media/v4l/dev-overlay.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
11 Video overlay devices have the ability to genlock (TV-)video into the
12 (VGA-)video signal of a graphics card, or to store captured images
37 capturing and overlay with a single file descriptor for compatibility
59 Video overlay devices shall support :ref:`audio input <audio>`,
62 :ref:`streaming parameter <streaming-par>` ioctls as needed. The
63 :ref:`video input <video>` and :ref:`video standard <standard>`
93 1. Chroma-keying displays the overlaid image only where pixels in the
162 ------------------
165     Size and position of the window relative to the top, left corner of
181     When chroma-keying has been negotiated with
187     :ref:`V4L2_PIX_FMT_BGR24 <V4L2-PIX-FMT-BGR32>` the value should
192     When chroma-keying has *not* been negotiated and
198     relative to the top, left corner of the frame buffer. However
202     x-y or y-x bands, or the order of rectangles, is not defined. When
217     When chroma-keying has *not* been negotiated and
227 .. code-block:: c
239 both, or despite negotiating chroma-keying, the results are undefined.
249     :ref:`framebuffer-flags`).
256    parent structure with padding bytes at the end, are not affected.
262 -----------------------
265     Coordinates of the clipping rectangle, relative to the top, left
278 ----------------
280 ``__s32 left``
281     Horizontal offset of the top, left corner of the rectangle, in
285     Vertical offset of the top, left corner of the rectangle, in pixels.
304    restrict this ability by requiring a single file descriptor, as in
310    Hence as a complexity trade-off drivers *must* support two file
311    descriptors and *may* support single fd operation.
325    BoxRec { short x1, y1, x2, y2; }`` with ``width = x2 - x1`` and
326    ``height = y2 - y1``, so one cannot pass X11 clip lists directly.