Codec Central - MJPEG Codec



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M-JPEG

General Information

Overview
There are three JPEG-based codecs built into QuickTime. These are: Photo-JPEG, MJPEG-A and MJPEG-B. MJPEG stands for "Motion JPEG," and is identical to Photo-JPEG except that the MJPEG codecs have translators built-in to support the different capture cards.

MJPEG is not the same as MPEG, although the names are confusingly similar. The primary difference is that MPEG provides temporal compression, while MJPEG only provides spatial compression.

Architectures Supported

QuickTime

Pros, Cons & Tips

Pros

MJPEG codecs are often used as storage formats for large files that need to be archived with good quality. It is a lossy codec, but at 100% quality, the image degradation is minimal.
At WWW data rates (5-20K), JPEG may produce better results than Cinepak.

Cons

All the JPEG codecs require significant amounts of CPU power and are not well suited to video playback at CD-ROM or higher data rates, except when assisted by a hardware capture card.
Large image and/or high frame rate movies usually don't play smoothly.

Tips

Avoid saving the same file multiple times with any JPEG codec, as the JPEG artifacts may build up and become objectionable.

Ideal source material	Video
Supported bit depths	24-bit color, 8-bit greyscale
Compression time	Asymmetrical
Temporal compression?	No
Special features	Supports Media Cleaner Pro 2.0's advanced data rate limiting
Encoder requirements	Any MacOS or Windows
Decoder requirements	Any MacOS or Windows
Encoder availability	Built into QuickTime 2.5
Decoder availability	Built into QuickTime 2.5
Algorithm	Discrete Cosine Transform (DCT)
Manufacturer	Apple

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