diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/dev-overlay.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/dev-overlay.rst | 34 |
1 files changed, 19 insertions, 15 deletions
diff --git a/Documentation/media/uapi/v4l/dev-overlay.rst b/Documentation/media/uapi/v4l/dev-overlay.rst index 92b4471b0c6e..9be14b55e305 100644 --- a/Documentation/media/uapi/v4l/dev-overlay.rst +++ b/Documentation/media/uapi/v4l/dev-overlay.rst @@ -19,7 +19,9 @@ video into a window. Video overlay devices are accessed through the same character special files as :ref:`video capture <capture>` devices. -.. note:: The default function of a ``/dev/video`` device is video +.. note:: + + The default function of a ``/dev/video`` device is video capturing. The overlay function is only available after calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. @@ -41,7 +43,7 @@ Querying Capabilities Devices supporting the video overlay interface set the ``V4L2_CAP_VIDEO_OVERLAY`` flag in the ``capabilities`` field of struct -:ref:`v4l2_capability <v4l2-capability>` returned by the +:c:type:`v4l2_capability` returned by the :ref:`VIDIOC_QUERYCAP` ioctl. The overlay I/O method specified below must be supported. Tuners and audio inputs are optional. @@ -117,17 +119,17 @@ at minimum requires to reset the parameters to defaults. An example is given in :ref:`crop`. The overlay window is described by a struct -:ref:`v4l2_window <v4l2-window>`. It defines the size of the image, +:c:type:`v4l2_window`. It defines the size of the image, its position over the graphics surface and the clipping to be applied. To get the current parameters applications set the ``type`` field of a -struct :ref:`v4l2_format <v4l2-format>` to +struct :c:type:`v4l2_format` to ``V4L2_BUF_TYPE_VIDEO_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 overlay window applications set the ``type`` field of a -struct :ref:`v4l2_format <v4l2-format>` to +struct :c:type:`v4l2_format` to ``V4L2_BUF_TYPE_VIDEO_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 the actual @@ -137,7 +139,7 @@ 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. The scaling factor of the overlaid image is implied by the width and -height given in struct :ref:`v4l2_window <v4l2-window>` and the size +height given in struct :c:type:`v4l2_window` and the size of the cropping rectangle. For more information see :ref:`crop`. When simultaneous capturing and overlay is supported and the hardware @@ -147,7 +149,7 @@ takes precedence. The attempt to capture or overlay as well code or return accordingly modified parameters. -.. _v4l2-window: +.. c:type:: v4l2_window struct v4l2_window ------------------ @@ -173,7 +175,7 @@ struct v4l2_window :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` applications set this field to the desired pixel value for the chroma key. The format is the same as the pixel format of the framebuffer (struct - :ref:`v4l2_framebuffer <v4l2-framebuffer>` ``fmt.pixelformat`` + :c:type:`v4l2_framebuffer` ``fmt.pixelformat`` field), with bytes in host order. E. g. for :ref:`V4L2_PIX_FMT_BGR24 <V4L2-PIX-FMT-BGR32>` the value should be 0xRRGGBB on a little endian, 0xBBGGRR on a big endian host. @@ -236,13 +238,15 @@ exceeded are undefined. [#f3]_ :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>`, :ref:`framebuffer-flags`). - .. note:: This field was added in Linux 2.6.23, extending the - structure. However the :ref:`VIDIOC_[G|S|TRY]_FMT <VIDIOC_G_FMT>` - ioctls, which take a pointer to a :ref:`v4l2_format <v4l2-format>` - parent structure with padding bytes at the end, are not affected. +.. note:: + + This field was added in Linux 2.6.23, extending the + structure. However the :ref:`VIDIOC_[G|S|TRY]_FMT <VIDIOC_G_FMT>` + ioctls, which take a pointer to a :c:type:`v4l2_format` + parent structure with padding bytes at the end, are not affected. -.. _v4l2-clip: +.. c:type:: v4l2_clip struct v4l2_clip [#f4]_ ----------------------- @@ -258,7 +262,7 @@ struct v4l2_clip [#f4]_ linked list of clipping rectangles. -.. _v4l2-rect: +.. c:type:: v4l2_rect struct v4l2_rect ---------------- |