Path: chuka.playstation.co.uk!news From: "JohnT" Newsgroups: scee.yaroze.beginners Subject: Re: Questions about VSync. Date: Mon, 4 May 1998 02:45:05 +0100 Organization: PlayStation Net Yaroze (SCEE) Lines: 51 Message-ID: <6ij6jd$jpr18@chuka.playstation.co.uk> References: <354C8851.709D2E83@chowfam.demon.co.uk> NNTP-Posting-Host: nettech.demon.co.uk X-Newsreader: Microsoft Outlook Express 4.72.3007.0 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3007.0 James Chow wrote in message <354C8851.709D2E83@chowfam.demon.co.uk>... >I realise the most relevant way to obtain an timer function is to >use VSync(). >Initially I was using VSync(-1) to get some sort of indication of >the length of time passed. Unfortunately this increments in steps >of 1/50sec for PAL and 1/60sec for NTSC, which are slightly too >big. > > >This means using the number of hsyncs which can be gotten from by >VSync(0 or 1). Unfortunately, this is the thing which I am confused >about. > >I get the indication (from the docs) that each horizontal line >drawn represents a hsync. And all the hsyncs on the screen >represent a vsync. Yes? >OK. So if I set the graphics system to 256 lines in PAL, does this >mean I should get 256 hsyncs per vsync? >If not, why not? > >If this is correct, then why does it say in the User Guide >(paper version, page 38) that PAL gives 312 hsyncs per vsync and >262 hsyncs per vsync for NTSC? >And just to confuse me even more, we only have 311 hsyncs per vsync >(v1.1 electronic p37). Now what has happened to the other number? >Or do PAL and NTSC outputs give the same number of hsyncs per vsync? Ok James, it seems you are slightly confused here which is not surprising considering the poor information contained in the Yaroze manuals! vsyncs and hsyncs are nothing to do with the Yaroze display that you use in your demo/game. They are in fact hardware timings for the TV display. The Yaroze can sync itself to these timings. An hsync is the horizontal time for a beam to travel across the TV screen and the vsync is the overall time for the to reset to the top left corner after reaching the bottom right. It is usual for any gaming system that displays to a TV set to use the vsync time to refresh the display to create a flicker free image. The PAL system has more vertical definition at a cost of speed. 312 lines is probably right and the 311 figure is probably due to computers counting from 0 (I.E. 0 - 311 = 312 lines) NTSC has less lines so it can work faster to reduce flicker even further. (Typical of the Americans, if it can't be bigger it has to be faster!) I hope this clears things up for you :) Regards, JohnT