Pure C Code For Video Encoding

I'm doing some computer hardware architectural explorations and I was eager to test different tasks on my prototype. so I need some code to simulate the task of video encoding and/or decoding (H264 would be perfect but other codecs are also ok). Is there anything that I can use? It doesn't have to be exactly encoding/decoding, just some code that can roughly estimate the same workload with same kind of computations so I can get some performance/power consumption results. Oh yeah and it's gotta be in "pure C", and without using any sophisticated libraries (math.h is fine) since I'm gonna have to put that onto a hardware module. Thanks in advance