MKV is a container format for holding multiple audio, video, picture, and text data such as subtitle tracks. It is similar to other common containers like MP4 and AVI, although MKV is open in the specification. For video contents, MKV uses a .mkv filename extension, .mka for audios, and .mks for subtitles.
MPC-HC, KMPlayer VLC Media Player MKV File Player MPV
AIF (Audio Interchange File/Apple Interchange File Format) is a sound format used on Windows. It comes with a .aif filename extension and .aiff when used on Mac. An AIF file features raw sound data like sample rate, bit depth, and channel (mono/stereo). This file format is also accepted on most CD writers.
File Viewer Plus Apple iTunes QuickTime Player Windows Media Player