The Digital Fact Book - Quantel

DDitherIn digital television, analog original pictures are converted to digits: a continuous range ofluminance and chrominance values is translated into a finite range of numbers. While someanalog values will correspond exactly to numbers, others will, inevitably, fall in between.Given that there will always be some degree of noise in the original analog signal the numbersmay dither by one Least Significant Bit (LSB) between the two nearest values. This has theadvantage of providing a means by which the digital system can describe analog valuesbetween LSBs to give a very accurate digital rendition of the analog world.LSBLSB ditherAnalogue output of originalanalogue input via ADC/DAC processIf the image is produced by a computer, or is the result of digital processing, it may havevirtually no noise and so the digital dither may not exist – which can lead to contouringeffects. With the use of Dynamic Rounding dither can be intelligently added to picturesto give more accurate, better looking results.DivXA video codec created by DivX, Inc. which can compress long video segments into relativelysmall data spaces while maintaining reasonable picture quality. It uses MPEG-4 H.264or AVC compression to balance quality against file size and is commonly associated withtransferring DVD audio and video to hard disks. ‘DivX Certified’ DVD players can play DivXencoded movies.66