@Izzy Hey. Thanks for answering. I'm unfortunately trying to cut in width/height. I read about NDK and FFMpeg but I have zero knowledge in that area and I think this is such a big thing (many apps have custom camera activities, such as instagram) that there SHOULD be an easier way or atleast some tutorials/documentation. :(

@JonasB Agreed, and I admit I wonder there is no such thing currently. As the one behind the site I've linked in my previous comment, I think I have some insight in what apps exist and what not. There might be some having escaped me, but for this kind I specifically checked and found nothing that "sounded convincing".

@Izzy I've been to every corner of Google and forums but there has not been any good information at all. I (just) found xuggler (xuggle.com), which seemed to have some useful features and included information. I will check as soon as I can and get back to you if it was any useful.

@JonasB Please do! If you find a corresponding and useful app, make sure to let me know – so I can include it in the mentioned list. You'll usually always find me in chat here (at least logged-in and "monitoring"). Thanks in advance!