I don't understand your statement that this change to the margin size (if odd) is necessary to ensure accurate per-channel black level calculation.
Surely if you apply the per channel calculation to the "Image" area (i.e. NOT including the frame) using the CFA pattern (filter) fr that area, then the calculation will be correct.
I can understand that if you used the CFA for the image area to calculate a per channel black level against the entire sensor area that might not work right, but I am sure you wouldn't do that.
So please explain why you believe my reasoning is incorrect.
I don't understand your statement that this change to the margin size (if odd) is necessary to ensure accurate per-channel black level calculation.
Surely if you apply the per channel calculation to the "Image" area (i.e. NOT including the frame) using the CFA pattern (filter) fr that area, then the calculation will be correct.
I can understand that if you used the CFA for the image area to calculate a per channel black level against the entire sensor area that might not work right, but I am sure you wouldn't do that.
So please explain why you believe my reasoning is incorrect.