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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _vidioc-querystd:
+
+*********************
+ioctl VIDIOC_QUERYSTD
+*********************
+
+*man VIDIOC_QUERYSTD(2)*
+
+Sense the video standard received by the current input
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, int request, v4l2_std_id *argp )
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``request``
+    VIDIOC_QUERYSTD
+
+``argp``
+
+
+Description
+===========
+
+The hardware may be able to detect the current video standard
+automatically. To do so, applications call ``VIDIOC_QUERYSTD`` with a
+pointer to a :ref:`v4l2_std_id <v4l2-std-id>` type. The driver
+stores here a set of candidates, this can be a single flag or a set of
+supported standards if for example the hardware can only distinguish
+between 50 and 60 Hz systems. If no signal was detected, then the driver
+will return V4L2_STD_UNKNOWN. When detection is not possible or fails,
+the set must contain all standards supported by the current video input
+or output.
+
+Please note that drivers shall *not* switch the video standard
+automatically if a new video standard is detected. Instead, drivers
+should send the ``V4L2_EVENT_SOURCE_CHANGE`` event (if they support
+this) and expect that userspace will take action by calling
+``VIDIOC_QUERYSTD``. The reason is that a new video standard can mean
+different buffer sizes as well, and you cannot change buffer sizes on
+the fly. In general, applications that receive the Source Change event
+will have to call ``VIDIOC_QUERYSTD``, and if the detected video
+standard is valid they will have to stop streaming, set the new
+standard, allocate new buffers and start streaming again.
+
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+ENODATA
+    Standard video timings are not supported for this input or output.
+
+
+.. ------------------------------------------------------------------------------
+.. This file was automatically converted from DocBook-XML with the dbxml
+.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
+.. from the linux kernel, refer to:
+..
+.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
+.. ------------------------------------------------------------------------------