concat source audio

.gitignore

@@ -15,6 +15,7 @@ dist
 .env.test.local
 .env.production.local
 .cache
+.vscode
 
 temp
 out.mp4

lib/extract-audio.js

@@ -0,0 +1,29 @@
+'use strict'
+
+const ffmpeg = require('fluent-ffmpeg')
+
+module.exports = (opts) => {
+  const {
+    log,
+    videoPath,
+    outputFileName,
+    start,
+    duration
+  } = opts
+
+  return new Promise((resolve, reject) => {
+    const cmd = ffmpeg(videoPath)
+      .noVideo()
+      .audioCodec('libmp3lame')
+      .on('start', cmd => log({ cmd }))
+      .on('end', () => resolve(outputFileName))
+      .on('error', (err) => reject(err))
+    if (start) {
+      cmd.seekInput(start)
+    }
+    if (duration) {
+      cmd.duration(duration)
+    }
+    cmd.save(outputFileName)
+  })
+}

lib/index.js

@@ -5,6 +5,7 @@ const tempy = require('tempy')
 
 const initFrames = require('./init-frames')
 const renderFrames = require('./render-frames')
+const renderAudio = require('./render-audio')
 const transcodeVideo = require('./transcode-video')
 
 const noop = () => { }
@@ -31,6 +32,7 @@ module.exports = async (opts) => {
     console.time(`init-frames`)
     const {
       frames,
+      scenes,
       theme
     } = await initFrames({
       log,
@@ -39,7 +41,8 @@ module.exports = async (opts) => {
       transition,
       transitions,
       outputDir: temp,
-      frameFormat
+      frameFormat,
+      renderAudio: !audio
     })
     console.timeEnd(`init-frames`)
 
@@ -57,12 +60,24 @@ module.exports = async (opts) => {
     })
     console.timeEnd(`render-frames`)
 
+    console.time(`render-audio`)
+    let concatAudioFile = audio
+    if (!audio && scenes.filter(s => s.sourceAudioPath).length === scenes.length) {
+      concatAudioFile = await renderAudio({
+        log,
+        scenes,
+        outputDir: temp,
+        fileName: 'audioConcat.mp3'
+      })
+    }
+    console.timeEnd(`render-audio`)
+
     console.time(`transcode-video`)
     await transcodeVideo({
       log,
       framePattern,
       frameFormat,
-      audio,
+      audio: concatAudioFile,
       output,
       theme,
       onProgress: (p) => {

lib/index.test.js

@@ -14,6 +14,11 @@ const videos = [
   path.join(fixturesPath, '1.mp4'),
   path.join(fixturesPath, '2.mp4')
 ]
+const videosWithAudio = [
+  path.join(fixturesPath, '0a.mp4'),
+  path.join(fixturesPath, '0a.mp4'),
+  path.join(fixturesPath, '0a.mp4')
+]
 
 test('concat 3 mp4s with using constant 500ms transitions', async (t) => {
   const output = tempy.file({ extension: 'mp4' })
@@ -86,3 +91,31 @@ test('concat 9 mp4s with unique transitions', async (t) => {
 
   await rmfr(output)
 })
+
+test('concat 3 mp4s with source audio and unique transitions', async (t) => {
+  const output = tempy.file({ extension: 'mp4' })
+  await concat({
+    log: console.log,
+    output,
+    videos: videosWithAudio,
+    transitions: [
+      {
+        name: 'circleOpen',
+        duration: 1000
+      },
+      {
+        name: 'crossWarp',
+        duration: 1000
+      }
+    ]
+  })
+
+  const probe = await ffmpegProbe(output)
+  t.is(probe.width, 1280)
+  t.is(probe.height, 720)
+  t.is(probe.streams.length, 2)
+  t.truthy(probe.duration >= 11000)
+  t.truthy(probe.duration <= 15000)
+
+  await rmfr(output)
+})

lib/init-frames.js

@@ -7,6 +7,7 @@ const path = require('path')
 const pMap = require('p-map')
 
 const extractVideoFrames = require('./extract-video-frames')
+const extractAudio = require('./extract-audio')
 
 module.exports = async (opts) => {
   const {
@@ -16,7 +17,8 @@ module.exports = async (opts) => {
     transition,
     transitions,
     frameFormat,
-    outputDir
+    outputDir,
+    renderAudio = false
   } = opts
 
   if (transitions && videos.length - 1 !== transitions.length) {
@@ -31,7 +33,8 @@ module.exports = async (opts) => {
       transition,
       transitions,
       frameFormat,
-      outputDir
+      outputDir,
+      renderAudio
     })
   }, {
     concurrency
@@ -94,7 +97,8 @@ module.exports.initScene = async (opts) => {
     transition,
     transitions,
     frameFormat,
-    outputDir
+    outputDir,
+    renderAudio
   } = opts
 
   const video = videos[index]
@@ -124,7 +128,9 @@ module.exports.initScene = async (opts) => {
   }
 
   const fileNamePattern = `scene-${index}-%012d.${frameFormat}`
+  const audioFileName = `scene-${index}.mp3`
   const framePattern = path.join(outputDir, fileNamePattern)
+  const audioPath = path.join(outputDir, audioFileName)
   await extractVideoFrames({
     log,
     videoPath: scene.video,
@@ -147,5 +153,19 @@ module.exports.initScene = async (opts) => {
     }
   }
 
+  if (renderAudio && probe.streams && probe.streams.filter(s => s.codec_type === 'audio').length) {
+    const previousTransition = (index > 0 && transitions ? transitions[ index - 1 ] : transition)
+    const previousTransitionDuration = index === 0 ? 0 : (previousTransition.duration || 500)
+
+    await extractAudio({
+      log,
+      videoPath: scene.video,
+      outputFileName: audioPath,
+      start: previousTransitionDuration / 2000,
+      duration: scene.duration / 1000 - previousTransitionDuration / 2000 - scene.transition.duration / 2000
+    })
+    scene.sourceAudioPath = audioPath
+  }
+
   return scene
 }

lib/render-audio.js

@@ -0,0 +1,38 @@
+'use strict'
+
+const fs = require('fs-extra')
+const path = require('path')
+const ffmpeg = require('fluent-ffmpeg')
+
+module.exports = async (opts) => {
+  const {
+    log,
+    scenes,
+    outputDir,
+    fileName
+  } = opts
+
+  return new Promise((resolve, reject) => {
+    const concatListPath = path.join(outputDir, 'audioConcat.txt')
+    const toConcat = scenes.filter(scene => scene.sourceAudioPath).map(scene => `file '${scene.sourceAudioPath}'`)
+    const outputFileName = path.join(outputDir, fileName)
+    fs.outputFile(concatListPath, toConcat.join('\n')).then(() => {
+      log(`created ${concatListPath}`)
+      const cmd = ffmpeg()
+        .input(concatListPath)
+        .inputOptions(['-f concat', '-safe 0'])
+        .on('start', cmd => log(cmd))
+        .on('end', () => resolve(outputFileName))
+        .on('error', (err, stdout, stderr) => {
+          if (err) {
+            console.error('failed to concat audio', err, stdout, stderr)
+          }
+          reject(err)
+        })
+      cmd.save(outputFileName)
+    }).catch(err => {
+      console.error(`failed to concat audio ${err}`)
+      reject(err)
+    })
+  })
+}