1 .. SPDX-License-Identifier: GPL-2.0
3 The Virtual Video Test Driver (vivid)
4 =====================================
6 This driver emulates video4linux hardware of various types: video capture, video
7 output, vbi capture and output, metadata capture and output, radio receivers and
8 transmitters, touch capture and a software defined radio receiver. In addition a
9 simple framebuffer device is available for testing capture and output overlays.
11 Up to 64 vivid instances can be created, each with up to 16 inputs and 16 outputs.
13 Each input can be a webcam, TV capture device, S-Video capture device or an HDMI
14 capture device. Each output can be an S-Video output device or an HDMI output
17 These inputs and outputs act exactly as a real hardware device would behave. This
18 allows you to use this driver as a test input for application development, since
19 you can test the various features without requiring special hardware.
21 This document describes the features implemented by this driver:
23 - Support for read()/write(), MMAP, USERPTR and DMABUF streaming I/O.
24 - A large list of test patterns and variations thereof
25 - Working brightness, contrast, saturation and hue controls
26 - Support for the alpha color component
27 - Full colorspace support, including limited/full RGB range
28 - All possible control types are present
29 - Support for various pixel aspect ratios and video aspect ratios
30 - Error injection to test what happens if errors occur
31 - Supports crop/compose/scale in any combination for both input and output
32 - Can emulate up to 4K resolutions
33 - All Field settings are supported for testing interlaced capturing
34 - Supports all standard YUV and RGB formats, including two multiplanar YUV formats
35 - Raw and Sliced VBI capture and output support
36 - Radio receiver and transmitter support, including RDS support
37 - Software defined radio (SDR) support
38 - Capture and output overlay support
39 - Metadata capture and output support
40 - Touch capture support
42 These features will be described in more detail below.
44 Configuring the driver
45 ----------------------
47 By default the driver will create a single instance that has a video capture
48 device with webcam, TV, S-Video and HDMI inputs, a video output device with
49 S-Video and HDMI outputs, one vbi capture device, one vbi output device, one
50 radio receiver device, one radio transmitter device and one SDR device.
52 The number of instances, devices, video inputs and outputs and their types are
53 all configurable using the following module options:
57 number of driver instances to create. By default set to 1. Up to 64
58 instances can be created.
62 which devices should each driver instance create. An array of
63 hexadecimal values, one for each instance. The default is 0x1d3d.
64 Each value is a bitmask with the following meaning:
66 - bit 0: Video Capture node
67 - bit 2-3: VBI Capture node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both
68 - bit 4: Radio Receiver node
69 - bit 5: Software Defined Radio Receiver node
70 - bit 8: Video Output node
71 - bit 10-11: VBI Output node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both
72 - bit 12: Radio Transmitter node
73 - bit 16: Framebuffer for testing overlays
74 - bit 17: Metadata Capture node
75 - bit 18: Metadata Output node
76 - bit 19: Touch Capture node
78 So to create four instances, the first two with just one video capture
79 device, the second two with just one video output device you would pass
80 these module options to vivid:
84 n_devs=4 node_types=0x1,0x1,0x100,0x100
88 the number of inputs, one for each instance. By default 4 inputs
89 are created for each video capture device. At most 16 inputs can be created,
90 and there must be at least one.
94 the input types for each instance, the default is 0xe4. This defines
95 what the type of each input is when the inputs are created for each driver
96 instance. This is a hexadecimal value with up to 16 pairs of bits, each
97 pair gives the type and bits 0-1 map to input 0, bits 2-3 map to input 1,
98 30-31 map to input 15. Each pair of bits has the following meaning:
100 - 00: this is a webcam input
101 - 01: this is a TV tuner input
102 - 10: this is an S-Video input
103 - 11: this is an HDMI input
105 So to create a video capture device with 8 inputs where input 0 is a TV
106 tuner, inputs 1-3 are S-Video inputs and inputs 4-7 are HDMI inputs you
107 would use the following module options:
111 num_inputs=8 input_types=0xffa9
115 the number of outputs, one for each instance. By default 2 outputs
116 are created for each video output device. At most 16 outputs can be
117 created, and there must be at least one.
121 the output types for each instance, the default is 0x02. This defines
122 what the type of each output is when the outputs are created for each
123 driver instance. This is a hexadecimal value with up to 16 bits, each bit
124 gives the type and bit 0 maps to output 0, bit 1 maps to output 1, bit
125 15 maps to output 15. The meaning of each bit is as follows:
127 - 0: this is an S-Video output
128 - 1: this is an HDMI output
130 So to create a video output device with 8 outputs where outputs 0-3 are
131 S-Video outputs and outputs 4-7 are HDMI outputs you would use the
132 following module options:
136 num_outputs=8 output_types=0xf0
140 give the desired videoX start number for each video capture device.
141 The default is -1 which will just take the first free number. This allows
142 you to map capture video nodes to specific videoX device nodes. Example:
146 n_devs=4 vid_cap_nr=2,4,6,8
148 This will attempt to assign /dev/video2 for the video capture device of
149 the first vivid instance, video4 for the next up to video8 for the last
150 instance. If it can't succeed, then it will just take the next free
155 give the desired videoX start number for each video output device.
156 The default is -1 which will just take the first free number.
160 give the desired vbiX start number for each vbi capture device.
161 The default is -1 which will just take the first free number.
165 give the desired vbiX start number for each vbi output device.
166 The default is -1 which will just take the first free number.
170 give the desired radioX start number for each radio receiver device.
171 The default is -1 which will just take the first free number.
175 give the desired radioX start number for each radio transmitter
176 device. The default is -1 which will just take the first free number.
180 give the desired swradioX start number for each SDR capture device.
181 The default is -1 which will just take the first free number.
185 give the desired videoX start number for each metadata capture device.
186 The default is -1 which will just take the first free number.
190 give the desired videoX start number for each metadata output device.
191 The default is -1 which will just take the first free number.
195 give the desired v4l-touchX start number for each touch capture device.
196 The default is -1 which will just take the first free number.
200 specify the allowed video capture crop/compose/scaling combination
201 for each driver instance. Video capture devices can have any combination
202 of cropping, composing and scaling capabilities and this will tell the
203 vivid driver which of those is should emulate. By default the user can
204 select this through controls.
206 The value is either -1 (controlled by the user) or a set of three bits,
207 each enabling (1) or disabling (0) one of the features:
211 Enable crop support. Cropping will take only part of the
215 Enable compose support. Composing will copy the incoming
216 picture into a larger buffer.
220 Enable scaling support. Scaling can scale the incoming
221 picture. The scaler of the vivid driver can enlarge up
222 or down to four times the original size. The scaler is
223 very simple and low-quality. Simplicity and speed were
226 Note that this value is ignored by webcam inputs: those enumerate
227 discrete framesizes and that is incompatible with cropping, composing
232 specify the allowed video output crop/compose/scaling combination
233 for each driver instance. Video output devices can have any combination
234 of cropping, composing and scaling capabilities and this will tell the
235 vivid driver which of those is should emulate. By default the user can
236 select this through controls.
238 The value is either -1 (controlled by the user) or a set of three bits,
239 each enabling (1) or disabling (0) one of the features:
243 Enable crop support. Cropping will take only part of the
248 Enable compose support. Composing will copy the incoming
249 buffer into a larger picture frame.
253 Enable scaling support. Scaling can scale the incoming
254 buffer. The scaler of the vivid driver can enlarge up
255 or down to four times the original size. The scaler is
256 very simple and low-quality. Simplicity and speed were
261 select whether each device instance supports multi-planar formats,
262 and thus the V4L2 multi-planar API. By default device instances are
265 This module option can override that for each instance. Values are:
267 - 1: this is a single-planar instance.
268 - 2: this is a multi-planar instance.
272 enable driver debugging info
276 if set disable the error injecting controls. This option is
277 needed in order to run a tool like v4l2-compliance. Tools like that
278 exercise all controls including a control like 'Disconnect' which
279 emulates a USB disconnect, making the device inaccessible and so
280 all tests that v4l2-compliance is doing will fail afterwards.
282 There may be other situations as well where you want to disable the
283 error injection support of vivid. When this option is set, then the
284 controls that select crop, compose and scale behavior are also
285 removed. Unless overridden by ccs_cap_mode and/or ccs_out_mode the
286 will default to enabling crop, compose and scaling.
290 memory allocator selection, default is 0. It specifies the way buffers
298 specifies if the device should set queues' user-space cache and memory
299 consistency hint capability (V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS).
300 The hints are valid only when using MMAP streaming I/O. Default is 0.
305 Taken together, all these module options allow you to precisely customize
306 the driver behavior and test your application with all sorts of permutations.
307 It is also very suitable to emulate hardware that is not yet available, e.g.
308 when developing software for a new upcoming device.
314 This is probably the most frequently used feature. The video capture device
315 can be configured by using the module options num_inputs, input_types and
316 ccs_cap_mode (see section 1 for more detailed information), but by default
317 four inputs are configured: a webcam, a TV tuner, an S-Video and an HDMI
318 input, one input for each input type. Those are described in more detail
321 Special attention has been given to the rate at which new frames become
322 available. The jitter will be around 1 jiffie (that depends on the HZ
323 configuration of your kernel, so usually 1/100, 1/250 or 1/1000 of a second),
324 but the long-term behavior is exactly following the framerate. So a
325 framerate of 59.94 Hz is really different from 60 Hz. If the framerate
326 exceeds your kernel's HZ value, then you will get dropped frames, but the
327 frame/field sequence counting will keep track of that so the sequence
328 count will skip whenever frames are dropped.
334 The webcam input supports three framesizes: 320x180, 640x360 and 1280x720. It
335 supports frames per second settings of 10, 15, 25, 30, 50 and 60 fps. Which ones
336 are available depends on the chosen framesize: the larger the framesize, the
337 lower the maximum frames per second.
339 The initially selected colorspace when you switch to the webcam input will be
343 TV and S-Video Inputs
344 ~~~~~~~~~~~~~~~~~~~~~
346 The only difference between the TV and S-Video input is that the TV has a
347 tuner. Otherwise they behave identically.
349 These inputs support audio inputs as well: one TV and one Line-In. They
350 both support all TV standards. If the standard is queried, then the Vivid
351 controls 'Standard Signal Mode' and 'Standard' determine what
354 These inputs support all combinations of the field setting. Special care has
355 been taken to faithfully reproduce how fields are handled for the different
356 TV standards. This is particularly noticeable when generating a horizontally
357 moving image so the temporal effect of using interlaced formats becomes clearly
358 visible. For 50 Hz standards the top field is the oldest and the bottom field
359 is the newest in time. For 60 Hz standards that is reversed: the bottom field
360 is the oldest and the top field is the newest in time.
362 When you start capturing in V4L2_FIELD_ALTERNATE mode the first buffer will
363 contain the top field for 50 Hz standards and the bottom field for 60 Hz
364 standards. This is what capture hardware does as well.
366 Finally, for PAL/SECAM standards the first half of the top line contains noise.
367 This simulates the Wide Screen Signal that is commonly placed there.
369 The initially selected colorspace when you switch to the TV or S-Video input
372 The pixel aspect ratio will depend on the TV standard. The video aspect ratio
373 can be selected through the 'Standard Aspect Ratio' Vivid control.
374 Choices are '4x3', '16x9' which will give letterboxed widescreen video and
375 '16x9 Anamorphic' which will give full screen squashed anamorphic widescreen
376 video that will need to be scaled accordingly.
378 The TV 'tuner' supports a frequency range of 44-958 MHz. Channels are available
379 every 6 MHz, starting from 49.25 MHz. For each channel the generated image
380 will be in color for the +/- 0.25 MHz around it, and in grayscale for
381 +/- 1 MHz around the channel. Beyond that it is just noise. The VIDIOC_G_TUNER
382 ioctl will return 100% signal strength for +/- 0.25 MHz and 50% for +/- 1 MHz.
383 It will also return correct afc values to show whether the frequency is too
386 The audio subchannels that are returned are MONO for the +/- 1 MHz range around
387 a valid channel frequency. When the frequency is within +/- 0.25 MHz of the
388 channel it will return either MONO, STEREO, either MONO | SAP (for NTSC) or
389 LANG1 | LANG2 (for others), or STEREO | SAP.
391 Which one is returned depends on the chosen channel, each next valid channel
392 will cycle through the possible audio subchannel combinations. This allows
393 you to test the various combinations by just switching channels..
395 Finally, for these inputs the v4l2_timecode struct is filled in in the
396 dequeued v4l2_buffer struct.
402 The HDMI inputs supports all CEA-861 and DMT timings, both progressive and
403 interlaced, for pixelclock frequencies between 25 and 600 MHz. The field
404 mode for interlaced formats is always V4L2_FIELD_ALTERNATE. For HDMI the
405 field order is always top field first, and when you start capturing an
406 interlaced format you will receive the top field first.
408 The initially selected colorspace when you switch to the HDMI input or
409 select an HDMI timing is based on the format resolution: for resolutions
410 less than or equal to 720x576 the colorspace is set to SMPTE-170M, for
411 others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings).
413 The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it
414 set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV
415 standard, and for all others a 1:1 pixel aspect ratio is returned.
417 The video aspect ratio can be selected through the 'DV Timings Aspect Ratio'
418 Vivid control. Choices are 'Source Width x Height' (just use the
419 same ratio as the chosen format), '4x3' or '16x9', either of which can
420 result in pillarboxed or letterboxed video.
422 For HDMI inputs it is possible to set the EDID. By default a simple EDID
423 is provided. You can only set the EDID for HDMI inputs. Internally, however,
424 the EDID is shared between all HDMI inputs.
426 No interpretation is done of the EDID data with the exception of the
427 physical address. See the CEC section for more details.
429 There is a maximum of 15 HDMI inputs (if there are more, then they will be
430 reduced to 15) since that's the limitation of the EDID physical address.
436 The video output device can be configured by using the module options
437 num_outputs, output_types and ccs_out_mode (see section 1 for more detailed
438 information), but by default two outputs are configured: an S-Video and an
439 HDMI input, one output for each output type. Those are described in more detail
442 Like with video capture the framerate is also exact in the long term.
448 This output supports audio outputs as well: "Line-Out 1" and "Line-Out 2".
449 The S-Video output supports all TV standards.
451 This output supports all combinations of the field setting.
453 The initially selected colorspace when you switch to the TV or S-Video input
460 The HDMI output supports all CEA-861 and DMT timings, both progressive and
461 interlaced, for pixelclock frequencies between 25 and 600 MHz. The field
462 mode for interlaced formats is always V4L2_FIELD_ALTERNATE.
464 The initially selected colorspace when you switch to the HDMI output or
465 select an HDMI timing is based on the format resolution: for resolutions
466 less than or equal to 720x576 the colorspace is set to SMPTE-170M, for
467 others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings).
469 The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it
470 set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV
471 standard, and for all others a 1:1 pixel aspect ratio is returned.
473 An HDMI output has a valid EDID which can be obtained through VIDIOC_G_EDID.
475 There is a maximum of 15 HDMI outputs (if there are more, then they will be
476 reduced to 15) since that's the limitation of the EDID physical address. See
477 also the CEC section for more details.
482 There are three types of VBI capture devices: those that only support raw
483 (undecoded) VBI, those that only support sliced (decoded) VBI and those that
484 support both. This is determined by the node_types module option. In all
485 cases the driver will generate valid VBI data: for 60 Hz standards it will
486 generate Closed Caption and XDS data. The closed caption stream will
487 alternate between "Hello world!" and "Closed captions test" every second.
488 The XDS stream will give the current time once a minute. For 50 Hz standards
489 it will generate the Wide Screen Signal which is based on the actual Video
490 Aspect Ratio control setting and teletext pages 100-159, one page per frame.
492 The VBI device will only work for the S-Video and TV inputs, it will give
493 back an error if the current input is a webcam or HDMI.
499 There are three types of VBI output devices: those that only support raw
500 (undecoded) VBI, those that only support sliced (decoded) VBI and those that
501 support both. This is determined by the node_types module option.
503 The sliced VBI output supports the Wide Screen Signal and the teletext signal
504 for 50 Hz standards and Closed Captioning + XDS for 60 Hz standards.
506 The VBI device will only work for the S-Video output, it will give
507 back an error if the current output is HDMI.
513 The radio receiver emulates an FM/AM/SW receiver. The FM band also supports RDS.
514 The frequency ranges are:
516 - FM: 64 MHz - 108 MHz
517 - AM: 520 kHz - 1710 kHz
518 - SW: 2300 kHz - 26.1 MHz
520 Valid channels are emulated every 1 MHz for FM and every 100 kHz for AM and SW.
521 The signal strength decreases the further the frequency is from the valid
522 frequency until it becomes 0% at +/- 50 kHz (FM) or 5 kHz (AM/SW) from the
523 ideal frequency. The initial frequency when the driver is loaded is set to
526 The FM receiver supports RDS as well, both using 'Block I/O' and 'Controls'
527 modes. In the 'Controls' mode the RDS information is stored in read-only
528 controls. These controls are updated every time the frequency is changed,
529 or when the tuner status is requested. The Block I/O method uses the read()
530 interface to pass the RDS blocks on to the application for decoding.
532 The RDS signal is 'detected' for +/- 12.5 kHz around the channel frequency,
533 and the further the frequency is away from the valid frequency the more RDS
534 errors are randomly introduced into the block I/O stream, up to 50% of all
535 blocks if you are +/- 12.5 kHz from the channel frequency. All four errors
536 can occur in equal proportions: blocks marked 'CORRECTED', blocks marked
537 'ERROR', blocks marked 'INVALID' and dropped blocks.
539 The generated RDS stream contains all the standard fields contained in a
540 0B group, and also radio text and the current time.
542 The receiver supports HW frequency seek, either in Bounded mode, Wrap Around
543 mode or both, which is configurable with the "Radio HW Seek Mode" control.
549 The radio transmitter emulates an FM/AM/SW transmitter. The FM band also supports RDS.
550 The frequency ranges are:
552 - FM: 64 MHz - 108 MHz
553 - AM: 520 kHz - 1710 kHz
554 - SW: 2300 kHz - 26.1 MHz
556 The initial frequency when the driver is loaded is 95.5 MHz.
558 The FM transmitter supports RDS as well, both using 'Block I/O' and 'Controls'
559 modes. In the 'Controls' mode the transmitted RDS information is configured
560 using controls, and in 'Block I/O' mode the blocks are passed to the driver
564 Software Defined Radio Receiver
565 -------------------------------
567 The SDR receiver has three frequency bands for the ADC tuner:
573 The RF tuner supports 50 MHz - 2000 MHz.
575 The generated data contains the In-phase and Quadrature components of a
576 1 kHz tone that has an amplitude of sqrt(2).
582 The Metadata capture generates UVC format metadata. The PTS and SCR are
583 transmitted based on the values set in vivid contols.
585 The Metadata device will only work for the Webcam input, it will give
586 back an error for all other inputs.
592 The Metadata output can be used to set brightness, contrast, saturation and hue.
594 The Metadata device will only work for the Webcam output, it will give
595 back an error for all other outputs.
601 The Touch capture generates touch patterns simulating single tap, double tap,
602 triple tap, move from left to right, zoom in, zoom out, palm press (simulating
603 a large area being pressed on a touchpad), and simulating 16 simultaneous
609 Different devices support different controls. The sections below will describe
610 each control and which devices support them.
613 User Controls - Test Controls
614 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
616 The Button, Boolean, Integer 32 Bits, Integer 64 Bits, Menu, String, Bitmask and
617 Integer Menu are controls that represent all possible control types. The Menu
618 control and the Integer Menu control both have 'holes' in their menu list,
619 meaning that one or more menu items return EINVAL when VIDIOC_QUERYMENU is called.
620 Both menu controls also have a non-zero minimum control value. These features
621 allow you to check if your application can handle such things correctly.
622 These controls are supported for every device type.
625 User Controls - Video Capture
626 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
628 The following controls are specific to video capture.
630 The Brightness, Contrast, Saturation and Hue controls actually work and are
631 standard. There is one special feature with the Brightness control: each
632 video input has its own brightness value, so changing input will restore
633 the brightness for that input. In addition, each video input uses a different
634 brightness range (minimum and maximum control values). Switching inputs will
635 cause a control event to be sent with the V4L2_EVENT_CTRL_CH_RANGE flag set.
636 This allows you to test controls that can change their range.
638 The 'Gain, Automatic' and Gain controls can be used to test volatile controls:
639 if 'Gain, Automatic' is set, then the Gain control is volatile and changes
640 constantly. If 'Gain, Automatic' is cleared, then the Gain control is a normal
643 The 'Horizontal Flip' and 'Vertical Flip' controls can be used to flip the
644 image. These combine with the 'Sensor Flipped Horizontally/Vertically' Vivid
647 The 'Alpha Component' control can be used to set the alpha component for
648 formats containing an alpha channel.
651 User Controls - Audio
652 ~~~~~~~~~~~~~~~~~~~~~
654 The following controls are specific to video capture and output and radio
655 receivers and transmitters.
657 The 'Volume' and 'Mute' audio controls are typical for such devices to
658 control the volume and mute the audio. They don't actually do anything in
665 These vivid custom controls control the image generation, error injection, etc.
668 Test Pattern Controls
669 ^^^^^^^^^^^^^^^^^^^^^
671 The Test Pattern Controls are all specific to video capture.
675 selects which test pattern to use. Use the CSC Colorbar for
676 testing colorspace conversions: the colors used in that test pattern
677 map to valid colors in all colorspaces. The colorspace conversion
678 is disabled for the other test patterns.
682 selects whether the text superimposed on the
683 test pattern should be shown, and if so, whether only counters should
684 be displayed or the full text.
686 - Horizontal Movement:
688 selects whether the test pattern should
689 move to the left or right and at what speed.
693 does the same for the vertical direction.
697 show a two-pixel wide border at the edge of the actual image,
698 excluding letter or pillarboxing.
702 show a square in the middle of the image. If the image is
703 displayed with the correct pixel and image aspect ratio corrections,
704 then the width and height of the square on the monitor should be
707 - Insert SAV Code in Image:
709 adds a SAV (Start of Active Video) code to the image.
710 This can be used to check if such codes in the image are inadvertently
711 interpreted instead of being ignored.
713 - Insert EAV Code in Image:
715 does the same for the EAV (End of Active Video) code.
717 - Insert Video Guard Band
719 adds 4 columns of pixels with the HDMI Video Guard Band code at the
720 left hand side of the image. This only works with 3 or 4 byte RGB pixel
721 formats. The RGB pixel value 0xab/0x55/0xab turns out to be equivalent
722 to the HDMI Video Guard Band code that precedes each active video line
723 (see section 5.2.2.1 in the HDMI 1.3 Specification). To test if a video
724 receiver has correct HDMI Video Guard Band processing, enable this
725 control and then move the image to the left hand side of the screen.
726 That will result in video lines that start with multiple pixels that
727 have the same value as the Video Guard Band that precedes them.
728 Receivers that will just keep skipping Video Guard Band values will
729 now fail and either loose sync or these video lines will shift.
732 Capture Feature Selection Controls
733 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
735 These controls are all specific to video capture.
737 - Sensor Flipped Horizontally:
739 the image is flipped horizontally and the
740 V4L2_IN_ST_HFLIP input status flag is set. This emulates the case where
741 a sensor is for example mounted upside down.
743 - Sensor Flipped Vertically:
745 the image is flipped vertically and the
746 V4L2_IN_ST_VFLIP input status flag is set. This emulates the case where
747 a sensor is for example mounted upside down.
749 - Standard Aspect Ratio:
751 selects if the image aspect ratio as used for the TV or
752 S-Video input should be 4x3, 16x9 or anamorphic widescreen. This may
753 introduce letterboxing.
755 - DV Timings Aspect Ratio:
757 selects if the image aspect ratio as used for the HDMI
758 input should be the same as the source width and height ratio, or if
759 it should be 4x3 or 16x9. This may introduce letter or pillarboxing.
763 selects when the timestamp for each buffer is taken.
767 selects which colorspace should be used when generating the image.
768 This only applies if the CSC Colorbar test pattern is selected,
769 otherwise the test pattern will go through unconverted.
770 This behavior is also what you want, since a 75% Colorbar
771 should really have 75% signal intensity and should not be affected
772 by colorspace conversions.
774 Changing the colorspace will result in the V4L2_EVENT_SOURCE_CHANGE
775 to be sent since it emulates a detected colorspace change.
779 selects which colorspace transfer function should be used when
780 generating an image. This only applies if the CSC Colorbar test pattern is
781 selected, otherwise the test pattern will go through unconverted.
782 This behavior is also what you want, since a 75% Colorbar
783 should really have 75% signal intensity and should not be affected
784 by colorspace conversions.
786 Changing the transfer function will result in the V4L2_EVENT_SOURCE_CHANGE
787 to be sent since it emulates a detected colorspace change.
791 selects which Y'CbCr encoding should be used when generating
792 a Y'CbCr image. This only applies if the format is set to a Y'CbCr format
793 as opposed to an RGB format.
795 Changing the Y'CbCr encoding will result in the V4L2_EVENT_SOURCE_CHANGE
796 to be sent since it emulates a detected colorspace change.
800 selects which quantization should be used for the RGB or Y'CbCr
801 encoding when generating the test pattern.
803 Changing the quantization will result in the V4L2_EVENT_SOURCE_CHANGE
804 to be sent since it emulates a detected colorspace change.
806 - Limited RGB Range (16-235):
808 selects if the RGB range of the HDMI source should
809 be limited or full range. This combines with the Digital Video 'Rx RGB
810 Quantization Range' control and can be used to test what happens if
811 a source provides you with the wrong quantization range information.
812 See the description of that control for more details.
814 - Apply Alpha To Red Only:
816 apply the alpha channel as set by the 'Alpha Component'
817 user control to the red color of the test pattern only.
819 - Enable Capture Cropping:
821 enables crop support. This control is only present if
822 the ccs_cap_mode module option is set to the default value of -1 and if
823 the no_error_inj module option is set to 0 (the default).
825 - Enable Capture Composing:
827 enables composing support. This control is only
828 present if the ccs_cap_mode module option is set to the default value of
829 -1 and if the no_error_inj module option is set to 0 (the default).
831 - Enable Capture Scaler:
833 enables support for a scaler (maximum 4 times upscaling
834 and downscaling). This control is only present if the ccs_cap_mode
835 module option is set to the default value of -1 and if the no_error_inj
836 module option is set to 0 (the default).
838 - Maximum EDID Blocks:
840 determines how many EDID blocks the driver supports.
841 Note that the vivid driver does not actually interpret new EDID
842 data, it just stores it. It allows for up to 256 EDID blocks
843 which is the maximum supported by the standard.
845 - Fill Percentage of Frame:
847 can be used to draw only the top X percent
848 of the image. Since each frame has to be drawn by the driver, this
849 demands a lot of the CPU. For large resolutions this becomes
850 problematic. By drawing only part of the image this CPU load can
854 Output Feature Selection Controls
855 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
857 These controls are all specific to video output.
859 - Enable Output Cropping:
861 enables crop support. This control is only present if
862 the ccs_out_mode module option is set to the default value of -1 and if
863 the no_error_inj module option is set to 0 (the default).
865 - Enable Output Composing:
867 enables composing support. This control is only
868 present if the ccs_out_mode module option is set to the default value of
869 -1 and if the no_error_inj module option is set to 0 (the default).
871 - Enable Output Scaler:
873 enables support for a scaler (maximum 4 times upscaling
874 and downscaling). This control is only present if the ccs_out_mode
875 module option is set to the default value of -1 and if the no_error_inj
876 module option is set to 0 (the default).
879 Error Injection Controls
880 ^^^^^^^^^^^^^^^^^^^^^^^^
882 The following two controls are only valid for video and vbi capture.
884 - Standard Signal Mode:
886 selects the behavior of VIDIOC_QUERYSTD: what should it return?
888 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
889 to be sent since it emulates a changed input condition (e.g. a cable
890 was plugged in or out).
894 selects the standard that VIDIOC_QUERYSTD should return if the
895 previous control is set to "Selected Standard".
897 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
898 to be sent since it emulates a changed input standard.
901 The following two controls are only valid for video capture.
903 - DV Timings Signal Mode:
905 selects the behavior of VIDIOC_QUERY_DV_TIMINGS: what
908 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
909 to be sent since it emulates a changed input condition (e.g. a cable
910 was plugged in or out).
914 selects the timings the VIDIOC_QUERY_DV_TIMINGS should return
915 if the previous control is set to "Selected DV Timings".
917 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
918 to be sent since it emulates changed input timings.
921 The following controls are only present if the no_error_inj module option
922 is set to 0 (the default). These controls are valid for video and vbi
923 capture and output streams and for the SDR capture device except for the
924 Disconnect control which is valid for all devices.
926 - Wrap Sequence Number:
928 test what happens when you wrap the sequence number in
929 struct v4l2_buffer around.
933 test what happens when you wrap the timestamp in struct
936 - Percentage of Dropped Buffers:
938 sets the percentage of buffers that
939 are never returned by the driver (i.e., they are dropped).
943 emulates a USB disconnect. The device will act as if it has
944 been disconnected. Only after all open filehandles to the device
945 node have been closed will the device become 'connected' again.
947 - Inject V4L2_BUF_FLAG_ERROR:
949 when pressed, the next frame returned by
950 the driver will have the error flag set (i.e. the frame is marked
953 - Inject VIDIOC_REQBUFS Error:
955 when pressed, the next REQBUFS or CREATE_BUFS
956 ioctl call will fail with an error. To be precise: the videobuf2
957 queue_setup() op will return -EINVAL.
959 - Inject VIDIOC_QBUF Error:
961 when pressed, the next VIDIOC_QBUF or
962 VIDIOC_PREPARE_BUFFER ioctl call will fail with an error. To be
963 precise: the videobuf2 buf_prepare() op will return -EINVAL.
965 - Inject VIDIOC_STREAMON Error:
967 when pressed, the next VIDIOC_STREAMON ioctl
968 call will fail with an error. To be precise: the videobuf2
969 start_streaming() op will return -EINVAL.
971 - Inject Fatal Streaming Error:
973 when pressed, the streaming core will be
974 marked as having suffered a fatal error, the only way to recover
975 from that is to stop streaming. To be precise: the videobuf2
976 vb2_queue_error() function is called.
979 VBI Raw Capture Controls
980 ^^^^^^^^^^^^^^^^^^^^^^^^
982 - Interlaced VBI Format:
984 if set, then the raw VBI data will be interlaced instead
985 of providing it grouped by field.
988 Digital Video Controls
989 ~~~~~~~~~~~~~~~~~~~~~~
991 - Rx RGB Quantization Range:
993 sets the RGB quantization detection of the HDMI
994 input. This combines with the Vivid 'Limited RGB Range (16-235)'
995 control and can be used to test what happens if a source provides
996 you with the wrong quantization range information. This can be tested
997 by selecting an HDMI input, setting this control to Full or Limited
998 range and selecting the opposite in the 'Limited RGB Range (16-235)'
999 control. The effect is easy to see if the 'Gray Ramp' test pattern
1002 - Tx RGB Quantization Range:
1004 sets the RGB quantization detection of the HDMI
1005 output. It is currently not used for anything in vivid, but most HDMI
1006 transmitters would typically have this control.
1010 sets the transmit mode of the HDMI output to HDMI or DVI-D. This
1011 affects the reported colorspace since DVI_D outputs will always use
1016 sets the presence of a "display" on the HDMI output. This affects
1017 the tx_edid_present, tx_hotplug and tx_rxsense controls.
1020 FM Radio Receiver Controls
1021 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1025 set if the RDS receiver should be enabled.
1036 - RDS Traffic Announcement:
1039 - RDS Traffic Program:
1044 these are all read-only controls. If RDS Rx I/O Mode is set to
1045 "Block I/O", then they are inactive as well. If RDS Rx I/O Mode is set
1046 to "Controls", then these controls report the received RDS data.
1049 The vivid implementation of this is pretty basic: they are only
1050 updated when you set a new frequency or when you get the tuner status
1053 - Radio HW Seek Mode:
1055 can be one of "Bounded", "Wrap Around" or "Both". This
1056 determines if VIDIOC_S_HW_FREQ_SEEK will be bounded by the frequency
1057 range or wrap-around or if it is selectable by the user.
1059 - Radio Programmable HW Seek:
1061 if set, then the user can provide the lower and
1062 upper bound of the HW Seek. Otherwise the frequency range boundaries
1065 - Generate RBDS Instead of RDS:
1067 if set, then generate RBDS (the US variant of
1068 RDS) data instead of RDS (European-style RDS). This affects only the
1069 PICODE and PTY codes.
1073 this can be "Block I/O" where the RDS blocks have to be read()
1074 by the application, or "Controls" where the RDS data is provided by
1075 the RDS controls mentioned above.
1078 FM Radio Modulator Controls
1079 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
1096 - RDS Artificial Head:
1105 - RDS Traffic Announcement:
1108 - RDS Traffic Program:
1113 these are all controls that set the RDS data that is transmitted by
1118 this can be "Block I/O" where the application has to use write()
1119 to pass the RDS blocks to the driver, or "Controls" where the RDS data
1120 is Provided by the RDS controls mentioned above.
1122 Metadata Capture Controls
1123 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1127 if set, then the generated metadata stream contains Presentation timestamp.
1131 if set, then the generated metadata stream contains Source Clock information.
1133 Video, VBI and RDS Looping
1134 --------------------------
1136 The vivid driver supports looping of video output to video input, VBI output
1137 to VBI input and RDS output to RDS input. For video/VBI looping this emulates
1138 as if a cable was hooked up between the output and input connector. So video
1139 and VBI looping is only supported between S-Video and HDMI inputs and outputs.
1140 VBI is only valid for S-Video as it makes no sense for HDMI.
1142 Since radio is wireless this looping always happens if the radio receiver
1143 frequency is close to the radio transmitter frequency. In that case the radio
1144 transmitter will 'override' the emulated radio stations.
1146 Looping is currently supported only between devices created by the same
1147 vivid driver instance.
1150 Video and Sliced VBI looping
1151 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1153 The way to enable video/VBI looping is currently fairly crude. A 'Loop Video'
1154 control is available in the "Vivid" control class of the video
1155 capture and VBI capture devices. When checked the video looping will be enabled.
1156 Once enabled any video S-Video or HDMI input will show a static test pattern
1157 until the video output has started. At that time the video output will be
1158 looped to the video input provided that:
1160 - the input type matches the output type. So the HDMI input cannot receive
1161 video from the S-Video output.
1163 - the video resolution of the video input must match that of the video output.
1164 So it is not possible to loop a 50 Hz (720x576) S-Video output to a 60 Hz
1165 (720x480) S-Video input, or a 720p60 HDMI output to a 1080p30 input.
1167 - the pixel formats must be identical on both sides. Otherwise the driver would
1168 have to do pixel format conversion as well, and that's taking things too far.
1170 - the field settings must be identical on both sides. Same reason as above:
1171 requiring the driver to convert from one field format to another complicated
1172 matters too much. This also prohibits capturing with 'Field Top' or 'Field
1173 Bottom' when the output video is set to 'Field Alternate'. This combination,
1174 while legal, became too complicated to support. Both sides have to be 'Field
1175 Alternate' for this to work. Also note that for this specific case the
1176 sequence and field counting in struct v4l2_buffer on the capture side may not
1179 - field settings V4L2_FIELD_SEQ_TB/BT are not supported. While it is possible to
1180 implement this, it would mean a lot of work to get this right. Since these
1181 field values are rarely used the decision was made not to implement this for
1184 - on the input side the "Standard Signal Mode" for the S-Video input or the
1185 "DV Timings Signal Mode" for the HDMI input should be configured so that a
1186 valid signal is passed to the video input.
1188 The framerates do not have to match, although this might change in the future.
1190 By default you will see the OSD text superimposed on top of the looped video.
1191 This can be turned off by changing the "OSD Text Mode" control of the video
1194 For VBI looping to work all of the above must be valid and in addition the vbi
1195 output must be configured for sliced VBI. The VBI capture side can be configured
1196 for either raw or sliced VBI. Note that at the moment only CC/XDS (60 Hz formats)
1197 and WSS (50 Hz formats) VBI data is looped. Teletext VBI data is not looped.
1203 As mentioned in section 6 the radio receiver emulates stations are regular
1204 frequency intervals. Depending on the frequency of the radio receiver a
1205 signal strength value is calculated (this is returned by VIDIOC_G_TUNER).
1206 However, it will also look at the frequency set by the radio transmitter and
1207 if that results in a higher signal strength than the settings of the radio
1208 transmitter will be used as if it was a valid station. This also includes
1209 the RDS data (if any) that the transmitter 'transmits'. This is received
1210 faithfully on the receiver side. Note that when the driver is loaded the
1211 frequencies of the radio receiver and transmitter are not identical, so
1212 initially no looping takes place.
1215 Cropping, Composing, Scaling
1216 ----------------------------
1218 This driver supports cropping, composing and scaling in any combination. Normally
1219 which features are supported can be selected through the Vivid controls,
1220 but it is also possible to hardcode it when the module is loaded through the
1221 ccs_cap_mode and ccs_out_mode module options. See section 1 on the details of
1222 these module options.
1224 This allows you to test your application for all these variations.
1226 Note that the webcam input never supports cropping, composing or scaling. That
1227 only applies to the TV/S-Video/HDMI inputs and outputs. The reason is that
1228 webcams, including this virtual implementation, normally use
1229 VIDIOC_ENUM_FRAMESIZES to list a set of discrete framesizes that it supports.
1230 And that does not combine with cropping, composing or scaling. This is
1231 primarily a limitation of the V4L2 API which is carefully reproduced here.
1233 The minimum and maximum resolutions that the scaler can achieve are 16x16 and
1234 (4096 * 4) x (2160 x 4), but it can only scale up or down by a factor of 4 or
1235 less. So for a source resolution of 1280x720 the minimum the scaler can do is
1236 320x180 and the maximum is 5120x2880. You can play around with this using the
1237 qv4l2 test tool and you will see these dependencies.
1239 This driver also supports larger 'bytesperline' settings, something that
1240 VIDIOC_S_FMT allows but that few drivers implement.
1242 The scaler is a simple scaler that uses the Coarse Bresenham algorithm. It's
1243 designed for speed and simplicity, not quality.
1245 If the combination of crop, compose and scaling allows it, then it is possible
1246 to change crop and compose rectangles on the fly.
1252 The driver supports all the regular packed and planar 4:4:4, 4:2:2 and 4:2:0
1253 YUYV formats, 8, 16, 24 and 32 RGB packed formats and various multiplanar
1256 The alpha component can be set through the 'Alpha Component' User control
1257 for those formats that support it. If the 'Apply Alpha To Red Only' control
1258 is set, then the alpha component is only used for the color red and set to
1261 The driver has to be configured to support the multiplanar formats. By default
1262 the driver instances are single-planar. This can be changed by setting the
1263 multiplanar module option, see section 1 for more details on that option.
1265 If the driver instance is using the multiplanar formats/API, then the first
1266 single planar format (YUYV) and the multiplanar NV16M and NV61M formats the
1267 will have a plane that has a non-zero data_offset of 128 bytes. It is rare for
1268 data_offset to be non-zero, so this is a useful feature for testing applications.
1270 Video output will also honor any data_offset that the application set.
1276 Note: capture overlay support is implemented primarily to test the existing
1277 V4L2 capture overlay API. In practice few if any GPUs support such overlays
1278 anymore, and neither are they generally needed anymore since modern hardware
1279 is so much more capable. By setting flag 0x10000 in the node_types module
1280 option the vivid driver will create a simple framebuffer device that can be
1281 used for testing this API. Whether this API should be used for new drivers is
1284 This driver has support for a destructive capture overlay with bitmap clipping
1285 and list clipping (up to 16 rectangles) capabilities. Overlays are not
1286 supported for multiplanar formats. It also honors the struct v4l2_window field
1287 setting: if it is set to FIELD_TOP or FIELD_BOTTOM and the capture setting is
1288 FIELD_ALTERNATE, then only the top or bottom fields will be copied to the overlay.
1290 The overlay only works if you are also capturing at that same time. This is a
1291 vivid limitation since it copies from a buffer to the overlay instead of
1292 filling the overlay directly. And if you are not capturing, then no buffers
1293 are available to fill.
1295 In addition, the pixelformat of the capture format and that of the framebuffer
1296 must be the same for the overlay to work. Otherwise VIDIOC_OVERLAY will return
1299 In order to really see what it going on you will need to create two vivid
1300 instances: the first with a framebuffer enabled. You configure the capture
1301 overlay of the second instance to use the framebuffer of the first, then
1302 you start capturing in the second instance. For the first instance you setup
1303 the output overlay for the video output, turn on video looping and capture
1304 to see the blended framebuffer overlay that's being written to by the second
1305 instance. This setup would require the following commands:
1307 .. code-block:: none
1309 $ sudo modprobe vivid n_devs=2 node_types=0x10101,0x1
1310 $ v4l2-ctl -d1 --find-fb
1311 /dev/fb1 is the framebuffer associated with base address 0x12800000
1312 $ sudo v4l2-ctl -d2 --set-fbuf fb=1
1313 $ v4l2-ctl -d1 --set-fbuf fb=1
1314 $ v4l2-ctl -d0 --set-fmt-video=pixelformat='AR15'
1315 $ v4l2-ctl -d1 --set-fmt-video-out=pixelformat='AR15'
1316 $ v4l2-ctl -d2 --set-fmt-video=pixelformat='AR15'
1319 $ v4l2-ctl -d2 -c horizontal_movement=4
1320 $ v4l2-ctl -d1 --overlay=1
1321 $ v4l2-ctl -d0 -c loop_video=1
1322 $ v4l2-ctl -d2 --stream-mmap --overlay=1
1324 And from another console:
1326 .. code-block:: none
1328 $ v4l2-ctl -d1 --stream-out-mmap
1330 And yet another console:
1332 .. code-block:: none
1336 and start streaming.
1338 As you can see, this is not for the faint of heart...
1344 Note: output overlays are primarily implemented in order to test the existing
1345 V4L2 output overlay API. Whether this API should be used for new drivers is
1348 This driver has support for an output overlay and is capable of:
1351 - list clipping (up to 16 rectangles)
1356 - local inverse alpha
1358 Output overlays are not supported for multiplanar formats. In addition, the
1359 pixelformat of the capture format and that of the framebuffer must be the
1360 same for the overlay to work. Otherwise VIDIOC_OVERLAY will return an error.
1362 Output overlays only work if the driver has been configured to create a
1363 framebuffer by setting flag 0x10000 in the node_types module option. The
1364 created framebuffer has a size of 720x576 and supports ARGB 1:5:5:5 and
1367 In order to see the effects of the various clipping, chromakeying or alpha
1368 processing capabilities you need to turn on video looping and see the results
1369 on the capture side. The use of the clipping, chromakeying or alpha processing
1370 capabilities will slow down the video loop considerably as a lot of checks have
1371 to be done per pixel.
1374 CEC (Consumer Electronics Control)
1375 ----------------------------------
1377 If there are HDMI inputs then a CEC adapter will be created that has
1378 the same number of input ports. This is the equivalent of e.g. a TV that
1379 has that number of inputs. Each HDMI output will also create a
1380 CEC adapter that is hooked up to the corresponding input port, or (if there
1381 are more outputs than inputs) is not hooked up at all. In other words,
1382 this is the equivalent of hooking up each output device to an input port of
1383 the TV. Any remaining output devices remain unconnected.
1385 The EDID that each output reads reports a unique CEC physical address that is
1386 based on the physical address of the EDID of the input. So if the EDID of the
1387 receiver has physical address A.B.0.0, then each output will see an EDID
1388 containing physical address A.B.C.0 where C is 1 to the number of inputs. If
1389 there are more outputs than inputs then the remaining outputs have a CEC adapter
1390 that is disabled and reports an invalid physical address.
1393 Some Future Improvements
1394 ------------------------
1396 Just as a reminder and in no particular order:
1398 - Add a virtual alsa driver to test audio
1399 - Add virtual sub-devices and media controller support
1400 - Some support for testing compressed video
1401 - Add support to loop raw VBI output to raw VBI input
1402 - Add support to loop teletext sliced VBI output to VBI input
1403 - Fix sequence/field numbering when looping of video with alternate fields
1404 - Add support for V4L2_CID_BG_COLOR for video outputs
1405 - Add ARGB888 overlay support: better testing of the alpha channel
1406 - Improve pixel aspect support in the tpg code by passing a real v4l2_fract
1407 - Use per-queue locks and/or per-device locks to improve throughput
1408 - Add support to loop from a specific output to a specific input across
1410 - The SDR radio should use the same 'frequencies' for stations as the normal
1411 radio receiver, and give back noise if the frequency doesn't match up with
1413 - Make a thread for the RDS generation, that would help in particular for the
1414 "Controls" RDS Rx I/O Mode as the read-only RDS controls could be updated
1416 - Changing the EDID should cause hotplug detect emulation to happen.