The Digital Fact Book - Quantel

RS 422Not to be confused with 4:2:2 sampling or 422P MPEG, this is a standard for serial datacommunications defined by EIA standard RS-422. It uses current-loop, balanced signalingwith a twisted pair of conductors per channel, two pairs for bi-directional operation. It is morecostly than RS232 but has a high level of immunity to interference and can operate overreasonably long distances – up to 300m/1000 ft. RS 422 is widely used for control linksaround production and post areas for a range of equipment – VTRs, mixers, etc.RSNReal Soon Now. A phrase coined by Jerry Pournelle to satirize the tendency in the computerindustry to discuss (and even offer for sale) things that are not actually available yet.Run-length codingA system for compressing data. The principle is to store a pixel value along with a messagedetailing the number of adjacent pixels with that same value. This gives a very efficient wayof storing large areas of flat color and text but is not so efficient with pictures from a camera,where the random nature of the information, including noise, may actually mean that moredata is produced than was needed for the original picture.RSSafe areaThe area of picture into which it is considered safe to place material, graphics, text or action,so that it will be viewable when received at home. Initially this was necessary with 4:3 aspectratio screens as they were always overscanned to avoid showing the black that surroundsthe active picture. Typically 5% in from the edges was considered safe. More recently thewhole Safe Area issue has become far more complicated as there are both 4:3 and 16:9displays, as well as 4:3, 16:9 and sometimes 14:9 (a compromised version of 16:9 that ismore acceptable to those viewing on, generally analog, 4:3 screens) aspect ratios for programoutput. The transition to HD, always 16:9, ensures safe areas will need careful attention formany years yet. In the UK action has been taken to make all commercials able to conveytheir message whichever display aspect is used. The EBU website referenced below providesa very practical reference document as a download.See also: Aspect ratio (of pictures)Website: document R95-2000 at (www.ebu.ch) – best found by Internet search engineSAIT-2SuperAdvanced IntelligentTape format that uses a 12.7mm (half-inch) wide tape and a helicalscan format. It is designed forthe general data storage market and is also used for the archiveand transfer of file-based media data. SAIT-2 tape has a native capacity of 1 TB and a transferrate of 60 MB/s, offering lossless compressed storage of 2.6 TB and transfer of 144 MB/s.There is a roadmap for SAIT-3 and SAIT-4 that speculatively predicts doubling of performancefor each generation, projected for completion by 2010.148