0545e9dc6d
commit d1edce71135cc6d98c0a4b5729774542b676e769 Author: sophgo-forum-service <forum_service@sophgo.com> Date: Fri Mar 15 16:07:33 2024 +0800 [fix] recommend using ssh method to clone repo. [fix] fix sensor driver repo branch name.
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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. c:namespace:: V4L
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.. _streaming-par:
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********************
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Streaming Parameters
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********************
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Streaming parameters are intended to optimize the video capture process
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as well as I/O. Presently applications can request a high quality
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capture mode with the :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctl.
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The current video standard determines a nominal number of frames per
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second. If less than this number of frames is to be captured or output,
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applications can request frame skipping or duplicating on the driver
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side. This is especially useful when using the
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:c:func:`read()` or :c:func:`write()`, which are
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not augmented by timestamps or sequence counters, and to avoid
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unnecessary data copying.
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Finally these ioctls can be used to determine the number of buffers used
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internally by a driver in read/write mode. For implications see the
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section discussing the :c:func:`read()` function.
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To get and set the streaming parameters applications call the
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:ref:`VIDIOC_G_PARM <VIDIOC_G_PARM>` and
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:ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctl, respectively. They take
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a pointer to a struct :c:type:`v4l2_streamparm`, which
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contains a union holding separate parameters for input and output
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devices.
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These ioctls are optional, drivers need not implement them. If so, they
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return the ``EINVAL`` error code.
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