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diff --git a/Documentation/DocBook/media/v4l/dev-osd.xml b/Documentation/DocBook/media/v4l/dev-osd.xml deleted file mode 100644 index 54853329140b..000000000000 --- a/Documentation/DocBook/media/v4l/dev-osd.xml +++ /dev/null @@ -1,149 +0,0 @@ - <title>Video Output Overlay Interface</title> - <subtitle>Also known as On-Screen Display (OSD)</subtitle> - - <para>Some video output devices can overlay a framebuffer image onto -the outgoing video signal. Applications can set up such an overlay -using this interface, which borrows structures and ioctls of the <link -linkend="overlay">Video Overlay</link> interface.</para> - - <para>The OSD function is accessible through the same character -special file as the <link linkend="capture">Video Output</link> function. -Note the default function of such a <filename>/dev/video</filename> device -is video capturing or output. The OSD function is only available after -calling the &VIDIOC-S-FMT; ioctl.</para> - - <section> - <title>Querying Capabilities</title> - - <para>Devices supporting the <wordasword>Video Output -Overlay</wordasword> interface set the -<constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant> flag in the -<structfield>capabilities</structfield> field of &v4l2-capability; -returned by the &VIDIOC-QUERYCAP; ioctl.</para> - </section> - - <section> - <title>Framebuffer</title> - - <para>Contrary to the <wordasword>Video Overlay</wordasword> -interface the framebuffer is normally implemented on the TV card and -not the graphics card. On Linux it is accessible as a framebuffer -device (<filename>/dev/fbN</filename>). Given a V4L2 device, -applications can find the corresponding framebuffer device by calling -the &VIDIOC-G-FBUF; ioctl. It returns, amongst other information, the -physical address of the framebuffer in the -<structfield>base</structfield> field of &v4l2-framebuffer;. The -framebuffer device ioctl <constant>FBIOGET_FSCREENINFO</constant> -returns the same address in the <structfield>smem_start</structfield> -field of struct <structname>fb_fix_screeninfo</structname>. The -<constant>FBIOGET_FSCREENINFO</constant> ioctl and struct -<structname>fb_fix_screeninfo</structname> are defined in the -<filename>linux/fb.h</filename> header file.</para> - - <para>The width and height of the framebuffer depends on the -current video standard. A V4L2 driver may reject attempts to change -the video standard (or any other ioctl which would imply a framebuffer -size change) with an &EBUSY; until all applications closed the -framebuffer device.</para> - - <example> - <title>Finding a framebuffer device for OSD</title> - - <programlisting> -#include <linux/fb.h> - -&v4l2-framebuffer; fbuf; -unsigned int i; -int fb_fd; - -if (-1 == ioctl(fd, VIDIOC_G_FBUF, &fbuf)) { - perror("VIDIOC_G_FBUF"); - exit(EXIT_FAILURE); -} - -for (i = 0; i < 30; i++) { - char dev_name[16]; - struct fb_fix_screeninfo si; - - snprintf(dev_name, sizeof(dev_name), "/dev/fb%u", i); - - fb_fd = open(dev_name, O_RDWR); - if (-1 == fb_fd) { - switch (errno) { - case ENOENT: /* no such file */ - case ENXIO: /* no driver */ - continue; - - default: - perror("open"); - exit(EXIT_FAILURE); - } - } - - if (0 == ioctl(fb_fd, FBIOGET_FSCREENINFO, &si)) { - if (si.smem_start == (unsigned long)fbuf.base) - break; - } else { - /* Apparently not a framebuffer device. */ - } - - close(fb_fd); - fb_fd = -1; -} - -/* fb_fd is the file descriptor of the framebuffer device - for the video output overlay, or -1 if no device was found. */ -</programlisting> - </example> - </section> - - <section> - <title>Overlay Window and Scaling</title> - - <para>The overlay is controlled by source and target rectangles. -The source rectangle selects a subsection of the framebuffer image to -be overlaid, the target rectangle an area in the outgoing video signal -where the image will appear. Drivers may or may not support scaling, -and arbitrary sizes and positions of these rectangles. Further drivers -may support any (or none) of the clipping/blending methods defined for -the <link linkend="overlay">Video Overlay</link> interface.</para> - - <para>A &v4l2-window; defines the size of the source rectangle, -its position in the framebuffer and the clipping/blending method to be -used for the overlay. To get the current parameters applications set -the <structfield>type</structfield> field of a &v4l2-format; to -<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY</constant> and call the -&VIDIOC-G-FMT; ioctl. The driver fills the -<structname>v4l2_window</structname> substructure named -<structfield>win</structfield>. It is not possible to retrieve a -previously programmed clipping list or bitmap.</para> - - <para>To program the source rectangle applications set the -<structfield>type</structfield> field of a &v4l2-format; to -<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY</constant>, initialize -the <structfield>win</structfield> substructure and call the -&VIDIOC-S-FMT; ioctl. The driver adjusts the parameters against -hardware limits and returns the actual parameters as -<constant>VIDIOC_G_FMT</constant> does. Like -<constant>VIDIOC_S_FMT</constant>, the &VIDIOC-TRY-FMT; ioctl can be -used to learn about driver capabilities without actually changing -driver state. Unlike <constant>VIDIOC_S_FMT</constant> this also works -after the overlay has been enabled.</para> - - <para>A &v4l2-crop; defines the size and position of the target -rectangle. The scaling factor of the overlay is implied by the width -and height given in &v4l2-window; and &v4l2-crop;. The cropping API -applies to <wordasword>Video Output</wordasword> and <wordasword>Video -Output Overlay</wordasword> devices in the same way as to -<wordasword>Video Capture</wordasword> and <wordasword>Video -Overlay</wordasword> devices, merely reversing the direction of the -data flow. For more information see <xref linkend="crop" />.</para> - </section> - - <section> - <title>Enabling Overlay</title> - - <para>There is no V4L2 ioctl to enable or disable the overlay, -however the framebuffer interface of the driver may support the -<constant>FBIOBLANK</constant> ioctl.</para> - </section> |