[vlc-devel] [PATCH 00/17] Restart the display module on format changes

[Rémi Denis-Courmont]

Le perjantaina 20. marraskuuta 2020, 16.44.50 EET Steve Lhomme a écrit :
> As previously discussed, in push it's possible added filters will change the
> output of the filter chain(s).

It's also possible in pull model. Push model makes it easier because you don't 
need to worry about pools, but there's really nothing new here.

> The display may be able to cope with the
> change but in case it doesn't we need to restart the display.

That's not how we usually solve that problem. As was already mentioned at the 
last workshop, we already have a simple and robust solution for that, that has 
been used for years. The display requests up-front whatever format is most 
convenient, and lets the the filter chains figure insert any necessary 
conversion.

> This patchset adds support for this (worst case) scenario. If the last
> filter chain output is different than the previous one, the display is
> restarted, no matter what.

Creating the display before the filters is but an historical artefact of the 
pull model. If you are going to destroy the display and make a new one before 
showing a single picture, then you might as well not create the the (first) 
display.

> There can be some time between the time the old display is removed and the
> new one is added and displays the new picture. So there is a display
> glitch. It's different than the window glitch the push was supposed to get
> rid of but still a glitch.

That problem is introduced by the patchset... We have had support for changing 
conversion filters for years, that avoids changing the display.

-- 
Rémi Denis-Courmont
http://www.remlab.net/