black and white films with tmpg

[cptshamrock]

Im trying to encode a mpeg2 file and the source file is black and white. Is there a way to tell tmpg that the source is black and white and so is the output so that encoding time is sped up?

[jojo15]

If correct, tmpgenc "recognizes" it as b/w..
so i think the encoding time will be shorter right away..

[cweb]

The use of avisynth filters might not keep the picture completely b/w (you'll get some tinges of colour), so I generally use greyscale() to fix this (or prevent it from happening).