The width of the data port in the video_out can be selected from Vivado IDE, under CSI-2 Options TDATA width. MIPI CSI-2 RX Subsystem follows the Recommended Memory Storage section of the MIPI CSI-2 specifications to output pixels when a video format bridge is not present.
For more information on the data type packing, refer MIPI Alliance Standard for Camera Serial Interface CSI-2 Specification .