Overview of different color spaces and possible problems

[flashandpan007]

I have searched and viewed many threads here in the forum, but the more I read, the more I get lost.
Is there an overview of the different color spaces and the propably resulting problems which may appear when doing something wrong, like wrong colors after conversion or Rendering in NLE?
And to be sure what is to do with 0-255 and 16-235? -> Too bright like this https://www.youtube.com/watch?v=dG9fPvD40Ag

[hello_hello]

In theory colorspace problems, including luminance levels, only happen when video is converted from YUV to RGB or RGB to YUV. That's when it's decided which colorimetry to use, which means it's also eventually decided on playback when YUV is converted to RGB and displayed on a monitor TV. If a video is YUV and is processed in YUV the colorimetry and levels shouldn't be effected. It's only when some sort of YUV to RGB conversion takes place there might be problems. In theory, the only time you should have to worry about colorimetry when re-encoding YUV video is if you upscale or downscale, as SD and HD use a slightly different method for converting to RGB on playback.

Problems occur when programs do things differently. RGB should be full range (0-255). Any program converting RGB to YUV should, by default, convert to limited range levels (16-235). By default, when that YUV is converted to RGB again, even if it's just on playback, the levels should be expanded again.

When it comes to colorimetry SD uses Rec.601 and HD uses Rec.709 (they both use the same limited range luminance levels). Therefore HD RGB should be converted to YUV using rec.709. They're only a little different, but if you were to convert HD RGB to YUV using rec.709 and it's converted back to RGB on playback using rec.601, the colours can look a little "off". Red gets a bit darker and I think green a blue a bit brighter.

I keep saying "in theory" as different NLE's might do different things. Most Avisynth filters work in YUV, but even if a program/filter converts to RGB and the video is converted back to YUV, as long as the same method is used each time the colorimetry won't change.

You can create an Avisynth script yourself to open a video and change the luminance levels (if you're familiar with Avisynth). Or you could decode a video with ffdshow and enable it's Avisynth filter to play around if you also have Avisynth installed. That might be even easier than modifying and re-opening scripts.

ColorYUV(Levels="PC->TV")
ColorYUV(Levels="TV->PC")
or
ColorMatrix(mode="Rec.709->Rec.601", clamp=0)
ColorMatrix(mode="Rec.601->Rec.709", clamp=0)

Thinking about it, the colour conversion needs the ColorMatrix plugin. Stick it in the Avisynth plugins folder and that'll work. For some reason I can't find a working link for it, which seems odd as it comes with a lot of Avisynth based GUIs, but I've attached it for you.

Usually if the levels are wrong the picture looks a bit dark, or a bit "washed" out, whatever the case may be. The colour difference can be subtle, but have a play yourself.

[jagabo]

Some basic info:
https://software.intel.com/en-us/node/503873
http://fourcc.org/
https://forum.videohelp.com/threads/329866-incorrect-collor-display-in-video-playback?p...=1#post2045830

[flashandpan007]

Thank you for the information.