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Diffstat (limited to 'Documentation/media/uapi/v4l/dev-meta.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/dev-meta.rst | 44 |
1 files changed, 29 insertions, 15 deletions
diff --git a/Documentation/media/uapi/v4l/dev-meta.rst b/Documentation/media/uapi/v4l/dev-meta.rst index f7ac8d0d3af1..c5dbe882be65 100644 --- a/Documentation/media/uapi/v4l/dev-meta.rst +++ b/Documentation/media/uapi/v4l/dev-meta.rst @@ -1,4 +1,11 @@ -.. -*- coding: utf-8; mode: rst -*- +.. Permission is granted to copy, distribute and/or modify this +.. document under the terms of the GNU Free Documentation License, +.. Version 1.1 or any later version published by the Free Software +.. Foundation, with no Invariant Sections, no Front-Cover Texts +.. and no Back-Cover Texts. A copy of the license is included at +.. Documentation/media/uapi/fdl-appendix.rst. +.. +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections .. _metadata: @@ -7,21 +14,27 @@ Metadata Interface ****************** Metadata refers to any non-image data that supplements video frames with -additional information. This may include statistics computed over the image -or frame capture parameters supplied by the image source. This interface is -intended for transfer of metadata to userspace and control of that operation. +additional information. This may include statistics computed over the image, +frame capture parameters supplied by the image source or device specific +parameters for specifying how the device processes images. This interface is +intended for transfer of metadata between the userspace and the hardware and +control of that operation. -The metadata interface is implemented on video capture device nodes. The device -can be dedicated to metadata or can implement both video and metadata capture -as specified in its reported capabilities. +The metadata interface is implemented on video device nodes. The device can be +dedicated to metadata or can support both video and metadata as specified in its +reported capabilities. Querying Capabilities ===================== -Device nodes supporting the metadata interface set the ``V4L2_CAP_META_CAPTURE`` -flag in the ``device_caps`` field of the +Device nodes supporting the metadata capture interface set the +``V4L2_CAP_META_CAPTURE`` flag in the ``device_caps`` field of the :c:type:`v4l2_capability` structure returned by the :c:func:`VIDIOC_QUERYCAP` -ioctl. That flag means the device can capture metadata to memory. +ioctl. That flag means the device can capture metadata to memory. Similarly, +device nodes supporting metadata output interface set the +``V4L2_CAP_META_OUTPUT`` flag in the ``device_caps`` field of +:c:type:`v4l2_capability` structure. That flag means the device can read +metadata from memory. At least one of the read/write or streaming I/O methods must be supported. @@ -35,12 +48,13 @@ to the basic :ref:`format` ioctls, the :c:func:`VIDIOC_ENUM_FMT` ioctl must be supported as well. To use the :ref:`format` ioctls applications set the ``type`` field of the -:c:type:`v4l2_format` structure to ``V4L2_BUF_TYPE_META_CAPTURE`` and use the -:c:type:`v4l2_meta_format` ``meta`` member of the ``fmt`` union as needed per -the desired operation. Both drivers and applications must set the remainder of -the :c:type:`v4l2_format` structure to 0. +:c:type:`v4l2_format` structure to ``V4L2_BUF_TYPE_META_CAPTURE`` or to +``V4L2_BUF_TYPE_META_OUTPUT`` and use the :c:type:`v4l2_meta_format` ``meta`` +member of the ``fmt`` union as needed per the desired operation. Both drivers +and applications must set the remainder of the :c:type:`v4l2_format` structure +to 0. -.. _v4l2-meta-format: +.. c:type:: v4l2_meta_format .. tabularcolumns:: |p{1.4cm}|p{2.2cm}|p{13.9cm}| |