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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Is R3D 4:4:4 or 4:2:2?

Adam Watson

Adam Watson

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The title says it all. Maybe there is a concept of it that I don't understand but I can't seem to find any indication of whether Red RAW is 4:4:4 in nature or 4:2:2. Anyone know for sure?

I know you can output 4:4:4 in transcode but is that 4:4:4 level of color information actually there to begin with?
 
Neither - it's RAW. 4:2:2 etc. refers to the situation where chroma bandwidth is reduced in a Y'CbCr encoded signal to achieve a smaller bandwidth.

Graeme
 
so it can be transcoded into whatever, got it.
 
Are R3Ds 16 bit or 12 bit?

Is there a way to change the recording bit depth on the Epic?

Is the Epic-X a 16 bit system?
 
Adam Watson said:
The title says it all. Maybe there is a concept of it that I don't understand but I can't seem to find any indication of whether Red RAW is 4:4:4 in nature or 4:2:2. Anyone know for sure?

I know you can output 4:4:4 in transcode but is that 4:4:4 level of color information actually there to begin with?
Click to expand...

First off, if you're talking 1080p... sure RED has 4:4:4 level of detail.

But at 4K or 5K:

The Bayer sensor reconstruction can get you more than 4:2:2 quality in some cases... but for all practical purposes, no: you have either a red or a green or a blue pixel, not a RGB pixel. It's a real stretch to see how you can possibly get high-quality 4:4:4 info out of this sucker.

Personally I have been doing tests and am moving my post pipeline to 4K... but at 4:2:2.

I really haven't seen the RED getting enough chroma detail beyond 4:2:2 for it to be worth the massive increase in disk space that 4:4:4 requires.

If you compare a 1.8GB folder of 4K DPX files... you can do OpenEXR at 4:2:2 with light B44 compression and get practically identical quality but at 577MB.

Unless you have a lot of stock investments in hard drive companies, 4:4:4 4K just doesn't make sense to me.

Bruce Allen
www.boacinema.com
 
Bruce, please don't use imprecise terminology. 4:2:2 etc. don't apply to a measure of chroma resolution in any sense, but a process by which resolution is deliberately reduced by some circuitry or process for bandwidth reduction reasons.

For instance, you could record a VHS tape onto Digibeta at 4:2:2. At which point you definitely have a 4:2:2 signal, but that actually tells you nothing about the measured chroma resolution of the signal. Similarly a BetaSP dub to the same Digibeta would be 4:2:2 but the actual measured chroma resolution would be vastly superior. A direct camera recording to that Digibeta would also be 4:2:2 and depending on the camera could have a vastly superior measured chroma resolution.

The reason, of course, why such analogue era compression as 4:2:2 works so well is that we don't see much detail in chroma compared to luma.

The issue of how colour filter array sensors see colour resolution compared to luma resolution is a different issue. In such a system we're dealing with broad colour filters where any detail is visible in all three channels in most circumstances.

Graeme
 
Okay, this makes sense. Thanks for the response.
 
Graeme, well your assessment about imprecise technical terminology is useful, I think Bruce's point is a very apt one when working in workflows above HD, which is this:

At what point does maximum chroma resolution at a 4K source become a waste of bandwidth for a given application.

By offering RAW Red gives us the choice about this, unlike in the video world where traditional workflows have had video engineers basically make this call for us by the limitations/expectations of industry standard hardware. What they said was 'good enough' became the status quo, or the ideal, when in reality it's all a compromise.

When we are actually working with files in a RAW originated - all digital workflow, we each individually become a lot more enabled, but also responsible, as we can shoot ourselves in the foot by not using suitable compression.

If at 4K there is generally a negligible difference delivering 4:2:2 Y'Cb'Cr compressed footage from a compressed Bayer pattern sensor that shoots a RAW master at 5-4k versus delivering 4:4:4 Y'Cb'Cr footage from the same, then that's something that is useful to know when working with 4K files.

As you state we don't see much detail in chroma compared to luma and as you say 4:2:2 compresssion works well.

Do you think, given the increase of digital workflows we can expect to work with increasingly either RGB compressed signals or we are likely to continue to use Y'Cb'Cr formats for the forseeable future, not just for legacy reasons but also for the compression efficiency they provide.

To put it in a form similar to the original question: What are the advantages to moving R3D RAW footage into a 4:4:4 Y'Cb'Cr format at a given resolution, over moving to a 4:2:2 Y'Cb'Cr format at a given resolution.

Also a question for Bruce - if you are working in a 4K colour space with a 4:2:2 resolution, within your workflow is there a difference if you downrez that to 1920x1080 in a 4:4:4 Y'Cb'Cr supported format over downrez to a 4:2:2 Y'Cb'Cr format, or do you find the tools you have throw the additional chroma resolution that could be obtained from the higher resolution source footage away so once in 4:2:2 format you are effectively stuck there (without further intermediary transforms, such as to full bit depth RGB file format, and then going back to 4:4:4 Y'Cb'Cr?.

Also I wonder if somewhat counter intuitively, you could effectively result in more chroma detail artifacting if the down conversion to 4:4:4 from a 4:2:2 source over going to a 4:2:2 if the down conversion isn't a nice round number - i.e if it's the down conversion maths is messy, would you sometimes be better off with slightly less detailed chroma regions to 'blur' artifacting from an imprecise downscale?

I presume high end compositing software would get this sort of thing right (internally moving everything into RGB and then back out to your new format at the maximum bit depth possible), but I'd be curious if After Effects or general purpose NLE's/finishing software gets this right
 
Craig, that's another question altogether! It's a question that applies to all footage. What I'd suggest is to keep the quality as high as possible as long as possible, only reducing it significantly for any distribution codec.

In terms of compression the reduction from 4:4:4 to 4:2:2 reduces the pre-compression bandwidth by 1/3, and usually in a very visually transparent way, making good use of the foibles of the human visual system. However, it is my opinion that instead of such a simple decimation, you'd actually get a better image by keeping the chroma resolution full, and using a slightly more lossy compression on the chroma to make-up for that 1/3 head-start that 4:2:2 gets over 4:4:4.

Graeme
 
Graeme Nattress said:
Craig, that's another question altogether! It's a question that applies to all footage. What I'd suggest is to keep the quality as high as possible as long as possible, only reducing it significantly for any distribution codec.
Click to expand...

You hit the nail on the head.

People should do their own tests to determine if their combination of the RED Mysterium-X sensor, lenses, filters, etc. warrant keeping the chroma resolution at its maximum setting through a given workflow. If you feel it's invisible to the naked eye and/or you don't have the disk space/bandwidth to cope with this problem, then by all means subsample the chroma channels.
 
It's threads like this which make REDUSER such a valuable use of my time. So thanks to all!

Graeme Nattress said:
However, it is my opinion that instead of such a simple decimation, you'd actually get a better image by keeping the chroma resolution full, and using a slightly more lossy compression on the chroma
Click to expand...

Wait. Did you mean 'luminance' there? Anyway I don't pretend to understand this stuff in great detail. However, Bruce's opinion makes sense as a default approach on the matter (even before correction and grading are done) based on my limited experience with this kind of topic.
 
Nope, I meant chroma. I'm suggesting a modern codec might work better by keeping the chroma resolution full and just compressing it harder, than decimating it's resolution first then compressing it less.

Graeme
 
Graeme Nattress said:
In terms of compression the reduction from 4:4:4 to 4:2:2 reduces the pre-compression bandwidth by 1/3, and usually in a very visually transparent way, making good use of the foibles of the human visual system. However, it is my opinion that instead of such a simple decimation, you'd actually get a better image by keeping the chroma resolution full, and using a slightly more lossy compression on the chroma to make-up for that 1/3 head-start that 4:2:2 gets over 4:4:4.
Click to expand...

Graeme, I've been waiting since 2007 for you to do exactly that with RedCode RGB. Or for Cineform to make a codec that isn't buggy on Macs.

Since neither of these have happened yet, I am going with my next best option:
OpenEXR with 4:2:2 and B44 compression.

Maybe there will be a 4K version of Avid DNxHD444 soon.

Again, I don't see much real chroma info being lost in my real-world tests. But please point me to an alternate compression method if there's one out there that can work with all of my apps?

Bruce Allen
www.boacinema.com
 
I wish there was time in the day to come up with something there for you Bruce!

Of course, as you know there's not so much detail in chroma to begin with which is why the human eye didn't adapt to seeing it and why YCbCr 4:2:2 etc. compression systems have been used so successfully.

Graeme
 
Graeme Nattress said:
I wish there was time in the day to come up with something there for you Bruce!

Of course, as you know there's not so much detail in chroma to begin with which is why the human eye didn't adapt to seeing it and why YCbCr 4:2:2 etc. compression systems have been used so successfully.

Graeme
Click to expand...

Graeme, you are a very nice man.

I wish you some days off first, instead!

If I ever start a post on my 4K 4:2:2 compressed OpenEXR 48fps stereo workflow I will make sure to include an Honorary Graeme Disclaimer that:

"the moment a good compressed 4:4:4 RGB codec becomes available, ditch this chroma-subsampling nonsense! It makes no sense in the digital world! But here's my kludge for now..."

Cheers :)

Bruce Allen
www.boacinema.com
 
Yaque Silva-Doyle said:
Epic R3ds are 16 bit
Click to expand...


what about the A/D conversion? is the sensor natively 14 bit going into a 16 container? 16 to 16? 14 to 12 than padded in a 16 bit container? r1 mx was a 12 bit codec, I'm wondering if the A/D stayed the same off the r1 to the Epic and if it's just 12 bits spread out in a 16 bit container.
 
I admit my question was a bit cheeky, because I knew it was an altogether different question, but I also knew it would get the sort of responses I was looking for, which is that:

A) Theoretically modern RGB compression could do a better job than 4:2:2 downsampling pre compression, but hell, 4:2:2 is fast, known and visually pretty hard to spot so heck, so rather than bemoan the world we live in going with that for now makes sense.

and

B) Bruce might write up his 4:2:2 Open EXR workflow in a post, which is a workflow that makes a heck of a lot of sense in my head theoretically, but isn't one that would be considered the 'norm' in tradition heavy iron type workflows where a lot of the literature comes from (especially not at 4K resolution.) and one that I would need to do a bit of research to implement. Bruce, if you are ever in Auckland, New Zealand, let me buy you a beer. :)

Having only really had my head in the post game for about 5 years, and having spent much of that scrounging around for scraps of information on prosumer centric forums or boffiny personal websites of video engineers to get to grips with a lot of these concepts (because somewhat surprisingly at first I discovered even a lot of people who worked day to day in industry really had no idea about what was actually going on under the hood and would spout misinformation at the drop of a hat.) I am truly thankful for the quality of communication and openness with information that is on Reduser!
 
Graeme Nattress said:
The reason, of course, why such analogue era compression as 4:2:2 works so well is that we don't see much detail in chroma compared to luma.

The issue of how colour filter array sensors see colour resolution compared to luma resolution is a different issue. In such a system we're dealing with broad colour filters where any detail is visible in all three channels in most circumstances.

Graeme
Click to expand...

Raw also reduces the resolution of the blue and red channels (effectively the chroma, or parts that are less important for luma), to make best use of the available total resolution of the sensor. The ratio 2(G):1(R):1(B) is exactly the same ratio as 4:2:2..

The reasons may be different, and your debayer may extend the luma further.. but lets not beat about the bush, bayer is not 4:4:4, its much nearer 4:2:2..

Of course the colour filters aren't perfect at filtering out R, G or B.. and each pixel must contain some quatity of R,G and B.. and sure, 3 chip systems don't align perfectly etc etc ..but why don't you just say a 4k raw downsampled to 2k is similar to 8:4:4.. ;)
 
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