30 fps vs 29.97 fps.

yirm wrote on 9/30/2002, 1:18 PM

Can someone tell me briefly or point me to a link where the distinction is, why it is, etc., and what this means to me as a person using VV3 and outputting to tape/DVD?

-Jeremy

Comments

Tyler.Durden wrote on 9/30/2002, 1:34 PM

Hi Jeremy,

When the gods of US (NTSC) television made color-TV, in order to make it possible for the owners of B&W set to see a color program in B&W (and vice-versa) they had to slow-down the framerate a touch. (The math involved is very boring.)

If you need to output for video, 29.97 is your friend.

HTH, MPH

Lajko wrote on 9/30/2002, 11:31 PM

I understood 29.97 was to aid original, old, analog TVs to sync properly. They didn't have crystals so oscillators were analog (rememebr the vertical and horizontal hold knobs?). The TV used your household 60hz AC as a sync. Frame rates slightly under 60hz allowed TV to display a frame, then wait a little and start the next - 60 times per second (interlace anyone?). If frames were 30 or more persecond, it would have been nearly impossible for old TVs to stay in sync.

Tyler.Durden wrote on 10/1/2002, 6:57 AM

FWIW, It was thought 30p had too much flicker, and 60i looked better at the time, even for black & white sets. (It is true that 60hz was selected to lock to AC line frequency even for 30p.) Ironic, how so many folks are now trying to put the flicker back in.

NTSC 29.97 came about beacuse of trying to reconcile the color subcarrrier to the horizonal scaning frequency and the audio freq. 3.58Mhz was the lowest common multiple they could arrive at for the color freq., and to do it frame rate had to be slowed and it still really takes two frames for the subcarrier to come full cycle (NTSC "color-frame").

HTH, MPH