Is it possible to run a pic slideshow that includes mp4s? If so, how?
Video files won't be included in a slideshow automatically, but if you explicitly select them before clicking the Slideshow button then they will be included.
The slideshow will still advance to the next file after the specified timeout, not after the videos finish, so it may not do what you want, depending on what that is.
If you want to play several complete videos in sequence, making a button which sends them to a video player will work better.
Nope, didn't work. Would that be because I am using DO 11?
What I am trying to do is use a slideshow of pics and videos as a feed to a tv being used as a picture frame. It seems that it is almost impossible to get an app to do that under Win 10. I had it running on an Android stick computer, but Android sucks.
There were some changes made to the slideshow command recently but I'm not sure if they would be what's making it work here.
Do the videos play in the Opus preview pane for you?
Thanks Leo.
Yep videos play perfectly. Well they play, but they do frequently tend to lock the video file so it can't be renamed or moved after focus is removed.
File locking up to the involved video splitter DLL, I believe.
Thanks Leo. I need a translation of what that meant. 
A DLL is a file that helps a program "do things". In your case, something invokes a DLL (to run like a program) which is then playing the video file for you. The programmer who wrote the DLL may not have been very careful in releasing the video file after you are done viewing. This is usually considered a no-no.
Thanks DDwarf. I know what a DLL is, just couldn't understand Leo's reply.
Just wondering if there is a way to tell what DLL is causing the problem. I use 'Unlocker' to unlock locked files; always works a treat, but never in these cases. When the DO viewer leaves them locked, even Unlocker can't find a locking handle - nor can it unlock the file.
Boy have we gone off topic. to get back on topic: Anyone know of a way to get DO to work as a slideshow with both pics and videos?
(Using Unlocker is generally a bad idea, and can lead to data corruption (not just of the file that was unlocked) if the file handles are recycled. I'd keep it for last-resort situations only.)
Are the video files locked while playing, or do they remain locked when the video player has been closed or moved to playing another file?
Thanks for the heads up on Unlocker Leo. I was blissfully oblivious to all that.
The video files are locked after playing. I frequently preview them in DO and then delete, re-name and/or move them to a permanent folder. The deleting, re-naming, moving them is generally impossible until the next re-boot.