Resizing rules of program in floating mode are ignored

[nadomodan]

MPV player includes the following functionality:

--no-keepaspect-window, --keepaspect-window
    --keepaspect-window (the default) will lock the window size to the video aspect. 

Resizing the window in openbox for example respects this, window maintains aspect ratio as it is resized, in spectrwm keepaspect-window is ignored, window is freely resized in both dimensions so the video ends up padded with black bars if window aspect and video aspect mismatch.