Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) .. c:namespace:: V4L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) .. _streaming-par:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) ********************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) Streaming Parameters
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) ********************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) Streaming parameters are intended to optimize the video capture process
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) as well as I/O. Presently applications can request a high quality
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) capture mode with the :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctl.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) The current video standard determines a nominal number of frames per
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) second. If less than this number of frames is to be captured or output,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) applications can request frame skipping or duplicating on the driver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) side. This is especially useful when using the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) :c:func:`read()` or :c:func:`write()`, which are
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) not augmented by timestamps or sequence counters, and to avoid
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) unnecessary data copying.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) Finally these ioctls can be used to determine the number of buffers used
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) internally by a driver in read/write mode. For implications see the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) section discussing the :c:func:`read()` function.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) To get and set the streaming parameters applications call the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) :ref:`VIDIOC_G_PARM <VIDIOC_G_PARM>` and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctl, respectively. They take
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) a pointer to a struct :c:type:`v4l2_streamparm`, which
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) contains a union holding separate parameters for input and output
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) devices.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) These ioctls are optional, drivers need not implement them. If so, they
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) return the ``EINVAL`` error code.