Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!samsung!think.com!linus!linus!linus!mbunix!eachus From: eachus@aries.mitre.org (Robert I. Eachus) Newsgroups: comp.sys.amiga.hardware Subject: Re: A2320 Message-ID: Date: 19 Feb 91 21:46:37 GMT References: <1991Jan29.054742.18143@cs.mcgill.ca> <3898@rwthinf.UUCP> <18245@cbmvax.commodore.com> <3901@rwthinf.UUCP> <189bc930.ARN13b6@venus.UUCP> <18435@cbmvax.commodore.com> <189ee486.ARN13cf@venus.UUCP> <18528@cbmvax.commodore.co <18695@c Sender: news@linus.mitre.org (News Service) Organization: The Mitre Corp., Bedford, MA. Lines: 48 In-Reply-To: colas@lemur.inria.fr's message of 11 Feb 91 12:11:17 GMT Nntp-Posting-Host: aries.mitre.org In article <1991Feb11.131117@lemur.inria.fr> colas@lemur.inria.fr (Colas Nahaboo) writes: In article <18695@cbmvax.commodore.com>, jesup@cbmvax.commodore.com (Randell Jesup) writes: > Movies are shot at 24 fps, but a) they're displayed in dark theatres, > and b) they double-rate them (show each frame twice, for 48 fps effective). This I don't beleive. Perhaps you are referring to latest cinemascope techniques, but I'm pretty sure most movies made aren't double-framed *. (and even if they do, this is different from video, since there is a black screen between each image in movies that you don't get in video, where the image is not changed at once, but by the spot) (*) Could somebody in the know share some light on this subject? To "fool the eye" 35 mm (& 16mm) movies are filmed at 24 frames per second, but each frame is projected twice. If you have looked inside a movie projector, there is a film gate which holds the film steady for a while then jerks it downward to show the next frame. There is, of course, a rotating shutter (usually between the collimating lens and the film) which closes to keep you from seeing the film moved, but it actually closes TWICE per frame to give the impression that the actual frame rate is twice what it is. I think the old (does anyone still use it?) 8mm "home movie" format was 16 fps with each frame projected three times... When 24 fps movies are shown on U.S. 30 fps (f is now field :-) television, alternate frames are shown twice and three times. For most motion pictures this causes no problems, but it ruins some special effects, for example the hologram projected by R2D2 in Star Wars. :-( I don't know what they do in Europe when recording films for TV, but I suspect that they either just run them 4% fast (fine for the movie, yeetch for the sound, four per cent is enough for musicians to tell that the tuning is bright), or repeat one frame an extra time every half second (would tend to make smooth motion slightly jerky). I guess a good adaptation would use sound clipping to run the sound track on frequency, but take out odd bits... -- Robert I. Eachus Our troops will have the best possible support in the entire world. And they will not be asked to fight with one hand tied behind their back. President George Bush, January 16, 1991