v4l2src:
-------

Video input devices may have more than one input, and V4L2 allow to select which one must be used with VIDIOC_S_INPUT ioctl.

Gstreamer doesn't allow to select which input must be used, and users have to make the ioctl by their own (or calling v4l2-ctl --set-input=X)

It would be good that GStreamer allows to select the input as a property, as a cap, or in any other convenient way. For example:
v4l2src device=/dev/video0 input=2 ! autovideosink


v4l2sink:
--------

I haven't used video output devices so I don't know how they work, but I guess it is more or less the same, but with outputs instead of inputs. I see that VIDIOC_S_OUTPUT ioctl exists in V4L2.


related bug: https://bugzilla.gnome.org/show_bug.cgi?id=796908