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GH4 - 4k 4:2:0 to 1080p 4:4:4 using Adobe CC

Enthusiast ,
May 27, 2014

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There's much talk about the ability to "downsample" GH4 footage shot internally in 4k to 1080p and the added benefit of it going from 4:2:0 to 4:4:4. But there's not much talk on HOW best to do this using Adobe Premiere Pro CC (or other software). So how is this done exactly? I imagine simply placing a 4k shot onto a 1080p timeline will just scale it, right? So how does one get that added color space benefit? What are the steps to making this happen when editing with the Adobe Creative Suite. Thanks!

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Correct answer by R Neil Haugen | Adobe Community Professional

The GH4 puts out 4k-10bit only through the HDMI out, not by internal recording. So ... to get real after-editing full 10bit 1080p 4:4:4 one needs to output 4k-10bit 4:2:0 and then in transcoding that into 1080p it can become full-blown 1080p 10bit 4:4:4 through a "natural" trans-mogrification of extra luma data to color data. I've seen the wonderful scientific discussions on it, yes, it does work that way. Full-blown 10-bt 4:4:4.

A slight problem at the moment ... there apparently are no portable recorders that can record the full range of framerates the GH4 shoots at 4k-10bit. One very expensive one might, but none of the say Atomos ones. So ... IF you've also got Panny's YAGH (or "the brick")  unit attached to your GH4, with the way it converts the HDMI outs to SDI, AND you happen to have an SDI-connectable recorder with 4k/10-bit any-framerate capability sitting there, you can get your GH4 footage in an awesome wrapper for editing delivery.

I've also seen the scientific discussion as to why taking the 4k-8bit 4:2:0 out and transcoding to 1080p does get some improvement in color depth data ... to roughly 8.67 bits equivalence. Which as one person noted, being as this is not an arithmetic scale is still a significant improvement in color "depth" data. Much more than 8bit yet nowhere near 10bit.

We have arrived in no-man's land! 

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GH4 - 4k 4:2:0 to 1080p 4:4:4 using Adobe CC

Enthusiast ,
May 27, 2014

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There's much talk about the ability to "downsample" GH4 footage shot internally in 4k to 1080p and the added benefit of it going from 4:2:0 to 4:4:4. But there's not much talk on HOW best to do this using Adobe Premiere Pro CC (or other software). So how is this done exactly? I imagine simply placing a 4k shot onto a 1080p timeline will just scale it, right? So how does one get that added color space benefit? What are the steps to making this happen when editing with the Adobe Creative Suite. Thanks!

Adobe Community Professional
Correct answer by R Neil Haugen | Adobe Community Professional

The GH4 puts out 4k-10bit only through the HDMI out, not by internal recording. So ... to get real after-editing full 10bit 1080p 4:4:4 one needs to output 4k-10bit 4:2:0 and then in transcoding that into 1080p it can become full-blown 1080p 10bit 4:4:4 through a "natural" trans-mogrification of extra luma data to color data. I've seen the wonderful scientific discussions on it, yes, it does work that way. Full-blown 10-bt 4:4:4.

A slight problem at the moment ... there apparently are no portable recorders that can record the full range of framerates the GH4 shoots at 4k-10bit. One very expensive one might, but none of the say Atomos ones. So ... IF you've also got Panny's YAGH (or "the brick")  unit attached to your GH4, with the way it converts the HDMI outs to SDI, AND you happen to have an SDI-connectable recorder with 4k/10-bit any-framerate capability sitting there, you can get your GH4 footage in an awesome wrapper for editing delivery.

I've also seen the scientific discussion as to why taking the 4k-8bit 4:2:0 out and transcoding to 1080p does get some improvement in color depth data ... to roughly 8.67 bits equivalence. Which as one person noted, being as this is not an arithmetic scale is still a significant improvement in color "depth" data. Much more than 8bit yet nowhere near 10bit.

We have arrived in no-man's land! 

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May 27, 2014 0
LEGEND ,
May 27, 2014

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I would use Prelude, convert to DNxHD using the 10 bit 175X preset.  It will only be 4:2:2, but to get 4:4:4, you have to move to 350 Mb/s, and I don't think that would make enough of a difference to warrant the storage costs.

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May 27, 2014 0
Enthusiast ,
May 27, 2014

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So when people say "all you need to do is downsample the 4k footage"...they just mean transcode to a different format like DNxHD 10bit or ProRes, etc.?

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May 27, 2014 0
LEGEND ,
May 28, 2014

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Not necessarily.  My advice to transcode is more from a usability standpoint.  DNxHD plays and scrubs soooooooo much better than H.264, even I-frame H.264.  DNx works more like DV.  While I haven't yet tested, I imagine that difference will be even more noticeable at 4K than it is at HD.

Transcoding takes care of both the playability and the color space.

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May 28, 2014 0
Enthusiast ,
May 29, 2014

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So...just curious...

1) While I realize playability would get much better by transcoding, does simply throwing that native 4k 4:2:0 clip on a 1080p timeline have any benefits with regards to color space?

2) How far can you zoom in (%) on a 4k clip in a 1080p timeline and still maintain at least full HD resolution?

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May 29, 2014 0
Adobe Community Professional ,
May 27, 2014

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Simply transcoding to another codec won't guarantee you get what you want, you need to be specific of course. I've seen a couple examples on other forums of folks doing this ... and dang, I'd like to add a GH4 to my GH3 ... so here goes:

First ... most seem to import into PrPro, drop the GH4 4k footage on a new sequence, take settings from footage, and then output through AME  ... though I've heard of some folks who simply started in AME.

Next ... (as Fuzzy replied to someone some months back) ... on export choose the 1080p DNxHD 10-bit 444 option, and set the "Color levels" to the "709" button (rather than RGB). This should do it.

I can't imagine why one wanting to get to 444 for grading/fx would happily accept 422 ... yea, there's some other trade-offs but then, we're not choosing to shoot 480 are we? And in Prelude, I personally can't get options for different bit-depth "out" ...  

Neil

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May 27, 2014 0
LEGEND ,
May 28, 2014

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Fuzzy's advice was for QuickTime files, and doesn't apply to the far superior MXF format.

Whether or not one chooses 4:2:2 or 4:4:4 will depend on what one intends to do with the footage.  My projects are fairly simple.  I don't feel they'd benefit enough from the extra color information to justify the significant increase in bitrate required to get 4:4:4.  Other projects may well benefit and would be better off with the higher bitrate.

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May 28, 2014 0
Guide ,
May 29, 2014

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There's much talk about the ability to "downsample" GH4 footage shot internally in 4k to 1080p and the added benefit of it going from 4:2:0 to 4:4:4.

Being honest, I'd appreciate if someone could clarify how downscaling 4k to 1080 can convert this

to this

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May 29, 2014 0
Enthusiast ,
May 29, 2014

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Here's a video I found...it uses those same boxes in it's example:

Why Does 4K Look Better on 1080p Monitors - YouTube

But you mentioned downscaling...is that the same as "downsampling"?

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May 29, 2014 0
Guide ,
May 29, 2014

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Nope, downscaling means simply reducing a frame size (i.e. 'what' happens), while downsampling rather points to an approximation algorithm (i.e. 'how' it happens), which is not that simple and straightforward as it is claimed in the video. In terms of colour subsampling 'downsampling' would rather mean a transition from 4:4:4 to 4:2:2 or 4:2:0, whereas a transition from 4:2:0 to 4:4:4 would be called 'upsampling'.

PrPro will upsample 4:2:0 footage to 4:4:4 on decoding. Then some colour data approximation will take place on downscaling a footage from 4k to 1080. If there is a chance that Steve Hoeg comes across this thread, he can probably shed some light on how it happens under the hood in PrPro.

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May 29, 2014 0
Enthusiast ,
Jun 02, 2014

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Fuzzy Barsik wrote:

PrPro will upsample 4:2:0 footage to 4:4:4 on decoding. Then some colour data approximation will take place on downscaling a footage from 4k to 1080. If there is a chance that Steve Hoeg comes across this thread, he can probably shed some light on how it happens under the hood in PrPro.

Would love to know what's going on under the hood with Premiere Pro here and how the various options affect the 4k footage.

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Jun 02, 2014 0
Adobe Community Professional ,
Jun 04, 2014

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The GH4 puts out 4k-10bit only through the HDMI out, not by internal recording. So ... to get real after-editing full 10bit 1080p 4:4:4 one needs to output 4k-10bit 4:2:0 and then in transcoding that into 1080p it can become full-blown 1080p 10bit 4:4:4 through a "natural" trans-mogrification of extra luma data to color data. I've seen the wonderful scientific discussions on it, yes, it does work that way. Full-blown 10-bt 4:4:4.

A slight problem at the moment ... there apparently are no portable recorders that can record the full range of framerates the GH4 shoots at 4k-10bit. One very expensive one might, but none of the say Atomos ones. So ... IF you've also got Panny's YAGH (or "the brick")  unit attached to your GH4, with the way it converts the HDMI outs to SDI, AND you happen to have an SDI-connectable recorder with 4k/10-bit any-framerate capability sitting there, you can get your GH4 footage in an awesome wrapper for editing delivery.

I've also seen the scientific discussion as to why taking the 4k-8bit 4:2:0 out and transcoding to 1080p does get some improvement in color depth data ... to roughly 8.67 bits equivalence. Which as one person noted, being as this is not an arithmetic scale is still a significant improvement in color "depth" data. Much more than 8bit yet nowhere near 10bit.

We have arrived in no-man's land! 

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Jun 04, 2014 0
dinceror LATEST
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Aug 03, 2014

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how aboutgiving project to customer are you taking out h264 mp4 ?

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Aug 03, 2014 0