JPEG 2000 (.JP2)

This is another image compression system from the Joint Photographic Experts Group (ISO/ITU-T). JPEG 2000 is very different from the original JPEG; whereas JPEG is DCT-based and examines images in a series of 8 x 8 pixel blocks, JPEG 2000 is wavelet-based using Discrete Wavelet Transform (DWT), to analyze the detail of pictures in a different way. Both coding and decoding require far more processing than JPEG, MPEG-2 or MPEG-4. Also JPEG 2000 is intra-frame only; there are no predictive frames (as in MPEG). Whereas MPEG tends to show macro blocks as it starts to fail, and the original JPEG shows ‘mosquito wings’ or ringing effects, JPEG 2000 can switch to lower data rates that can cause a softening of picture areas, which is far less noticeable. There are two file-name extensions; .JP2 is for ISO/IEC 15444-1 files and .JPX for ISO/IEC 15444-2 files.

JPEG 2000 is about twice as efficient as the equivalent I-only MPEG-2, and excels at high bit rates. It is used at up to 250Mb/s for DCI Digital Cinema applications, usually showing 24 pictures per second in 2K and 4K formats. It lends itself to a wide range of uses from portable digital cameras through to advanced pre-press and television acquisition – as well as Digital Cinema. Some favor it for use in TV distribution. The company intoPix, a specialist in JPEG 2000 technology, offers a video-over-IP solution using JPEG 2000 for HD and 4K UHD via 1Gb/s media networks with 10ms of latency. Its further technology developments are aimed at expanding the use of JPEG 2000 in TV.

See also: Compression, Compression ratio, DCT, Huffman coding, MPEG