This quote says it all (I believe it was Einar who said this in an email but I could be wrong):
"There will always be more bugs!"
What is the problem with Chroma Key (HSV)? I can't find the original discussion.
There was not much discussion, but this is the email that mentioned it and has a reference to where it was stated there was a problem, but no description of what it was:
It seems to me that CinGG has problems when dealing with the alpha
channel, so in overlays, Keys, etc.
See also here (without taking offense at the jibes he throws toward
CinGG users):
It is useful to point out bugs in CinGG -- criticism is welcome/helpful and no offense is taken.
the following problems in CinGG (comparing with CV and HV):
1- Color rendering
2- Overlays
3- Conversion between color models (Adam has made updates, but states
that Cin will always have problems with YUV(A) and recommends using
only RGBA-FLOAT)
4- Blur
A most useful feature of CinGG is that if Blur does not work the way you expect it to, you can always use one of the 6 other FFmpeg blur plugins instead with various differences: F_gblur, F_avgblur, F_boxblur, F_dblur, F_smartblur, F_yaepblur.
Same thing with Chromakey and ChromakeyHSV - you can use F_chromakey, F_chromahold, F_chromanr, F_chromashift.
P.S. On the other side, look at the number of "Yes" versus "No" for Features in: