Understanding timecode

[Pietro Impagliazzo]

So there's all these 23.97 and 30s Drop Frames and Non Drops...

I thought regular video would drop frames, because of the broken number (29.97) but the timecode is called non-drop so this is all a really big mess in my head.

I'd to like to be educated on which is which and when should I use them.

Any literature or internet links you guys can point me to?

Thanks a lot in advance.

 

[Philip Hodgetts]

It would be more accurate to call "drop frame" Timecode "skip count" timecode as no frames are ever dropped, just the count is skipped for some frames to 'catch up' to the real-world time (29.97 fps is slower than 30 fps, so 2.2 fewer frames are played each minute). I totally understand your confusion - I had to create this graphic to help me understand.

http://www.philiphodgetts.com/2009/10/20/what-is-drop-frame-timecode/

Philip

 

[Neil Uchitel]

Here's a basic primer. Maybe somebody has some other insights they can lend. Sorry if I'm giving information you might already know.

Film = 24fps. When video was invented, video frame rates needed a sync source for consistency, so frame rates for video are based upon the AC electric current of the host country. For the US, that's 60 Hz (thus 60 fields or 30 interlaced fps) and for Europe and most other countries, that's 50Hz (thus 50 fields or 25 interlaced fps). TC was invented after the invention of video, to provide absolute frame identification like keycode for film, but in the US there were some issues with color timing in broadcast that could only be corrected by ever-so slightly slowing down the video frame rate. Thus, the morass of TC framerates in the US was born. PAL and SECAM don't have these issues.

FPS Description

23.976-----24p color video edited for NTSC broadcast

24-----24 frame film, or 24 progressive scan video (aka 24p). This is used if the video program will be output to film.

25-----PAL (625 line) Video (Phase Alternating Line) - a video format used in Europe because electricity is 50hz (as opposed to 60 Hz here); also SECAM (Sequential Color with Memory) video is 25 fps. Used in France, Eastern Europe and the Middle East. The difference between PAL and SECAM is how it deals with color.

29.97 ND-----NTSC (525 line) Video, non-drop (non-skip) frame. Color. The standard for most things that go to broadcast, esp. commercials.

29.97 DF-----NTSC Video, drop frame - this format is usu. used for long-format works (like episodic TV) where you want the TC to match the actual length of the program material.

30 ND-----Original B&W broadcast spec. Not used too often, except for animated or other material that probably won't go to broadcast. Music videos? In the non-broadcast internet digital world, we probably should go back to this, methinks.

30 DF-----Used when the film shot for long format works is transferred to video and ultimately delivered on NTSC video. In the transfer it becomes 29.97 DF.

 

[Karl Lohninger]

The easy rules are: for 'production' (that is when you're shooting) always use non-drop. Picture as well as audio. Only in case the editing department concocted some weird stew and asks you specifically to use drop frame, then you do.

Generally: drop frame is used only for distribution so the numbers add up with the 'real time'. So, a one hour long piece would actually be 'one hour long' - important for broadcast programming!

Again, for production there is no need to use drop frame.

 

[Frank Cueto]

I would add...

23.976 is a good format to shoot if you are going to film and do0n't have oodles of budget to have everyone on 24P (exact) systems.

It is just a matter of converting the audio to the right speed when you do the film out.
(23.976 is EXACTLY 0.001% slower than 24FPS. Once you print every frame of your master to 24FPX, you have in effect accelerated you video, and you must accelerate your audio to match, right guys?