Settings to Optimize for Grayscale?

[turnkit]

Are there any settings that can be made to optimize the encode for grayscale -- i.e. to tell the encoder to only encode in grayscale -- skipping all the data to save for chroma?

Seems like a lot of bandwidth could be saved when I know the material is gray-only.

[Woodstock]

Does the Grayscale checkbox on the Filters tab not work?

[JohnAStebbins]

Seems like a lot of bandwidth could be saved when I know the material is gray-only

Only if it's "dirty" gray. I.e. if it's an unclean transfer that has significant low level noise in the color components, then it'll use quite a lot more space if you don't enable the grayscale filter. But if it's clean, those color planes are duplicated and unchanging for every video frame and the encoders are very good at detecting this and optimizing compression for it.