studio RGB, computer RGB - still not getting it

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NickHope wrote on 10/4/2016, 3:52 AM

Fixed the link now. https://www.vegascreativesoftware.info/us/forum/new-hd-grayscales-for-vegas-editors--83243/ This forum often does weird things with links (I'm getting sick of that cow!). The Belle Nuit chart is good for things like sussing out if you're getting Rec.709 or Rec.601 from encoders, because the colours change. Musicvid's chart is better for just seeing what the luminance is doing.

Musicvid wrote on 10/4/2016, 8:43 AM

@Nick, Actually for the current poster's questions, I recommend your swatches, and hope you still have them available someplace. Please share a link.

@concept,

Compositing gamma != Monitor gamma != Scene gamma != Storage gamma != Anything to do directly with endpoint luminance levels.

I don't know any other way to say this, except dig.

Please leave it alone for this discussion and feel encouraged to start your own thread on advanced compositing techniques, once you have tested them per the "linear light" article and can show us your results. I'm sure everyone participating this thread, titled "studio RGB, computer RGB - still not getting it" will want to participate in that entirely unrelated discussion. Sometime around Thankgsgiving, I'll write a little tutorial on gamma for video editing, and many people will be surprised to learn that it has surprisingly little to do with anything but creative purposes since OSX and Windows finally agreed on screen gamma around a decade ago. "Gamma" is the second most often misused word in editing lingo, following only "bandwidth" on the insipidness scale.

 

I believe Premiere looks at the flag here, maps 16 YUV to 0  and 235 YUV to 255 thus clipping highlights. If I follow recommended standard practices about VEGAS mentioned in this thread, the output from VEGAS seems better, with a bit more detail in the highlights. Is it possible that the "limited" flag throws Premiere off in such cases?

Again, entirely unrelated to anything having to do with Vegas' preview or output, since it is a Windows competitor to Apple, and does not support VUI flags natively, at least through version 13. Really, implementation and recognition of these flags is so spotty across decoders (still unreliable in vlc, last time I tested), that I again think you should start your own discussion.

But since you asked, you made a good stab at it, and I think the behavior in Premiere is exactly the opposite, mimicking that of Quicktime (where it was introduced as an off-spec option), as well as Flash, Youtube, ffmpeg (when it works), and I assume html5. 

What you are calling the --limited flag, is actually the mp4 / REC709 default. It is often designated yuv420, and is a placeholder, the often-unrecognized equivalent of no flag at all, going back to the original REC601/709 luminance standard, many, many years ago.

What Premiere does, I believe, is recognize and honor the --yuvj420 flag, or --fullrange, as do some other Quicktime-aware decoders, and changes the preview to remap native 16-235 yuv to 0-255, while Vegas preview merely expresses 16-235 natively on a 0-255 rgb serving platter.

Bad on Vegas, or bad on Quicktime, which is it?

Well, consider this: Only a fraction of the hundreds of billions of consumer videos being incorrectly shot today on phones and devices carry the --fullrange flag, and not all decoders recognize it when it is present.

So, what happens to decoders and players when either of the above two conditions exist, or the --yuvj420 flag is present on a video conversion from already-compliant source, as many freeware converters do blindly? See "clipped Shirley" and "tv Shirley" in my earlier article for the results.

Many consumers have become so used to seeing clipped Shirley from their own camera footage that they now prefer it (yes, you can find the survey on this forum, and it aggravates me). It's simply a losing battle for anyone that understands the concept of bit depth in a relatively sparse 8-bit-per-channel environment. Every time someone adds another "stupid switch" to a decoder, graphics card, hardware player, software player, monitor, teevee, or device, the number of possible combinations of redundat, destructive on-off commands is raised by another power of ^2. Unfortunately, one cannot put the toothpaste back in the tube, and alchemic thinking has become the operative mindset for all too many hobbyists. It gets really confusing for my pea-brain when middle-school math and superstition get all mixed up like that.

So what's the logical, absurd outcome of all this? Well, if I repeated the bit-killing iterations enough times, beautiful Shirley would wind up looking like this:

 'Nuff said with this thread. If you want higher-level discussions with Nick and the other real pros in our midst, head on over to doom9.org Otherwise, show us, your peers, new thread topics with examples to accompany your questions. Best.

 

concept wrote on 10/4/2016, 9:28 AM

I understand the different gammas and will leave it alone for this thread if you deem it irrelevant. I only asked because it is an option only under Fullrange RGB and for this reason assumed it is also related to levels. But like you said, it may very well become the topic of another thread.

What Premiere does, I believe, is recognize and honor the --yuvj420 flag, or --fullrange, as do some other Quicktime-aware decoders, and changes the preview to remap native 16-235 yuv to 0-255, while Vegas preview merely expresses 16-235 natively on a 0-255 rgb serving platter

I believe this was also my interepretation. So in this case any existing superwhites would be discarded if the file has data in the range 16-255. It appears Vegas is much better here not to take guesses based on flags.

Anyways, thanks for taking the time to provide your reply. Appreciate it.