[vlc-devel] Video filter - picture_t versus subpicture_t

[Peter Tap]

Hello,

Having written a stream filter, I am somewhat experienced with VLC development. For my current requirements, I need to extend VLC so that small image(s) can be displayed at specific times while a movie is being played. The closest to what I am doing is probably "dynamic logos." In my case, the picture has to be generated dynamically as it contains current time information.


To understand how to write this, I have been looking at the code for dynamic logos. However, the code is a bit complex to grasp. I would appreciate your help in understanding the basic concepts:
1. What is the difference between picture_t and subpicture_t? I was thinking a subpicture is only a small part of the picture and that is what I need to blend with the actual picture. However, it appears filter_Blend requires picture_t and not subpicture_t as parameter.
2. In general, what are the steps to create a picture and merge it with the existing picture?

3. What is the simplest example I can look at for writing a filter?

Thank you in advance for your help.

Regards,
Peter
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