Drop frames: what's the deal?

[Bruce Findleton]

That's right, drop frames!

The fact that I'm supposed to drop a frame every minute (except, of course, minute 10) has me kinda weirded out. I want all my frames, thank you very much.

Where can I find the skinny on drop frames? I went to the SMPTE.ORG site and it seems that to peruse the SMPTE standards I either have to join ($150) or BUY CDs of the standards. For an allegedly public standard? This is a .org I'm talking about. What am I missing?

Now I'm not the worlds best web searcher but I can't find the standard online anywhere. Can someone point me to a lucid, direct explaination of drop frames or, barring that, somewhere I can get access to the SMPTE standards?

Your help will be much obliged.

Thanks,

Bruce

[Adrian Douglas]

Bruce, you are obviously talking about the NTSC drop-frame time code. I've never used it myself but I did a quick search and came up with some links that may help

Glossary of video terms and definitions
http://www.acvl.org/9e.htm

Dictonary of tech terms
http://www.grassvalleygroup.com/docs/Miscellaneous/Dictionary/DictionaryB2_N.html

About Premiere Time Codes
http://www.adobe.com/support/techguides/premiere/time_options/main.html

I'm just assuming your using Premiere with the last one.

If they're no good, try punching 'drop frame time code' into Google. There were quite a few hits there.

[Ed Frazier]

I think Bruce is referring to Drop-Frame Time Code which is defined in my RT2500 User Guide as:

" For NTSC video, time code is normally produced by a generator that counts at 30 frames per second. NTSC color signals, however, actually have a display frequency rate close to 29.97 frames per second. Drop-frame time code compensates for this time difference by dropping two frames from the count every minute except for every tenth minute so that the time code matches the clock time."

If this is correct, it sounds like it is dropping two frames from the counter, not two frames of video.

I have edited many hours of video using the Drop-Frame setting in Premiere and am certain that two video frames are not being dropped every minute.

[Rob Lohman]

Adobe also has an PDF online about this issue:

http://www.adobe.com/support/techguides/digitalvideo/timecode/timecode.pdf

[Chris Hurd]

To state Ed Frazier's reply in a slightly different way, you don't "drop frames" at all between drop-frame and non-drop-frame time code.

Once again: you're not losing frames *at all.*

All that changes are the numbers. See this page for a quick and dirty explanation: "The Low-Down on Time Code" at www.matlin.com/timecodepage.html

To quote:

"Drop-frame time code drops two frame numbers every minute except every tenth minute. No physical film or video frames are dropped, only the time code frame numbers, (:00 and :01) are dropped."

Hope this helps,

[Bruce Findleton]

Thanks all. Good stuff, as usual.

Bruce