Caps: no easy way to create multi structs caps
We currently don't have any API to easily create multi structures
Caps. The only way is to create one and then call
Caps::merge_structure() for each structure we want to add.
I was thinking about extending
Caps::Builder so we could do something like this:
gst::Caps::builder("video/x-raw") .struct("audio/x-raw") .build()