })
+
+  if (onDone) {
+    child.on('exit', function (code) {
+      if (code === 0) {
+        setTimeout(function () {
+          onDone(null, outputInfo)
+        }, 50)
+      } else {
+        onDone(new Error('Recording error'))
+      }
+    })
+  }
+
+  return child.stdin
+
+  // scoped
+
+  function writeOutputInfo () {
+    fs.writeFile(outputFile, JSON.stringify(outputInfo))
+  }
+}