The Digital Fact Book - Quantel

DVTRDVTR – Digital Video Tape Recorder. Sony showed the first DVTR for commercial use in1986, working to the ITU-R BT.601 component digital video standard and the associated D1standard for DVTRs. It used 19 mm cassettes recording 34, 78 or (using thinner tape) 94minutes. Today all new VTR formats are digital and are available for HD as well as SD andfrom professional to consumer standards. Due to its relatively high cost, D1 is rarely usedtoday. Other formats D2 and D3 that recorded digitized composite PAL and NTSC arebecoming extinct. All modern tape recorders are digital and use some form of compressedcomponent video – the exception being Thomson’s VooDoo Media Recorder (a.k.a. D6).DProvided there is no re-coding or transcoding, DVTRs do not suffer ‘generation loss’ due tore-recordings as tape noise, moiré, etc., and dropouts are mostly invisible due to sophisticatedcorrection and concealment techniques. However tape is subject to wear and tear and theresulting errors and dropouts necessitate complex error concealment circuitry. In extremecases multiple passes can introduce cumulative texturing or other artifacts.Today, tape is generally widely used in acquisition and for distributing programs, but the postproduction is nearly all disk-based.See also: Betacam SX, D5, D9, DV, DVCPRO, HDCAMDylan ®Media storage technology first developed by Quantel in 1993 to support SD editing andcompositing systems. It has continually expanded and today provides features beyondthose of generic video storage solutions including FrameMagic with multi-channel realtimeaccess to any frame and large bandwidth for realtime operation up to multiple uncompressed4K streams. It makes an excellent store for nonlinear systems (eQ, iQ, Pablo) and for servers(sQ server).There is RAID-5 protection so that, should a disk drive fail, operation continues and no datais lost. Implemented in Quantel’s generationQ systems it is resolution co-existent, holdingany mix of formats including SD, HD and film, and color space independent storing RGBand Y,Cr,Cb, etc. It does not need de-fragmenting and the total storage capacity is thereforealways available – regardless of fragmentation.See also: Color space, FrameMagic, RAID, True random accessDynamic rangeFor images – the measurement of the range of brightness in a scene expressed as a ratioor the Log 10 of the ratio. Typically a lighting cameraman will try to keep a scene to less than40:1 (Log = 1.6) to avoid loss of detail in the print. A 100:1 (Log = 2) contrast range in thescene is a typical maximum.See also: Cineon file77