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Adventures with ffmpeg and color ranges

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Re: Adventures with ffmpeg and color ranges

#41

Post by hiisukun »

Not sure if this kind of meta-comment is appropriate, but I find it difficult to follow a link like this because of the lack of human readable information contained in the URL.

If the story was hosted on a personal blog I recognised (like Julia Evans to take a random example), then perhaps the domain would be enough for me to choose to read the article to see if the content is interesting.

If the link was to a broader domain that hosts many writers, I might use the parts after the domain to filter my interest: example.com/news-opinion vs example.com/science-blog gives me more information that might not be clear from the post title.

With a site like Facebook, which hosts so much different value levels of content, it is harder for me to visit facebook.com/233555323 rather than facebook.com/ffmpeg-interest-group/post6665443. For whatever reason, the URL remains something I use to filter my internet consumption.

Perhaps it has something to do with the amount of scams or other general reasons not to trust non-human readable URLs, or perhaps it is more due to my distrust of article titles (sensationalism) and seeking a second source to verify my interest. Perhaps I simply bias against Facebook - I don't know.

Regardless, I visited the story after thinking about this, and was very surprised to see it was an article by John Carmack - an author I certainly respect. It is a shame for me that both the URL and the title don't reflect that.

Re: Adventures with ffmpeg and color ranges

#42

Post by hoseja »

whatshisface wrote: post #19
enneff wrote: post #16

Earlier quoted context omitted.

Just as the .plan files were mirrored by some enthusiasts, so too will his Facebook posts.

Are they mirrored already? I don't want to visit facebook.

In this very comment section.

https://news.ycombinator.com/item?id=20036710

Re: Adventures with ffmpeg and color ranges

#43

Post by josteink »

bscphil wrote: post #40
_Gyan_ wrote: post #39

Earlier quoted context omitted.

No, limited range is the most common and expected range for YUV videos. Many players don't look or respect the container metadata such as nclx in MP4 or the bitstream VUI flags and assume limited range.

This is correct. In fact, the following statement from the post is nonsense: > For arcane reasons related to TV broadcast limitations, many video formats restrict the YUV color components to be in the 16..235 or 16..240 range instead of the full 0..255 range. Losing 14% of the already-barely-enough 8 bit dynamic range is bad enough, but it also often results in the black range starting at a quite visible grey value b…

Interesting post!

I have one question about terminology though: when you refer to “players“, do you mean all kinds of players or just physical hardware devices like Blu-ray players?

I ask because I haven’t had/observed any issues or defects with colour in software/PC-based desktop serious at all.

Disclaimer: not in the Blu-ray-authoring business.

Re: Adventures with ffmpeg and color ranges

#44

Post by dtf »

hiisukun wrote: post #41

Not sure if this kind of meta-comment is appropriate, but I find it difficult to follow a link like this because of the lack of human readable information contained in the URL. If the story was hosted on a personal blog I recognised (like Julia Evans to take a random example), then perhaps the domain would be enough for me to choose to read the article to see if the content is interesting. If the link was to a broade…

Another site that comes to mind is the Financial Times, which uses UUIDs for article urls, with no other indication of content.

https://www.ft.com/

https://www.ft.com/content/13be9132-8149-11e9-b592-5fe435b57...

Re: Adventures with ffmpeg and color ranges

#45

Post by bscphil »

josteink wrote: post #43
bscphil wrote: post #40

Earlier quoted context omitted.

This is correct. In fact, the following statement from the post is nonsense: > For arcane reasons related to TV broadcast limitations, many video formats restrict the YUV color components to be in the 16..235 or 16..240 range instead of the full 0..255 range. Losing 14% of the already-barely-enough 8 bit dynamic range is bad enough, but it also often results in the black range starting at a quite visible grey value b…

Interesting post! I have one question about terminology though: when you refer to “players“, do you mean all kinds of players or just physical hardware devices like Blu-ray players? I ask because I haven’t had/observed any issues or defects with colour in software/PC-based desktop serious at all. Disclaimer: not in the Blu-ray-authoring business.

I'm referring to both. It's more likely, I suppose, that software players could have problems in this area, but that's simply because many of them are free and they don't have to pass any kind of certification process. As a matter of fact, all well known software players I've encountered seem to do this right. Regular limited range YUV works pretty much everywhere. Doubly compressed YUV (the encoding mistake I was talking about) works nowhere because the data in the file is incorrect and has to be manually filtered to repair the damage.

Re: Adventures with ffmpeg and color ranges

#46

Post by layoutIfNeeded »

bscphil wrote: post #40
_Gyan_ wrote: post #39

Earlier quoted context omitted.

No, limited range is the most common and expected range for YUV videos. Many players don't look or respect the container metadata such as nclx in MP4 or the bitstream VUI flags and assume limited range.

This is correct. In fact, the following statement from the post is nonsense: > For arcane reasons related to TV broadcast limitations, many video formats restrict the YUV color components to be in the 16..235 or 16..240 range instead of the full 0..255 range. Losing 14% of the already-barely-enough 8 bit dynamic range is bad enough, but it also often results in the black range starting at a quite visible grey value b…

This.

Carmack is in the wrong here.

Re: Adventures with ffmpeg and color ranges

#47

Post by layoutIfNeeded »

josteink wrote: post #43
bscphil wrote: post #40

Earlier quoted context omitted.

This is correct. In fact, the following statement from the post is nonsense: > For arcane reasons related to TV broadcast limitations, many video formats restrict the YUV color components to be in the 16..235 or 16..240 range instead of the full 0..255 range. Losing 14% of the already-barely-enough 8 bit dynamic range is bad enough, but it also often results in the black range starting at a quite visible grey value b…

Interesting post! I have one question about terminology though: when you refer to “players“, do you mean all kinds of players or just physical hardware devices like Blu-ray players? I ask because I haven’t had/observed any issues or defects with colour in software/PC-based desktop serious at all. Disclaimer: not in the Blu-ray-authoring business.

It’s pretty easy to verify: create a uniform white png and convert it to yuv420p h264 via ffmpeg:

ffmpeg -i input.png -pix_fmt yuv420p movie.mp4

Open in VLC or your favourite player and take a screenshot. Now check with a color picker whether you have white as 255 or 235.

Update: checked with VLC and QuickTime Player, both handled it correctly and displayed white as 255.

Re: Adventures with ffmpeg and color ranges

#48

Post by jerrre »

hiisukun wrote: post #41

Not sure if this kind of meta-comment is appropriate, but I find it difficult to follow a link like this because of the lack of human readable information contained in the URL. If the story was hosted on a personal blog I recognised (like Julia Evans to take a random example), then perhaps the domain would be enough for me to choose to read the article to see if the content is interesting. If the link was to a broade…

> very surprised to see it was an article by John Carmack

John Carmack works for Oculus/Facebook, so that's probably part of the reason he posts on Facebook, but you might mean you were surprised because the URL gave no indication.

Re: Adventures with ffmpeg and color ranges

#49

Post by jakear »

pvg wrote: post #36
jakear wrote: post #27

Earlier quoted context omitted.

More that the company’s culture says you should post things using the company’s platform, and to not do so might be making a statement he doesn’t want to make. Otherwise, why would he move away from .plan?

You said 'it wasn't his decision to make' not 'perhaps he wants to use his employer's platform'. If you don't want to imply it's coercive, you should phrase it in a way that doesn't imply it's coercive.

I believe it’s a “perhaps he feels he should be using his employer’s platform”. A murky coercion middle ground.

Re: Adventures with ffmpeg and color ranges

#50

Post by pvg »

jakear wrote: post #49
pvg wrote: post #36

Earlier quoted context omitted.

You said 'it wasn't his decision to make' not 'perhaps he wants to use his employer's platform'. If you don't want to imply it's coercive, you should phrase it in a way that doesn't imply it's coercive.

I believe it’s a “perhaps he feels he should be using his employer’s platform”. A murky coercion middle ground.

Ok, but "I don't think it's his decision" is then a weirdly overwrought (or less charitably, thoughtlessly provocative) thing to say. It's totally his decision. Nor do I think anyone at FB would be stupid enough to tell him where to post random ffmpeg things. He's also active on twitter - as you can see in the post we're discussing.
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