Ideal for cartoons or anime. It increases the use of I-frames (keyframes) to handle rapid scene changes and reduces blocking in large, solid color areas typical of 2D animation.
When you see attached to a movie title like Undertone , it refers to the video encoding standard used to compress the file for digital distribution. undertone x264
The x264 -tune option is the easiest way to apply specialized "undertones" for specific types of content: Ideal for cartoons or anime