PC to TV Levels -- A Comedy of Errors

Musicvid wrote on 7/19/2017, 9:16 PM

This ridiculous exercise is here to amuse and enlighten those just dipping their toes in the swamp, to the multitude of errors that can and are introduced by downstream "fixes" for so-called "fullrange yuv," which in itself is an oxymoron, if not an extremely common one.

This is Fullrange Shirley, also called RGB or simply PC Shirley. If there weren't still a lot of analog TVs that would choke on her, everything would be dandy. If you can't see gradation between 0-16 and 235-255, drop back in when your monitor is calibrated correctly. Calibrize is cool, Spyder is amazing in concert with a trained pair of eyes.

This is Limited, or YUV Shirley, happy and correctly stored at 16-235. She will, by design, play back the same as RGB Shirley above, but represents a compromise because she will play on older TVs correctly, too. We didn't used to see her much in the wild, except when their were first-tier flag errors (more to come on that).

This is Clipped Shirley. We see her a lot, because most cell phones, tablets, DSLRs, and pocket cams shoot "Fullrange YUV," which I said is an oxymoron. It's a sad commentary that many (most?) uninformed consumers actually prefer this mutation, because that's what they're used to seeing, almost everywhere. This first thing an informed viewer will see is a clipped image, with 0-16 and 235-255 completely blocked up, leaving blotches in the hair and facial tones, but then 5 Billion consumers can't be wrong, right?

This is Overcorrected Shirley, happens when correct YUV Shirley gets flagged as Incorrect Fullrange Shirley, run through a converter, then gets played back on one of the players that recognizes the flag. This happens a lot actually, because the "converters" that do this assume it's cellphone video, and have no way of knowing if it's already been corrected. Just ran into this again last week.

This is "almost" the worse case. YUV Shirley flagged as Fullrange, run through a converter, flag recognized by player, and the smart kid left the Dynamic Contrast hardware filter on to boot. It actually happens, and the inevitable complaint is that the encoder messed up. The encoder, for those who don't understand by now, is the only thing that WASN'T messed up by operator error.

OK, so Smart Kid thinks he'll just adjust the contrast and brightness to "fix" it. Let's say he actually gets it back to 0-255 playback levels. Only catch is, he's lost almost 40% of native bit depth, so it looks kind of like pre-16 bit monitors, or maybe Swiss cheese (note the histogram.) The banding at HD resolution is nothing short of horrible. Is this really what he wanted? How would YOU go about undoing all the misinformation that led up to this? Will this kid work part-time at a ski resort for the rest of his life?

The moral?
Deliver only16-235 YUV, not a kludge, and hope for the best. The rest of the nonsense actually presents a compelling case of the cure being worse than the ailment.
YUV delivery media include .mpg, .mp4, m4v, DVD/BluRay, AVC/h264 x265, and a few nonstandard AVI. Best.


ushere wrote on 7/20/2017, 2:01 AM

excellent summation musicvid - unfortunately, there's still a lot of people who eyeball their cc'ing on uncalibrated monitors and then wonder WTF!?

Grazie wrote on 7/20/2017, 2:21 AM

Great work musicvid. Great stuff, thanks for sharing your expertise. I always learn something from you.

I gotta tell you that for the first time EVER, about 4 days back, I sent a PAL TEST chart to my SONY BRAVIA from my iPad Air2 via Apple TV Share. Woah...... And, as per my other monitors, I did the simple 3-Bar Contrast adjust. Night and day difference. Now I KNOW that the screen is as good as I can get it.

I also invited your RGB Shirley onto the screen, also from my Airplay Mirror, and I see what you mean.

This and that "other" thread I've filled in even more gaps in my knowledge.




set wrote on 7/20/2017, 4:35 AM


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Musicvid wrote on 7/20/2017, 8:19 AM

Well, the model I found on the Internet is high key and easy to look washed out.

Sometime I'll find a new one.

She was graded on a Sony laptop calibrated with a Spyder. But as we all know that's no guarantee that mine is representative of the norm.

SphinxRa40 wrote on 7/20/2017, 8:57 AM

Totally new to this all, didn't even know about "spider", but this is interesting, had to google for that spider thing, is the Datacolor Spider Express good enough? does this all apply for video's too? Can it be used on TV's? or only monitors?

Musicvid wrote on 7/20/2017, 9:46 AM

Correct spelling is Spyder, and it's a fun toy.

Foreknowledge of color theory (rgbcmyk) is most helpful.

Dr Zen wrote on 7/20/2017, 11:14 AM

Thank you Musicvid for putting this excellent presentation together 👍👍
You just helped unscramble my brain, after following the other active thread that blew up on this topic.

Musicvid wrote on 12/8/2018, 3:08 PM

Ran across this in an old box -- it's the Noritsu C41 "Shirley" from the eighties.

Yes, she's a Caucasion dummy. Like me.

fr0sty wrote on 12/9/2018, 11:53 AM

Thankfully we are moving away from anyone having an "old analog TV". I hate having to kill dynamic range to ensure compatibility with old devices.

Musicvid wrote on 12/9/2018, 2:21 PM

Yes, and once againApple's maverick "cure" (VUI flag) has shown to be worse than the disease. The next flavor of ATSC may accommodate your wishes, but don't count on it. Log compression is probably a long way away for OTA viewers.

Musicvid wrote on 5/6/2020, 3:41 PM

Here's a zipped Vegas 14+ project in a parallel thread.