Oops, logger would not catch output this way.

ffmpeg.py

@@ -179,7 +179,9 @@ def run(self):
                                                                                                  vol=self.vol))
                 try:
                     logger.info(convert_audio(track, file, self.rate, self.vol))
-                except subprocess.CalledProcessError:
+                except subprocess.CalledProcessError as e:
+                    logging.exception("FFmpeg converter: Couldn't convert {track}".format(track=track))
+                    logging.critical("FFmpeg converter: Error output log\n" + e.output.decode('ascii', 'replace'))
                     errors.append(track)
                     # File's headers aren't stripped, which normally would increase self.converted by 1.
                     self.converted += 1