Exporting edited scanned family films and videos: What frame rates and resolution?

NTSC is 29.97 fps. I'd import such near-30 fps footage to 30 fps project and maybe use Modify > Retime > Automatic Speed so all frames are as unique as they can be. Old films might be 12-18-24 fps or so, but it depends how the service scanned them. I let the service scan my Super 8 films 18 fps frame by frame and slowed it down in FCP 72% for normal speed (18/25 = 0.72) in my 25 fps project (my TV plays such 25 fps more smoothly than 18 fps which is somewhat jerky). So you might use 18/30 = 60% speed.

4:3 NTSC analog/DV footage is 720x480 rectangular pixels and must be scaled to 640x480 square pixels unless the service has already done that. 16:9 footage needs letterboxing.

So a 640x480 30 fps project might be good setting to start.

> 18fps media is difficult to obtain. I would like to practice on my own project

The service which scanned my old Super 8 films uses Rank Cintel 4K scanner. It scans frame by frame to ProRes 422HQ 1080p format. They add black borders to the 5.79 x 4.01 mm (0.228 x 0.158") Super 8 frame to fit it to the 1920x1080 ratio.

I asked them save as 18fps but they recommend 25fps because 18fps is incompatible with TV standards and editors. They tried to use Premiere to export at 18fps but they said that the exported file played at the wrong frame rate anyway or that the file didn't otherwise seem to be correct. So they ended up using 25fps for the frame by frame output. That can then be edited, slowed down and exported at any desired fps anyway so that was a good choice in the end (*).

Anyway, I tested how my LG B6 4K 55" OLED TV handles 18 fps. Final Cut Pro does not support 18fps export. DaVinci Resolve v14.2 added support for 16 and 18fps and v16.1.2 seemed to output 18fps ProRes 422 HQ OK.

My LG TV can play 18fps .mp4 from DaVinci Resolve but the movements are clearly jerkier than with the regular 25 fps (with some frames duplicated here and there). So that TV does not properly support 18fps.

It is also possible to use mkvmerge (part of mkvtoolnix suite) and ffmpeg to output 18fps. For example, losslessly convert ProRes 25fps to 18fps in two steps (with muted audio):

mkvmerge --default-duration 0:18fps --fix-bitstream-timing-information 0 --no-audio movie_25fps.mov -o temp-video.mkv

ffmpeg -i temp-video.mkv -c:v copy -an movie_18fps.mov

(*) I first thought that I'd have to slow down a 30fps FCP project to 60% (18/30 = 0.6). But if I drop such 25fps ProRes clip to a 30fps timeline, FCP duplicates frames to keep its duration and 100% speed the same. So also in the 30fps project a 72% "slow-motion" is needed for normal speed (then frames are duplicated in a steady 122 duplicate frame pattern because in effect a 18->30fps conversion is made). That same 72% applies also to 50fps and 60fps projects. (FCP sees ProRes clip's speed as 100% while in reality it is fast-motion ~139% (25/18 ~ 1.39) from Super 8's 18fps. ~1.39 x 0.72 = 1 i.e. normal speed).

On the other hand, FCP does 25->24fps conversion by doing a 96% (24/25 = 0.96) slow-motion behind the scenes while misleadingly still showing 100% speed thus making the clip slightly longer (obviously this is the standard way of doing 25<->24fps conversions). So such a 24fps project needs 75% (0.96 x 0.75 = 0.72) slow-motion to keep the duration exactly the same -- frames are then duplicated in a steady 112 pattern because 18->24fps conversion is made.

Below are 1-3 second sample clips of the fast-motion unique frame 25fps ProRes 422HQ 1080p material (clipped losslessly with MPEG Streamclip). There is also one clip converted to 18fps with mkvmerge and ffmpeg. The clips can be downloaded for testing without logging into Dropbox for a while at:

https://www.dropbox.com/sh/0hmh90bz0b33xt3/AAAqgG3WGFA26J21NoOr9Gb9a?dl=0

Do I need to re-edit and export to the original fps?

Please show me the screenshot below.

• Project properties (select project →Inspector: Change)
• Properties of each clip with different frame rate (select the clip in the browser →Inspector: General)

I let the service scan my Super 8 films 18 fps frame by frame and slowed it down in FCP 72% for normal speed (18/25 = 0.72) in my 25 fps project

I see! I learned a lot from you, thanks Matti! I voted helpful.✋ Placing 18fps media in a 25fps project will compensate for the same frames. I think it's a good idea to adjust the speed.👍

18fps media is difficult to obtain. I would like to practice on my own project, but is it possible to share a sample with you?

> My LG TV can play 18fps .mp4 from DaVinci Resolve but the movements are clearly jerkier than with the regular 25 fps (with some frames duplicated here and there). So that TV does not properly support 18fps.

I re-did that test (with new footage from iPhone etc) and now also the same movies converted from 25fps to 18fps play quite OK on that TV. Of course 18fps versions had that cinematic "Saving Private Ryan" strobe effect in some pans while even 25fps had somewhat smoother "Hobbit" feel because the frame rate is faster.

(When using mkvmerge and ffmpeg I now made sure to remove audio track in both 25fps and 18fps versions because leaving it might produce very jerky movements if the slow-motion video continues beyond audio. It is possible to slow down also audio and preserve pitch with those tools but I now left audio out because those Super 8 films were silent).

There are many slightly different recommendations how to convert NTSC or PAL rectangular pixels to square pixels. Luckily usually the error goes unnoticed unless you look for it.

For NTSC 4:3 720x480 .dv rectangular pixels to 640x480 square pixels the page below recommends that source 720x480 must be resampled to 648x480 and cropped 4+4 pixels from both sides to 640x480 (or cropped 4+5 pixels from both sides to 711x480 and scaled to 640x480).

PAL 4:3 .dv to 768x576 square pixels source must be resampled to 788x576 and cropped 10+10 pixels from both sides to 768x576 (or cropped 9+9 pixels from both sides to 702x576 and scaled to 768x576).

Non-analog footage might have content in the whole PAL 720x576 area so optionally it can be left at 788x576 but that is a non-standard resolution.

Maybe ScanCafe used the same approach to make sure all possible content on the sides were scanned from NTSC.

http://web.archive.org/web/20140218044518/http://lipas.uwasa.fi/~f76998/video/conversion/