Converting 4k 4:2:0 to 1080p 4:2:2

Hi,

I just purchased a 4k Panasonic GH4, in short my intentions are to export all my videos in 1080p at the best possible quality. My research has shown that 4k downscaled to 1080p generally looks better than if actually shot in 1080p.

I have read various ways to downscale correctly to achieve this but honestly I'm a bit confused.

For example if I were to just import my 4k camera footage into lets say After Effects and export as 1080p... would that do the trick or is there another step.

Thank you.

Regards.

Scaling 4K to 1080 gives better quality "in theory". A lot can effect that. Codec of original 4K, amount of movement, color pallet, contrast range, the encoder, etc. Unless you're needing 4K for reframing or some other specific technical requirement, I'd shoot and edit in 1080. In our studio we've not seen anything a client notices by shooting 4K and editing 1080, once it is exported and delivered. In fact, we've seen 4K clips look worse once downscaled to 1080 on occasion. This issue is highly debatable, different folks have different results, there's no universal about it.

But, if you wanted to transcode from 4K to 1080 before editing, Compressor does the trick just fine. And if you're using 4K for effects and such, then stay 4K in the edit. Reduce to 1080 only upon export for delivery. That would retain as much quality as possible.

Let me inject this into the conversation before it takes off. Back in the day when HDV first came out, we found HD shots, edited as HD, reduced to SD upon export did in fact 100% of the time give better image quality. But we were not making nearly as huge of a leap in frame size and lost data as one finds going from 4K to 1080. That's a MUCH larger leap. Enlarging looses quality quickly. Shrinking looses quality much more slowly, but still, quality loss will eventually happen.

Tec4k wrote: ...I just purchased a 4k Panasonic GH4, in short my intentions are to export all my videos in 1080p at the best possible quality. My research has shown that 4k downscaled to 1080p generally looks better than if actually shot in 1080p...I have read various ways to downscale correctly to achieve this but honestly I'm a bit confused...

There are several advantages to shooting in 4k for distribution in 1080p:

- Allows recomposing in post. Walter Murch discusses this from 06:00 to 09:30: www.fcp.co/final-cut-pro/articles/1744-p...-talks-4k-and-beyond

- Better preserves shelf life of the material. IOW it's like shooting a 1966 TV show with color film. It's more expensive but better enables future use.

- Each 4k frame is an 8 megapixel still, which allows frame grabs for various uses. In some cases those are good enough to substitute for a still.

- May produce better quality if downscaled to 1080p. I have done a few tests and can't see much difference but this could vary based on conversion sequence. In theory 4k at 8 bit 4:2:0 can be converted to 1080 at 10 bit 4:4:4: www.eoshd.com/2014/02/discovery-4k-8bit-...rts-1080p-10bit-444/

That might require using a separate transcode sequence external to FCP X, but I don't know. One utility is 5DtoRGB: rarevision.com/5dtorgb/

We shoot almost all 4k now, I'll try to test that if I have time.

That said, 4k entails a significant cost. You need a top-notch computer to edit 4k, and it consumes about 4x the disk space per minute. High quality 1080p is very good, and good quality 1080p is better than poor quality 4k. To my knowledge ABC, Fox, ESPN, ESPN2, Disney, A&E and MLB Network capture and broadcast exclusively in 720p/60.

We shoot 4K for 1080 exports most of the time and 1080 for 1080 post some of the time (depending on the project). The 4K footage always looks better to me (along with giving the advantages that have already been mentioned). Also, I would never downscale the footage before editing unless I was using proxy footage for the cut and later conforming to 4K.

I wouldn't use what news shooters are doing necessarily as an example of best practice either. My friends that shoot news are always on the tail end of technology. The new news helicopter will always beat out new cameras.

---> Jarrod