What is 29.97p???? at DVinfo.net

Bill Edmunds · November 6th, 2007, 06:48 PM

The camera lists one of the shooting rates as 29.97p ...I assume this is the same as what other companies call 30p???

Carl Middleton · November 6th, 2007, 10:32 PM

I would think so. 29.97 is 30 fps drop-frame.

C

Serena Steuart · November 7th, 2007, 12:54 AM

http://www.tvtechnology.com/features...f-rh-smp.shtml

David Heath · November 7th, 2007, 02:27 AM

As Serenas link states: "Monochrome NTSC ran at a rate of exactly 30 frames per second, and so did 1125/60 analog HDTV and 30 fps film. Color NTSC runs at a rate of 30 frames per second multiplied by 1/1.001, or approximately 29.97 fps."

When the NTSC system was being developed, they realised that the subcarrier frequency had to be an exact multiple of line frequency, itself an exact multiple of frame rate. Unfortunately, the necessary frequency that derived from 30Hz was found to interfere very badly with the sound subcarrier on some early monochrome receivers. The easy fix at the time was to move it by defining the frame rate as stated above.

Then time code came along, and the necessity of drop frame modes to keep it in sync with real time. Ease of downconversion is why these rates are kept into HDTV systems.

November 6th, 2007, 06:48 PM	#1
Bill Edmunds Major Player Join Date: Aug 2003 Location: Conway, NH Posts: 574	What is 29.97p???? The camera lists one of the shooting rates as 29.97p ...I assume this is the same as what other companies call 30p???

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

November 6th, 2007, 10:32 PM	#2
Carl Middleton Major Player Join Date: Sep 2007 Location: Fernandina Beach, FL Posts: 562	I would think so. 29.97 is 30 fps drop-frame. C

November 7th, 2007, 12:54 AM	#3
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	http://www.tvtechnology.com/features...f-rh-smp.shtml

November 7th, 2007, 02:27 AM	#4
David Heath Inner Circle Join Date: Jan 2006 Posts: 2,699	As Serenas link states: "Monochrome NTSC ran at a rate of exactly 30 frames per second, and so did 1125/60 analog HDTV and 30 fps film. Color NTSC runs at a rate of 30 frames per second multiplied by 1/1.001, or approximately 29.97 fps." When the NTSC system was being developed, they realised that the subcarrier frequency had to be an exact multiple of line frequency, itself an exact multiple of frame rate. Unfortunately, the necessary frequency that derived from 30Hz was found to interfere very badly with the sound subcarrier on some early monochrome receivers. The easy fix at the time was to move it by defining the frame rate as stated above. Then time code came along, and the necessity of drop frame modes to keep it in sync with real time. Ease of downconversion is why these rates are kept into HDTV systems.