timecode: drop vs. non-drop

[Matthew Brunn]

Drop frame is just a numbering system for the timecode. It doesn’t affect the video at all. It “drops” a frame every second or so to keep the broadcast network time synced. Other than that lame explanation I forgot the rest. Sounds like your client doesn’t know what they are talking about either.

[Andrew Wise]

Thanks for the reply Matthew. I thought it was kind of a strange request…especially since this project is not for broadcast.
Andrew

[Thaxter Clavemarlton]

[Matthew Brunn] “It “drops” a frame every second or so to keep the broadcast network time synced.”

Well, not every SECOND or so…

DF TC skips the first two frame numbers (0,1) at the start of each MINUTE, except minutes 0, 10, 20, 30, 40, and 50 (for mathmatical and timing purposes).

Now, back to the OP’s question:

If you are shooting on 90% of today’s DV SP camcorders, you CAN’T CHANGE the TC setting, it will ALWAYS be DROP-Frame by default.

If you happen to own a DVCAM unit, most allow the TC to be set and changed to non-drop-frame, if desired.

So, if you are shooting for a client who requests NON-drop-frame TC, and your camcorder can’t be set for that, you need to explain that:

A. It won’t matter in the least for editing purposes (you can use both DF and NDF TC intermixed in the same timeline/edit.

B. It won’t matter in the least for QUALITY (has nothing to do with adui or video).

C. It won’t matter in the least in the length of the footage or the project (see “A.” above.)

D. It won’t matter in the least for the editor of the project (see “A.” above.)

[Ed Dooley]

This is a pretty good explaination from the CSIF (a Canadian independent film group)
Ed

>>>Drop and non-drop timecodes are both methods of counting video frames. You would be correct to think of them like two languages. Just like “non” in French equals “no” in English. Each timecode counts and keeps tracks of video frames – they do not alter or drop video frames. They only count video frames and they count differently. In fact, drop frame timecode counts video frames accurately in relationship to real time. This is why all the networks and cable companies require that the final tape masters to be delivered are on drop-frame timecode.
Everyone refers to NTSC video as 30 fps, but in actual, factual, gorey detail it is really 29.97 frames per second. No human has dared create a timecode that counts hundredths of frames (it would be too confusing,) – hence we have drop and non-drop. Clock time (electricity) operates at 60 Hz but the NTSC standard television operates at 59.94 Hz. If you double 29.97, you get 59.94 – hence – two fields per video frame. For now, that’s all we’ll say about “fields”. Because of this speed difference between 59.94 Hz and 60Hz, there is an expanding elapsed time difference between the clock and timecode readings.

Drop-frame timecode counts each video frame but when that .03 finally adds up to a video frame – it skips ahead (or drops) a number. It does not drop a film or video frame, it merely skips a number and continues counting. This allows it to keep accurate time. So if you’re cutting a scene using drop frame time code, and the duration reads as, say, 30 minutes and 0 frames, then you can be assured the duration is really 30 minutes.

Non-drop timecode counts (labels) every single video frame and does not make any allowances for the fact that it is really 29.97 fps. Therefore, if you cut a scene using non-drop time code and the time reads as, say 30 minutes and 0 frames, this is not the actual running time of the scene. The total time must be converted in order to know the true running time. This is why non-drop lengths are always shorter than the real time. For example – it’s counting 3000 frames for 100 seconds when it’s really 2997 frames that equals 100 seconds. In other words, non-drop time code will count/label 3000 frames as 100 seconds, when it is actually 100 seconds and 3 frames. This is why the networks and cable companies require that their masters be delivered on drop frame time code.
The actual difference amounts to 108 frames per hour, or 86 seconds for each 24 hour period. This equals 54 video frames per 30 minutes. So if you are cutting a show using non-drop timecode, at the end of a 30 minute program, you would need to add 1 second, 24 video frames to get the accurate time. It can be roughly calculated that a program using non-drop timecode is two seconds shorter per half hour than the non-drop timecode displayed.

Remember, both timecodes are merely labeling methods and do not alter the visual picture in any way, shape or form. Therefore, choosing whether to edit in drop or non-drop normally is the editors’ choice or may be determined by the preference of your post supervisor, tape house or editing system limitations. Drop and non-drop have one thing in common – hour 1:00:00:00. (The hour actually doesn’t matter as long as it’s 00:00:00.) This is why you can take an output (tape assembly) of a non-drop timecode show and insert edit it onto a drop-frame video master at 1:00:00:00 and it will lay across perfectly. It’s the same reason you can take a non-drop show, and create a drop-frame online list using 1:00:00:00 as the record in.<<<

[Daryl K davis]

Reminds me of a funny story that happened years ago. A neophyte ‘producer’ who hired me on a project insisted everything be done in Drop-Frame, only because that is what broadcasters used, so it MUST be better quality.

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DK Davis / Editor/ Post Super
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[Tony]

Actually,

Your client may know what they really want which is why they are requesting that the timecode mode be
NDF.

1) They may already have an existing volume of tapes which have all been shot NDF and that is there internal company specifications for all camera masters.

2) They may wish to do a linear on line at a later date and avoid the mess created when mixing NDF and DF source tapes. (Trust me on this one I used to have to deal with this when I was an online CMX editor and it slows down the rapid assembly process when you EDL list contains mixed mode source timecode) Not the biggest issue but an issue to avoid if you have a large amount of source footage that you can avoid mixing the timecode mode.

3) The majority of non broadcaster users by default use NDF timecode instead of DF because
A) They have never had a need for DF
B) They don’t or never will understand the differences between the two
C) It’s just so damn confusing “so let’s keep it simple and do what we did last time and the time before that.”
D) The editor (some high school digital genius who really has no clue) told the producer that recording in a different tc mode will screw up the NLE system as well as the fry the editor’s brain when he has to manually calculate how to add back the missing frames on the DF camera masters.

4) DF is great for time of day accuracy, logging in the field and using a watch which is synced to the DF free running time of day timecode starting time.

5) The place where NDF and DF make the greatest impact are in the final edited master which is intended for broadcast. In this case it is essential that the edited master, air master etc all be in DF.

6) FYI most broadcasters and networks (not all) by default use DF on their source footage in addition to the edited masters.

7) The difference between the two modes
NDF is based on 30.00 with no regard to the actual 29.97 recording frame rate. So clock time does not match timecode time after one hour.
DF accounts for the 29.97 frame rate and drops a frame every minute except for the zero minute and every 10 minutes thereafter. The end result is one hour of tape time will equal one hour of clock time.
Essential for broadcast operations if you are using a countdown or countup clock to determine when and where to cut to commericals or the next program.

FYI In 24P mode there is no such thing as DF timecode yet, In PAL which is 25.00 frames DF does not apply.
DF is unique to the NTSC 29.97 standard.

Tony Salgado

[Mark Raudonis]

ED,

that’s a great explanation of the difference. This should be posted as a FAQ.

In my opinion, the engineers should never have used the word “frame” in their description of the two types of timecode. Drop “number” would have been much less confusing. “Frame” implies actual frames are discarded when it’s really only numbers. This is what causes most confusion.

mark

[Andrew Wise]

Thanks Tony, (and Matthew, Ed, Mark, Thax and DKD)
You’ve cleared up an issue that has (suprisingly) never come up (for me) before.
Very much appreciated!!
Andrew

[Baba Goof]

i generally like to use ndf for all of the post process and
save df for the master as it makes calculating the length
of a clip simpler to do in my head. for example, if i’m
looking at a clip that spans an even minute in the timecode
display and i want to know how many frames long it is, it’s
easy to make a mistake if the code is df; i might think the
clip is a couple of frames longer than it actually is because
a couple of frames are dropped from the displayed tc count.
manual calculations are easier with ndf.

[Chris Poisson]

Yes, I agree with BabaG. I was using drop frame for a long time and I was always having a hard time making sure multiple spots on the same sequence were all exactly the right length. For commercials, it makes it much easier to use ndf, especially when you want each one to start on an exact even minute when you edit to tape. The ndf tapes I have made in this way seem to be fine, and I have never had one rejected by a station.

Have a wonderful day.