0-255 vs 16-235 Cineform in 8.0

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GlennChan wrote on 4/1/2009, 6:40 PM
1. In your table you indicate if the output is MPEG2 DVD, 8 bit projects decode to and want to see studio RGB levels, but 32 bit projects decode to and want to see computer RGB levels. This suggests there are separate MPEG2 codecs for 8 bit and 32 bit projects, with the 32 bit codec expecting to see studio RGB levels, but still producing 16-235 MPEG2s, correct?
Yes*.

*Please be careful in that you are following the units / types of values correctly. There is Y'CbCr and RGB... they are different things. MPEG2s store video as Y'CbCr values, and there is only one standard for this / only one proper way of doing it (*of course there is equipment which will do it incorrectly... but they are nonstandard).

When it comes to RGB... there are two different ways of doing RGB (computer RGB and studio RGB levels). They aren't supposed to be used interchangeably, but it is easy to do so. But anyways, this is why you need to know whether you're dealing with studio RGB, computer RGB, or Y'CbCr.

Anyways, if you encode MPEG-2 in a 32-bit Vegas project, send the codec computer RGB levels... it will produce proper Y'CbCr values this way. It is expecting / designed to map computer RGB to Y'CbCr. It will screw up if you send it studio RGB levels.

2. You mention that the Vegas scopes won't help us - is this a blanket statement, or are there any project types where the scopes can be used?
They are useful, but they won't help you figure out what's going on in my opinion.

Here's why: Under the settings for the scopes, there are 2 checkboxes. The 4 combinations of these checkboxes will change what the scopes show... even though *nothing* has happened to your video. At most only 1 of these 4 combinations can be correct...

Anyways, don't use the scopes to try to figure out what's going on. They can be useful for color correction.
e.g. as outlined here:
http://www.sundancemediagroup.com/articles/glennchan/levels_in_sony_vegas_part_one.htm

2- The way to figure out what's going on is to use tools that can read Y'CbCr values directly, e.g. a real hardware set of scopes.
TeetimeNC wrote on 4/2/2009, 2:14 AM
Excellent Glenn. Thanks to the persistence of you and others here, I think it is beginning to sink in.

Let me test my understanding on a specific scenario. I have a project with a mix of HMC150 AVCHD (0-255) and DV produced by a GL2 (16-255?). I say the GL2 is 16-255 because that is what I see in the histrogram for this footage. I assume the GL2 is recording superwhites.

So, from looking at your chart I believe for producing a DVD from an 8 bit project, I should apply computer RGB -> studio RGB to both of these and then render my MPEG2. Correct?

It also looks like I would do the same if rendering a BD from AVCHD in an 8 bit project. Correct again?

In what scenario would you recommend switching to a 32 bit project? I do have a basic understanding of linear light obtained from After Effects 7.0 Studio Techniques by Mark Christiansen, but haven't yet tried this is Vegas.

Jerry
Andy E wrote on 4/2/2009, 2:22 AM
So, from looking at your chart I believe for producing a DVD from an 8 bit project, I should apply computer RGB -> studio RGB to both of these and then render my MPEG2. Correct?

No, if I've understood the workflow correctly you leave the DV untouched - it's already at Studio RGB which is what the MPEG2 encoder expects.
TeetimeNC wrote on 4/2/2009, 6:01 AM
No, if I've understood the workflow correctly you leave the DV untouched - it's already at Studio RGB which is what the MPEG2 encoder expects.

Andy, you may be right, but I assume with the GL2 shooting with superwhites (16-255) I should apply the Studio RGB filter. No?

Jerry
Andy E wrote on 4/2/2009, 6:10 AM
but I assume with the GL2 shooting with superwhites (16-255) I should apply the Studio RGB filter. No?

Jerry,

Ah misread that 16-255 as 16-235. I would suggest that the answer is still that you don't apply the standard preset because that will screw your blacks. You can always create your own preset if needed.
kairosmatt wrote on 4/2/2009, 7:16 AM
So AVCD is computerRGB huh? Interesting...

As far as the superwhites, I don't think there is a specific filter you want to apply across the board to all DV. I would think you just adjust the input out level based on each different clip/event.

kairosmatt

Edit: It should be output end, not input out
LarsHD wrote on 4/2/2009, 11:41 AM
David, I don't agree with you. Please read... ;)
--------------

"We do not offer a YUV full range switch for Canon 5D, as that would make the 5D incompatible with every NLE (including Vegas), and it would have the 5D levels incompatible with all other cameras."

---------------

A switch / checkbox in that conversion utilty app of yours wouldn't make things less compatible at all. It would instead make Neo *more* compatible.

Who is to decide if the owner of a 5D2 0-255 video camera shall have 0-255 or 16-235? The owner and user of course. (Not Cineform...)

A checkbox that you check if you want 0-255 unaltered dynamic original range and you uncheck it if you want the 16-235.

Surely that is technically very possible and it would not introduce any compatiblity issues all. It would make Neo appear VERY compatible and attractive to even more users...

The Neo scene does a marvelous job in producing small files that play fast. Wonderful performance!

Now please let *me* decide myself if I want the dynamics altered or not... I purchased this conversiom utility for what it said it would do, produce AVI-files that played back better. Only to find out - after I bought it - that it altered the dynamic range...

So... can you please introduce a checkbox in prefs for 0-255 / 16-235 in your next update next week...?


Best & thanks in advance,
Lars


PS. And David... please, please make that Neo run in Vegas 8.1 as well.

8.1 gives better frame rates than 8.0 so feel a bit silly that I
have purchased conversion utility from you to speed up the FPS - only to find - after I bought it - it does NOT run on the fastest platform Vista 64 and the fastest version of Vegas 8.1... :(


Regardless if it is Sony or Cine, please just make it work together. I don't think this is rocket science at this stage.

Both of you make such great products but it feels you haven't got them working together yet...

GlennChan wrote on 4/2/2009, 1:03 PM
I have a project with a mix of HMC150 AVCHD (0-255) and DV produced by a GL2 (16-255?).
AVC HD decodes to computer RGB levels in a 32-bit project, but it decodes to studio RGB levels in an 8-bit project. It seems like you are working in an 8-bit project?

I say the GL2 is 16-255 because that is what I see in the histrogram for this footage. I assume the GL2 is recording superwhites.
Yes... most cameras record illegal values above white.

One way of dealing with them:
http://www.glennchan.info/articles/vegas/color-correction/tutorial.htm

GlennChan wrote on 4/2/2009, 1:17 PM
Who is to decide if the owner of a 5D2 0-255 video camera shall have 0-255 or 16-235? The owner and user of course. (Not Cineform...)
In my opinion, Cineform should have sensible defaults in its product. And it does. Period.
(Whereas Vegas does not have sensible defaults... it defaults into a mess. If you throw DV and a still image onto the timeline, you will get incorrect levels without manual intervention. That is not a good default behaviour.)

A checkbox that you check if you want 0-255 unaltered dynamic original range and you uncheck it if you want the 16-235.
I think you're confused as to how one would maximize dynamic range.

First off, there's a big difference between Y'CbCr color space (Cineform incorrectly refers to this as "YUV") and both of the RGB color spaces (computer RGB and studio RGB). The Y'CbCr color space is much larger than both of the RGB color spaces and contains (illegal) colors that can't be represented in either of the RGB color spaces.
When you convert from Y'CbCr, you are throwing away these values and thus lowering dynamic range. If the camera records illegal colors (e.g. superwhites), then you want to convert to studio RGB to reduce clipping.

The downside to very large color spaces is that your bits are spread out more, so quantization error / quantization 'noise' is higher. In practice, these errors are insignificant for images with noise in them. Y'CbCr is bigger than studio RGB, which is bigger than computer RGB.

*There are actually different Y'CbCr color spaces, but the distinctions between them aren't relevant to this discussion.
LarsHD wrote on 4/2/2009, 1:55 PM
Think I have a very functional workflow now... Both for 16-235 and 0-255.... I'll be back in a couple of days... :)


Best,
Lars
LarsHD wrote on 4/4/2009, 12:49 PM
0-255 works best for the stuff I'm woring with.

There are lots of 5D2 stills and Hasselbald H3D-II stills etc and they are all 0-255.

Also we need to freeze lots of images from the timeline sometimes. It's great then to work in 0-255. We don't want to switch back and forth between 0 and 16.


That said:

NEO SCENE IS A GREAT PRODUCT.

It really transcodes the footage in a most efficient way maintaining quality. And files sies are really small compared to the alternative: rendering super-HUGE AVI's from Vegas that are 10 times bigger!

We've been carefully studying image quality of the Neo output and there is no doubt Cineform know what they are doing!

For our particular needs, we can clearly say that it would have been an advantage of selecting 0-255 instead of being forced to 16-235.

BUT... we would like to use 16-235 sometimes too, so a switch in the conversion utility would be very welcome David! Actually it works fin today if you're not involving Vegas 8.1 that doesn't support the codec (yet?),

Please contact me directly if you want to discuss this in depth and perhaps you will understand how we worlk and why this would be good.

After editing is done, we have found it quite easy to get the product into either 0-255 or 16-235 and have had a chance to test with some european broadcasters the standard of this and it works now.

So *while editing and during post pro* it is - for us - a clear advantage working in 0-255. The material we have, the way it is used, the way we interact with our clients makes 0-255 a lot safer and a lot faster and a lot more convenient.


Thanks for all who got involved and it really helped to experiment and get to a conclusion.

And Neo is fine :)

Please please speak with Sony and do you guys can to make this codec work in 8.1 as well.


Best & thanks David and Glenn and all other for your good advice!
Lars