Software encoder

The CPU compresses each frame in software, which gives finer control and generally better image quality per bit than the fixed hardware encoders built into graphics cards. The cost is processor load, and on a single machine that load competes directly with whatever you are capturing.

Presets set the trade. Slower presets look better at the same bitrate and eat more CPU, faster presets free up headroom and soften detail. Streamers who game and broadcast on one machine usually move to a hardware encoder such as NVENC, or split the job across two machines. Dropped frames and a stuttering game are the usual sign the preset is too ambitious.