Which is better: 60i deinterlaced or 30p?

[SameSelf]

I have seen some people mention that they shoot primarily in 50i then de-interlace to 25p in ProRes 422. Now, de-interlacing HD video is a bear. But I was wondering if my results would be better? Does anyone have any experience with a similar workflow?

[Cornucopia]

You WILL get a different look. 2 reasons:

1. 50i, like 50p, captures a distinct image every 1/50th of a second, which means that the likely shutter speed is 1/100th sec. 25p usually has a shutter speed of 1/50th of a sec. There will be much more blur in the latter than the former, even after (proper) deinterlacing the former to 25p. This may be what you want, or not, depending upon the look you are going for.

2. A native full-frame, single-timeslice image is going to be sharper than a blended/interpolated/stretched formerly-interlaced image. Advanced forms of deinterlacing may smartly use non-moving sections of earlier or later fields to combine with the current field, but there's only so much that can be figured out, so only very still segments will have that same clarity that a true progressive image has natively. Again, depends on the look you're going for.

..."Better", based on what criteria?

Scott

[pandy]

I have seen some people mention that they shoot primarily in 50i then de-interlace to 25p in ProRes 422.

This doesn't have any sense - if your intention is to have 25p then you should avoid 50i as your results will be always worse than shooting in native 25p - however if you deinterlace 50i to 50p then results should be better than 25p for most of situations.
50i allow to balance between smooth motion (twice higher resolution in temporal domain than 25p) - for static and quasi-static scenes spatial resolution will be very close to 25p.

[SameSelf]

All very good responses. Thank you. I admit I was surprised too when I saw someone with a professional background describing their workflow as such.

[jagabo]

I was surprised too when I saw someone with a professional background describing their workflow as such.

That may have been a particular situation. For example, 1080p60 isn't valid for Blu-ray or broadcast in the USA. So maybe he was shooting 1080i30 for broadcast and deinterlacing to 1080p30 when he needed progressive video for online usage.

[hello_hello]

What's the quality of the ProRes de-interlacer like?

QTGMC has "shutter speed" settings for increasing the motion blur when de-interlacing to 25p or 30p. I haven't used them much as I normally de-interlace to 50p, but using the shutter speed options when deinterlacing to 25p definitely makes it appear a little smoother. Still not as good as de-interlacing to 50p, assuming you don't dislike the "soap opera" effect it creates. It doesn't bother me in the slightest.
Because QTGMC's de-interlacing denoises a little as a by-product, and it can sharpen very slightly, even de-interlacing progressive video can improve some aspects of it. I use QTGMC in progressive mode on progressive video regularly to denoise it (with it's denoising enabled).

I can't speak for all de-interlacing methods in respect to how well they do it, but when using QTGMC I tend to de-interlace 1080i50 to 720p50. Partly because 50fps looks smother, partly because there's usually no picture detail loss through resizing, or almost none, and because it's more likely a player will play 720p50 than 1080p50. You could probably speed up the de interlacing a little by resizing 1920x1080 to 1280x1080, de-interlacing, then resizing to 1280x720. Well you could using Avisynth. I don't know about ProRes.

Of course ideally you'd shoot the video at the frame rate you're wanting for the final output, but maybe they shoot it as interlaced so they have a 1080i25 copy but still have the option of de-interlacing to 1080p25, or 720p50, or 720p25.

[SameSelf]

That may have been a particular situation. For example, 1080p60 isn't valid for Blu-ray or broadcast in the USA. So maybe he was shooting 1080i30 for broadcast and deinterlacing to 1080p30 when he needed progressive video for online usage.

Actually, he described 50i to 25p as his normal workflow, not some bespoke workflow, while he shoots in 50p only when he needs slow motion in 25p. I imagine that his camera setup has fast enough lenses and that he always lights his shoots, so that a 1/100 sec shutter speed is not a problem. He made no mention of the de-interlacer that he uses. If I were to hazard a guess, it would be cliptoolz, but I have no idea if it even has a de-interlacer. One thing is for certain, anytime you are talking to someone in the professional arena, the tools they use are completely different from the ones you see regularly mentioned on this forum; although ffmpeg seems to be widely respected.

[videobruce]

1080p60 isn't valid for Blu-ray

I thought BluRay was 1080p60??

[jagabo]

1080p60 isn't valid for Blu-ray

I thought BluRay was 1080p60??

No. https://www.videohelp.com/hd#tech