Meanwhile, JPEG — short for Joint Photographic Experts Group — was originally developed as a compression standard for still images. With modern processors, however, it is now possible to take a video signal and save each frame as a separate JPEG file, creating a video format known as Motion-JPEG.
Several years after the JPEG team created its first compression scheme, it reconvened to develop an even more efficient and flexible system. Released in 2000, its new JPEG compression was called JPEG 2000. The original JPEG used discrete cosine transform (DCT), the same techniques used in MPEG, to reduce data into blocks of 8 x 8 pixels. JPEG 2000 uses discrete wavelet transform (DWT), which performs simultaneous multiresolution image analysis.
The resulting wavelet coefficients are gathered in sub-bands, each of which is partitioned into small “code blocks” and independently coded by an adaptive binary arithmetic encoder. Finally, the output of the arithmetic encoder is organized as a compressed bit stream that offers a significant degree of flexibility.
Wavelet compression provides the same processing for all pixels, and with each video frame being compressed individually, there is no error propagation from one picture to the next. As a result, there is no macroblocking at low bit rates; instead, there is blurring on the images. JPEG works on a single image, stripping away redundant data and encoding each video frame independently for consistent high-quality images. As a result, editing may be performed on any frame in a sequence of images because each video frame contains its own picture information.
With no dependency on other images, JPEG 2000 has low latency, less than 1.5 frames encode and/or decode, and maintains sync between the video and audio. In contrast, MPEG and other compression schemes that rely on predictive frames and motion estimation algorithms have high latency.
JPEG 2000 and its underlying wavelet compression can allocate 10 bits or even 12 bits at 4:4:4 quality, a level in line with the demands of digital cinema post production. In fact, there are several systems that use wavelet compression techniques similar to JPEG 2000. REDCODE and CineForm, for example, are used successfully for digital cinema production, which demonstrates the quality and robustness of wavelet compression.