Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst

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System
Linux kernel
Corpus path
Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst
Extension
.rst
Size
3106 bytes
Lines
125
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _VIDIOC_G_JPEGCOMP:

******************************************
ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP
******************************************

Name
====

VIDIOC_G_JPEGCOMP - VIDIOC_S_JPEGCOMP

Synopsis
========

.. c:macro:: VIDIOC_G_JPEGCOMP

``int ioctl(int fd, VIDIOC_G_JPEGCOMP, v4l2_jpegcompression *argp)``

.. c:macro:: VIDIOC_S_JPEGCOMP

``int ioctl(int fd, VIDIOC_S_JPEGCOMP, const v4l2_jpegcompression *argp)``

Arguments
=========

``fd``
    File descriptor returned by :c:func:`open()`.

``argp``
    Pointer to struct :c:type:`v4l2_jpegcompression`.

Description
===========

These ioctls are **deprecated**. New drivers and applications should use
:ref:`JPEG class controls <jpeg-controls>` for image quality and JPEG
markers control.

[to do]

Ronald Bultje elaborates:

APP is some application-specific information. The application can set it
itself, and it'll be stored in the JPEG-encoded fields (eg; interlacing
information for in an AVI or so). COM is the same, but it's comments,
like 'encoded by me' or so.

jpeg_markers describes whether the huffman tables, quantization tables
and the restart interval information (all JPEG-specific stuff) should be
stored in the JPEG-encoded fields. These define how the JPEG field is
encoded. If you omit them, applications assume you've used standard
encoding. You usually do want to add them.

.. tabularcolumns:: |p{1.2cm}|p{3.0cm}|p{13.1cm}|

.. c:type:: v4l2_jpegcompression

.. flat-table:: struct v4l2_jpegcompression
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2

    * - int
      - ``quality``
      - Deprecated. If
	:ref:`V4L2_CID_JPEG_COMPRESSION_QUALITY <jpeg-quality-control>`
	control is exposed by a driver applications should use it instead

Annotation

Implementation Notes