1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _VIDIOC_QUERY_DV_TIMINGS: 11 12***************************** 13ioctl VIDIOC_QUERY_DV_TIMINGS 14***************************** 15 16Name 17==== 18 19VIDIOC_QUERY_DV_TIMINGS - VIDIOC_SUBDEV_QUERY_DV_TIMINGS - Sense the DV preset received by the current input 20 21 22Synopsis 23======== 24 25.. c:function:: int ioctl( int fd, VIDIOC_QUERY_DV_TIMINGS, struct v4l2_dv_timings *argp ) 26 :name: VIDIOC_QUERY_DV_TIMINGS 27 28.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_QUERY_DV_TIMINGS, struct v4l2_dv_timings *argp ) 29 :name: VIDIOC_SUBDEV_QUERY_DV_TIMINGS 30 31 32Arguments 33========= 34 35``fd`` 36 File descriptor returned by :ref:`open() <func-open>`. 37 38``argp`` 39 Pointer to struct :c:type:`v4l2_dv_timings`. 40 41 42Description 43=========== 44 45The hardware may be able to detect the current DV timings automatically, 46similar to sensing the video standard. To do so, applications call 47:ref:`VIDIOC_QUERY_DV_TIMINGS` with a pointer to a struct 48:c:type:`v4l2_dv_timings`. Once the hardware detects 49the timings, it will fill in the timings structure. 50 51.. note:: 52 53 Drivers shall *not* switch timings automatically if new 54 timings are detected. Instead, drivers should send the 55 ``V4L2_EVENT_SOURCE_CHANGE`` event (if they support this) and expect 56 that userspace will take action by calling :ref:`VIDIOC_QUERY_DV_TIMINGS`. 57 The reason is that new timings usually mean different buffer sizes as 58 well, and you cannot change buffer sizes on the fly. In general, 59 applications that receive the Source Change event will have to call 60 :ref:`VIDIOC_QUERY_DV_TIMINGS`, and if the detected timings are valid they 61 will have to stop streaming, set the new timings, allocate new buffers 62 and start streaming again. 63 64If the timings could not be detected because there was no signal, then 65ENOLINK is returned. If a signal was detected, but it was unstable and 66the receiver could not lock to the signal, then ``ENOLCK`` is returned. If 67the receiver could lock to the signal, but the format is unsupported 68(e.g. because the pixelclock is out of range of the hardware 69capabilities), then the driver fills in whatever timings it could find 70and returns ``ERANGE``. In that case the application can call 71:ref:`VIDIOC_DV_TIMINGS_CAP` to compare the 72found timings with the hardware's capabilities in order to give more 73precise feedback to the user. 74 75 76Return Value 77============ 78 79On success 0 is returned, on error -1 and the ``errno`` variable is set 80appropriately. The generic error codes are described at the 81:ref:`Generic Error Codes <gen-errors>` chapter. 82 83ENODATA 84 Digital video timings are not supported for this input or output. 85 86ENOLINK 87 No timings could be detected because no signal was found. 88 89ENOLCK 90 The signal was unstable and the hardware could not lock on to it. 91 92ERANGE 93 Timings were found, but they are out of range of the hardware 94 capabilities. 95