MicroHD is a video file created from HD

High-definition video

High-definition video or HD video refers to any video system of higher resolution than standard-definition video, and most commonly involves display resolutions of 1,280×720 pixels or 1,920×1,080 pixels...

 sources using H.264/MPEG-4 AVC

H.264/MPEG-4 AVC

H.264/MPEG-4 Part 10 or AVC is a standard for video compression, and is currently one of the most commonly used formats for the recording, compression, and distribution of high definition video...

 video compression and AAC

Advanced Audio Coding

Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....

 audio compression standards. mHD differs from other HD formats by its small file size (300-500 MB for ~90 minutes of audio/video). It has low video resolution (examples run from 1280 x 544 px down to 640 x 272 px) compared to the common high-definition video modes of 1280×720 px or 1920×1080 px, and a low audio sampling rate (48,000 Hz as opposed to 96,000 Hz or 192,000 Hz for true HD).