Pre-processing on the noise before the OptiX denoiser is applied will not produce better results. It is not trained with any smoothed images. It requires the original noise.
It’s also not going to work very nicely with very few samples because there is often not enough information present inside the input image.
It’s also not guaranteed that adding albedo or albedo+normal buffers will always result in a better image.
Means simply keep providing the original noisy RGB image. The more samples that has accumulated already, the better.
Then try if adding albedo or albedo+normal inputs actually improve the result.
The albedo buffer is supposed to help most with high frequency color details in textures, for example.
I’ve been using the OptiX denoiser on motion blur data which is similar and it was not that bad.
https://github.com/nvpro-samples/optix_advanced_samples/tree/master/src/optixIntroduction/optixIntro_10
A depth of field camera for that application framework can be found in this post:
https://forums.developer.nvidia.com/t/dof-lens-shader/78089/2