1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_G_DV_TIMINGS:
5
6**********************************************
7ioctl VIDIOC_G_DV_TIMINGS, VIDIOC_S_DV_TIMINGS
8**********************************************
9
10Name
11====
12
13VIDIOC_G_DV_TIMINGS - VIDIOC_S_DV_TIMINGS - VIDIOC_SUBDEV_G_DV_TIMINGS - VIDIOC_SUBDEV_S_DV_TIMINGS - Get or set DV timings for input or output
14
15Synopsis
16========
17
18.. c:macro:: VIDIOC_G_DV_TIMINGS
19
20``int ioctl(int fd, VIDIOC_G_DV_TIMINGS, struct v4l2_dv_timings *argp)``
21
22.. c:macro:: VIDIOC_S_DV_TIMINGS
23
24``int ioctl(int fd, VIDIOC_S_DV_TIMINGS, struct v4l2_dv_timings *argp)``
25
26.. c:macro:: VIDIOC_SUBDEV_G_DV_TIMINGS
27
28``int ioctl(int fd, VIDIOC_SUBDEV_G_DV_TIMINGS, struct v4l2_dv_timings *argp)``
29
30.. c:macro:: VIDIOC_SUBDEV_S_DV_TIMINGS
31
32``int ioctl(int fd, VIDIOC_SUBDEV_S_DV_TIMINGS, struct v4l2_dv_timings *argp)``
33
34Arguments
35=========
36
37``fd``
38    File descriptor returned by :c:func:`open()`.
39
40``argp``
41    Pointer to struct :c:type:`v4l2_dv_timings`.
42
43Description
44===========
45
46To set DV timings for the input or output, applications use the
47:ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl and to get the current timings,
48applications use the :ref:`VIDIOC_G_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl. The detailed timing
49information is filled in using the structure struct
50:c:type:`v4l2_dv_timings`. These ioctls take a
51pointer to the struct :c:type:`v4l2_dv_timings`
52structure as argument. If the ioctl is not supported or the timing
53values are not correct, the driver returns ``EINVAL`` error code.
54
55Calling ``VIDIOC_SUBDEV_S_DV_TIMINGS`` on a subdev device node that has been
56registered in read-only mode is not allowed. An error is returned and the errno
57variable is set to ``-EPERM``.
58
59The ``linux/v4l2-dv-timings.h`` header can be used to get the timings of
60the formats in the :ref:`cea861` and :ref:`vesadmt` standards. If
61the current input or output does not support DV timings (e.g. if
62:ref:`VIDIOC_ENUMINPUT` does not set the
63``V4L2_IN_CAP_DV_TIMINGS`` flag), then ``ENODATA`` error code is returned.
64
65Return Value
66============
67
68On success 0 is returned, on error -1 and the ``errno`` variable is set
69appropriately. The generic error codes are described at the
70:ref:`Generic Error Codes <gen-errors>` chapter.
71
72EINVAL
73    This ioctl is not supported, or the :ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>`
74    parameter was unsuitable.
75
76ENODATA
77    Digital video timings are not supported for this input or output.
78
79EBUSY
80    The device is busy and therefore can not change the timings.
81
82EPERM
83    ``VIDIOC_SUBDEV_S_DV_TIMINGS`` has been called on a read-only subdevice.
84
85.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
86
87.. c:type:: v4l2_bt_timings
88
89.. flat-table:: struct v4l2_bt_timings
90    :header-rows:  0
91    :stub-columns: 0
92    :widths:       1 1 2
93
94    * - __u32
95      - ``width``
96      - Width of the active video in pixels.
97    * - __u32
98      - ``height``
99      - Height of the active video frame in lines. So for interlaced
100	formats the height of the active video in each field is
101	``height``/2.
102    * - __u32
103      - ``interlaced``
104      - Progressive (``V4L2_DV_PROGRESSIVE``) or interlaced (``V4L2_DV_INTERLACED``).
105    * - __u32
106      - ``polarities``
107      - This is a bit mask that defines polarities of sync signals. bit 0
108	(``V4L2_DV_VSYNC_POS_POL``) is for vertical sync polarity and bit
109	1 (``V4L2_DV_HSYNC_POS_POL``) is for horizontal sync polarity. If
110	the bit is set (1) it is positive polarity and if is cleared (0),
111	it is negative polarity.
112    * - __u64
113      - ``pixelclock``
114      - Pixel clock in Hz. Ex. 74.25MHz->74250000
115    * - __u32
116      - ``hfrontporch``
117      - Horizontal front porch in pixels
118    * - __u32
119      - ``hsync``
120      - Horizontal sync length in pixels
121    * - __u32
122      - ``hbackporch``
123      - Horizontal back porch in pixels
124    * - __u32
125      - ``vfrontporch``
126      - Vertical front porch in lines. For interlaced formats this refers
127	to the odd field (aka field 1).
128    * - __u32
129      - ``vsync``
130      - Vertical sync length in lines. For interlaced formats this refers
131	to the odd field (aka field 1).
132    * - __u32
133      - ``vbackporch``
134      - Vertical back porch in lines. For interlaced formats this refers
135	to the odd field (aka field 1).
136    * - __u32
137      - ``il_vfrontporch``
138      - Vertical front porch in lines for the even field (aka field 2) of
139	interlaced field formats. Must be 0 for progressive formats.
140    * - __u32
141      - ``il_vsync``
142      - Vertical sync length in lines for the even field (aka field 2) of
143	interlaced field formats. Must be 0 for progressive formats.
144    * - __u32
145      - ``il_vbackporch``
146      - Vertical back porch in lines for the even field (aka field 2) of
147	interlaced field formats. Must be 0 for progressive formats.
148    * - __u32
149      - ``standards``
150      - The video standard(s) this format belongs to. This will be filled
151	in by the driver. Applications must set this to 0. See
152	:ref:`dv-bt-standards` for a list of standards.
153    * - __u32
154      - ``flags``
155      - Several flags giving more information about the format. See
156	:ref:`dv-bt-flags` for a description of the flags.
157    * - struct :c:type:`v4l2_fract`
158      - ``picture_aspect``
159      - The picture aspect if the pixels are not square. Only valid if the
160        ``V4L2_DV_FL_HAS_PICTURE_ASPECT`` flag is set.
161    * - __u8
162      - ``cea861_vic``
163      - The Video Identification Code according to the CEA-861 standard.
164        Only valid if the ``V4L2_DV_FL_HAS_CEA861_VIC`` flag is set.
165    * - __u8
166      - ``hdmi_vic``
167      - The Video Identification Code according to the HDMI standard.
168        Only valid if the ``V4L2_DV_FL_HAS_HDMI_VIC`` flag is set.
169    * - __u8
170      - ``reserved[46]``
171      - Reserved for future extensions. Drivers and applications must set
172	the array to zero.
173
174.. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{7.0cm}|p{3.5cm}|
175
176.. c:type:: v4l2_dv_timings
177
178.. flat-table:: struct v4l2_dv_timings
179    :header-rows:  0
180    :stub-columns: 0
181    :widths:       1 1 2
182
183    * - __u32
184      - ``type``
185      - Type of DV timings as listed in :ref:`dv-timing-types`.
186    * - union {
187      - (anonymous)
188    * - struct :c:type:`v4l2_bt_timings`
189      - ``bt``
190      - Timings defined by BT.656/1120 specifications
191    * - __u32
192      - ``reserved``\ [32]
193      -
194    * - }
195      -
196
197.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
198
199.. _dv-timing-types:
200
201.. flat-table:: DV Timing types
202    :header-rows:  0
203    :stub-columns: 0
204    :widths:       1 1 2
205
206    * - Timing type
207      - value
208      - Description
209    * -
210      -
211      -
212    * - ``V4L2_DV_BT_656_1120``
213      - 0
214      - BT.656/1120 timings
215
216.. tabularcolumns:: |p{4.5cm}|p{12.8cm}|
217
218.. _dv-bt-standards:
219
220.. flat-table:: DV BT Timing standards
221    :header-rows:  0
222    :stub-columns: 0
223
224    * - Timing standard
225      - Description
226    * - ``V4L2_DV_BT_STD_CEA861``
227      - The timings follow the CEA-861 Digital TV Profile standard
228    * - ``V4L2_DV_BT_STD_DMT``
229      - The timings follow the VESA Discrete Monitor Timings standard
230    * - ``V4L2_DV_BT_STD_CVT``
231      - The timings follow the VESA Coordinated Video Timings standard
232    * - ``V4L2_DV_BT_STD_GTF``
233      - The timings follow the VESA Generalized Timings Formula standard
234    * - ``V4L2_DV_BT_STD_SDI``
235      - The timings follow the SDI Timings standard.
236	There are no horizontal syncs/porches at all in this format.
237	Total blanking timings must be set in hsync or vsync fields only.
238
239.. tabularcolumns:: |p{7.0cm}|p{10.5cm}|
240
241.. _dv-bt-flags:
242
243.. flat-table:: DV BT Timing flags
244    :header-rows:  0
245    :stub-columns: 0
246
247    * - Flag
248      - Description
249    * - ``V4L2_DV_FL_REDUCED_BLANKING``
250      - CVT/GTF specific: the timings use reduced blanking (CVT) or the
251	'Secondary GTF' curve (GTF). In both cases the horizontal and/or
252	vertical blanking intervals are reduced, allowing a higher
253	resolution over the same bandwidth. This is a read-only flag,
254	applications must not set this.
255    * - ``V4L2_DV_FL_CAN_REDUCE_FPS``
256      - CEA-861 specific: set for CEA-861 formats with a framerate that is
257	a multiple of six. These formats can be optionally played at 1 /
258	1.001 speed to be compatible with 60 Hz based standards such as
259	NTSC and PAL-M that use a framerate of 29.97 frames per second. If
260	the transmitter can't generate such frequencies, then the flag
261	will also be cleared. This is a read-only flag, applications must
262	not set this.
263    * - ``V4L2_DV_FL_REDUCED_FPS``
264      - CEA-861 specific: only valid for video transmitters or video
265        receivers that have the ``V4L2_DV_FL_CAN_DETECT_REDUCED_FPS``
266	set. This flag is cleared otherwise. It is also only valid for
267	formats with the ``V4L2_DV_FL_CAN_REDUCE_FPS`` flag set, for other
268	formats the flag will be cleared by the driver.
269
270	If the application sets this flag for a transmitter, then the
271	pixelclock used to set up the transmitter is divided by 1.001 to
272	make it compatible with NTSC framerates. If the transmitter can't
273	generate such frequencies, then the flag will be cleared.
274
275	If a video receiver detects that the format uses a reduced framerate,
276	then it will set this flag to signal this to the application.
277    * - ``V4L2_DV_FL_HALF_LINE``
278      - Specific to interlaced formats: if set, then the vertical
279	frontporch of field 1 (aka the odd field) is really one half-line
280	longer and the vertical backporch of field 2 (aka the even field)
281	is really one half-line shorter, so each field has exactly the
282	same number of half-lines. Whether half-lines can be detected or
283	used depends on the hardware.
284    * - ``V4L2_DV_FL_IS_CE_VIDEO``
285      - If set, then this is a Consumer Electronics (CE) video format.
286	Such formats differ from other formats (commonly called IT
287	formats) in that if R'G'B' encoding is used then by default the
288	R'G'B' values use limited range (i.e. 16-235) as opposed to full
289	range (i.e. 0-255). All formats defined in CEA-861 except for the
290	640x480p59.94 format are CE formats.
291    * - ``V4L2_DV_FL_FIRST_FIELD_EXTRA_LINE``
292      - Some formats like SMPTE-125M have an interlaced signal with a odd
293	total height. For these formats, if this flag is set, the first
294	field has the extra line. Else, it is the second field.
295    * - ``V4L2_DV_FL_HAS_PICTURE_ASPECT``
296      - If set, then the picture_aspect field is valid. Otherwise assume that
297        the pixels are square, so the picture aspect ratio is the same as the
298	width to height ratio.
299    * - ``V4L2_DV_FL_HAS_CEA861_VIC``
300      - If set, then the cea861_vic field is valid and contains the Video
301        Identification Code as per the CEA-861 standard.
302    * - ``V4L2_DV_FL_HAS_HDMI_VIC``
303      - If set, then the hdmi_vic field is valid and contains the Video
304        Identification Code as per the HDMI standard (HDMI Vendor Specific
305	InfoFrame).
306    * - ``V4L2_DV_FL_CAN_DETECT_REDUCED_FPS``
307      - CEA-861 specific: only valid for video receivers, the flag is
308        cleared by transmitters.
309        If set, then the hardware can detect the difference between
310	regular framerates and framerates reduced by 1000/1001. E.g.:
311	60 vs 59.94 Hz, 30 vs 29.97 Hz or 24 vs 23.976 Hz.
312