How cut and render video by most effective way ?

[Claupacius]

Hello.

Can anybody give me a direction for implementing the following flow using libvlc :

1. There is a source video, played back on custom window inside the player.
2. There is a number of irregular-shaped rectangular-like areas, defined by user
3. Every area should be played back in separate window, the area form will be transformed to a proper rectangular.
4. The renderer is OpenGL.

The straightforward way is to get a raw frame, cut the needed areas and form a memory stream, as a new source.
But this is a very resource-consuming step, taking in account that the source video resolution is huge.
Is there a more elegant way to implement the above-mentioned flow ? May be using a renderer textures, which probably can be copied across the contexts ?

Thank you in advance for pointing me to the proper approach.