AIiF (Apple Interchange File Format/Audio Interchange File) is a sound format used on Mac OS X. It comes with a .aiif filename extension and .aif when used on Windows. 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.
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HEVC MKV is a digital media format that uses HEVC codec, instead of the usual H.264, which is used on typical MKV files. HEVC MKV files are encoded at lower bitrates than H.264 MKV, making them smaller by up to 50%. However, software and hardware support for HEVC MKV files is quite limited as opposed to H.264 MKV, which ranks among the most popular media formats today.
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