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Switching scenes too fast messes up fading
Operating System Info
macOS 12
Other OS
No response
OBS Studio Version
27.2.4
OBS Studio Version (Other)
No response
OBS Studio Log URL
n/a
OBS Studio Crash Log URL
No response
Expected Behavior
Only blue and green scenes are visible on the screen.
Current Behavior
The screen shows all three: red, green, and blue scenes.
Steps to Reproduce
- Increase your transition time, or be able to click/move very fast
- Create three scenes: all red, all blue, all green
- Click red scene
- Quickly click between the blue and green scenes over and over... blue... green... blue... green... blue... green... blue... green... blue... green... blue... green...
Anything else we should know?
I am using the iPad and Apple Pencil as a second display for the scenes. So this makes it easy to switch between the blue and green scenes.
And quickly clicking back and forth is no big deal, this is a normal thing that would happen during a broadcast. In fact I use this to switch between two scenes where one of them has a badge on top. Going back and forth would have the intended effect of blinking the badge.
As you are clicking you will see these transitions:
Red -> green Red -> blue Red -> green Red -> blue
where I was expecting
Red -> green green -> blue blue -> green green -> blue
Can confirm that this issue also occurs on Windows 10 and Windows 11 (both x64)
Sounds to me like the "active" scene is changed in UI, but not necessarily inside the compositor, because the observed behaviour matches what would happen if the reference to the currently active scene is only set by the callback of a finished transition.
As you don't allow the transition to finish however, the internal "source" for the transition isn't changed, to switching to yet another scene creates a new transition between the (still unchanged) internal source scene to the new destination scene.
After having looked into a similar issues with stinger transitions, this is indeed "as implemented" - only after a transition has finished will the active scene be switched.
When you click on yet another scene while the transition is ongoing, the old transition will be aborted and a new transition will be triggered. A transition will always use the current active scene as the "source" and the clicked scene as the "destination". As the prior transition did not finish, the source scene will stay the same.
Alas as implemented, the transition system creates a confusion between "visual" state of a transition and the actual state as understood by the compositor. For now, this works as intended.