Hi when I use C:\Program Files (x86)\VideoLAN\VLC\vlc.exe mymusic.mp3 –audio-filter=mono It works well . When I use libvlc in C or C++ char const *vlc_argv[] = { "--audio-filter=mono" }; int vlc_argc = sizeof(vlc_argv) / sizeof(*vlc_argv); libvlc = libvlc_new(vlc_argc, vlc_argv); It seems ...