Pure code for video encoding

I do some computer hardware architectural research, and I really wanted to test different tasks on my prototype. so I need some code to simulate the task of encoding and / or decoding a video (H264 would be ideal, but other codecs are fine too).

Is there anything I can use? It doesn't have to be exactly encoding / decoding, just some code that can roughly estimate the same workload with the same calculations so that I can get some performance / power consumption results.

Oh yes, and it should be in "pure C", and without using any complex libraries (math.h is fine), since I will need to put this on a hardware module.

Thanks in advance