[MPlayer-users] No vf_ commands for -slave?

[Reimar Döffinger]

On Mon, Jun 08, 2020 at 09:21:34PM +0100, Dave Wood wrote:
> On 08/06/20 14:04,
> Kevan Hashemi <hashemi at opensourceinstruments.com> put forth the proposition:
> > Dear Reimar,
> >
> > Thanks for your attention.
> >
> > > I don't know what you're trying, but mostly I'd say that the result wouldn't make any sense.
> >
> > I expect that I'm using the word "scaling" wrong. When the user changes the size of the window, the video display changes size also. I don't know what that's called. Maybe it's "zoom", because that's the command I use to have the same effect. I'd like to be able to tell the slave to change the value of "zoom".
> >
> > > If you want the window a different size you can just make the window a different size
> >
> > I can't as the process sending commands into the slave MPlayer. So far as I know, only the user of my program can change the window size.
> >
> > > Similar for expand.
> >
> > As above: I doubt I know what you mean by "expand".
> 
> Just to make clearer what I would like to do and what is meant by
> `expand', I have a few different profiles that use -vf-pre:
> 
> [win-1]
> vf-pre=scale=640:-2
> 
> [win-2]
> vf-pre=scale=768:-2
> 
> [win-3]
> vf-pre=scale=800:-2
> 
> ... etc.
> 
> In [general] I have:
> 
> vf=expand=-8:-40:4:35,scale

To be honest, ideally these would all be replaced by a combination
of -geometry an -panscan instead.
You should be able to get the same effect and without all the
processing.
Admittedly at those resolutions it might not matter, but filters
aren't really the right way to do it.
Well, except maybe vf_dscale.
I'll admit that calculating the right values to use for -panscan and
-geometry might be a good bit trickier, depending on use-case.

> The result is a profile for each size with `expand' in [general]
> making black borders.  The top border is big enough to hold the OSD
> for the time code (that depends on the font scale too though).
> 
> I'd like to be able to change the `vf' setting via the fifo, to
> (hopefully) switch window sizes on-the-fly.

My problem is exactly with this:
"change the vf setting to switch window sizes".
Why that round-about way? Why not simply changing window sizes?
Ideally with some existing feature of a window manager, but
possibly through slave commands.

As to the af_switch: I don't think that ever worked reliably,
and it will be MUCH harder to do with vf.

> It looks like starting a new slave with the relevant settings (or
> profile) is the only way that would work, but I can see that starting
> a new slave from the parent, and then exiting the parent process
> could be a problem though.

If you can accept the delay/need to restart I'm not sure what the point
would be in the extra indirection in fact.
Note that command-line options are per file though, so if it's
only on switching files that the settings needs to change that might
already be possible.