J

Jack

An electrical connector found on tape recorders, patch panels, VCR’s, etc.

Jam Synch

Process of synchronizing a secondary time code generator with a selected master time code, i.e., synchronizing the smart slate and the audio time code to the same clock.

Java

Developed by Sun Microsystems, Java is a programming language that is specifically designed for writing programs that can be safely downloaded to your computer through the Internet. Using small Java programs (Applets), Web pages can include functions such as animations, calculators, and other fancy tricks.

Javascript

A scripting language for Web pages. Scripts written with JavaScript can be embedded into HTML documents. With JavaScript, you have many possibilities for enhancing your Web page with interesting elements.

JEC (Joint Engineering Committee of EIA and NCTA)

Jitter

The variation of digital signals’ transitions from their ideal positions in time. Also random picture instability, usually of the whole frame

Jitter Transfer

Jitter at the output of equipment resulting from applied input jitter.

Jitter Transfer Function

Ratio of the output jitter to the applied input jitter as a function of frequency.

JPEG/JPG (Joint Photographic Experts Group)

The term referring to the image compression draft standard developed by an international body. JPEG was developed to compress still images, such as photographs, a single video frame, something scanned into the computer, etc. You can run JPEG at any speed that the application requires. For a still picture database such as mug shots, the algorithm doesn't have to be too fast. If you run JPEG fast enough, though, you can compress motion video-which means that JPEG would have to run at 30 frames per second. You might want to do this if you were designing a video editing or authoring platform. JPEG running at 30 frames per second is not as efficient as MPEG running at 30 frames per second because MPEG was designed to take advantage of certain aspects of motion video. So in a video editing platform, you would have to trade off the lower bit rate (high compression) of MPEG with the ability to do frame-by-frame edits in JPEG (but not in MPEG). Both standards have their place in a video compression strategy and both standards usually exist in a computer system simultaneously.