Apart of the generic format negotiation functions a special ioctl to
enumerate all image formats supported by video capture, overlay or
-output devices is available. [1]_
+output devices is available. [#f1]_
The :ref:`VIDIOC_ENUM_FMT` ioctl must be supported
by all drivers exchanging image data with applications.
If necessary driver writers should publish an example conversion
routine or library for integration into applications.
-.. [1]
+.. [#f1]
Enumerating formats an application has no a-priori knowledge of
(otherwise it could explicitly ask for them and need not enumerate)
seems useless, but there are applications serving as proxy between