rongchen@nunki.usc.edu (DragonSlayer) (04/17/91)
This is probably the closest group I can find for this question I want to ask. HDTV is going digital. And once in a while the 16:9 aspect ratio is mentioned to compared with the 4:3 ratio to hint the advantage of the 16:9 mature. What really is the advantage of the 16:9 aspect ratio in HDTV? I know what this ratio is, but I don't see the big deal behind it. Can someone help on this one? Thanks. -- __ | Cheers! |(rongchen@alcor.usc.edu) | / | _ _ _ _ _ | |Disclaimer: Certainly USC didn't teach | /__/ / `/_L /_/ /_/ / > - slayer |me anything I said on this net. It's too| _ / |_________|expensive for anybody to learn anything.|
rustyh@wam.umd.edu (Michael Katzmann) (04/17/91)
In article <16642@chaph.usc.edu> rongchen@nunki.usc.edu (DragonSlayer) writes: >This is probably the closest group I can find for this question I want >to ask. HDTV is going digital. And once in a while the 16:9 aspect ratio >is mentioned to compared with the 4:3 ratio to hint the advantage of >the 16:9 mature. You have done for the English language what Saddam did for democracy. :-) What really is the advantage of the 16:9 aspect ratio in >HDTV? I know what this ratio is, but I don't see the big deal behind it. >Can someone help on this one? Thanks. > It means that a "Panavision" type film can be broadcast without chopping off the sides (you know "The Magnificent 5" syndrome), or having black stripes on the top and bottom of the screen. Its also a way that the HDTV people can counter the EDTV (extended) people. (Although there are schemes to send the extra edge information for EDTV). -- Michael Katzmann (VK2BEA/G4NYV/NV3Z) Please email to this address | Broadcast Sports Technology | 2135 Espey Ct. #4 \|/ Crofton MD 21114-2442 (301) 721-5151 ...uunet!opel!vk2bea!michael
grege@gold.gvg.tek.com (Greg Ebert) (04/18/91)
In article <16642@chaph.usc.edu> rongchen@nunki.usc.edu (DragonSlayer) writes: >This is probably the closest group I can find for this question I want >to ask. HDTV is going digital. And once in a while the 16:9 aspect ratio >is mentioned to compared with the 4:3 ratio to hint the advantage of >the 16:9 mature. What really is the advantage of the 16:9 aspect ratio in >HDTV? I know what this ratio is, but I don't see the big deal behind it. >Can someone help on this one? Thanks. > The film industry uses 35mm and 70mm media which have a 16:9 aspect ratio. Current TV uses 4:3, so when movies are televised, part of the screen is truncated (except when credits are shown, then people look like string beans). Having matching aspect ratios will improve home viewing considerably, especially with a projection TV. A 16:9 tube seems quite wide compared to a standard TV tube. I saw some HDTV demonstrations at NAB this week, and they are visually impressive. Although there were demos by NHK (Japan), General Instruments, ATT/Zenith, and David Sarnoff Labs, I only had enough time to inspect the system by ATT/Zenith in great detail. The GI booth also gave out a pamphlet describing the American TV Alliance, which is a joint venture between GI and MIT. The ATT/Zenith method uses digitzed images which are compressed from a 1.2 Gbit/sec stream into 20-25 Mbits/sec. No typos; that's a 50:1 compression. I don't know how the data is compressed or transmitted, but power spectrum graphs show that it does fall within the 6Mhz band. An interesting feature is that power is spread more evenly over the channel, whereas NTSC has peaks at the carrier, color sub-carrier, and the sound carrier. The encryption algorithm focuses on change-information over multiple frames. Even with rapidly moving images, resolution is maintained. Also demo'd were the effects of signal degradation, which cause localized glitches in fast-moving portions of images. The effect of channel-changing was also shown, and you could see details fill-in around objects for a few frames (a fraction of a second). Note, though, this is NOT the same as keying the source video at the studio, because that occurs prior to encoding. GI's DigiCipher technique also has a 50:1 compression from 1.2Gbits/sec. I overheard 'QPSK' being said by someone at a GI demo, so I assume they use quadrature phase-shift-keying to encode the compressed data stream. That makes some sense to me because the ~24 Mbit/sec stream when QPSK encoded with a 16-point constellation (I think that's the term), produces 6Mega-thingeys per second. I saw a vectorscope with 16 spots on it, which seems to confirm the QPSK theory. An NHK demo showed considerable horizontal artifacts for moving objects, but I don't know if it was MUSE or some other format. Another vendor (Sony ?) showed another system which transmits 20Mhz luminance / 7Mhz chroma. Though unacceptable for general broadcast because of it's high bandwidth, it was targeted for sports bars, etc on special cable or satellite channels; it had excellent clarity even on a projection system. - - - - Designing ASICs for 10-Bit D2 (140 mbits/sec) is challenging enough. I'm going to have a lot of sleepless nights when HDTV arrives ;-] .
charlies@hpnmdla.hp.com (Charlie Sallberg) (04/18/91)
Well, for one thing, it would allow you to see the entire picture of a movie, instead of the center or one-side only as with the present system. Videophiles nowadays are buying "letterbox" versions of LaserDiscs to get the full wide-screen image on their TV sets, but with black bands above and below (in other words, sacrificing vertical height to get the full horizontal picture). HDTV with 16:9 aspect ratio would solve that problem. Charlie
wrf@mab.ecse.rpi.edu (Wm Randolph Franklin) (04/20/91)
The 16:9 aspect ratio also allows computer graphics people to have lots of fun (aka heart attacks) working with rectangular pixels. The pixels are at about 21:20. Image processing people, at least ones I have spoken to here at RPI, see no advantage in square pixels. They've never wanted to rotate an image 90 degrees, for instance. -- Wm. Randolph Franklin Internet: wrf@ecse.rpi.edu (or @cs.rpi.edu) Bitnet: Wrfrankl@Rpitsmts Telephone: (518) 276-6077; Telex: 6716050 RPI TROU; Fax: (518) 276-6261 Paper: ECSE Dept., 6026 JEC, Rensselaer Polytechnic Inst, Troy NY, 12180
bill@thd.tv.tek.com (William K. McFadden) (04/20/91)
Another reason for preferring 16:9 over 4:3 is that the field of vision
is much wider than it is high. Hence, the wide aspect ratio more
closely matches the way we see.
--
Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077
bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
Phone: (503) 627-6920 "SCUD: Shoots Crooked, Usually Destroyed"dimitrov@lab.ultra.nyu.edu (Isaac Dimitrovsky) (04/23/91)
In article <2193@gold.gvg.tek.com> grege@gold.gvg.tek.com (Greg Ebert) writes: >I saw some HDTV demonstrations at NAB this week, and they are visually >impressive. Although there were demos by NHK (Japan), General Instruments, >ATT/Zenith, and David Sarnoff Labs, I only had enough time to inspect the >system by ATT/Zenith in great detail. Another pretty impressive demo was given by Scientific Atlanta (they were giving it in a room at the Sands). They showed a digitally encoded and decoded signal at 5 Mbits/second and 8 Mbits/second for a normal TV signal, which looked very nice, as well as a HDTV transmission system which I didn't pay as much attention to. One thing I remember was that they don't use interframe compression (in fact, every encoded frame was the same size). To demonstrate this all of their demo footage included violent motion to such an extent that I felt vaguely seasick afterwards. Isaac Dimitrovsky