Microprocessor board with Linux and Multithreading support ?

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I am working an opencv Application on Linux plateform. It is to have multi-threaded architecture. Demand of processing is on a higher side: +Generating real time disparity maps from live video feed from two cams. +Edge detection and further processing. +Object Recognition and Detection in real time. +Face detection and recognition in real time.

All processing is to be done on the same video feed in real time on threads in parallel.

I want to move this application on to a portable processing board in order to get a highly portable system that is really compact and light. (like a medium sized hand held device)

What board should i go for ?

PS: I do not have any knowledge of working with any these boards.