Fix progress reported as Infinity% when ffmpeg line output is spread …

…across several chunks

lib/ffmpeg.js

@@ -1,5 +1,9 @@
 const childProcess = require('child_process')
+const trace = require('debug')('thumbsup:trace')
+const debug = require('debug')('thumbsup:debug')
 const EventEmitter = require('events')
+const split = require('split')
+
 class ProgressEmitter extends EventEmitter {}
 
 // Duration: 00:01:00.10
@@ -11,20 +15,23 @@ const REGEX_PROGRESS = /time=(\d\d):(\d\d):(\d\d).\d\d/
 exports.exec = function (args, callback) {
   const progressEmitter = new ProgressEmitter()
   var durationSeconds = 0
-  const child = childProcess.spawn('ffmpeg', args, {
-  })
-  child.stderr.on('data', (data) => {
+  const child = childProcess.spawn('ffmpeg', args, {})
+  child.stderr.pipe(split()).on('data', (data) => {
     if (!durationSeconds) {
-      durationSeconds = parseTime(data.toString(), REGEX_DURATION)
+      durationSeconds = parseTime(data, REGEX_DURATION)
     }
-    const progressSeconds = parseTime(data.toString(), REGEX_PROGRESS)
+    const progressSeconds = parseTime(data, REGEX_PROGRESS)
     if (progressSeconds) {
       const percent = Math.floor(progressSeconds * 100 / durationSeconds)
       progressEmitter.emit('progress', percent)
     }
   })
-  child.on('error', err => callback(err))
+  child.on('error', err => {
+    debug('ffmpeg error:', err)
+    callback(err)
+  })
   child.on('exit', (code, signal) => {
+    trace(`ffmpeg exited with code ${code}`)
     if (code > 0) callback(new Error(`ffmpeg exited with code ${code}`))
     else callback(null)
   })