GH4 downscale/transcode voodoo from 2014

[GH4Shooter]

I found this old 2014 article regarding the GH4. If you record internally at 4K 8-bit, this article claimed that you could downscale and transcode it using Cineform codec into a 1080 10-bit 4:2:2 video, great for editing/grading. I've asked about this on GH4 forums and they argue that theoretically this idea is silly. It's now close to 2017. Has anyone tried this trick? Do you gain any benefits from doing it? more latitude or less banding when you push the video around? Would love to see comparison videos. I'm trying a backyard test now but not quite sure if I'm following the suggested steps. Article says that it involves using After Effects with a 10-bit comp, convert to RGB color, then do the transcode using CineForm codec. A bit over my head.

original article: http://www.eoshd.com/2014/02/discovery-4k-8bit-420-panasonic-gh4-converts-1080p-10bit-444/

[TheRenaissanceMan]

It's since been mostly debunked. There's a slight benefit in grading latitude because of the extra data, but 4K does not replace high bit depth.

[dantheman]

So 4K 8bit 4:2:0 cannot be downsampled to 2K 10 bit 1080p 4:4:4? Maybe I am misunderstanding that older article but that is what David from cineform is trying to let us believe. Maybe on paper it sums up to this but in reality it's another story?

[Don Kotlos]

13 minutes ago, dantheman said:

So 4K 8bit 4:2:0 cannot be downsampled to 2K 10 bit 1080p 4:4:4? Maybe I am misunderstanding that older article but that is what David from cineform is trying to let us believe. Maybe on paper it sums up to this but in reality it's another story?

Think of it like this, you cannot get any extra information from the original file. So whatever information is in the original 4K 8bit 4:2:0 clip, that or most probably less than that will be in the file that you would transcode to. But of course an original 10bit 1080p 4:4:4 file from another camera file could very well carry more color information from a compressed 4K 8bit 4:2:0 file. 

Most of the time you will be better off editing/grading the original 4K file even if you final output is 1080p 10bit. 

[Cary Knoop]

When you down scale 2160p 4:2:0 properly you do get 1080p  4:4:4. 

Whether it is really 10 bit is arguable but it is certainly better than 8 bit.

You are not limited to using Cineform you can downscale your source with Avisynth or Vapoursynth and for instance encode it with I-frame only H.264.

However I have problems with H.264 10bit 4:4:4 sources in Premiere Pro 2017, but in Resolve they work just fine.

 

[no_connection]

In theory it's not a bad idea. In practice, it's likely more debatable.
Large scale banding won't go away as all four pixels sampled would have the same luminance and would still show same stair steps.
Now if the source was "noise shaped" you would gain some bit depth at the same rate as the noise is reduced (at least I theorize so). So you end up with maybe 9bit luma?
But if it was proper noise shaped(dithered) from the beginning you would not see banding anyway.