How is GstVideoCropMeta supposed to be used?

[Carlos Rafael Giani]

Hello,

after looking at GstVideoCropMeta, I am confused. I found many sinks 
inside the plugin packages that support it, only a couple of decoder 
plugins are adding this to GstBuffers. I thought the videoparse element 
might work by simply adding this metadata to incoming buffers, but 
instead, it copies the pixels from within the crop rectangle.

What would the typical use cases of GstVideoCropMeta be? Is it only 
supposed to be used by decoders, in case their decoded frames have 
borders or padding? Wouldn't it also be useful to remove black borders 
from movies for example?

cheers