Which Frame Rate and Mode to Use
Most probably, you will be using 23.976 (aka 23.97 aka 23.98) timecode for all HD, 2K, 4K, etc. video projects; or true 24fps Native for sprocketed film (24fps) and electronic cinema (24fps). But always ask! (And the current industry standard for digital audio is 24bit/48k for any project that may be released as a DCP.)
If you are recording for an SD video shoot, then use whatever mode (drop or non-drop) that the videotape recorder is using. Traditionally, video intended for (Standard Definition) television broadcast prefers to use the drop-frame mode, for the (real time clock) reasons discussed above. But always check with the engineer or camera operator just to be sure.
Standard Definition Video (SD) records at 29.97 fps, so that would be the correct timecode speed for your audio recorder: match the settings of the master video recorder both in terms of 29.97 and whether or not to use drop frame or non-drop frame timecode.
However, if you are shooting in HD, the camera and timecode may be running at 23.976. Note that most video cameras mistakenly refer to 23.976 as 24, so make sure you verify the actual frame rate. Some of the higher grade cameras can run at a true 24. If you are, in fact, shooting at 23.976 -- then set your audio timecode rate to 23.976. If your recorder does not offer that option, then use 29.97 non-drop.
If you are recording audio for a film shoot, the settings are different.
Film style editors generally (but not always) prefer to use non-drop timecode for ease of keeping track of frames, since it eliminates confusion during post-production if dealing with complex special effects or when converting from edited video back to film. So unless otherwise instructed, use non-drop timecode on film shoots.
The traditional frame rate for recording audio that will be sync'd to film cameras is 30 fps, irregardless of whether the film camera is running at 24fps or 30fps! The reason for this is that the audio does not have to correspond to the film speed but rather to the video speed, since the editing is being done in video!
When the film is transferred to video (for editing), it is slowed down by one tenth of one percent. Video runs at 29.97. You cannot easily change a whole number such as 24 into a fractional number such as 29.97, unless you alter the speed by a fraction (0.1%).
Film shot at 24fps is slowed down so that it ends up at the equivalent film speed of 23.97, which is then converted in real time to 29.97 for video. The process involves what is known as a 3:2 pull-down, in which 12 half-frames (aka video fields) are created and added to the 23.97 frames, thus making a total of 29.97 frames. Every other picture frame is scanned or digitized with one extra field. Adding the 12 fields does not alter the running speed of the picture, since it is only slicing the same size bread into smaller slices, so to speak.
It goes something like this: 1,1,1, 2,2, 3,3,3, 4,4, 5,5,5, 6,6, 7,7,7, 8,8, 9,9,9, 10,10, 11,11,11, 12,12, 13,13,13, 14,14, 15,15,15, 16,16, 17,17,17, 18,18, 19,19,19, 20,20, 21,21,21, 22,22, 23,23,23, 24,24. If you count the extra fields, there are 12. So, two fields equate one frame; 24 frames plus 12 extra fields gives us our needed frame count to pad 24 into 30. (Actually, 23.97 becomes 29.97)
Film shot at 30fps film speed would end up at 29.97 film speed in video.
Back to the nuts and bolts. The picture shot in our film camera is slowed down during transfer to video. For audio to remain in sync, it must be slowed down by the same percentage. So if we record audio on the set at 30fps timecode, and then transfer it into the edit system at 29.97 fps (which also happens to be video sync) -- the audio will end up in perfect sync with the picture.
When the editing is completed, the audio will be speeded up from 29.97 to 30 in order to match back up with the actual film for creating release prints. But that is not your concern as a Production Mixer. The post production people and the film labs deal with that issue.
Therefore, unless instructed otherwise, the industry standard for production sound (film shoot) has been to set the timecode in your audio recorder to 30fps Non-drop. However, most (not all) of the newer editing workflows are now using 24fps timecode -- but always check with the post production supervisor before using it.
Although the new workflow does not always involve a 3:2 pulldown to correct for 23.976 to 29.97 additional frames, you still have to account for the 0.1% pulldown that occurs when converting from true 24fps to 23.976 video, and vice versa. Some editing systems can handle this automatically, or by selecting the proper checkbox during import.
The author suggests that you always include a tail slate along with the usual head slates on the first day of production, so that the editor can readily verify that the import settings are correct.
If anyone tells you to use a particular setting, make sure that you get it in writing and witnessed! That way you cannot be held accountable for problems that may be encountered by the production company later on.
Believe me, in today's world of video cameras running at 29.97, or 23.976, or true 24 fps -- there is a lot of room for mistakes. Ask, ask again, and get it in writing!
If they tell you over the phone, put someone else on the line to witness what they instructed you to do.
