2016-06-30 21:18:56 +08:00
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.. -*- coding: utf-8; mode: rst -*-
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2016-07-02 00:42:29 +08:00
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.. _VIDIOC_CROPCAP:
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2016-06-30 21:18:56 +08:00
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********************
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ioctl VIDIOC_CROPCAP
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********************
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2016-07-06 02:14:35 +08:00
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Name
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2016-07-05 18:58:48 +08:00
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====
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2016-06-30 21:18:56 +08:00
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2016-07-05 18:58:48 +08:00
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VIDIOC_CROPCAP - Information about the video cropping and scaling abilities
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2016-06-30 21:18:56 +08:00
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2016-07-06 02:14:35 +08:00
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Synopsis
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2016-06-30 21:18:56 +08:00
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========
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2016-08-19 23:00:43 +08:00
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.. c:function:: int ioctl( int fd, int request, struct v4l2_cropcap *argp )
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2016-06-30 21:18:56 +08:00
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2016-07-05 18:58:48 +08:00
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2016-07-06 02:14:35 +08:00
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Arguments
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2016-06-30 21:18:56 +08:00
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``request``
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VIDIOC_CROPCAP
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``argp``
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2016-07-06 02:14:35 +08:00
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Description
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2016-06-30 21:18:56 +08:00
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===========
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Applications use this function to query the cropping limits, the pixel
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aspect of images and to calculate scale factors. They set the ``type``
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field of a v4l2_cropcap structure to the respective buffer (stream)
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2016-07-02 01:33:56 +08:00
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type and call the :ref:`VIDIOC_CROPCAP` ioctl with a pointer to this
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structure. Drivers fill the rest of the structure. The results are
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constant except when switching the video standard. Remember this switch
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can occur implicit when switching the video input or output.
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Do not use the multiplanar buffer types. Use
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``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of
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``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use
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``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of
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``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``.
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This ioctl must be implemented for video capture or output devices that
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support cropping and/or scaling and/or have non-square pixels, and for
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overlay devices.
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.. _v4l2-cropcap:
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[media] docs-rst: add tabularcolumns to all tables
LaTeX doesn't handle too well auto-width on tables, and ReST
markup requires an special tag to give it the needed hints.
As we're using A4 paper, we have 17cm of useful spaces. As
most media tables have widths, let's use it to generate the
needed via the following perl script:
my ($line_size, $table_header, $has_cols) = (17.5, 0, 0);
my $out;
my $header = "";
my @widths = ();
sub round { $_[0] > 0 ? int($_[0] + .5) : -int(-$_[0] + .5) }
while (<>) {
if (!$table_header) {
$has_cols = 1 if (m/..\s+tabularcolumns::/);
if (m/..\s+flat-table::/) {
$table_header = 1;
$header = $_;
next;
}
$out .= $_;
next;
}
$header .= $_;
@widths = split(/ /, $1) if (m/:widths:\s+(.*)/);
if (m/^\n$/) {
if (!$has_cols && @widths) {
my ($tot, $t, $i) = (0, 0, 0);
foreach my $v(@widths) { $tot += $v; };
$out .= ".. tabularcolumns:: |";
for ($i = 0; $i < scalar @widths - 1; $i++) {
my $v = $widths[$i];
my $w = round(10 * ($v * $line_size) / $tot) / 10;
$out .= sprintf "p{%.1fcm}|", $w;
$t += $w;
}
my $w = $line_size - $t;
$out .= sprintf "p{%.1fcm}|\n\n", $w;
}
$out .= $header;
$table_header = 0;
$has_cols = 0;
$header = "";
@widths = ();
}
}
print $out;
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
2016-08-17 19:14:19 +08:00
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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2016-06-30 21:18:56 +08:00
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.. flat-table:: struct v4l2_cropcap
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2
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- .. row 1
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- __u32
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- ``type``
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- Type of the data stream, set by the application. Only these types
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are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
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``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and
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``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :ref:`v4l2-buf-type`.
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- .. row 2
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- struct :ref:`v4l2_rect <v4l2-rect-crop>`
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- ``bounds``
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- Defines the window within capturing or output is possible, this
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may exclude for example the horizontal and vertical blanking
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areas. The cropping rectangle cannot exceed these limits. Width
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and height are defined in pixels, the driver writer is free to
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choose origin and units of the coordinate system in the analog
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domain.
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- .. row 3
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- struct :ref:`v4l2_rect <v4l2-rect-crop>`
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- ``defrect``
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- Default cropping rectangle, it shall cover the "whole picture".
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Assuming pixel aspect 1/1 this could be for example a 640 × 480
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rectangle for NTSC, a 768 × 576 rectangle for PAL and SECAM
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centered over the active picture area. The same co-ordinate system
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as for ``bounds`` is used.
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- .. row 4
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- struct :ref:`v4l2_fract <v4l2-fract>`
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- ``pixelaspect``
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- This is the pixel aspect (y / x) when no scaling is applied, the
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ratio of the actual sampling frequency and the frequency required
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to get square pixels.
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When cropping coordinates refer to square pixels, the driver sets
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``pixelaspect`` to 1/1. Other common values are 54/59 for PAL and
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SECAM, 11/10 for NTSC sampled according to [:ref:`itu601`].
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.. _v4l2-rect-crop:
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[media] docs-rst: add tabularcolumns to all tables
LaTeX doesn't handle too well auto-width on tables, and ReST
markup requires an special tag to give it the needed hints.
As we're using A4 paper, we have 17cm of useful spaces. As
most media tables have widths, let's use it to generate the
needed via the following perl script:
my ($line_size, $table_header, $has_cols) = (17.5, 0, 0);
my $out;
my $header = "";
my @widths = ();
sub round { $_[0] > 0 ? int($_[0] + .5) : -int(-$_[0] + .5) }
while (<>) {
if (!$table_header) {
$has_cols = 1 if (m/..\s+tabularcolumns::/);
if (m/..\s+flat-table::/) {
$table_header = 1;
$header = $_;
next;
}
$out .= $_;
next;
}
$header .= $_;
@widths = split(/ /, $1) if (m/:widths:\s+(.*)/);
if (m/^\n$/) {
if (!$has_cols && @widths) {
my ($tot, $t, $i) = (0, 0, 0);
foreach my $v(@widths) { $tot += $v; };
$out .= ".. tabularcolumns:: |";
for ($i = 0; $i < scalar @widths - 1; $i++) {
my $v = $widths[$i];
my $w = round(10 * ($v * $line_size) / $tot) / 10;
$out .= sprintf "p{%.1fcm}|", $w;
$t += $w;
}
my $w = $line_size - $t;
$out .= sprintf "p{%.1fcm}|\n\n", $w;
}
$out .= $header;
$table_header = 0;
$has_cols = 0;
$header = "";
@widths = ();
}
}
print $out;
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
2016-08-17 19:14:19 +08:00
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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2016-06-30 21:18:56 +08:00
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.. flat-table:: struct v4l2_rect
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2
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- .. row 1
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- __s32
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- ``left``
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- Horizontal offset of the top, left corner of the rectangle, in
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pixels.
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- .. row 2
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- __s32
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- ``top``
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- Vertical offset of the top, left corner of the rectangle, in
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pixels.
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2016-06-30 21:18:56 +08:00
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- .. row 3
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- __u32
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- ``width``
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- Width of the rectangle, in pixels.
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- .. row 4
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- __u32
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- ``height``
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- Height of the rectangle, in pixels.
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2016-07-06 02:14:35 +08:00
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The struct :ref:`v4l2_cropcap <v4l2-cropcap>` ``type`` is
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invalid.
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