Mono audio filter is a channel_mixer and not a convertor.

[vlc] / modules / audio_filter / channel_mixer / Modules.am

SOURCES_trivial_channel_mixer = trivial.c
SOURCES_simple_channel_mixer = simple.c
SOURCES_headphone_channel_mixer = headphone.c
SOURCES_dolby_surround_decoder = dolby.c
SOURCES_mono = mono.c