meta,
    seek=true,
    handles-states=true,
    args = {
         "videotestsrc !  aspectratiocrop name=cropper ! $(videosink)",
    }

pause
set-property, playback-time=0.0, target-element-name=cropper, property-name=aspect-ratio, property-value="16/9"
play
stop, playback-time=1.0