Support for Color profiles

[eltouco]

Some shadering work is being done this summer.

Cool

I'm a bit litterate in color science and video standards, if needed, I could help by writing a spec on how accuretly handle color in video rendering.

For instance, I don't know if it is well implemented in VLC, but there is a common mistake amongst various video software player, that is the color space of HD video is different from SD video (the way Luma is calculate is different and the Red, Blue, Green primaries are different between SD and HD) therefore the video rendering process should be different when handling SD or HD.

more details on this, on this well explained page :

http://www.glennchan.info/articles/tech ... -space.htm

Touco

[Jean-Baptiste Kempf]

Oh, no, the mistake is in the video drivers usually.

[eltouco]

Oh, no, the mistake is in the video drivers usually.

Really ? but how the video driver is aware of whether using REC 601 standard (SD video) or REC 709 standard (HD video) ?
You mean this parameter is passed through by VLC to the video driver ?

[DGMurdockIII]

take a look at this http://forum.doom9.org/showthread.php?t=154719 and this http://yesgrey.com/ycms.html Color management wiki ( very good info) - http://www.colorwiki.com/wiki/ColorWiki_Home

yCMS is a Color Management System (CMS) that uses 3-dimensional lookup tables ("3D LUTs") to perform the conversion between the input and output color representations.

The idea of using 3D LUTs was due to the intensive computing that needs to be performed when converting video data between different color spaces. When using 3D LUTs all computing is performed offline during its creation. The computed 3D LUTs (three, one for each component) are then written to a file which can later be used, when playing videos or viewing photos, simply by mapping the input data through the 3D LUTs. This way, the conversion can be performed at runtime using lower computational power and leaving more CPU available for other tasks. Since all the computing is performed offline its precision can be increased by using 64bit floating point (per component) through out all the conversion chain.

Windows Color System - http://download.microsoft.com/download/ ... em_API.ppt

[eltouco]

take a look at this http://forum.doom9.org/showthread.php?t=154719 and this http://yesgrey.com/ycms.html Color management wiki ( very good info) - http://www.colorwiki.com/wiki/ColorWiki_Home

yCMS is a Color Management System (CMS) that uses 3-dimensional lookup tables ("3D LUTs") to perform the conversion between the input and output color representations.

The idea of using 3D LUTs was due to the intensive computing that needs to be performed when converting video data between different color spaces. When using 3D LUTs all computing is performed offline during its creation. The computed 3D LUTs (three, one for each component) are then written to a file which can later be used, when playing videos or viewing photos, simply by mapping the input data through the 3D LUTs. This way, the conversion can be performed at runtime using lower computational power and leaving more CPU available for other tasks. Since all the computing is performed offline its precision can be increased by using 64bit floating point (per component) through out all the conversion chain.

Windows Color System - http://download.microsoft.com/download/ ... em_API.ppt

thanks for the info, however, ideally VLC should be able to do this conversion internally without the help of an external software

[DGMurdockIII]

bump to not loose the info

[eltouco]

bump to not loose the info

Ycms is a great initiative, it works with Madvr which is a wonderful render, unfortunetly, as seen here viewtopic.php?f=7&t=79902&p=265811&hilit=madvr#p265811
it is very unlikey that we see a support for MaDVR in VLC.
nevertheless, maybe a color managed VLC could be possible if done natively in it (can some VLC developers confirm that ?)

I'm not able to write code for VLC but I could write a precise specifications in order to handle colr the right way if it can help.

Touco

[VLC_help]

One video filter would be enough if you use VOUT that doesn't do any color changes.

[eltouco]

One video filter would be enough if you use VOUT that doesn't do any color changes.

yes, but it is precisely why a feature request is needed
sending straight away RGB value to the video output is not the right thing to do regarding to color management.
you have to take into account whether or not the video is SD or HD (the primaries are different for the YcrCb->RGB conversion) and it should take into account the display ICC profile.

for instance what if the screen doesn't have a 2.2 gamma but a lower gamma ? if VLC is color managed it will do some gamma correction the scene will be displayed the same as on a 2.2 gamma screen, currently with VLC the scene will be darker thand it should.

[mcantu]

i'd also like to request ICC profile support. mpc-hc has recently added full color management but i would much rather use vlc...

[sblantipodi]

is there some news about VLC and color management?

is it color managed now?

[VLC_help]

Shader support is in VLC 1.2.0, so you can do manual corrections.

[sblantipodi]

manual correction is something, support for color management is another.
I asked if VLC supports color profile.

[mcantu]

any word on possible color profile support?

[VLC_help]

AFAIK nobody is working with this.

[mcantu]

thats too bad. mpc-hc has had it for almost 2 years now. i think color profile support would go a long way towards giving VLC more acceptance in the HTPC community (which seems to go mainly to mpc-hc)

[Jean-Baptiste Kempf]

True. Although, one would argue that the HTPC enthusiast community is still quite small and not really helping on VLC... Patches are welcome though...

[Rucha99]

There is "Shader support in the OpenGL output, for colorspace conversion, including 10bits." announced in latest 2.0 version of VLC Media Player in the website.
But I cannot find any settings and documentation for this.
How to use this feature?

[Jean-Baptiste Kempf]

It is automatic, you cannot provide your own scripts yet.

[Rucha99]

How can it be automatic? What is logic of conversion? I don't see any changes compare to previous version. I think it does not work at all.

[VLC_help]

The code is in
http://git.videolan.org/?p=vlc.git;a=bl ... t/opengl.c
(lines 299-333)

OpenGL does the chroma conversion automatically, if the formats are supported. So there isn't a CPU chroma conversion in that case.

[mcantu]

thank you!!

does OpenGL need to be selected as the output method for the color profile support to work?

[Jean-Baptiste Kempf]

Yes, it does YUV->RGB conversion in shaders.

[eltouco]

I think there is a misunderstanding, this code is only about the YUV->RGB conversion nothing about color profile.

I made some test using directX and OpenGL, i don't see any difference in color although i have an ICC profile set up.

[Jean-Baptiste Kempf]

There is a misunderstanding, the code does not do it yet. Sorry.