[vlc-devel] Video output size policy

[Alexandre Janniaux]

Hi,

On Mon, May 27, 2019 at 05:31:54PM +0300, Rémi Denis-Courmont wrote:
> Le maanantaina 27. toukokuuta 2019, 13.34.51 EEST Alexandre Janniaux a écrit :
> > > Currently, we request a resizeif the user changes AR, crop or zoom. The
> > > question is whether we should also request a resize when the source
> > > changes, or when the source format changes, or neither.
> >
> > I don't really know the background of either one choice or the other, but
> > resizing when the source format change would raise usability issue with
> > adaptive streaming, wouldn't it ?
>
> Either options will cause issues on format changes, in different circumstances.
>
> If the resolution of an adaptive stream increases, the window should not keep
> the old smaller resolution size, otherwise the user won't even notice that the
> resolution increased.

I'm a tile window manager user so I'm not the best example to define window
user experience, but in this case, if the user has resized, he will see the
improvement in the image. And if he hasn't resized but we don't resize, he
won't see any changement if the window is the size of the video but I find
it intuitively better than changing size 5 seconds after the beginning of the
video, while the user might even be trying to resize the window itself, and
is maybe followed by another resize because it fall back to a lower resolution
than the second try. Moreover, the case "keeping the window at a small size"
which would be the first segment resolution seems unlikely to me in the real
world.

In non-adaptive scenario it might not fit 100%, but not resizing after the
first resize also avoid buggy user experience with media changing format each
frame, even if changing format is rare in general. And for the majority of use
case, keeping the previous size seems more reasonable to me, as either the
user is choosing the next media to play and has probably moved vlc, or has
setup a playlist, setup it's window or fullscreen option and is probably not
wanting the window to change. Resizing would be useful for zoom in multiscreen
corner cases, but we don't even change zoom in playback time.

I would be very interested in some cases where this UX is worse than resizing.

--
Alexandre Janniaux
VideoLabs