[vdr] Re: OT: 100Hz TV technology ?

[Christian Berger <einStein@donau.de>]

Am Freitag, 9. August 2002 08:40 schrieben Sie:
> Hi,
>
> i know it's offtopic, but can anyone explain to me, how 100Hz TV handle
> the normal TV picture ?

This largely depends on the TV. Old ones simply did display each field 2 
times: 
Original input:
 A B A B
Output
  AABBAABB
which gives you an overall good image, except for the interlace flicker 
which is still there. Early systems only used 7 bit colour (7 bit 
brightness, 7bit color)

Then some sets did store a whole frame (whoa). Which probybly looked like 
this:
Input
 A B A B
Output
 ABABABAB
This resulted in the typical Computer-TV image. So the image by itself was 
flicker free, but movements on live recordings looked horribly.

Good sets switch betwenn both modes on a pixel-to-pixel base, resulting on 
a better image. Some cheaper ones rely on a little signal which is 
transmitted with the image to switch betwen those modes on a show-to-show 
base and some simply stay in one mode.

> Is it compatible to VDR (of course yes) - but how are the 50Hz
> consisting of 2fields (so 25fps) converted to 100Hz ?

Look up. Those 100Hz are the fieldrate, not the framerate.

> Advertises talking about "Advanced 100Hz Digital Scan" - but what does
> that mean ? Is one field dropped ? Are both fields interpolated to
> create 50 full frames and each one shown twice for 100Hz ?

Well if you want to look at how it can be done, look at EffecTV 
http://effectv.sourceforge.net download and install it and look into the 
effects directory for an effect named "DeinterlaceTV.c"

> I want to know to decide which format is best for reencoding (interlaced
> or not ...) to be compatible for future viewing.

Well....Most shows are transmitted interlaced nowadays and there is no 
indication that is going to change. However if you have a good 
deinterlacer or linedoubler (like DeinterlaceTV tries to be), you should 
use progressive scan (not interlaced). ZDF seems to already show many 
movies in progressive scan so you will not experience any problems.

With one of those HDTV monitors you should usually be on the save side 
since they support almoust any standard, but it might be cheaper to just 
get a CRT-Projector which is data-capable.

> Anyone ?
>
> Martin

Servus
  Casandro

-- 
#define T 1000
#define M T*T
int main(){int x,y;for(y=0;y<20;y++){for(x=0;x<70;x++){int
c=-1;int xr,yr,zr;int xp,yp,zp;xp=yp=zp=0;xr=(x-35);yr=(y-
10);zr=10;while(1){if(yp>T){c=5;if((((zp)/T)%2==1)^(((xp+M
)/T)%2==1))c=0;break;}if(zp>T*10){c=0;if (((yp*yp+xp*xp)/(
T*100))%2==1)c=2;break;}zp+=zr;xp+=xr;yp+=yr;}printf("%c",
c+32);}printf("\n");}};