By specifying MKV, the user is rejecting lower-quality streaming rips (often .mp4) and signaling a desire for a robust, feature-rich archival file.
Example FFmpeg command:
release effectively, you should focus on using a media player capable of handling high-frame-rate (60fps) video and advanced MKV containers. This specific file name suggests a high-quality, 60fps upscale or encode of the Bokura no Taiyou kana bokura no taiyou god06660fpsmkv better