Our ChromaKey is broken as demoed in previous emails with GG-BLUR.tar.bz2. I was trying to incorporate some changes in the version 8 (in GitHub) of HV but failed to just get it to work. But hopefully Andrew will figure it out.
Hi all,
I have written a new article about Chroma Key HSV
https://linuxvideoediting.blogspot.com/2024/04/chroma-key-hsv-cinelerra.htmlThe article consists of two parts. In the first part I describe what I already showed in the screencast
I added a small excursion into the history of the plugin and a few screenshots.
Read this msg from Jerome (2006)
Quote:
"I saw this (Avid's new chroma keyer): and I told myself that it would be cool to have a similar plugin for Cinelerra.
So I completely modified the chromakey plugin."--------
As you see, Jerome was trying to replicate the Avid's new chroma keyer (SpectraMatte).
https://resources.avid.com/SupportFiles/attach/Symphony_Effects_and_CC_Guide_v5.5.pdf (pages: 203 - 212, 691 - 703) but the problem seems to be harder than he thought.
The current ChromaKeyHSV (in CV*/GG and [HV_before-02.2024] ) is doing whatever Jerome Cornet had.
However, the original Avid algorithm is a lot more complex & might have been marketing.
ChromaKey HSV in HV_before-02.2024 (before upgrading) is Jerome's version.
The current implementation of ChromaKeyHSV in Cinelerra-HV_after-02.2024 is most of the SpectraMatte algorithm.
I describe it in the second part of the article. It contains many original screenshots.
If you delve into the operation of the 'Saturation Offset' parameter, the question arises: "What is the difference between it and 'Min Saturation'?"
If you watched the screencast, you saw that 'Saturation Offset' only takes effect if 'Min Saturation' is > 0. Both set the minimum. saturation level, but S.O. cannot set a level lower than that specified using M.S. I.e. in conjunction with S.O., M.S. may act as a limiter. That's all?
In theory, the purpose of the parameter is to shift the keying sector along the line of increasing saturation.
However, it appears that either Jerome did not complete the parameter, or the parameter is broken.
You can "squeeze" the following out of it: set 'In Slope' and 'Out Slope', then turn up 'Saturation Min' to maximum. And let's increase 'Sat.Offset' a little as in the screenshot
In addition, I encountered the fact that 'Spill Threshold' did not work properly in Cin-HV__before-02.2024 and Cin-GG (it was throwing artifacts).
I recorded a screencast and sent it to Adam. I attached to the letter the collected information on the plugin (who made it, when, goals) and links to the official SpectraMatte documentation.
A few days later, Adam made a number of bugfixes and innovations and wrote an algorithm for the plugin similar to the SM algorithm.
I quote Adam's comment in the code: "The current implementation is most of the SpectraMatte algorithm.".
'Saturation Offset' was first removed (with a verdict 'confused' and a transparent hint to ask Jerome himself what he wanted to tell the world with this parameter), and later was resurrected again, but in a new quality
