Em 29-09-2011 11:22, Tomasz Stanislawski escreveu: > This patch adds a documentation for VIDIOC_{G/S}_SELECTION ioctl. Moreover, the > patch adds the description of modeling of composing, cropping and scaling > features in V4L2. Finally, some examples are presented. Doesn't work: $ make htmldocs GEN /home/v4l/v4l/patchwork/Documentation/DocBook//v4l2.xml GEN /home/v4l/v4l/patchwork/Documentation/DocBook//media-entities.tmpl GEN /home/v4l/v4l/patchwork/Documentation/DocBook//media-indices.tmpl GEN /home/v4l/v4l/patchwork/Documentation/DocBook//videodev2.h.xml GEN /home/v4l/v4l/patchwork/Documentation/DocBook//audio.h.xml GEN /home/v4l/v4l/patchwork/Documentation/DocBook//ca.h.xml GEN /home/v4l/v4l/patchwork/Documentation/DocBook//frontend.h.xml GEN /home/v4l/v4l/patchwork/Documentation/DocBook//net.h.xml GEN /home/v4l/v4l/patchwork/Documentation/DocBook//dmx.h.xml GEN /home/v4l/v4l/patchwork/Documentation/DocBook//video.h.xml DOCPROC Documentation/DocBook/media_api.xml HTML Documentation/DocBook/media_api.html /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:232: parser error : Entity 'v4l2-selection' not defined <structname> &v4l2-selection; </structname> provides a lot of place for future ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:250: parser error : Entity 'v4l2-selection' not defined &v4l2-selection; sel = { ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:254: parser error : Entity 'VIDIOC-G-SELECTION' not defined ret = ioctl(fd, &VIDIOC-G-SELECTION;, &sel); ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:258: parser error : Entity 'VIDIOC-S-SELECTION' not defined ret = ioctl(fd, &VIDIOC-S-SELECTION;, &sel); ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:271: parser error : Entity 'v4l2-selection' not defined &v4l2-selection; sel = { ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:277: parser error : Entity 'VIDIOC-G-SELECTION' not defined ret = ioctl(fd, &VIDIOC-G-SELECTION;, &sel); ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:288: parser error : Entity 'VIDIOC-S-SELECTION' not defined ret = ioctl(fd, &VIDIOC-S-SELECTION;, &sel); ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:301: parser error : Entity 'v4l2-selection' not defined &v4l2-selection; compose = { ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:305: parser error : Entity 'v4l2-selection' not defined &v4l2-selection; crop = { ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:311: parser error : Entity 'VIDIOC-G-SELECTION' not defined ret = ioctl(fd, &VIDIOC-G-SELECTION;, &compose); ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:314: parser error : Entity 'VIDIOC-G-SELECTION' not defined ret = ioctl(fd, &VIDIOC-G-SELECTION;, &crop); ^ /home/v4l/v4l/patchwork/Documentation/DocBook/selection-api.xml:328: parser error : chunk is not well balanced ^ /home/v4l/v4l/patchwork/Documentation/DocBook/common.xml:1171: parser error : Failure to process entity sub-selection-api &sub-selection-api; ^ /home/v4l/v4l/patchwork/Documentation/DocBook/common.xml:1171: parser error : Entity 'sub-selection-api' not defined &sub-selection-api; ^ /home/v4l/v4l/patchwork/Documentation/DocBook/v4l2.xml:423: parser error : Failure to process entity sub-common &sub-common; ^ /home/v4l/v4l/patchwork/Documentation/DocBook/v4l2.xml:423: parser error : Entity 'sub-common' not defined &sub-common; ^ > > Signed-off-by: Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx> > Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > --- > Documentation/DocBook/media/v4l/common.xml | 2 + > Documentation/DocBook/media/v4l/compat.xml | 9 + > Documentation/DocBook/media/v4l/selection-api.xml | 327 ++++++++++++++++++++ > Documentation/DocBook/media/v4l/v4l2.xml | 1 + > .../DocBook/media/v4l/vidioc-g-selection.xml | 303 ++++++++++++++++++ > 5 files changed, 642 insertions(+), 0 deletions(-) > create mode 100644 Documentation/DocBook/media/v4l/selection-api.xml > create mode 100644 Documentation/DocBook/media/v4l/vidioc-g-selection.xml > > diff --git a/Documentation/DocBook/media/v4l/common.xml b/Documentation/DocBook/media/v4l/common.xml > index a86f7a0..9c8db86 100644 > --- a/Documentation/DocBook/media/v4l/common.xml > +++ b/Documentation/DocBook/media/v4l/common.xml > @@ -1168,6 +1168,8 @@ dheight = format.fmt.pix.height; > </section> > </section> > > + &sub-selection-api; > + > <section id="streaming-par"> > <title>Streaming Parameters</title> > > diff --git a/Documentation/DocBook/media/v4l/compat.xml b/Documentation/DocBook/media/v4l/compat.xml > index 91410b6..7c430ca 100644 > --- a/Documentation/DocBook/media/v4l/compat.xml > +++ b/Documentation/DocBook/media/v4l/compat.xml > @@ -2376,6 +2376,12 @@ that used it. It was originally scheduled for removal in 2.6.35. > <listitem> > <para>V4L2_CTRL_FLAG_VOLATILE was added to signal volatile controls to userspace.</para> > </listitem> > + <listitem> > + <para>Add selection API for extended control over cropping and > +composing. Does not affect the compatibility of current drivers and > +applications. See <link linkend="selection-api"> selection API </link> for > +details.</para> > + </listitem> > </orderedlist> > </section> > > @@ -2486,6 +2492,9 @@ ioctls.</para> > <listitem> > <para>Flash API. <xref linkend="flash-controls" /></para> > </listitem> > + <listitem> > + <para>Selection API. <xref linkend="selection-api" /></para> > + </listitem> > </itemizedlist> > </section> > > diff --git a/Documentation/DocBook/media/v4l/selection-api.xml b/Documentation/DocBook/media/v4l/selection-api.xml > new file mode 100644 > index 0000000..3b6dfe0 > --- /dev/null > +++ b/Documentation/DocBook/media/v4l/selection-api.xml > @@ -0,0 +1,327 @@ > +<section id="selection-api"> > + > + <title>Experimental API for cropping, composing and scaling</title> > + > + <note> > + <title>Experimental</title> > + > + <para>This is an <link linkend="experimental">experimental</link> > +interface and may change in the future.</para> > + </note> > + > + <section> > + <title>Introduction</title> > + > +<para>Some video capture devices can sample a subsection of a picture and > +shrink or enlarge it to an image of arbitrary size. Next, the devices can > +insert the image into larger one. Some video output devices can crop part of an > +input image, scale it up or down and insert it at an arbitrary scan line and > +horizontal offset into a video signal. We call these abilities cropping, > +scaling and composing.</para> > + > +<para>On a video <emphasis>capture</emphasis> device the source is a video > +signal, and the cropping target determine the area actually sampled. The sink > +is an image stored in a memory buffer. The composing area specifies which part > +of the buffer is actually written to by the hardware. </para> > + > +<para>On a video <emphasis>output</emphasis> device the source is an image in a > +memory buffer, and the cropping target is a part of an image to be shown on a > +display. The sink is the display or the graphics screen. The application may > +select the part of display where the image should be displayed. The size and > +position of such a window is controlled by the compose target.</para> > + > +<para>Rectangles for all cropping and composing targets are defined even if the > +device does supports neither cropping nor composing. Their size and position > +will be fixed in such a case. If the device does not support scaling then the > +cropping and composing rectangles have the same size.</para> > + > + </section> > + > + <section> > + <title>Selection targets</title> > + > + <figure id="sel-targets-capture"> > + <title>Cropping and composing targets</title> > + <mediaobject> > + <imageobject> > + <imagedata fileref="selection.png" format="PNG" /> > + </imageobject> > + <textobject> > + <phrase>Targets used by a cropping, composing and scaling > + process</phrase> > + </textobject> > + </mediaobject> > + </figure> > + </section> > + > + <section> > + > + <title>Configuration</title> > + > +<para>Applications can use the <link linkend="vidioc-g-selection">selection > +API</link> to select an area in a video signal or a buffer, and to query for > +default settings and hardware limits.</para> > + > +<para>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 <link > +linkend="v4l2-sel-flags"> constraint flags </link>.</para> > + > + <section> > + > + <title>Configuration of video capture</title> > + > +<para>See figure <xref linkend="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.</para> > + > +<para>The range of coordinates of the top left corner, width and height of > +areas that can be sampled is given by the <constant> V4L2_SEL_CROP_BOUNDS > +</constant> target. It is recommended for the driver developers to put the > +top/left corner at position <constant> (0,0) </constant>. The rectangle's > +coordinates are expressed in driver dependant units, although the coordinate > +system guarantees that if sizes of the active cropping and the active composing > +rectangles are equal then no scaling is performed. </para> > + > +<para>The top left corner, width and height of the source rectangle, that is > +the area actually sampled, is given by the <constant> V4L2_SEL_CROP_ACTIVE > +</constant> target. It uses the same coordinate system as <constant> > +V4L2_SEL_CROP_BOUNDS </constant>. 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.</para> > + > +<para>Each capture device has a default source rectangle, given by the > +<constant> V4L2_SEL_CROP_DEFAULT </constant> target. This rectangle shall over > +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.</para> > + > +<para>The composing targets refer to a memory buffer. The limits of composing > +coordinates are obtained using <constant> V4L2_SEL_COMPOSE_BOUNDS </constant>. > +All coordinates are expressed in natural unit for given formats. Pixels are > +highly recommended. The rectangle's top/left corner must be located at > +position <constant> (0,0) </constant>. The width and height are equal to the > +image size set by <constant> VIDIOC_S_FMT </constant>.</para> > + > +<para>The part of a buffer into which the image is inserted by the hardware is > +controlled by the <constant> V4L2_SEL_COMPOSE_ACTIVE </constant> 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 > +<link linkend="v4l2-sel-flags"> constraint flags </link>.</para> > + > +<para>For capture devices the default composing rectangle is queried using > +<constant> V4L2_SEL_COMPOSE_DEFAULT </constant>. It is usually equal to the > +bounding rectangle.</para> > + > +<para>The part of a buffer that is modified by the hardware is given by > +<constant> V4L2_SEL_COMPOSE_PADDED </constant>. It contains all pixels defined > +using <constant> V4L2_SEL_COMPOSE_ACTIVE </constant> plus all padding data > +modified by hardware during insertion process. All pixels outside this rectangle > +<emphasis>must not</emphasis> 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.</para> > + > + </section> > + > + <section> > + > + <title>Configuration of video output</title> > + > +<para>For output devices targets and ioctls are used similarly to the video > +capture case. The <emphasis> composing </emphasis> 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.</para> > + > +<para>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 <constant> V4L2_SEL_CROP_BOUNDS </constant>. All > +coordinates are expressed in natural units for a given format. Pixels are > +highly recommended. The top/left corner is always point <constant> (0,0) > +</constant>. The width and height is equal to the image size specified using > +<constant> VIDIOC_S_FMT </constant> ioctl.</para> > + > +<para>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 > +<constant> V4L2_SEL_CROP_ACTIVE </constant>. Its coordinates are expressed in > +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.</para> > + > +<para>For output devices the default cropping rectangle is queried using > +<constant> V4L2_SEL_CROP_DEFAULT </constant>. It is usually equal to the > +bounding rectangle.</para> > + > +<para>The part of a video signal or graphics display where the image is > +inserted by the hardware is controlled by <constant> V4L2_SEL_COMPOSE_ACTIVE > +</constant> target. The rectangle's coordinates are expressed in driver > +dependant units. The only exception are digital outputs where the units are > +pixels. For other types of devices, the coordinate system guarantees that if > +sizes of the active cropping and the active composing rectangles are equal then > +no scaling is performed. 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. </para> > + > +<para>The device has a default composing rectangle, given by the <constant> > +V4L2_SEL_COMPOSE_DEFAULT </constant> 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 <constant> (0,0) > +</constant>. Drivers shall set the active composing rectangle to the default > +one when the driver is first loaded.</para> > + > +<para>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 <constant> V4L2_SEL_COMPOSE_PADDED > +</constant> identifier. It must contain all pixels from the <constant> > +V4L2_SEL_COMPOSE_ACTIVE </constant> target.</para> > + > + </section> > + > + <section> > + > + <title>Scaling control.</title> > + > +<para>An application can detect if scaling is performed by comparing the width > +and the height of rectangles obtained using <constant> V4L2_SEL_CROP_ACTIVE > +</constant> and <constant> V4L2_SEL_COMPOSE_ACTIVE </constant> targets. If > +these are not equal then the scaling is applied. The application can compute > +the scaling ratios using these values.</para> > + > + </section> > + > + </section> > + > + <section> > + > + <title>Comparison with old cropping API.</title> > + > +<para>The selection API was introduced to cope with deficiencies of previous > +<link linkend="crop"> API </link>, that was designed to control simple capture > +devices. Later the cropping API was adopted by video output drivers. The ioctls > +are used to select a part of the display were the video signal is inserted. It > +should be considered as an API abuse because the described operation is > +actually the composing. The selection API makes a clear distinction between > +composing and cropping operations by setting the appropriate targets. The V4L2 > +API lacks any support for composing to and cropping from an image inside a > +memory buffer. The application could configure a capture device to fill only a > +part of an image by abusing V4L2 API. Cropping a smaller image from a larger > +one is achieved by setting the field <structfield> > +&v4l2-pix-format;::bytesperline </structfield>. Introducing an image offsets > +could be done by modifying field <structfield> &v4l2-buffer;::m:userptr > +</structfield> before calling <constant> VIDIOC_QBUF </constant>. Those > +operations should be avoided because they are not portable (endianness), and do > +not work for macroblock and Bayer formats and mmap buffers. The selection API > +deals with configuration of buffer cropping/composing in a clear, intuitive and > +portable way. Next, with the selection API the concepts of the padded target > +and constraints flags are introduced. Finally, <structname> &v4l2-crop; > +</structname> and <structname> &v4l2-cropcap; </structname> have no reserved > +fields. Therefore there is no way to extend their functionality. The new > +<structname> &v4l2-selection; </structname> provides a lot of place for future > +extensions. Driver developers are encouraged to implement only selection API. > +The former cropping API would be simulated using the new one. </para> > + > + </section> > + > + <section> > + <title>Examples</title> > + <example> > + <title>Resetting the cropping parameters</title> > + > + <para>(A video capture device is assumed; change <constant> > +V4L2_BUF_TYPE_VIDEO_CAPTURE </constant> for other devices; change target to > +<constant> V4L2_SEL_COMPOSE_* </constant> family to configure composing > +area)</para> > + > + <programlisting> > + > + &v4l2-selection; sel = { > + .type = V4L2_BUF_TYPE_VIDEO_CAPTURE, > + .target = V4L2_SEL_CROP_DEFAULT, > + }; > + ret = ioctl(fd, &VIDIOC-G-SELECTION;, &sel); > + if (ret) > + exit(-1); > + sel.target = V4L2_SEL_CROP_ACTIVE; > + ret = ioctl(fd, &VIDIOC-S-SELECTION;, &sel); > + if (ret) > + exit(-1); > + > + </programlisting> > + </example> > + > + <example> > + <title>Simple downscaling</title> > + <para>Setting a composing area on output of size of <emphasis> at most > +</emphasis> half of limit placed at a center of a display.</para> > + <programlisting> > + > + &v4l2-selection; sel = { > + .type = V4L2_BUF_TYPE_VIDEO_OUTPUT, > + .target = V4L2_SEL_COMPOSE_BOUNDS, > + }; > + struct v4l2_rect r; > + > + ret = ioctl(fd, &VIDIOC-G-SELECTION;, &sel); > + if (ret) > + exit(-1); > + /* setting smaller compose rectangle */ > + r.width = sel.r.width / 2; > + r.height = sel.r.height / 2; > + r.left = sel.r.width / 4; > + r.top = sel.r.height / 4; > + sel.r = r; > + sel.target = V4L2_SEL_COMPOSE_ACTIVE; > + sel.flags = V4L2_SEL_SIZE_LE; > + ret = ioctl(fd, &VIDIOC-S-SELECTION;, &sel); > + if (ret) > + exit(-1); > + > + </programlisting> > + </example> > + > + <example> > + <title>Querying for scaling factors</title> > + <para>A video output device is assumed; change <constant> > +V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> for other devices</para> > + <programlisting> > + > + &v4l2-selection; compose = { > + .type = V4L2_BUF_TYPE_VIDEO_OUTPUT, > + .target = V4L2_SEL_COMPOSE_ACTIVE, > + }; > + &v4l2-selection; crop = { > + .type = V4L2_BUF_TYPE_VIDEO_OUTPUT, > + .target = V4L2_SEL_CROP_ACTIVE, > + }; > + double hscale, vscale; > + > + ret = ioctl(fd, &VIDIOC-G-SELECTION;, &compose); > + if (ret) > + exit(-1); > + ret = ioctl(fd, &VIDIOC-G-SELECTION;, &crop); > + if (ret) > + exit(-1); > + > + /* computing scaling factors */ > + hscale = (double)compose.r.width / crop.r.width; > + vscale = (double)compose.r.height / crop.r.height; > + > + </programlisting> > + </example> > + > + </section> > + > +</section> > diff --git a/Documentation/DocBook/media/v4l/v4l2.xml b/Documentation/DocBook/media/v4l/v4l2.xml > index 40132c2..7f1b710 100644 > --- a/Documentation/DocBook/media/v4l/v4l2.xml > +++ b/Documentation/DocBook/media/v4l/v4l2.xml > @@ -500,6 +500,7 @@ and discussions on the V4L mailing list.</revremark> > &sub-g-output; > &sub-g-parm; > &sub-g-priority; > + &sub-g-selection; > &sub-g-sliced-vbi-cap; > &sub-g-std; > &sub-g-tuner; > diff --git a/Documentation/DocBook/media/v4l/vidioc-g-selection.xml b/Documentation/DocBook/media/v4l/vidioc-g-selection.xml > new file mode 100644 > index 0000000..e0ef3e7 > --- /dev/null > +++ b/Documentation/DocBook/media/v4l/vidioc-g-selection.xml > @@ -0,0 +1,303 @@ > +<refentry id="vidioc-g-selection"> > + > + <refmeta> > + <refentrytitle>ioctl VIDIOC_G_SELECTION, VIDIOC_S_SELECTION</refentrytitle> > + &manvol; > + </refmeta> > + > + <refnamediv> > + <refname>VIDIOC_G_SELECTION</refname> > + <refname>VIDIOC_S_SELECTION</refname> > + <refpurpose>Get or set one of the selection rectangles</refpurpose> > + </refnamediv> > + > + <refsynopsisdiv> > + <funcsynopsis> > + <funcprototype> > + <funcdef>int <function>ioctl</function></funcdef> > + <paramdef>int <parameter>fd</parameter></paramdef> > + <paramdef>int <parameter>request</parameter></paramdef> > + <paramdef>struct v4l2_selection *<parameter>argp</parameter></paramdef> > + </funcprototype> > + </funcsynopsis> > + </refsynopsisdiv> > + > + <refsect1> > + <title>Arguments</title> > + > + <variablelist> > + <varlistentry> > + <term><parameter>fd</parameter></term> > + <listitem> > + <para>&fd;</para> > + </listitem> > + </varlistentry> > + <varlistentry> > + <term><parameter>request</parameter></term> > + <listitem> > + <para>VIDIOC_G_SELECTION, VIDIOC_S_SELECTION</para> > + </listitem> > + </varlistentry> > + <varlistentry> > + <term><parameter>argp</parameter></term> > + <listitem> > + <para></para> > + </listitem> > + </varlistentry> > + </variablelist> > + </refsect1> > + > + <refsect1> > + <title>Description</title> > + > + <note> > + <title>Experimental</title> > + <para>This is an <link linkend="experimental"> experimental </link> > + interface and may change in the future.</para> > + </note> > + > + <para>The ioctls are used to query and configure selection rectangles.</para> > + > +<para> To query the cropping (composing) rectangle set <structfield> > +&v4l2-selection;::type </structfield> to the respective buffer type. Do not > +use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE > +</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE > +</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of > +<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is > +setting <structfield> &v4l2-selection;::target </structfield> to value > +<constant> V4L2_SEL_CROP_ACTIVE </constant> (<constant> V4L2_SEL_COMPOSE_ACTIVE > +</constant>). Please refer to table <xref linkend="v4l2-sel-target" /> or > +<xref linkend="selection-api" /> for additional targets. Fields <structfield> > +&v4l2-selection;::flags </structfield> and <structfield> > +&v4l2-selection;::reserved </structfield> are ignored and they must be filled > +with zeros. The driver fills the rest of the structure or returns &EINVAL; if > +incorrect buffer type or target was used. If cropping (composing) is not > +supported then the active rectangle is not mutable and it is always equal to > +the bounds rectangle. Finally, structure <structfield> &v4l2-selection;::r > +</structfield> is filled with the current cropping (composing) coordinates. The > +coordinates are expressed in driver-dependent units. The only exception are > +rectangles for images in raw formats, whose coordinates are always expressed in > +pixels. </para> > + > +<para> To change the cropping (composing) rectangle set <structfield> > +&v4l2-selection;::type </structfield> to the respective buffer type. Do not > +use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE > +</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE > +</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of > +<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is > +setting <structfield> &v4l2-selection;::target </structfield> to value > +<constant> V4L2_SEL_CROP_ACTIVE </constant> (<constant> V4L2_SEL_COMPOSE_ACTIVE > +</constant>). Please refer to table <xref linkend="v4l2-sel-target" /> or <xref > +linkend="selection-api" /> for additional targets. Set desired active area > +into the field <structfield> &v4l2-selection;::r </structfield>. Field > +<structfield> &v4l2-selection;::reserved </structfield> is ignored and must be > +filled with zeros. The driver may adjust the rectangle coordinates. An > +application may introduce constraints to control rounding behaviour. Set the > +field <structfield> &v4l2-selection;::flags </structfield> to one of values: > + > +<itemizedlist> > + <listitem> > +<para><constant>0</constant> - The driver can adjust the rectangle size freely > +and shall choose a crop/compose rectangle as close as possible to the requested > +one.</para> > + </listitem> > + <listitem> > +<para><constant>V4L2_SEL_SIZE_GE</constant> - The driver is not allowed to > +shrink the rectangle. The original rectangle must lay inside the adjusted > +one.</para> > + </listitem> > + <listitem> > +<para><constant>V4L2_SEL_SIZE_LE</constant> - The driver is not allowed to > +enlarge the rectangle. The adjusted rectangle must lay inside the original > +one.</para> > + </listitem> > + <listitem> > +<para><constant>V4L2_SEL_SIZE_GE | V4L2_SEL_SIZE_LE</constant> - The driver > +must choose the size exactly the same as in the requested rectangle.</para> > + </listitem> > +</itemizedlist> > + > +Please refer to <xref linkend="sel-const-adjust" />. > + > +</para> > + > +<para> The driver may have to adjusts the requested dimensions against hardware > +limits and other parts as the pipeline, i.e. the bounds given by the > +capture/output window or TV display. The closest possible values of horizontal > +and vertical offset and sizes are chosen according to following priority: > + > +<orderedlist> > + <listitem> > + <para>Satisfy constraints from <structfield>&v4l2-selection;::flags</structfield>.</para> > + </listitem> > + <listitem> > + <para>Adjust width, height, left, and top to hardware limits and alignments.</para> > + </listitem> > + <listitem> > + <para>Keep center of adjusted rectangle as close as possible to the original one.</para> > + </listitem> > + <listitem> > + <para>Keep width and height as close as possible to original ones.</para> > + </listitem> > + <listitem> > + <para>Keep horizontal and vertical offset as close as possible to original ones.</para> > + </listitem> > +</orderedlist> > + > +On success the field <structfield> &v4l2-selection;::r </structfield> contains > +the adjusted rectangle. When the parameters are unsuitable the application may > +modify the cropping (composing) or image parameters and repeat the cycle until > +satisfactory parameters have been negotiated. If constraints flags have to be > +violated at then ERANGE is returned. The error indicates that <emphasis> there > +exist no rectangle </emphasis> that satisfies the constraints.</para> > + > + </refsect1> > + > + <refsect1> > + <table frame="none" pgwide="1" id="v4l2-sel-target"> > + <title>Selection targets.</title> > + <tgroup cols="3"> > + &cs-def; > + <tbody valign="top"> > + <row> > + <entry><constant>V4L2_SEL_CROP_ACTIVE</constant></entry> > + <entry>0</entry> > + <entry>area that is currently cropped by hardware</entry> > + </row> > + <row> > + <entry><constant>V4L2_SEL_CROP_DEFAULT</constant></entry> > + <entry>1</entry> > + <entry>suggested cropping rectangle that covers the "whole picture"</entry> > + </row> > + <row> > + <entry><constant>V4L2_SEL_CROP_BOUNDS</constant></entry> > + <entry>2</entry> > + <entry>limits for the cropping rectangle</entry> > + </row> > + <row> > + <entry><constant>V4L2_SEL_COMPOSE_ACTIVE</constant></entry> > + <entry>256</entry> > + <entry>area to which data are composed by hardware</entry> > + </row> > + <row> > + <entry><constant>V4L2_SEL_COMPOSE_DEFAULT</constant></entry> > + <entry>257</entry> > + <entry>suggested composing rectangle that covers the "whole picture"</entry> > + </row> > + <row> > + <entry><constant>V4L2_SEL_COMPOSE_BOUNDS</constant></entry> > + <entry>258</entry> > + <entry>limits for the composing rectangle</entry> > + </row> > + <row> > + <entry><constant>V4L2_SEL_COMPOSE_PADDED</constant></entry> > + <entry>259</entry> > + <entry>the active area and all padding pixels that are inserted or modified by the hardware</entry> > + </row> > + </tbody> > + </tgroup> > + </table> > + </refsect1> > + > + <refsect1> > + <table frame="none" pgwide="1" id="v4l2-sel-flags"> > + <title>Selection constraint flags</title> > + <tgroup cols="3"> > + &cs-def; > + <tbody valign="top"> > + <row> > + <entry><constant>V4L2_SEL_SIZE_GE</constant></entry> > + <entry>0x00000001</entry> > + <entry>indicate that adjusted rectangle must contain a rectangle from <structfield>&v4l2-selection;::r</structfield></entry> > + </row> > + <row> > + <entry><constant>V4L2_SEL_SIZE_LE</constant></entry> > + <entry>0x00000002</entry> > + <entry>indicate that adjusted rectangle must be inside a rectangle from <structfield>&v4l2-selection;::r</structfield></entry> > + </row> > + </tbody> > + </tgroup> > + </table> > + </refsect1> > + > + <section> > + <figure id="sel-const-adjust"> > + <title>Size adjustments with constraint flags.</title> > + <mediaobject> > + <imageobject> > + <imagedata fileref="constraints.png" format="PNG" /> > + </imageobject> > + <textobject> > + <phrase>Behaviour of rectangle adjustment for different constraint > + flags.</phrase> > + </textobject> > + </mediaobject> > + </figure> > + </section> > + > + <refsect1> > + <table pgwide="1" frame="none" id="v4l2-selection"> > + <title>struct <structname>v4l2_selection</structname></title> > + <tgroup cols="3"> > + &cs-str; > + <tbody valign="top"> > + <row> > + <entry>__u32</entry> > + <entry><structfield>type</structfield></entry> > + <entry>Type of the buffer (from &v4l2-buf-type;)</entry> > + </row> > + <row> > + <entry>__u32</entry> > + <entry><structfield>target</structfield></entry> > + <entry>used to select between <link linkend="v4l2-sel-target"> cropping and composing rectangles </link></entry> > + </row> > + <row> > + <entry>__u32</entry> > + <entry><structfield>flags</structfield></entry> > + <entry>control over coordinates adjustments, refer to <link linkend="v4l2-sel-flags">selection flags</link></entry> > + </row> > + <row> > + <entry>&v4l2-rect;</entry> > + <entry><structfield>r</structfield></entry> > + <entry>selection rectangle</entry> > + </row> > + <row> > + <entry>__u32</entry> > + <entry><structfield>reserved[9]</structfield></entry> > + <entry>Reserved fields for future use</entry> > + </row> > + </tbody> > + </tgroup> > + </table> > + </refsect1> > + > + <refsect1> > + &return-value; > + <variablelist> > + <varlistentry> > + <term><errorcode>EINVAL</errorcode></term> > + <listitem> > + <para>The buffer <structfield> &v4l2-selection;::type </structfield> > +or <structfield> &v4l2-selection;::target </structfield> is not supported, or > +the <structfield> &v4l2-selection;::flags </structfield> are invalid.</para> > + </listitem> > + </varlistentry> > + <varlistentry> > + <term><errorcode>ERANGE</errorcode></term> > + <listitem> > + <para>it is not possible to adjust a rectangle <structfield> > +&v4l2-selection;::r </structfield> that satisfies all contraints from > +<structfield> &v4l2-selection;::flags </structfield>.</para> > + </listitem> > + </varlistentry> > + <varlistentry> > + <term><errorcode>EBUSY</errorcode></term> > + <listitem> > + <para>it is not possible to apply change of selection rectangle at the moment. > +Usually because streaming is in progress.</para> > + </listitem> > + </varlistentry> > + </variablelist> > + </refsect1> > + > +</refentry> -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html