assuming that umc_video_enc_con has been compiled using an OpenMP enabled compiler, and that OpenMP was actually enabled, you should be able to increase performance by increasing the number of thread used for encoding. When using umc_video_enc_con you can specify that using the -t argument to set the number of thread you want to use to encode. For example -t 2 to have 2 threads.
However it isn't a good idea to have more thread than you actually have core/HT so for example if you have a single core machine without HT, 1 thread should be the best. If you have an HT (HyperThreading) on a single core machine, you can set 2 thread. With a 2 core machine with hyperthreading, 4 threads might give you the best performance.