mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-02 16:44:10 +08:00
82559ac027
All those files are under GFDL 1.1 or later, with no invariant sections. Tag them as such. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
157 lines
4.5 KiB
ReStructuredText
157 lines
4.5 KiB
ReStructuredText
.. Permission is granted to copy, distribute and/or modify this
|
|
.. document under the terms of the GNU Free Documentation License,
|
|
.. Version 1.1 or any later version published by the Free Software
|
|
.. Foundation, with no Invariant Sections, no Front-Cover Texts
|
|
.. and no Back-Cover Texts. A copy of the license is included at
|
|
.. Documentation/media/uapi/fdl-appendix.rst.
|
|
..
|
|
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
|
|
|
|
.. _VIDIOC_G_ENC_INDEX:
|
|
|
|
************************
|
|
ioctl VIDIOC_G_ENC_INDEX
|
|
************************
|
|
|
|
Name
|
|
====
|
|
|
|
VIDIOC_G_ENC_INDEX - Get meta data about a compressed video stream
|
|
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:function:: int ioctl( int fd, VIDIOC_G_ENC_INDEX, struct v4l2_enc_idx *argp )
|
|
:name: VIDIOC_G_ENC_INDEX
|
|
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :ref:`open() <func-open>`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`v4l2_enc_idx`.
|
|
|
|
|
|
Description
|
|
===========
|
|
|
|
The :ref:`VIDIOC_G_ENC_INDEX <VIDIOC_G_ENC_INDEX>` ioctl provides meta data about a compressed
|
|
video stream the same or another application currently reads from the
|
|
driver, which is useful for random access into the stream without
|
|
decoding it.
|
|
|
|
To read the data applications must call :ref:`VIDIOC_G_ENC_INDEX <VIDIOC_G_ENC_INDEX>` with a
|
|
pointer to a struct :c:type:`v4l2_enc_idx`. On success
|
|
the driver fills the ``entry`` array, stores the number of elements
|
|
written in the ``entries`` field, and initializes the ``entries_cap``
|
|
field.
|
|
|
|
Each element of the ``entry`` array contains meta data about one
|
|
picture. A :ref:`VIDIOC_G_ENC_INDEX <VIDIOC_G_ENC_INDEX>` call reads up to
|
|
``V4L2_ENC_IDX_ENTRIES`` entries from a driver buffer, which can hold up
|
|
to ``entries_cap`` entries. This number can be lower or higher than
|
|
``V4L2_ENC_IDX_ENTRIES``, but not zero. When the application fails to
|
|
read the meta data in time the oldest entries will be lost. When the
|
|
buffer is empty or no capturing/encoding is in progress, ``entries``
|
|
will be zero.
|
|
|
|
Currently this ioctl is only defined for MPEG-2 program streams and
|
|
video elementary streams.
|
|
|
|
|
|
.. tabularcolumns:: |p{3.8cm}|p{5.6cm}|p{8.1cm}|
|
|
|
|
.. c:type:: v4l2_enc_idx
|
|
|
|
.. flat-table:: struct v4l2_enc_idx
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 3 8
|
|
|
|
* - __u32
|
|
- ``entries``
|
|
- The number of entries the driver stored in the ``entry`` array.
|
|
* - __u32
|
|
- ``entries_cap``
|
|
- The number of entries the driver can buffer. Must be greater than
|
|
zero.
|
|
* - __u32
|
|
- ``reserved``\ [4]
|
|
- Reserved for future extensions. Drivers must set the
|
|
array to zero.
|
|
* - struct :c:type:`v4l2_enc_idx_entry`
|
|
- ``entry``\ [``V4L2_ENC_IDX_ENTRIES``]
|
|
- Meta data about a compressed video stream. Each element of the
|
|
array corresponds to one picture, sorted in ascending order by
|
|
their ``offset``.
|
|
|
|
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. c:type:: v4l2_enc_idx_entry
|
|
|
|
.. flat-table:: struct v4l2_enc_idx_entry
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u64
|
|
- ``offset``
|
|
- The offset in bytes from the beginning of the compressed video
|
|
stream to the beginning of this picture, that is a *PES packet
|
|
header* as defined in :ref:`mpeg2part1` or a *picture header* as
|
|
defined in :ref:`mpeg2part2`. When the encoder is stopped, the
|
|
driver resets the offset to zero.
|
|
* - __u64
|
|
- ``pts``
|
|
- The 33 bit *Presentation Time Stamp* of this picture as defined in
|
|
:ref:`mpeg2part1`.
|
|
* - __u32
|
|
- ``length``
|
|
- The length of this picture in bytes.
|
|
* - __u32
|
|
- ``flags``
|
|
- Flags containing the coding type of this picture, see
|
|
:ref:`enc-idx-flags`.
|
|
* - __u32
|
|
- ``reserved``\ [2]
|
|
- Reserved for future extensions. Drivers must set the array to
|
|
zero.
|
|
|
|
|
|
.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
|
|
|
|
.. _enc-idx-flags:
|
|
|
|
.. flat-table:: Index Entry Flags
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 1 4
|
|
|
|
* - ``V4L2_ENC_IDX_FRAME_I``
|
|
- 0x00
|
|
- This is an Intra-coded picture.
|
|
* - ``V4L2_ENC_IDX_FRAME_P``
|
|
- 0x01
|
|
- This is a Predictive-coded picture.
|
|
* - ``V4L2_ENC_IDX_FRAME_B``
|
|
- 0x02
|
|
- This is a Bidirectionally predictive-coded picture.
|
|
* - ``V4L2_ENC_IDX_FRAME_MASK``
|
|
- 0x0F
|
|
- *AND* the flags field with this mask to obtain the picture coding
|
|
type.
|
|
|
|
|
|
Return Value
|
|
============
|
|
|
|
On success 0 is returned, on error -1 and the ``errno`` variable is set
|
|
appropriately. The generic error codes are described at the
|
|
:ref:`Generic Error Codes <gen-errors>` chapter.
|