docs(example): update ffmpeg example (#818)

* remove audioonly and videoonly from ytdl calls
* start the progressbar when ffmpeg outputs data
* simplify ffmpeg arguments to represent a simple audio & video merge into file
* adjust parsing of the key=value pairs
* force close the program when done

example/ffmpeg.js

@@ -2,10 +2,12 @@
  * Reencode audio & video without creating files first
  *
  * Requirements: ffmpeg, ether via a manual installation or via ffmpeg-static
+ *
+ * If you need more complex features like an output-stream you can check the older, more complex example:
+ * https://github.com/fent/node-ytdl-core/blob/cc6720f9387088d6253acc71c8a49000544d4d2a/example/ffmpeg.js
  */
 
 // Buildin with nodejs
-const fs = require('fs');
 const cp = require('child_process');
 const readline = require('readline');
 // External modules
@@ -20,18 +22,20 @@ const tracker = {
   merged: { frame: 0, speed: '0x', fps: 0 },
 };
 
-// Get audio and video stream going
-const audio = ytdl(ref, { filter: 'audioonly', quality: 'highestaudio' })
+// Get audio and video streams
+const audio = ytdl(ref, { quality: 'highestaudio' })
   .on('progress', (_, downloaded, total) => {
     tracker.audio = { downloaded, total };
   });
-const video = ytdl(ref, { filter: 'videoonly', quality: 'highestvideo' })
+const video = ytdl(ref, { quality: 'highestvideo' })
   .on('progress', (_, downloaded, total) => {
     tracker.video = { downloaded, total };
   });
 
-// Get the progress bar going
-const progressbar = setInterval(() => {
+// Prepare the progress bar
+let progressbarHandle = null;
+const progressbarInterval = 1000;
+const showProgress = () => {
   readline.cursorTo(process.stdout, 0);
   const toMB = i => (i / 1024 / 1024).toFixed(2);
 
@@ -46,51 +50,55 @@ const progressbar = setInterval(() => {
 
   process.stdout.write(`running for: ${((Date.now() - tracker.start) / 1000 / 60).toFixed(2)} Minutes.`);
   readline.moveCursor(process.stdout, 0, -3);
-}, 1000);
+};
 
 // Start the ffmpeg child process
 const ffmpegProcess = cp.spawn(ffmpeg, [
   // Remove ffmpeg's console spamming
-  '-loglevel', '0', '-hide_banner',
-  // Redirect/enable progress messages
+  '-loglevel', '8', '-hide_banner',
+  // Redirect/Enable progress messages
   '-progress', 'pipe:3',
-  // 3 second audio offset
-  '-itsoffset', '3.0', '-i', 'pipe:4',
+  // Set inputs
+  '-i', 'pipe:4',
   '-i', 'pipe:5',
-  // Rescale the video
-  '-vf', 'scale=320:240',
-  // Choose some fancy codes
-  '-c:v', 'libx265', '-x265-params', 'log-level=0',
-  '-c:a', 'flac',
-  // Define output container
-  '-f', 'matroska', 'pipe:6',
+  // Map audio & video from streams
+  '-map', '0:a',
+  '-map', '1:v',
+  // Keep encoding
+  '-c:v', 'copy',
+  // Define output file
+  'out.mkv',
 ], {
   windowsHide: true,
   stdio: [
     /* Standard: stdin, stdout, stderr */
     'inherit', 'inherit', 'inherit',
-    /* Custom: pipe:3, pipe:4, pipe:5, pipe:6 */
-    'pipe', 'pipe', 'pipe', 'pipe',
+    /* Custom: pipe:3, pipe:4, pipe:5 */
+    'pipe', 'pipe', 'pipe',
   ],
 });
 ffmpegProcess.on('close', () => {
-  process.stdout.write('\n\n\n\n');
-  clearInterval(progressbar);
   console.log('done');
+  // Cleanup
+  process.stdout.write('\n\n\n\n');
+  clearInterval(progressbarHandle);
+  // Close the programm
+  process.exit(0);
 });
 
 // Link streams
 // FFmpeg creates the transformer streams and we just have to insert / read data
 ffmpegProcess.stdio[3].on('data', chunk => {
+  // Start the progress bar
+  if (!progressbarHandle) progressbarHandle = setInterval(showProgress, progressbarInterval);
   // Parse the param=value list returned by ffmpeg
   const lines = chunk.toString().trim().split('\n');
   const args = {};
   for (const l of lines) {
-    const [key, value] = l.trim().split('=');
-    args[key] = value;
+    const [key, value] = l.split('=');
+    args[key.trim()] = value.trim();
   }
   tracker.merged = args;
 });
 audio.pipe(ffmpegProcess.stdio[4]);
 video.pipe(ffmpegProcess.stdio[5]);
-ffmpegProcess.stdio[6].pipe(fs.createWriteStream('./out.mkv'));