요약·해설과 원문, 전문 번역을 서로 분리했습니다. API 이름, symbol, source path는 원문 표기를 사용합니다.
1. 요약·해설
원문의 핵심 논리와 kernel programming 관점의 보충 설명입니다. 아래의 전문 번역과는 별도로 작성했습니다.
2. 영어 원문 전체
번역 기준이 된 Linux v6.18.37 원문입니다. 줄 번호는 이 버전의 파일 좌표입니다.
원문 전체 펼치기
1
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
3
*************
4
Configuration
5
*************
7
Applications can use the :ref:`selection API <VIDIOC_G_SELECTION>` to
8
select an area in a video signal or a buffer, and to query for default
9
settings and hardware limits.
11
Video hardware can have various cropping, composing and scaling
12
limitations. It may only scale up or down, support only discrete scaling
13
factors, or have different scaling abilities in the horizontal and
14
vertical directions. Also it may not support scaling at all. At the same
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time the cropping/composing rectangles may have to be aligned, and both
16
the source and the sink may have arbitrary upper and lower size limits.
17
Therefore, as usual, drivers are expected to adjust the requested
18
parameters and return the actual values selected. An application can
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control the rounding behaviour using
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:ref:`constraint flags <v4l2-selection-flags>`.
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Configuration of video capture
24
==============================
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See figure :ref:`sel-targets-capture` for examples of the selection
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targets available for a video capture device. It is recommended to
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configure the cropping targets before to the composing targets.
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The range of coordinates of the top left corner, width and height of
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areas that can be sampled is given by the ``V4L2_SEL_TGT_CROP_BOUNDS``
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target. It is recommended for the driver developers to put the top/left
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corner at position ``(0,0)``. The rectangle's coordinates are expressed
34
in pixels.
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The top left corner, width and height of the source rectangle, that is
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the area actually sampled, is given by the ``V4L2_SEL_TGT_CROP`` target.
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It uses the same coordinate system as ``V4L2_SEL_TGT_CROP_BOUNDS``. The
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active cropping area must lie completely inside the capture boundaries.
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The driver may further adjust the requested size and/or position
41
according to hardware limitations.
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Each capture device has a default source rectangle, given by the
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``V4L2_SEL_TGT_CROP_DEFAULT`` target. This rectangle shall cover what the
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driver writer considers the complete picture. Drivers shall set the
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active crop rectangle to the default when the driver is first loaded,
47
but not later.
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The composing targets refer to a memory buffer. The limits of composing
50
coordinates are obtained using ``V4L2_SEL_TGT_COMPOSE_BOUNDS``. All
51
coordinates are expressed in pixels. The rectangle's top/left corner
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must be located at position ``(0,0)``. The width and height are equal to
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the image size set by :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`.
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The part of a buffer into which the image is inserted by the hardware is
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controlled by the ``V4L2_SEL_TGT_COMPOSE`` target. The rectangle's
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coordinates are also expressed in the same coordinate system as the
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bounds rectangle. The composing rectangle must lie completely inside
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bounds rectangle. The driver must adjust the composing rectangle to fit
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to the bounding limits. Moreover, the driver can perform other
61
adjustments according to hardware limitations. The application can
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control rounding behaviour using
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:ref:`constraint flags <v4l2-selection-flags>`.
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For capture devices the default composing rectangle is queried using
66
``V4L2_SEL_TGT_COMPOSE_DEFAULT``. It is usually equal to the bounding
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rectangle.
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The part of a buffer that is modified by the hardware is given by
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``V4L2_SEL_TGT_COMPOSE_PADDED``. It contains all pixels defined using
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``V4L2_SEL_TGT_COMPOSE`` plus all padding data modified by hardware
72
during insertion process. All pixels outside this rectangle *must not*
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be changed by the hardware. The content of pixels that lie inside the
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padded area but outside active area is undefined. The application can
75
use the padded and active rectangles to detect where the rubbish pixels
76
are located and remove them if needed.
79
Configuration of video output
80
=============================
82
For output devices targets and ioctls are used similarly to the video
83
capture case. The *composing* rectangle refers to the insertion of an
84
image into a video signal. The cropping rectangles refer to a memory
85
buffer. It is recommended to configure the composing targets before to
86
the cropping targets.
88
The cropping targets refer to the memory buffer that contains an image
89
to be inserted into a video signal or graphical screen. The limits of
90
cropping coordinates are obtained using ``V4L2_SEL_TGT_CROP_BOUNDS``.
91
All coordinates are expressed in pixels. The top/left corner is always
92
point ``(0,0)``. The width and height is equal to the image size
93
specified using :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl.
95
The top left corner, width and height of the source rectangle, that is
96
the area from which image date are processed by the hardware, is given
97
by the ``V4L2_SEL_TGT_CROP``. Its coordinates are expressed in the
98
same coordinate system as the bounds rectangle. The active cropping area
99
must lie completely inside the crop boundaries and the driver may
100
further adjust the requested size and/or position according to hardware
101
limitations.
103
For output devices the default cropping rectangle is queried using
104
``V4L2_SEL_TGT_CROP_DEFAULT``. It is usually equal to the bounding
105
rectangle.
107
The part of a video signal or graphics display where the image is
108
inserted by the hardware is controlled by ``V4L2_SEL_TGT_COMPOSE``
109
target. The rectangle's coordinates are expressed in pixels. The
110
composing rectangle must lie completely inside the bounds rectangle. The
111
driver must adjust the area to fit to the bounding limits. Moreover, the
112
driver can perform other adjustments according to hardware limitations.
114
The device has a default composing rectangle, given by the
115
``V4L2_SEL_TGT_COMPOSE_DEFAULT`` target. This rectangle shall cover what
116
the driver writer considers the complete picture. It is recommended for
117
the driver developers to put the top/left corner at position ``(0,0)``.
118
Drivers shall set the active composing rectangle to the default one when
119
the driver is first loaded.
121
The devices may introduce additional content to video signal other than
122
an image from memory buffers. It includes borders around an image.
123
However, such a padded area is driver-dependent feature not covered by
124
this document. Driver developers are encouraged to keep padded rectangle
125
equal to active one. The padded target is accessed by the
126
``V4L2_SEL_TGT_COMPOSE_PADDED`` identifier. It must contain all pixels
127
from the ``V4L2_SEL_TGT_COMPOSE`` target.
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Scaling control
131
===============
133
An application can detect if scaling is performed by comparing the width
134
and the height of rectangles obtained using ``V4L2_SEL_TGT_CROP`` and
135
``V4L2_SEL_TGT_COMPOSE`` targets. If these are not equal then the
136
scaling is applied. The application can compute the scaling ratios using
137
these values.
3. 한국어 전문 번역
영어 원문의 문단 순서와 의미를 유지한 전체 번역입니다. 코드, 함수명, symbol과 URL은 원문 표기를 유지합니다.
사각형 조정과 제약 조건
1-21선택 API는 비디오 신호나 버퍼에서 처리할 영역을 고르고, 기본값과 하드웨어 한계를 조회하는 인터페이스입니다. 장치는 확대만 또는 축소만 지원하거나, 정해진 배율만 허용하거나, 가로와 세로에서 서로 다른 능력을 제공할 수 있습니다. 배율 조정을 전혀 지원하지 않는 장치도 있습니다.
응용 프로그램이 요청한 자르기 및 합성 사각형이 정렬 조건이나 크기 한계를 벗어나면 드라이버가 지원 가능한 값으로 조정하고 실제 적용값을 되돌려 줍니다. 제약 플래그를 사용하면 이 반올림 방향을 제어할 수 있으므로, 호출자는 반환된 사각형을 최종 결과로 사용해야 합니다.
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
*************
Configuration
*************
Applications can use the :ref:`selection API <VIDIOC_G_SELECTION>` to
select an area in a video signal or a buffer, and to query for default
settings and hardware limits.
Video hardware can have various cropping, composing and scaling
limitations. It may only scale up or down, support only discrete scaling
factors, or have different scaling abilities in the horizontal and
vertical directions. Also it may not support scaling at all. At the same
time the cropping/composing rectangles may have to be aligned, and both
the source and the sink may have arbitrary upper and lower size limits.
Therefore, as usual, drivers are expected to adjust the requested
parameters and return the actual values selected. An application can
control the rounding behaviour using
:ref:`constraint flags <v4l2-selection-flags>`.
비디오 캡처 구성
22-78캡처 장치에서는 먼저 자르기 대상을 구성한 뒤 합성 대상을 구성합니다. 자르기는 입력 비디오 신호에서 실제로 샘플링할 부분을 고르고, 합성은 그 결과를 메모리 버퍼의 어느 영역에 기록할지 정합니다.
대상캡처 의미
V4L2_SEL_TGT_CROP_BOUNDS샘플링 가능한 입력 영역의 좌표 범위입니다. 왼쪽과 위쪽은 (0, 0)을 권장하며 단위는 픽셀입니다.
V4L2_SEL_TGT_CROP실제로 샘플링할 소스 사각형입니다. CROP_BOUNDS 안에 완전히 들어가야 하며 드라이버가 하드웨어 제약에 맞게 조정할 수 있습니다.
V4L2_SEL_TGT_CROP_DEFAULT완전한 화면에 해당하는 기본 자르기 영역입니다. 드라이버가 처음 적재될 때 활성 자르기의 초기값으로만 사용되고 이후 자동으로 다시 적용되지는 않습니다.
V4L2_SEL_TGT_COMPOSE_BOUNDS메모리 버퍼 전체를 나타냅니다. 왼쪽과 위쪽은 (0, 0)이고 너비와 높이는 VIDIOC_S_FMT로 설정한 이미지 크기와 같습니다.
V4L2_SEL_TGT_COMPOSE처리된 이미지를 메모리 버퍼에 삽입할 실제 영역입니다. COMPOSE_BOUNDS 안에 있어야 하며 드라이버가 경계와 배율 제약에 맞게 조정합니다.
V4L2_SEL_TGT_COMPOSE_DEFAULT일반적으로 COMPOSE_BOUNDS와 같은 기본 합성 영역입니다.
V4L2_SEL_TGT_COMPOSE_PADDED하드웨어가 수정할 수 있는 모든 픽셀 영역입니다. 활성 합성 영역과 패딩을 포함하며, 이 영역 밖의 픽셀은 바뀌지 않아야 합니다.
좌표계와 드라이버 조정 규칙을 대상별로 정리합니다.
COMPOSE_PADDED 안이면서 활성 COMPOSE 밖에 있는 픽셀 값은 정의되지 않습니다. 응용 프로그램은 이 대상을 조회해 유효 영상이 아닌 픽셀이 나타날 수 있는 위치를 식별할 수 있습니다.
Configuration of video capture
==============================
See figure :ref:`sel-targets-capture` for examples of the selection
targets available for a video capture device. It is recommended to
configure the cropping targets before to the composing targets.
The range of coordinates of the top left corner, width and height of
areas that can be sampled is given by the ``V4L2_SEL_TGT_CROP_BOUNDS``
target. It is recommended for the driver developers to put the top/left
corner at position ``(0,0)``. The rectangle's coordinates are expressed
in pixels.
The top left corner, width and height of the source rectangle, that is
the area actually sampled, is given by the ``V4L2_SEL_TGT_CROP`` target.
It uses the same coordinate system as ``V4L2_SEL_TGT_CROP_BOUNDS``. The
active cropping area must lie completely inside the capture boundaries.
The driver may further adjust the requested size and/or position
according to hardware limitations.
Each capture device has a default source rectangle, given by the
``V4L2_SEL_TGT_CROP_DEFAULT`` target. This rectangle shall cover what the
driver writer considers the complete picture. Drivers shall set the
active crop rectangle to the default when the driver is first loaded,
but not later.
The composing targets refer to a memory buffer. The limits of composing
coordinates are obtained using ``V4L2_SEL_TGT_COMPOSE_BOUNDS``. All
coordinates are expressed in pixels. The rectangle's top/left corner
must be located at position ``(0,0)``. The width and height are equal to
the image size set by :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`.
The part of a buffer into which the image is inserted by the hardware is
controlled by the ``V4L2_SEL_TGT_COMPOSE`` target. The rectangle's
coordinates are also expressed in the same coordinate system as the
bounds rectangle. The composing rectangle must lie completely inside
bounds rectangle. The driver must adjust the composing rectangle to fit
to the bounding limits. Moreover, the driver can perform other
adjustments according to hardware limitations. The application can
control rounding behaviour using
:ref:`constraint flags <v4l2-selection-flags>`.
For capture devices the default composing rectangle is queried using
``V4L2_SEL_TGT_COMPOSE_DEFAULT``. It is usually equal to the bounding
rectangle.
The part of a buffer that is modified by the hardware is given by
``V4L2_SEL_TGT_COMPOSE_PADDED``. It contains all pixels defined using
``V4L2_SEL_TGT_COMPOSE`` plus all padding data modified by hardware
during insertion process. All pixels outside this rectangle *must not*
be changed by the hardware. The content of pixels that lie inside the
padded area but outside active area is undefined. The application can
use the padded and active rectangles to detect where the rubbish pixels
are located and remove them if needed.
비디오 출력 구성
79-129출력 장치에서는 의미가 반대로 배치됩니다. 자르기는 메모리 버퍼에서 표시할 입력 부분을 고르고, 합성은 그 결과를 출력 비디오 신호나 화면의 어느 위치에 넣을지 정합니다. 구성 순서도 캡처와 반대로 합성 대상을 먼저 설정하고 자르기 대상을 나중에 설정합니다.
대상출력 의미
V4L2_SEL_TGT_CROP_BOUNDS소스 메모리 버퍼 전체입니다. 원점은 (0, 0)이고 크기는 VIDIOC_S_FMT로 설정한 이미지 크기와 같습니다.
V4L2_SEL_TGT_CROP버퍼에서 실제 처리할 데이터 영역입니다. CROP_BOUNDS 안에 있어야 하며 드라이버가 조정할 수 있습니다.
V4L2_SEL_TGT_CROP_DEFAULT일반적으로 CROP_BOUNDS와 같은 기본 자르기 영역입니다.
V4L2_SEL_TGT_COMPOSE출력 신호나 화면에 영상을 삽입할 영역입니다. COMPOSE_BOUNDS 안에 있어야 하며 하드웨어 제약에 맞게 조정될 수 있습니다.
V4L2_SEL_TGT_COMPOSE_DEFAULT완전한 화면에 해당하는 기본 합성 영역입니다. 원점은 (0, 0)을 권장하며 초기 드라이버 적재 시 설정됩니다.
V4L2_SEL_TGT_COMPOSE_PADDEDCOMPOSE의 모든 픽셀을 포함하는 하드웨어 의존 영역입니다. 드라이버는 가능하면 활성 합성 영역과 같게 제공하는 것이 권장됩니다.
출력 파이프라인에서 각 사각형이 가리키는 영역입니다.
출력 화면에는 테두리 같은 추가 내용이 존재할 수 있습니다. 따라서 COMPOSE_PADDED의 정확한 의미는 하드웨어에 따라 달라지지만, 언제나 활성 COMPOSE 사각형을 포함해야 합니다.
Configuration of video output
=============================
For output devices targets and ioctls are used similarly to the video
capture case. The *composing* rectangle refers to the insertion of an
image into a video signal. The cropping rectangles refer to a memory
buffer. It is recommended to configure the composing targets before to
the cropping targets.
The cropping targets refer to the memory buffer that contains an image
to be inserted into a video signal or graphical screen. The limits of
cropping coordinates are obtained using ``V4L2_SEL_TGT_CROP_BOUNDS``.
All coordinates are expressed in pixels. The top/left corner is always
point ``(0,0)``. The width and height is equal to the image size
specified using :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl.
The top left corner, width and height of the source rectangle, that is
the area from which image date are processed by the hardware, is given
by the ``V4L2_SEL_TGT_CROP``. Its coordinates are expressed in the
same coordinate system as the bounds rectangle. The active cropping area
must lie completely inside the crop boundaries and the driver may
further adjust the requested size and/or position according to hardware
limitations.
For output devices the default cropping rectangle is queried using
``V4L2_SEL_TGT_CROP_DEFAULT``. It is usually equal to the bounding
rectangle.
The part of a video signal or graphics display where the image is
inserted by the hardware is controlled by ``V4L2_SEL_TGT_COMPOSE``
target. The rectangle's coordinates are expressed in pixels. The
composing rectangle must lie completely inside the bounds rectangle. The
driver must adjust the area to fit to the bounding limits. Moreover, the
driver can perform other adjustments according to hardware limitations.
The device has a default composing rectangle, given by the
``V4L2_SEL_TGT_COMPOSE_DEFAULT`` target. This rectangle shall cover what
the driver writer considers the complete picture. It is recommended for
the driver developers to put the top/left corner at position ``(0,0)``.
Drivers shall set the active composing rectangle to the default one when
the driver is first loaded.
The devices may introduce additional content to video signal other than
an image from memory buffers. It includes borders around an image.
However, such a padded area is driver-dependent feature not covered by
this document. Driver developers are encouraged to keep padded rectangle
equal to active one. The padded target is accessed by the
``V4L2_SEL_TGT_COMPOSE_PADDED`` identifier. It must contain all pixels
from the ``V4L2_SEL_TGT_COMPOSE`` target.
자르기와 합성 크기로 배율 판별
130-137CROP과 COMPOSE의 너비 또는 높이가 다르면 파이프라인이 배율 조정을 수행합니다. 가로 배율은 `COMPOSE.width / CROP.width`, 세로 배율은 `COMPOSE.height / CROP.height`로 계산합니다. 두 사각형의 해당 치수가 같으면 그 축에서는 배율 조정이 없습니다.
Scaling control
===============
An application can detect if scaling is performed by comparing the width
and the height of rectangles obtained using ``V4L2_SEL_TGT_CROP`` and
``V4L2_SEL_TGT_COMPOSE`` targets. If these are not equal then the
scaling is applied. The application can compute the scaling ratios using
these values.
요약·해설
selection-api-configuration.rst:1-137캡처와 출력에서 CROP, COMPOSE 및 PADDED 대상을 설정하고 배율을 판별하는 방법을 설명합니다.