Differentiate between error and standard terminal log with ffmpeg - nodejs : <p>I'm using <code>ffmpeg</code> in node js. Both the standard terminal output and the error seems to be sent to stdout, so I don't know how to differentiate between error and success... Here's my code:</p>

<pre><code>var convertToMp3 = function(filePath) {
  var ffmpeg = child_process.spawn('ffmpeg',['-i', filePath, '-y', 'output.mp3']);
  var err = '';
  ffmpeg.stderr
    .on('data', function(c) { err += c; })
    .on('end', function() { console.log('stderr:', err); });
  var d = '';
  ffmpeg.stdout
    .on('data', function(c){d +=c;})
    .on('end', function(){ console.log('stdout', d); });
}
</code></pre>

<p>wether the conversion succeeds or fails, stdout is empty and stderr contains what I'd get if I'd run the corresponding command in the terminal</p>
