Linux/DM8107: Encode H264 in grayscale mode

Tool/software: Linux

Hi,

I try to encode a H264 color video 1920x1080p25 in grayscale.
I use DVRRDK link_api to develop my application.
I develop a video transcoding application.
I use encLink, decLink, deiLink and swmsLink to do this.

I don't found what parameters can allow me to force the color conversion before the encLink.
I have found on the H264_Encoder_HDVICP2 the parameters XDM_ChromatFormat with the value XDM_GRAY, but i don't know how use it ?

I think that the vpss module is able to do the color conversion between YUV420 et GRAY.
Thanks