Gumlet uses per-title-encoding to determine the lowest possible bitrate for a video by analyzing the material, maintaining the visual quality of the original video, and minimizing the size of the transcoded video.
For example:
Original Video:
Gumlet Per-title-encoded Video:
As you can see in the above movies, the original video is 151 MB and the per-title encoded video is 104 MB, so per-title-encoding allows us to accomplish a 47 percent reduction in size while maintaining the same visual quality.
For more please read the In-depth article on Per-title encoding