undefined local variable or method `filename' when using monitor command

[BPie]

https://github.com/JorenSix/Olaf/blob/0b08dd9e8bc3e45d9e6196a8d46bb3734777b7a5/olaf.rb#L91 I get an error when I try to use the monitor command (maybe it should be an audio_filename instead of filename)

/tmp/Olaf # olaf monitor input.mp3
/usr/local/bin/olaf:91:in `block (2 levels) in monitor': undefined local variable or method `filename' for main:Object (NameError)
	from /usr/local/bin/olaf:84:in `each'
	from /usr/local/bin/olaf:84:in `block in monitor'
	from /usr/local/bin/olaf:180:in `with_converted_audio_part'
	from /usr/local/bin/olaf:80:in `monitor'
	from /usr/local/bin/olaf:373:in `block in <main>'
	from /usr/local/bin/olaf:372:in `each'
	from /usr/local/bin/olaf:372:in `each_with_index'
	from /usr/local/bin/olaf:372:in `<main>'