API route to generate waveform images

server/controllers/ToolsController.js

@@ -1,4 +1,5 @@
 const Logger = require('../Logger')
+const ffmpegHelpers = require('../utils/ffmpegHelpers')
 
 class ToolsController {
   constructor() { }
@@ -98,6 +99,32 @@ class ToolsController {
     res.sendStatus(200)
   }
 
+  getAudioFileWaveform(req, res) {
+    let start = Number(req.query.start || 0)
+    let end = Number(req.query.end || 0)
+    if (isNaN(start) || isNaN(end) || start < 0 || end > req.libraryItem.media.duration || end <= start || end - start < 5) {
+      return res.status(400).send('Invalid start/end query params')
+    }
+
+    const paths = []
+    let currentTime = 0
+    let startOffset = 0
+    for (const track of req.libraryItem.media.tracks) {
+      currentTime += track.duration
+      if (currentTime > start) {
+        if (!paths.length) startOffset = track.startOffset
+        paths.push(track.metadata.path)
+      }
+      if (currentTime > end) {
+        break
+      }
+    }
+    start -= startOffset
+    end -= startOffset
+
+    ffmpegHelpers.generateWaveform(paths, start, end, res)
+  }
+
   middleware(req, res, next) {
     if (!req.user.isAdminOrUp) {
       Logger.error(`[LibraryItemController] Non-root user attempted to access tools route`, req.user)

server/routers/ApiRouter.js

@@ -275,6 +275,7 @@ class ApiRouter {
     this.router.delete('/tools/item/:id/encode-m4b', ToolsController.middleware.bind(this), ToolsController.cancelM4bEncode.bind(this))
     this.router.post('/tools/item/:id/embed-metadata', ToolsController.middleware.bind(this), ToolsController.embedAudioFileMetadata.bind(this))
     this.router.post('/tools/batch/embed-metadata', ToolsController.middleware.bind(this), ToolsController.batchEmbedMetadata.bind(this))
+    this.router.get('/tools/item/:id/waveform', ToolsController.middleware.bind(this), ToolsController.getAudioFileWaveform.bind(this))
 
     // 
     // RSS Feed Routes (Admin and up)

server/utils/ffmpegHelpers.js

@@ -152,3 +152,26 @@ module.exports.downloadPodcastEpisode = (podcastEpisodeDownload) => {
     ffmpeg.run()
   })
 }
+
+module.exports.generateWaveform = (filepaths, start, end, res) => {
+  let ffmpeg = null
+  if (filepaths.length === 1) ffmpeg = Ffmpeg(filepaths[0])
+  else {
+    ffmpeg = Ffmpeg(`concat:${filepaths.join('|')}`)
+  }
+  ffmpeg.inputOptions('-ss', start)
+  ffmpeg.inputOptions('-to', end)
+  ffmpeg.complexFilter('aformat=channel_layouts=mono,showwavespic=s=1280x240')
+  ffmpeg.frames(1)
+  ffmpeg.format('image2pipe')
+  ffmpeg.on('start', (cmd) => {
+    Logger.debug(`[FfmpegHelpers] generateWaveform: Cmd: ${cmd}`)
+  })
+  ffmpeg.on('error', (error) => {
+    Logger.error(`[FfmpegHelpers] generateWaveform: Error`, error)
+  }).on('end', () => {
+    Logger.debug(`[FfmpegHelpers] generateWaveform finished`)
+  }).pipe(res, {
+    end: true
+  })
+}