The following packages have unmet dependencies:
 qtox : Depends: libavcodec-ffmpeg56 (>= 7:2.4) but it is not installable or
                 libavcodec-ffmpeg-extra56 (>= 7:2.4) but it is not installable
        Depends: libavdevice-ffmpeg56 (>= 7:2.4) but it is not installable
        Depends: libavformat-ffmpeg56 (>= 7:2.4) but it is not installable
        Depends: libavutil-ffmpeg54 (>= 7:2.4) but it is not installable
        Depends: libswscale-ffmpeg3 (>= 7:2.4) but it is not installable
E: Unable to correct problems, you have held broken packages.