Microcontroller with Video input preferably composite
The bottom line is, most microcontrollers (particularly toy MCU's like Arduinos) are simply not capable of dealing with video in a useful way, especially if they're trying to do anything else at the same time.  The sheer volume of data defeats them.

There are system on chip devices like the ASC88xx line from NXP that are purpose-built video encoder/decoders but apart from being able to deal with video in a meaningful way they're unlikely to meet your needs (a powerful ARM CPU with video peripherals, in a BGA package, is not for hobbyists working at the Arduino level).

I'd suggest you restate your question and explain exactly what it is that you're trying to achieve.  What do you mean by "will take video input", for example; what are you going to do with the video once you've digitized it?