diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/dev-osd.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/dev-osd.rst | 26 |
1 files changed, 14 insertions, 12 deletions
diff --git a/Documentation/media/uapi/v4l/dev-osd.rst b/Documentation/media/uapi/v4l/dev-osd.rst index fadda131f020..71da85ed7e4b 100644 --- a/Documentation/media/uapi/v4l/dev-osd.rst +++ b/Documentation/media/uapi/v4l/dev-osd.rst @@ -16,7 +16,9 @@ this interface, which borrows structures and ioctls of the The OSD function is accessible through the same character special file as the :ref:`Video Output <capture>` function. -.. note:: The default function of such a ``/dev/video`` device is video +.. note:: + + The default function of such a ``/dev/video`` device is video capturing or output. The OSD function is only available after calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. @@ -26,7 +28,7 @@ Querying Capabilities Devices supporting the *Video Output Overlay* interface set the ``V4L2_CAP_VIDEO_OUTPUT_OVERLAY`` flag in the ``capabilities`` field of -struct :ref:`v4l2_capability <v4l2-capability>` returned by the +struct :c:type:`v4l2_capability` returned by the :ref:`VIDIOC_QUERYCAP` ioctl. @@ -39,11 +41,11 @@ accessible as a framebuffer device (``/dev/fbN``). Given a V4L2 device, applications can find the corresponding framebuffer device by calling the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` ioctl. It returns, amongst other information, the physical address of the framebuffer in the -``base`` field of struct :ref:`v4l2_framebuffer <v4l2-framebuffer>`. +``base`` field of struct :c:type:`v4l2_framebuffer`. The framebuffer device ioctl ``FBIOGET_FSCREENINFO`` returns the same address in the ``smem_start`` field of struct -:c:type:`struct fb_fix_screeninfo`. The ``FBIOGET_FSCREENINFO`` -ioctl and struct :c:type:`struct fb_fix_screeninfo` are defined in +struct :c:type:`fb_fix_screeninfo`. The ``FBIOGET_FSCREENINFO`` +ioctl and struct :c:type:`fb_fix_screeninfo` are defined in the ``linux/fb.h`` header file. The width and height of the framebuffer depends on the current video @@ -112,18 +114,18 @@ sizes and positions of these rectangles. Further drivers may support any (or none) of the clipping/blending methods defined for the :ref:`Video Overlay <overlay>` interface. -A struct :ref:`v4l2_window <v4l2-window>` defines the size of the +A struct :c:type:`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 ``type`` field of a struct -:ref:`v4l2_format <v4l2-format>` to +:c:type:`v4l2_format` to ``V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY`` and call the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl. The driver fills the -:ref:`struct v4l2_window <v4l2-window>` substructure named ``win``. It is not +struct :c:type:`v4l2_window` substructure named ``win``. It is not possible to retrieve a previously programmed clipping list or bitmap. To program the source rectangle applications set the ``type`` field of a -struct :ref:`v4l2_format <v4l2-format>` to +struct :c:type:`v4l2_format` to ``V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY``, initialize the ``win`` substructure and call the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. The driver adjusts the parameters against hardware limits and returns @@ -132,10 +134,10 @@ the :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl can be used to learn about driver capabilities without actually changing driver state. Unlike :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` this also works after the overlay has been enabled. -A struct :ref:`v4l2_crop <v4l2-crop>` defines the size and position +A struct :c:type:`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 struct :ref:`v4l2_window <v4l2-window>` -and struct :ref:`v4l2_crop <v4l2-crop>`. The cropping API applies to +the width and height given in struct :c:type:`v4l2_window` +and struct :c:type:`v4l2_crop`. The cropping API applies to *Video Output* and *Video Output Overlay* devices in the same way as to *Video Capture* and *Video Overlay* devices, merely reversing the direction of the data flow. For more information see :ref:`crop`. |