Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!mcnc!thorin!oscar!tell From: tell@oscar.cs.unc.edu (Stephen Tell) Newsgroups: comp.graphics Subject: Re: Looking for details of Sony D2 format... Keywords: Sony D2, digital video. Message-ID: <15201@thorin.cs.unc.edu> Date: 17 Jul 90 02:59:58 GMT References: <3714@altos86.Altos.COM> <2751@dftsrv.gsfc.nasa.gov> Sender: news@thorin.cs.unc.edu Reply-To: tell@oscar.cs.unc.edu (Stephen Tell) Organization: University Of North Carolina, Chapel Hill Lines: 125 In article <2751@dftsrv.gsfc.nasa.gov> buck@drax.UUCP (Loren (Buck) Buchanan) writes: >In article <3714@altos86.Altos.COM> dtynan@altos86.Altos.COM (Dermot Tynan) writes: >>Does anyone have a simple breakdown of this format, or know anything about >>it?? I'm even curious as to what kind of tape they use, or even if it *is* >>tape. Any help appreciated... > >Yes it is tape. I think the tape is physicaly 3/4" wide. The cassetes get rather large for long playing times. >2. What are the specifications for D2? Is it component or composite? How > many bits per sample? Etc.? D2 is digitized NTSC composite; 8 bits sampled at 14.31818. >My own interests lie elsewhere, so here are a few more questions: > >3. Is anyone marketing a D2 machine with a computer interface which is > useable for both video work, and general purpose computer work (backups, > data storage, etc.)? To quote the frequently asked questions posting: "Uhhhhh..." At >$60K for D2 and >$100K for D1, you might be better off with a dedicated tape drive. It would store a lot though, but the computer interface would have to do its own error correction (see below). >4. How is audio handled? How many samples per second, bits per pixel, is > it stereo, etc.? Audio is digital in both formats, I think 4 channels, "CD quality" (14 bits at 44.1Khz). Even though the audio is recorded by the helical scan rotary head, audio and video can be edited separately using a read-erase-write set of heads that fly by in that order. >5. Questions 1-4 with D1 substituted for D2. D1 is digital component; 8 bits for Y, R-Y, and B-Y. Y sampled 13.5Mhz, the others at half that. >Loren Buchanan | buck@drax.gsfc.nasa.gov | #include For more info, here's a posting from several months ago from rec.video, in which someone with more knowledge corrected a posting of mine and explained things better than I would have anyway. From thorin!mcnc!rutgers!mit-eddie!snorkelwacker!apple!gem.mps.ohio-state.edu!wuarchive!texbell!texsun!newstop!sun!vector!poynton Sat Nov 18 16:22:20 EST 1989 Article 7012 of rec.video: Path: thorin!mcnc!rutgers!mit-eddie!snorkelwacker!apple!gem.mps.ohio-state.edu!wuarchive!texbell!texsun!newstop!sun!vector!poynton >From: poynton@vector.Sun.COM (Charles A. Poynton) Newsgroups: rec.video Subject: D-1 and D-2 Message-ID: <127857@sun.Eng.Sun.COM> Date: 14 Nov 89 09:22:33 GMT References: <8911071850.AA05885@nsipo.arc.nasa.gov> <10410@thorin.cs.unc.edu> Sender: news@sun.Eng.Sun.COM Reply-To: poynton@sun.com (Charles A. Poynton) Organization: Sun Microsystems, Mountain View Lines: 69 Was: Re: LD "Best Practices" Sumary: D-1 is compoNENT digital 27 MB/s, D-2 is compoSITE digital 14.3 MB/s. Regarding speculation on the details of D-1 and D-2, Stephen Tell did a pretty good job of explaining, here's corrections and some more detail. [pardon the stilted style, this is edited 'vi'] Both D-1 and D-2 are 100% digital. (Well, OK, there's a scratch audio track, but one hopes that it will never be heard outside the post suite.) D-1 came first. It is a COMPONENT digital format, according to CCIR Rec. 601: YUV coding [luminance and two colour differences, Y=0.299R+0.587G+0.114B, U=(.5/.886)(B-Y), V=(.5/.701)(B-Y)], so-called 4:2:2, which means that the U and V components are horizontally subsampled 2-to-1. Luminance is sampled at 13.5 MHz, 720 samples per picture width. Aggregate data rate is roughly 27 MB/s (megabytes per second). The D-1 format was standardized back in the days that the industry thought it would make the transition from composite-analog to component-digital in one swell foop. No such luck. Ampex identified an opportunity to make a quick buck, whoops, do the industry a service by providing digital capability at a lower price, and worked up the D-2 format. D-2 uses exactly the same physical casette s D-1, but the recording format is entirely different. D-2 is COMPOSITE NTSC digital: digitized NTSC. The composite signal is sampled at four-times-colour-subcarrier, i.e. about 14.318 MHz. Aggregate data rate is, of course, 14.318 MB/s. All the impairments of NTSC, but with the reliability and generation performance of digital. Great for "on-air" use where the user is stuck with NTSC whether he likes it or not; not-so-great for post production applications where the user really wants separate components for production flexibility. Not only is the NTSC footprint permanently imprinted on a D-2 recording, but the luminance range from black to white encompasses only about seven bits [the remaining codes being required for sync and chroma excursions], as opposed to very nearly eight bits for D-1 (well, OK, 235 codes of 256). Oh yeah, almost forgot, 757 samples per picture width, 768 "active" but a few are blanking. There are three sizes of D-type cassettes, called S, M, and L (use your imagination to figure THAT out!). D-1 gets [I think] 22, 40, and 90 minutes, respectively. D-2 has half the data rate, half the tape speed, therefore twice the capacity on a tape; a maximum of about three hours or about 150 GB (gigabytes) per tape. Neither D-1 nor D-2 is totally error-free like a computer tape, however. Error correction techniques are used to record redundant information to enable perfect reconstruction of small numbers of error bits; large error bursts can be detected but not corrected. So, the samples written on tape are dispersed spatially ("shuffled") so that a single error burst affects isolated single samples dispersed spatially throughout a frame. The resulting error samples are concealed, that is, replaced by information interpolated from their neighbours. It is this error concealment which ultimately limits the generation performance of the tape. Pardon me for rambling, this is probably much more than you needed to know. On the other hand, this technology will be arriving on your doorstep in the form of a consumer digital VCR quite soon, and so you rec.video enthusiasts might as well learn about it now. Maybe since the wall is now being torn down, we can turn some of our defense budget toward television system R&D in America! Personal views only, of course, C.