AV/IT Glossary—27 Days of #AVabc—J



The Se7en Deadly J's!


Jitter—A video problem in which the displayed image is unstable or appears to shake. 



Jacket—Outer protective covering of a wire or cable. (See strain relief.)

Jaggies—A video problem in which stairstep-like lines appear where there should be straight-angled lines or smooth curves.

JOG—A control available on high quality VCRs to view individual fields or frames of a tape.

JPEG (Joint Photographic Experts Group)—Commonly used method of lossy compression for photographic images using a discreet cosine transfer function. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality. Produces blocking artifacts.

JPEG2000—A wavelet-based image compression standard and coding system. There is a modest increase in compression performance of JPEG 2000 compared to JPEG, the main advantage offered by JPEG 2000 is the significant flexibility of the codestream which allows for representing the image at various resolutions.

Judder—A distracting side effect of 3:2 Pulldown Detection or “Inverse 3:2 Pulldown” that occurs as a result of every other film frame lasting 1/60 of a second longer than the previous one. Extron’s True Rate™ eliminates this effect by causing the video display rate to increase from 60 fields per second to 72 fields per second.

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