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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _metadata:
+
+******************
+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.
+
+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.
+
+Querying Capabilities
+=====================
+
+Device nodes supporting the metadata 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.
+
+At least one of the read/write or streaming I/O methods must be supported.
+
+
+Data Format Negotiation
+=======================
+
+The metadata device uses the :ref:`format` ioctls to select the capture format.
+The metadata buffer content format is bound to that selected format. In addition
+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.
+
+.. _v4l2-meta-format:
+
+.. flat-table:: struct v4l2_meta_format
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+    * - __u32
+      - ``dataformat``
+      - The data format, set by the application. This is a little endian
+        :ref:`four character code <v4l2-fourcc>`. V4L2 defines metadata formats
+        in :ref:`meta-formats`.
+    * - __u32
+      - ``buffersize``
+      - Maximum buffer size in bytes required for data. The value is set by the
+        driver.