SMPTE Non-Drop vs Drop

slambubba wrote on 8/3/2004, 8:18 AM
i recently rendered my project to both NTSC AVI and MPEG and had my timeline set to SMPTE Drop in vegas. i did this because i read somewhere it was suggested for NTSC video projects. of course, i don't now why they suggested it.

i ran into some problems with markers and chapters when importing into DVDA. someone posted a link to the solution where someone from sony said to use SMPTE Non-Drop so time in vegas and DVDA match.

so, what's the difference between these two settings? what do you usually set yours to and does it matter, or just preference?

thanks.

Comments

Former user wrote on 8/3/2004, 8:26 AM
SMPTE drop frame is more accurate in its timing. But a little confusing because some timecode numbers do not exist (dropped). Non-drop frame is easier to work with if you are using timecode as your editing reference. You should be able to see this by setting your timeline to drop frame and advance 1 frame at a time across the 1:00:00 mark. It should jump from 59.28 to 1:00:02.

Drop came about because there is 29.97 frames per second (not 30 frames per second). So, similar to like a leap year, if your time code reports at 30 frames per second, you will eventually end up with a discrepency in the length reported by the timecode , and the actual length.

In an NLE system, it is better to work in Drop for accuracy of timing.
JaysonHolovacs wrote on 8/3/2004, 8:39 AM
This comes from the fact the NTSC video is not 30 frames per second, but 29.97 fps or some number like that. This affects how the frames are numbered:

1. In SMPTE Drop, certain predefined frames are dropped so that the time remains accurate. This does not mean actual frames of video are dropped, just certain frame numbers are skipped.

2. In SMTPE Non-Drop, all frames are retained, which I THINK causes the time to slowly drift and therefore the time numbers are not perfectly accurate.

The thread you reference says DVD-A2 DISPLAYS the information in SMTPE non-drop, so it doesn't match what you saw in Vegas. However, this is only the way it is displayed; I do not think it should have any effect on the final output.

None of my projects have required frame accurate chapter marker(anywhere in the black fade is fine for me), so I haven't noticed this. I like to use SMTPE drop because I like the fact that the time measurement is accurate.

-Jayson
rs170a wrote on 8/3/2004, 8:56 AM
FYI, the difference between drop frame and non-drop is 108 fames per hour with non-drop being the greater of the two.
BTW, Leitch has a great tutorial (650 KB pdf) on this at
http://www1.leitch.com/resources/applicationNotes/timecode.pdf

Mike
Rednroll wrote on 8/3/2004, 10:01 AM
I haven't done much syncing with Picture internal to Vegas....(ie Video and audio are both in Vegas). I have sank external tape machine Video to audio in Vegas. The general rule is that if you are syncing audio to Video to use 29.97 drop frame. If strictly doing audio work use 30 fps. The drop frame, is to allow time for the black burst sync signal.
slambubba wrote on 8/3/2004, 10:40 AM
thanks to all for the help.

Jayson - i actually end each chapter with fade to black and being each chapter full video. so, it was pretty obvious the markers that were off (completely black). i didn't want the markers on the black because in DVDA the scene selections would all be black by default.
JaysonHolovacs wrote on 8/3/2004, 12:45 PM
Slambubba,
Okay, I see your point. If that's what you want, you do have to get frame accuracy(or just always put your chapter markers a few frames in). But, I'm surprised you depend on the DVD-A2 defaults for your thumbnails. Call me picky, but I always set my thumbnails anyway, trying to find something that may be more meaningful and/or interesting than what just happens to be in the first frame of the chapter. I guess if you want the workflow time saved by having the chapter markers = thumbnails, then this will be pretty important to you.

-Jayson
slambubba wrote on 8/3/2004, 5:21 PM
jayson - have you found a good way to set the thumbnail for the chapers if you don't want it at the beginning? using that slider for the start time doesn't too precise. just wondering if you found an easier way to set it?
JaysonHolovacs wrote on 8/3/2004, 5:29 PM
Slambubba,
I play the movie using the DVD-A timeline. When I find the spot I want, I look at the number for the current time (hours:minutes:seconds;frames). Then I go to the properties window and manually type in that number in the thumbnail start time. It's a little cumbersome but not too bad, and it has frame accuracy.

-Jayson
B.Verlik wrote on 8/3/2004, 8:15 PM
You can zoom in on the timeline and be very accurate. But I watch the preview too, to get a general idea then go to the timeline and zoom in. I can get to the very frame I want, no problem.