C-Cube Microsystems Inc. unveiled a computer chip that it says is the first that can both record and play back video in digital format. The Milpitas-based maker of specialty computer chips said a single one of its DVx chips can replace up to three chips currently used to record and play back video in the MPEG-2 digital format. Many electronic devices, such as satellite TV, digital cable set-top boxes and digital videodisc players, use MPEG-2. A single, low-cost chip is the first step to making cheap video cameras and videodisc players that can play back and record in digital format. Video stored in a digital format, instead of analog tape, can be easily edited or transmitted through various media, including the Internet. Satellite TV equipment maker Scientific-Atlanta Inc. and consumer electronics giant JVC of Japan are testing C-Cube's chips for possible products, C-Cube said. C-Cube's stock rose 50 cents to close at $29 on Nasdaq.