Variable Frame Rate

From KickAssAnime Wiki

Variable Frame Rate (VFR) refers to certain encodes in which frame rate changes during playback. The only containers that allow VFR video are Matroska, MOV, and MP4.

VFR in anime

Anime are originally made at 23.976 fps, also known as the FILM standard. However, NTSC, the format used for TV and DVDs in USA and Japan, uses 29.97 fps. To solve the issue, for every four frames in the original video, one is added. This results in a jerky video, but that is barely noticeable when watching on a TV.

When groups encode anime, they reverse the anime back to its FILM nature via a process called decimation. This involves finding the duplicated frames and removing them. However, some times, when the anime is digitally processed, some effects such as scrolling text and some pans are recorded at 29.97 fps. Decimating these scenes results in an even jerkier scene than the 23.976 scenes with dupes. The solution to this is to use a timecode file and have a hybrid frame rate: 23.976 and 29.97 fps on the same video file. This is usually done using Yatta.