Write 10bit or 16bit video with VideoWriter and gstreamer

Is it possible to write 16Bit images to the videowriter with gstreamer?

I have a 16Bit gray stream which I want to encode and write to a file with the VideoWriter using gstreamer. I have been using the following code whereby the input image is a uint16 numpy array:
writer = cv2.VideoWriter('appsrc ! video/x-raw, format=GRAY16_LE ! videoconvert ! ximagesink', 0, cv2.CAP_GSTREAMER, framerate, frameSize, isColor=False)

But this results in the following error:
cvWriteFrame() needs images with depth - IPL_DEPTH_8U

Is there anyway around this restriction? 10Bit would also be okay and should be supported by gstreamer.