Editing Motion JPEG (section)

== Design ==

M-JPEG is an intraframe-only compression scheme (compared with the more computationally intensive technique of [[motion compensation|interframe prediction]]). Whereas modern interframe video formats, such as [[MPEG1]], [[MPEG2]] and [[H.264/MPEG-4 AVC]], achieve real-world compression ratios of 1:50 or better, M-JPEG's lack of interframe prediction limits its efficiency to 1:20 or lower, depending on the tolerance to spatial artifacting in the compressed output. Because frames are compressed independently of one another, M-JPEG imposes lower processing and memory requirements on hardware devices.

As a purely intraframe compression scheme, the image quality of M-JPEG is directly a function of each video frame's static (spatial) complexity. Frames with large smooth transitions or monotone surfaces compress well and are more likely to hold their original details with few visible compression artifacts. Frames exhibiting complex textures, fine curves and lines (such as writing on a newspaper) are prone to exhibit [[discrete cosine transform]] (DCT) artifacts such as [[Ringing artifacts|ringing]], smudging and [[Macroblock#Macroblocking|macroblocking]]. M-JPEG-compressed video is also insensitive to motion complexity, i.e. variation over time. It is neither hindered by highly random motion (such as the water-surface turbulence in a large waterfall), nor helped by the absence of motion (such as static landscape shot by tripod), which are two opposite extremes commonly used to test interframe video formats.

For [[QuickTime]] formats, Apple has defined two types of coding: MJPEG-A and MJPEG-B. MJPEG-B no longer retains valid JPEG Interchange Files within it, hence it is not possible to take a frame into a JPEG file without slightly modifying the headers.

JPEG is inefficient, using more bits to deliver similar quality, compared to more modern formats (such as [[JPEG 2000]] and [[H.264/MPEG-4 AVC]]). Since the development of the original JPEG standard in the early 1990s, technology improvements have been made not only to the JPEG format but to the [[Video compression#Intraframe versus interframe compression|interframe]] compression schemas possible as well.