About framerate's

[Firk99]

I am aware of the differences in framerates (Film, NTSC, PAL,...) but i don't understand why NTSC use such an odd value. Anyone knows why they have chosen this value ?

[redwudz]

Here's about the best explanation I can find. http://www.animemusicvideos.org/guides/avtech/video2_2.htm

[Cornucopia]

In a nutshell:

Both PAL and NTSC started by basing their field rate on their AC current frequency (PAL=50Hz, NTSC = 60Hz). 2 fields = 1 frame (PAL = 25fps, NTSC = 30fps). That's Black and White.

Along comes color.

PAL re-invented the wheel, PAL(2) was higher resolution and not compatible with the older equipment. Because of the politics of the member countries, this wasn't too difficult to implement, but it did take a while for the transition.

NTSC didn't want to have anything that was not compatible with the older (B/W) signal. The main bottleneck at the time was bandwidth (4.2 MHz, IIRC). In order to maintain the same Bandwidth, they chose to slow things down by a tiny amount so that the loose tolerance of the older equipment wouldn't go bonkers. This left enough room in the bandwidth of the signal for the color subcarrier, etc. Voila! 29.97.

Scott

[Firk99]

Thank you for the information !

[Firk99]

Thank you for the info