DVI capture format 800x600 config question

I use dvr_rdk 3.5  paltform and kernel.

when I try to get a DVI with 800x600 format, i  can't show capture vedio,and there are errs reported as follow:

VPSS_DCTRL: [Dctrl.c] :: failed to get the mode V4L2_DV_800x600

and the saved picture can't show normal,When i try to get a format with 1280x720,  the uart seng message ""

VPSS_GRPX : (0)- region(1920x1080) out of frame(1280x720).