Title editor design

Here's an attempt at summarizing the current situation for adding text on video with gstreamer. Please improve/correct this page with your knowledge.

The question in everyone's mind:

“What we should do in case of titles and text overlays with video compositing? Will be they considered as a video clip with corresponding properties?”

In the GES API reference manual, we can see GES.TitleSource and GES.TextOverlay.

• GES.TitleSource is a title clip/object as you'd imagine it. This is what we are using now.
• GES.TextOverlay, on the other hand, is something that is meant to be used really as an “overlay on top of an existing video stream” (ex: for subtitles). This probably corresponds to the GStreamer text overlay element.

In Pitivi, we would need one UI that does it all: allow creating a title clip/timeline object that may have a transparent background color. That way, if the user wants to use it as an overlay on video, he simply needs to set the background color to be fully transparent. Only one UI, only one workflow. More flexibility for the user and less confusion. As you can see in some other applications like this (or even in kdenlive, I think), having a single UI to do everything feels great. We can do a much better design than them, however!

We need to extend titlesource to be able to set a background color, or even a text border color:

• This is probably easy/trivial to fix in GES, you just need to expose the background-color property of GstVideoTestSrc into GESTrackVideoTestSource and the expose that in GESTitleSource.
• That way, we can ignore textoverlay completely (titlesource will just depend on video compositing being reimplemented later on)