1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L 2 .. c:namespace:: V4L
3 3
4 .. _VIDIOC_G_DV_TIMINGS: 4 .. _VIDIOC_G_DV_TIMINGS:
5 5
6 ********************************************** 6 **********************************************
7 ioctl VIDIOC_G_DV_TIMINGS, VIDIOC_S_DV_TIMINGS 7 ioctl VIDIOC_G_DV_TIMINGS, VIDIOC_S_DV_TIMINGS
8 ********************************************** 8 **********************************************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 VIDIOC_G_DV_TIMINGS - VIDIOC_S_DV_TIMINGS - VI 13 VIDIOC_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 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. c:macro:: VIDIOC_G_DV_TIMINGS 18 .. c:macro:: VIDIOC_G_DV_TIMINGS
19 19
20 ``int ioctl(int fd, VIDIOC_G_DV_TIMINGS, struc 20 ``int ioctl(int fd, VIDIOC_G_DV_TIMINGS, struct v4l2_dv_timings *argp)``
21 21
22 .. c:macro:: VIDIOC_S_DV_TIMINGS 22 .. c:macro:: VIDIOC_S_DV_TIMINGS
23 23
24 ``int ioctl(int fd, VIDIOC_S_DV_TIMINGS, struc 24 ``int ioctl(int fd, VIDIOC_S_DV_TIMINGS, struct v4l2_dv_timings *argp)``
25 25
26 .. c:macro:: VIDIOC_SUBDEV_G_DV_TIMINGS 26 .. c:macro:: VIDIOC_SUBDEV_G_DV_TIMINGS
27 27
28 ``int ioctl(int fd, VIDIOC_SUBDEV_G_DV_TIMINGS 28 ``int ioctl(int fd, VIDIOC_SUBDEV_G_DV_TIMINGS, struct v4l2_dv_timings *argp)``
29 29
30 .. c:macro:: VIDIOC_SUBDEV_S_DV_TIMINGS 30 .. c:macro:: VIDIOC_SUBDEV_S_DV_TIMINGS
31 31
32 ``int ioctl(int fd, VIDIOC_SUBDEV_S_DV_TIMINGS 32 ``int ioctl(int fd, VIDIOC_SUBDEV_S_DV_TIMINGS, struct v4l2_dv_timings *argp)``
33 33
34 Arguments 34 Arguments
35 ========= 35 =========
36 36
37 ``fd`` 37 ``fd``
38 File descriptor returned by :c:func:`open( 38 File descriptor returned by :c:func:`open()`.
39 39
40 ``argp`` 40 ``argp``
41 Pointer to struct :c:type:`v4l2_dv_timings 41 Pointer to struct :c:type:`v4l2_dv_timings`.
42 42
43 Description 43 Description
44 =========== 44 ===========
45 45
46 To set DV timings for the input or output, app 46 To set DV timings for the input or output, applications use the
47 :ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS 47 :ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl and to get the current timings,
48 applications use the :ref:`VIDIOC_G_DV_TIMINGS 48 applications use the :ref:`VIDIOC_G_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl. The detailed timing
49 information is filled in using the structure s 49 information is filled in using the structure struct
50 :c:type:`v4l2_dv_timings`. These ioctls take a 50 :c:type:`v4l2_dv_timings`. These ioctls take a
51 pointer to the struct :c:type:`v4l2_dv_timings 51 pointer to the struct :c:type:`v4l2_dv_timings`
52 structure as argument. If the ioctl is not sup 52 structure as argument. If the ioctl is not supported or the timing
53 values are not correct, the driver returns ``E 53 values are not correct, the driver returns ``EINVAL`` error code.
54 54
55 Calling ``VIDIOC_SUBDEV_S_DV_TIMINGS`` on a su 55 Calling ``VIDIOC_SUBDEV_S_DV_TIMINGS`` on a subdev device node that has been
56 registered in read-only mode is not allowed. A 56 registered in read-only mode is not allowed. An error is returned and the errno
57 variable is set to ``-EPERM``. 57 variable is set to ``-EPERM``.
58 58
59 The ``linux/v4l2-dv-timings.h`` header can be 59 The ``linux/v4l2-dv-timings.h`` header can be used to get the timings of
60 the formats in the :ref:`cea861` and :ref:`ves 60 the formats in the :ref:`cea861` and :ref:`vesadmt` standards. If
61 the current input or output does not support D 61 the current input or output does not support DV timings (e.g. if
62 :ref:`VIDIOC_ENUMINPUT` does not set the 62 :ref:`VIDIOC_ENUMINPUT` does not set the
63 ``V4L2_IN_CAP_DV_TIMINGS`` flag), then ``ENODA 63 ``V4L2_IN_CAP_DV_TIMINGS`` flag), then ``ENODATA`` error code is returned.
64 64
65 Return Value 65 Return Value
66 ============ 66 ============
67 67
68 On success 0 is returned, on error -1 and the 68 On success 0 is returned, on error -1 and the ``errno`` variable is set
69 appropriately. The generic error codes are des 69 appropriately. The generic error codes are described at the
70 :ref:`Generic Error Codes <gen-errors>` chapte 70 :ref:`Generic Error Codes <gen-errors>` chapter.
71 71
72 EINVAL 72 EINVAL
73 This ioctl is not supported, or the :ref:` 73 This ioctl is not supported, or the :ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>`
74 parameter was unsuitable. 74 parameter was unsuitable.
75 75
76 ENODATA 76 ENODATA
77 Digital video timings are not supported fo 77 Digital video timings are not supported for this input or output.
78 78
79 EBUSY 79 EBUSY
80 The device is busy and therefore can not c 80 The device is busy and therefore can not change the timings.
81 81
82 EPERM 82 EPERM
83 ``VIDIOC_SUBDEV_S_DV_TIMINGS`` has been ca 83 ``VIDIOC_SUBDEV_S_DV_TIMINGS`` has been called on a read-only subdevice.
84 84
85 .. c:type:: v4l2_bt_timings 85 .. c:type:: v4l2_bt_timings
86 86
87 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm 87 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
88 88
89 .. cssclass:: longtable 89 .. cssclass:: longtable
90 90
91 .. flat-table:: struct v4l2_bt_timings 91 .. flat-table:: struct v4l2_bt_timings
92 :header-rows: 0 92 :header-rows: 0
93 :stub-columns: 0 93 :stub-columns: 0
94 :widths: 1 1 2 94 :widths: 1 1 2
95 95
96 * - __u32 96 * - __u32
97 - ``width`` 97 - ``width``
98 - Width of the active video in pixels. 98 - Width of the active video in pixels.
99 * - __u32 99 * - __u32
100 - ``height`` 100 - ``height``
101 - Height of the active video frame in li 101 - Height of the active video frame in lines. So for interlaced
102 formats the height of the active video 102 formats the height of the active video in each field is
103 ``height``/2. 103 ``height``/2.
104 * - __u32 104 * - __u32
105 - ``interlaced`` 105 - ``interlaced``
106 - Progressive (``V4L2_DV_PROGRESSIVE``) 106 - Progressive (``V4L2_DV_PROGRESSIVE``) or interlaced (``V4L2_DV_INTERLACED``).
107 * - __u32 107 * - __u32
108 - ``polarities`` 108 - ``polarities``
109 - This is a bit mask that defines polari 109 - This is a bit mask that defines polarities of sync signals. bit 0
110 (``V4L2_DV_VSYNC_POS_POL``) is for ver 110 (``V4L2_DV_VSYNC_POS_POL``) is for vertical sync polarity and bit
111 1 (``V4L2_DV_HSYNC_POS_POL``) is for h 111 1 (``V4L2_DV_HSYNC_POS_POL``) is for horizontal sync polarity. If
112 the bit is set (1) it is positive pola 112 the bit is set (1) it is positive polarity and if is cleared (0),
113 it is negative polarity. 113 it is negative polarity.
114 * - __u64 114 * - __u64
115 - ``pixelclock`` 115 - ``pixelclock``
116 - Pixel clock in Hz. Ex. 74.25MHz->74250 116 - Pixel clock in Hz. Ex. 74.25MHz->74250000
117 * - __u32 117 * - __u32
118 - ``hfrontporch`` 118 - ``hfrontporch``
119 - Horizontal front porch in pixels 119 - Horizontal front porch in pixels
120 * - __u32 120 * - __u32
121 - ``hsync`` 121 - ``hsync``
122 - Horizontal sync length in pixels 122 - Horizontal sync length in pixels
123 * - __u32 123 * - __u32
124 - ``hbackporch`` 124 - ``hbackporch``
125 - Horizontal back porch in pixels 125 - Horizontal back porch in pixels
126 * - __u32 126 * - __u32
127 - ``vfrontporch`` 127 - ``vfrontporch``
128 - Vertical front porch in lines. For int 128 - Vertical front porch in lines. For interlaced formats this refers
129 to the odd field (aka field 1). 129 to the odd field (aka field 1).
130 * - __u32 130 * - __u32
131 - ``vsync`` 131 - ``vsync``
132 - Vertical sync length in lines. For int 132 - Vertical sync length in lines. For interlaced formats this refers
133 to the odd field (aka field 1). 133 to the odd field (aka field 1).
134 * - __u32 134 * - __u32
135 - ``vbackporch`` 135 - ``vbackporch``
136 - Vertical back porch in lines. For inte 136 - Vertical back porch in lines. For interlaced formats this refers
137 to the odd field (aka field 1). 137 to the odd field (aka field 1).
138 * - __u32 138 * - __u32
139 - ``il_vfrontporch`` 139 - ``il_vfrontporch``
140 - Vertical front porch in lines for the 140 - Vertical front porch in lines for the even field (aka field 2) of
141 interlaced field formats. Must be 0 fo 141 interlaced field formats. Must be 0 for progressive formats.
142 * - __u32 142 * - __u32
143 - ``il_vsync`` 143 - ``il_vsync``
144 - Vertical sync length in lines for the 144 - Vertical sync length in lines for the even field (aka field 2) of
145 interlaced field formats. Must be 0 fo 145 interlaced field formats. Must be 0 for progressive formats.
146 * - __u32 146 * - __u32
147 - ``il_vbackporch`` 147 - ``il_vbackporch``
148 - Vertical back porch in lines for the e 148 - Vertical back porch in lines for the even field (aka field 2) of
149 interlaced field formats. Must be 0 fo 149 interlaced field formats. Must be 0 for progressive formats.
150 * - __u32 150 * - __u32
151 - ``standards`` 151 - ``standards``
152 - The video standard(s) this format belo 152 - The video standard(s) this format belongs to. This will be filled
153 in by the driver. Applications must se 153 in by the driver. Applications must set this to 0. See
154 :ref:`dv-bt-standards` for a list of s 154 :ref:`dv-bt-standards` for a list of standards.
155 * - __u32 155 * - __u32
156 - ``flags`` 156 - ``flags``
157 - Several flags giving more information 157 - Several flags giving more information about the format. See
158 :ref:`dv-bt-flags` for a description o 158 :ref:`dv-bt-flags` for a description of the flags.
159 * - struct :c:type:`v4l2_fract` 159 * - struct :c:type:`v4l2_fract`
160 - ``picture_aspect`` 160 - ``picture_aspect``
161 - The picture aspect if the pixels are n 161 - The picture aspect if the pixels are not square. Only valid if the
162 ``V4L2_DV_FL_HAS_PICTURE_ASPECT`` flag 162 ``V4L2_DV_FL_HAS_PICTURE_ASPECT`` flag is set.
163 * - __u8 163 * - __u8
164 - ``cea861_vic`` 164 - ``cea861_vic``
165 - The Video Identification Code accordin 165 - The Video Identification Code according to the CEA-861 standard.
166 Only valid if the ``V4L2_DV_FL_HAS_CEA 166 Only valid if the ``V4L2_DV_FL_HAS_CEA861_VIC`` flag is set.
167 * - __u8 167 * - __u8
168 - ``hdmi_vic`` 168 - ``hdmi_vic``
169 - The Video Identification Code accordin 169 - The Video Identification Code according to the HDMI standard.
170 Only valid if the ``V4L2_DV_FL_HAS_HDM 170 Only valid if the ``V4L2_DV_FL_HAS_HDMI_VIC`` flag is set.
171 * - __u8 171 * - __u8
172 - ``reserved[46]`` 172 - ``reserved[46]``
173 - Reserved for future extensions. Driver 173 - Reserved for future extensions. Drivers and applications must set
174 the array to zero. 174 the array to zero.
175 175
176 .. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{7.0cm 176 .. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{7.0cm}|p{3.1cm}|
177 177
178 .. c:type:: v4l2_dv_timings 178 .. c:type:: v4l2_dv_timings
179 179
180 .. flat-table:: struct v4l2_dv_timings 180 .. flat-table:: struct v4l2_dv_timings
181 :header-rows: 0 181 :header-rows: 0
182 :stub-columns: 0 182 :stub-columns: 0
183 :widths: 1 1 2 183 :widths: 1 1 2
184 184
185 * - __u32 185 * - __u32
186 - ``type`` 186 - ``type``
187 - Type of DV timings as listed in :ref:` 187 - Type of DV timings as listed in :ref:`dv-timing-types`.
188 * - union { 188 * - union {
189 - (anonymous) 189 - (anonymous)
190 * - struct :c:type:`v4l2_bt_timings` 190 * - struct :c:type:`v4l2_bt_timings`
191 - ``bt`` 191 - ``bt``
192 - Timings defined by BT.656/1120 specifi 192 - Timings defined by BT.656/1120 specifications
193 * - __u32 193 * - __u32
194 - ``reserved``\ [32] 194 - ``reserved``\ [32]
195 - 195 -
196 * - } 196 * - }
197 - 197 -
198 198
199 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm 199 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
200 200
201 .. _dv-timing-types: 201 .. _dv-timing-types:
202 202
203 .. flat-table:: DV Timing types 203 .. flat-table:: DV Timing types
204 :header-rows: 0 204 :header-rows: 0
205 :stub-columns: 0 205 :stub-columns: 0
206 :widths: 1 1 2 206 :widths: 1 1 2
207 207
208 * - Timing type 208 * - Timing type
209 - value 209 - value
210 - Description 210 - Description
211 * - 211 * -
212 - 212 -
213 - 213 -
214 * - ``V4L2_DV_BT_656_1120`` 214 * - ``V4L2_DV_BT_656_1120``
215 - 0 215 - 0
216 - BT.656/1120 timings 216 - BT.656/1120 timings
217 217
218 .. tabularcolumns:: |p{6.5cm}|p{11.0cm}| 218 .. tabularcolumns:: |p{6.5cm}|p{11.0cm}|
219 219
220 .. cssclass:: longtable 220 .. cssclass:: longtable
221 221
222 .. _dv-bt-standards: 222 .. _dv-bt-standards:
223 223
224 .. flat-table:: DV BT Timing standards 224 .. flat-table:: DV BT Timing standards
225 :header-rows: 0 225 :header-rows: 0
226 :stub-columns: 0 226 :stub-columns: 0
227 227
228 * - Timing standard 228 * - Timing standard
229 - Description 229 - Description
230 * - ``V4L2_DV_BT_STD_CEA861`` 230 * - ``V4L2_DV_BT_STD_CEA861``
231 - The timings follow the CEA-861 Digital 231 - The timings follow the CEA-861 Digital TV Profile standard
232 * - ``V4L2_DV_BT_STD_DMT`` 232 * - ``V4L2_DV_BT_STD_DMT``
233 - The timings follow the VESA Discrete M 233 - The timings follow the VESA Discrete Monitor Timings standard
234 * - ``V4L2_DV_BT_STD_CVT`` 234 * - ``V4L2_DV_BT_STD_CVT``
235 - The timings follow the VESA Coordinate 235 - The timings follow the VESA Coordinated Video Timings standard
236 * - ``V4L2_DV_BT_STD_GTF`` 236 * - ``V4L2_DV_BT_STD_GTF``
237 - The timings follow the VESA Generalize 237 - The timings follow the VESA Generalized Timings Formula standard
238 * - ``V4L2_DV_BT_STD_SDI`` 238 * - ``V4L2_DV_BT_STD_SDI``
239 - The timings follow the SDI Timings sta 239 - The timings follow the SDI Timings standard.
240 There are no horizontal syncs/porches 240 There are no horizontal syncs/porches at all in this format.
241 Total blanking timings must be set in 241 Total blanking timings must be set in hsync or vsync fields only.
242 242
243 .. tabularcolumns:: |p{7.7cm}|p{9.8cm}| 243 .. tabularcolumns:: |p{7.7cm}|p{9.8cm}|
244 244
245 .. cssclass:: longtable 245 .. cssclass:: longtable
246 246
247 .. _dv-bt-flags: 247 .. _dv-bt-flags:
248 248
249 .. flat-table:: DV BT Timing flags 249 .. flat-table:: DV BT Timing flags
250 :header-rows: 0 250 :header-rows: 0
251 :stub-columns: 0 251 :stub-columns: 0
252 252
253 * - Flag 253 * - Flag
254 - Description 254 - Description
255 * - ``V4L2_DV_FL_REDUCED_BLANKING`` 255 * - ``V4L2_DV_FL_REDUCED_BLANKING``
256 - CVT/GTF specific: the timings use redu 256 - CVT/GTF specific: the timings use reduced blanking (CVT) or the
257 'Secondary GTF' curve (GTF). In both c 257 'Secondary GTF' curve (GTF). In both cases the horizontal and/or
258 vertical blanking intervals are reduce 258 vertical blanking intervals are reduced, allowing a higher
259 resolution over the same bandwidth. Th 259 resolution over the same bandwidth. This is a read-only flag,
260 applications must not set this. 260 applications must not set this.
261 * - ``V4L2_DV_FL_CAN_REDUCE_FPS`` 261 * - ``V4L2_DV_FL_CAN_REDUCE_FPS``
262 - CEA-861 specific: set for CEA-861 form 262 - CEA-861 specific: set for CEA-861 formats with a framerate that is
263 a multiple of six. These formats can b 263 a multiple of six. These formats can be optionally played at 1 /
264 1.001 speed to be compatible with 60 H 264 1.001 speed to be compatible with 60 Hz based standards such as
265 NTSC and PAL-M that use a framerate of 265 NTSC and PAL-M that use a framerate of 29.97 frames per second. If
266 the transmitter can't generate such fr 266 the transmitter can't generate such frequencies, then the flag
267 will also be cleared. This is a read-o 267 will also be cleared. This is a read-only flag, applications must
268 not set this. 268 not set this.
269 * - ``V4L2_DV_FL_REDUCED_FPS`` 269 * - ``V4L2_DV_FL_REDUCED_FPS``
270 - CEA-861 specific: only valid for video 270 - CEA-861 specific: only valid for video transmitters or video
271 receivers that have the ``V4L2_DV_FL_C 271 receivers that have the ``V4L2_DV_FL_CAN_DETECT_REDUCED_FPS``
272 set. This flag is cleared otherwise. I 272 set. This flag is cleared otherwise. It is also only valid for
273 formats with the ``V4L2_DV_FL_CAN_REDU 273 formats with the ``V4L2_DV_FL_CAN_REDUCE_FPS`` flag set, for other
274 formats the flag will be cleared by th 274 formats the flag will be cleared by the driver.
275 275
276 If the application sets this flag for 276 If the application sets this flag for a transmitter, then the
277 pixelclock used to set up the transmit 277 pixelclock used to set up the transmitter is divided by 1.001 to
278 make it compatible with NTSC framerate 278 make it compatible with NTSC framerates. If the transmitter can't
279 generate such frequencies, then the fl 279 generate such frequencies, then the flag will be cleared.
280 280
281 If a video receiver detects that the f 281 If a video receiver detects that the format uses a reduced framerate,
282 then it will set this flag to signal t 282 then it will set this flag to signal this to the application.
283 * - ``V4L2_DV_FL_HALF_LINE`` 283 * - ``V4L2_DV_FL_HALF_LINE``
284 - Specific to interlaced formats: if set 284 - Specific to interlaced formats: if set, then the vertical
285 frontporch of field 1 (aka the odd fie 285 frontporch of field 1 (aka the odd field) is really one half-line
286 longer and the vertical backporch of f 286 longer and the vertical backporch of field 2 (aka the even field)
287 is really one half-line shorter, so ea 287 is really one half-line shorter, so each field has exactly the
288 same number of half-lines. Whether hal 288 same number of half-lines. Whether half-lines can be detected or
289 used depends on the hardware. 289 used depends on the hardware.
290 * - ``V4L2_DV_FL_IS_CE_VIDEO`` 290 * - ``V4L2_DV_FL_IS_CE_VIDEO``
291 - If set, then this is a Consumer Electr 291 - If set, then this is a Consumer Electronics (CE) video format.
292 Such formats differ from other formats 292 Such formats differ from other formats (commonly called IT
293 formats) in that if R'G'B' encoding is 293 formats) in that if R'G'B' encoding is used then by default the
294 R'G'B' values use limited range (i.e. 294 R'G'B' values use limited range (i.e. 16-235) as opposed to full
295 range (i.e. 0-255). All formats define 295 range (i.e. 0-255). All formats defined in CEA-861 except for the
296 640x480p59.94 format are CE formats. 296 640x480p59.94 format are CE formats.
297 * - ``V4L2_DV_FL_FIRST_FIELD_EXTRA_LINE`` 297 * - ``V4L2_DV_FL_FIRST_FIELD_EXTRA_LINE``
298 - Some formats like SMPTE-125M have an i 298 - Some formats like SMPTE-125M have an interlaced signal with a odd
299 total height. For these formats, if th 299 total height. For these formats, if this flag is set, the first
300 field has the extra line. Else, it is 300 field has the extra line. Else, it is the second field.
301 * - ``V4L2_DV_FL_HAS_PICTURE_ASPECT`` 301 * - ``V4L2_DV_FL_HAS_PICTURE_ASPECT``
302 - If set, then the picture_aspect field 302 - If set, then the picture_aspect field is valid. Otherwise assume that
303 the pixels are square, so the picture 303 the pixels are square, so the picture aspect ratio is the same as the
304 width to height ratio. 304 width to height ratio.
305 * - ``V4L2_DV_FL_HAS_CEA861_VIC`` 305 * - ``V4L2_DV_FL_HAS_CEA861_VIC``
306 - If set, then the cea861_vic field is v 306 - If set, then the cea861_vic field is valid and contains the Video
307 Identification Code as per the CEA-861 307 Identification Code as per the CEA-861 standard.
308 * - ``V4L2_DV_FL_HAS_HDMI_VIC`` 308 * - ``V4L2_DV_FL_HAS_HDMI_VIC``
309 - If set, then the hdmi_vic field is val 309 - If set, then the hdmi_vic field is valid and contains the Video
310 Identification Code as per the HDMI st 310 Identification Code as per the HDMI standard (HDMI Vendor Specific
311 InfoFrame). 311 InfoFrame).
312 * - ``V4L2_DV_FL_CAN_DETECT_REDUCED_FPS`` 312 * - ``V4L2_DV_FL_CAN_DETECT_REDUCED_FPS``
313 - CEA-861 specific: only valid for video 313 - CEA-861 specific: only valid for video receivers, the flag is
314 cleared by transmitters. 314 cleared by transmitters.
315 If set, then the hardware can detect t 315 If set, then the hardware can detect the difference between
316 regular framerates and framerates redu 316 regular framerates and framerates reduced by 1000/1001. E.g.:
317 60 vs 59.94 Hz, 30 vs 29.97 Hz or 24 v 317 60 vs 59.94 Hz, 30 vs 29.97 Hz or 24 vs 23.976 Hz.
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