| blob | e35d376b7f645c84bec82b2e7b4faf3d547f4126 |
1 vivid: Virtual Video Test Driver
2 ================================
4 This driver emulates video4linux hardware of various types: video capture, video
5 output, vbi capture and output, radio receivers and transmitters and a software
6 defined radio receiver. In addition a simple framebuffer device is available for
7 testing capture and output overlays.
9 Up to 64 vivid instances can be created, each with up to 16 inputs and 16 outputs.
11 Each input can be a webcam, TV capture device, S-Video capture device or an HDMI
12 capture device. Each output can be an S-Video output device or an HDMI output
13 device.
15 These inputs and outputs act exactly as a real hardware device would behave. This
16 allows you to use this driver as a test input for application development, since
17 you can test the various features without requiring special hardware.
19 This document describes the features implemented by this driver:
21 - Support for read()/write(), MMAP, USERPTR and DMABUF streaming I/O.
22 - A large list of test patterns and variations thereof
23 - Working brightness, contrast, saturation and hue controls
24 - Support for the alpha color component
25 - Full colorspace support, including limited/full RGB range
26 - All possible control types are present
27 - Support for various pixel aspect ratios and video aspect ratios
28 - Error injection to test what happens if errors occur
29 - Supports crop/compose/scale in any combination for both input and output
30 - Can emulate up to 4K resolutions
31 - All Field settings are supported for testing interlaced capturing
32 - Supports all standard YUV and RGB formats, including two multiplanar YUV formats
33 - Raw and Sliced VBI capture and output support
34 - Radio receiver and transmitter support, including RDS support
35 - Software defined radio (SDR) support
36 - Capture and output overlay support
38 These features will be described in more detail below.
41 Table of Contents
42 -----------------
44 Section 1: Configuring the driver
45 Section 2: Video Capture
46 Section 2.1: Webcam Input
47 Section 2.2: TV and S-Video Inputs
48 Section 2.3: HDMI Input
49 Section 3: Video Output
50 Section 3.1: S-Video Output
51 Section 3.2: HDMI Output
52 Section 4: VBI Capture
53 Section 5: VBI Output
54 Section 6: Radio Receiver
55 Section 7: Radio Transmitter
56 Section 8: Software Defined Radio Receiver
57 Section 9: Controls
58 Section 9.1: User Controls - Test Controls
59 Section 9.2: User Controls - Video Capture
60 Section 9.3: User Controls - Audio
61 Section 9.4: Vivid Controls
62 Section 9.4.1: Test Pattern Controls
63 Section 9.4.2: Capture Feature Selection Controls
64 Section 9.4.3: Output Feature Selection Controls
65 Section 9.4.4: Error Injection Controls
66 Section 9.4.5: VBI Raw Capture Controls
67 Section 9.5: Digital Video Controls
68 Section 9.6: FM Radio Receiver Controls
69 Section 9.7: FM Radio Modulator
70 Section 10: Video, VBI and RDS Looping
71 Section 10.1: Video and Sliced VBI looping
72 Section 10.2: Radio & RDS Looping
73 Section 11: Cropping, Composing, Scaling
74 Section 12: Formats
75 Section 13: Capture Overlay
76 Section 14: Output Overlay
77 Section 15: Some Future Improvements
80 Section 1: Configuring the driver
81 ---------------------------------
83 By default the driver will create a single instance that has a video capture
84 device with webcam, TV, S-Video and HDMI inputs, a video output device with
85 S-Video and HDMI outputs, one vbi capture device, one vbi output device, one
86 radio receiver device, one radio transmitter device and one SDR device.
88 The number of instances, devices, video inputs and outputs and their types are
89 all configurable using the following module options:
91 n_devs: number of driver instances to create. By default set to 1. Up to 64
92 instances can be created.
94 node_types: which devices should each driver instance create. An array of
95 hexadecimal values, one for each instance. The default is 0x1d3d.
96 Each value is a bitmask with the following meaning:
97 bit 0: Video Capture node
98 bit 2-3: VBI Capture node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both
99 bit 4: Radio Receiver node
100 bit 5: Software Defined Radio Receiver node
101 bit 8: Video Output node
102 bit 10-11: VBI Output node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both
103 bit 12: Radio Transmitter node
104 bit 16: Framebuffer for testing overlays
106 So to create four instances, the first two with just one video capture
107 device, the second two with just one video output device you would pass
108 these module options to vivid:
110 n_devs=4 node_types=0x1,0x1,0x100,0x100
112 num_inputs: the number of inputs, one for each instance. By default 4 inputs
113 are created for each video capture device. At most 16 inputs can be created,
114 and there must be at least one.
116 input_types: the input types for each instance, the default is 0xe4. This defines
117 what the type of each input is when the inputs are created for each driver
118 instance. This is a hexadecimal value with up to 16 pairs of bits, each
119 pair gives the type and bits 0-1 map to input 0, bits 2-3 map to input 1,
120 30-31 map to input 15. Each pair of bits has the following meaning:
122 00: this is a webcam input
123 01: this is a TV tuner input
124 10: this is an S-Video input
125 11: this is an HDMI input
127 So to create a video capture device with 8 inputs where input 0 is a TV
128 tuner, inputs 1-3 are S-Video inputs and inputs 4-7 are HDMI inputs you
129 would use the following module options:
131 num_inputs=8 input_types=0xffa9
133 num_outputs: the number of outputs, one for each instance. By default 2 outputs
134 are created for each video output device. At most 16 outputs can be
135 created, and there must be at least one.
137 output_types: the output types for each instance, the default is 0x02. This defines
138 what the type of each output is when the outputs are created for each
139 driver instance. This is a hexadecimal value with up to 16 bits, each bit
140 gives the type and bit 0 maps to output 0, bit 1 maps to output 1, bit
141 15 maps to output 15. The meaning of each bit is as follows:
143 0: this is an S-Video output
144 1: this is an HDMI output
146 So to create a video output device with 8 outputs where outputs 0-3 are
147 S-Video outputs and outputs 4-7 are HDMI outputs you would use the
148 following module options:
150 num_outputs=8 output_types=0xf0
152 vid_cap_nr: give the desired videoX start number for each video capture device.
153 The default is -1 which will just take the first free number. This allows
154 you to map capture video nodes to specific videoX device nodes. Example:
156 n_devs=4 vid_cap_nr=2,4,6,8
158 This will attempt to assign /dev/video2 for the video capture device of
159 the first vivid instance, video4 for the next up to video8 for the last
160 instance. If it can't succeed, then it will just take the next free
161 number.
163 vid_out_nr: give the desired videoX start number for each video output device.
164 The default is -1 which will just take the first free number.
166 vbi_cap_nr: give the desired vbiX start number for each vbi capture device.
167 The default is -1 which will just take the first free number.
169 vbi_out_nr: give the desired vbiX start number for each vbi output device.
170 The default is -1 which will just take the first free number.
172 radio_rx_nr: give the desired radioX start number for each radio receiver device.
173 The default is -1 which will just take the first free number.
175 radio_tx_nr: give the desired radioX start number for each radio transmitter
176 device. The default is -1 which will just take the first free number.
178 sdr_cap_nr: give the desired swradioX start number for each SDR capture device.
179 The default is -1 which will just take the first free number.
181 ccs_cap_mode: specify the allowed video capture crop/compose/scaling combination
182 for each driver instance. Video capture devices can have any combination
183 of cropping, composing and scaling capabilities and this will tell the
184 vivid driver which of those is should emulate. By default the user can
185 select this through controls.
187 The value is either -1 (controlled by the user) or a set of three bits,
188 each enabling (1) or disabling (0) one of the features:
190 bit 0: Enable crop support. Cropping will take only part of the
191 incoming picture.
192 bit 1: Enable compose support. Composing will copy the incoming
193 picture into a larger buffer.
194 bit 2: Enable scaling support. Scaling can scale the incoming
195 picture. The scaler of the vivid driver can enlarge up
196 or down to four times the original size. The scaler is
197 very simple and low-quality. Simplicity and speed were
198 key, not quality.
200 Note that this value is ignored by webcam inputs: those enumerate
201 discrete framesizes and that is incompatible with cropping, composing
202 or scaling.
204 ccs_out_mode: specify the allowed video output crop/compose/scaling combination
205 for each driver instance. Video output devices can have any combination
206 of cropping, composing and scaling capabilities and this will tell the
207 vivid driver which of those is should emulate. By default the user can
208 select this through controls.
210 The value is either -1 (controlled by the user) or a set of three bits,
211 each enabling (1) or disabling (0) one of the features:
213 bit 0: Enable crop support. Cropping will take only part of the
214 outgoing buffer.
215 bit 1: Enable compose support. Composing will copy the incoming
216 buffer into a larger picture frame.
217 bit 2: Enable scaling support. Scaling can scale the incoming
218 buffer. The scaler of the vivid driver can enlarge up
219 or down to four times the original size. The scaler is
220 very simple and low-quality. Simplicity and speed were
221 key, not quality.
223 multiplanar: select whether each device instance supports multi-planar formats,
224 and thus the V4L2 multi-planar API. By default device instances are
225 single-planar.
227 This module option can override that for each instance. Values are:
229 1: this is a single-planar instance.
230 2: this is a multi-planar instance.
232 vivid_debug: enable driver debugging info
234 no_error_inj: if set disable the error injecting controls. This option is
235 needed in order to run a tool like v4l2-compliance. Tools like that
236 exercise all controls including a control like 'Disconnect' which
237 emulates a USB disconnect, making the device inaccessible and so
238 all tests that v4l2-compliance is doing will fail afterwards.
240 There may be other situations as well where you want to disable the
241 error injection support of vivid. When this option is set, then the
242 controls that select crop, compose and scale behavior are also
243 removed. Unless overridden by ccs_cap_mode and/or ccs_out_mode the
244 will default to enabling crop, compose and scaling.
246 Taken together, all these module options allow you to precisely customize
247 the driver behavior and test your application with all sorts of permutations.
248 It is also very suitable to emulate hardware that is not yet available, e.g.
249 when developing software for a new upcoming device.
252 Section 2: Video Capture
253 ------------------------
255 This is probably the most frequently used feature. The video capture device
256 can be configured by using the module options num_inputs, input_types and
257 ccs_cap_mode (see section 1 for more detailed information), but by default
258 four inputs are configured: a webcam, a TV tuner, an S-Video and an HDMI
259 input, one input for each input type. Those are described in more detail
260 below.
262 Special attention has been given to the rate at which new frames become
263 available. The jitter will be around 1 jiffie (that depends on the HZ
264 configuration of your kernel, so usually 1/100, 1/250 or 1/1000 of a second),
265 but the long-term behavior is exactly following the framerate. So a
266 framerate of 59.94 Hz is really different from 60 Hz. If the framerate
267 exceeds your kernel's HZ value, then you will get dropped frames, but the
268 frame/field sequence counting will keep track of that so the sequence
269 count will skip whenever frames are dropped.
272 Section 2.1: Webcam Input
273 -------------------------
275 The webcam input supports three framesizes: 320x180, 640x360 and 1280x720. It
276 supports frames per second settings of 10, 15, 25, 30, 50 and 60 fps. Which ones
277 are available depends on the chosen framesize: the larger the framesize, the
278 lower the maximum frames per second.
280 The initially selected colorspace when you switch to the webcam input will be
281 sRGB.
284 Section 2.2: TV and S-Video Inputs
285 ----------------------------------
287 The only difference between the TV and S-Video input is that the TV has a
288 tuner. Otherwise they behave identically.
290 These inputs support audio inputs as well: one TV and one Line-In. They
291 both support all TV standards. If the standard is queried, then the Vivid
292 controls 'Standard Signal Mode' and 'Standard' determine what
293 the result will be.
295 These inputs support all combinations of the field setting. Special care has
296 been taken to faithfully reproduce how fields are handled for the different
297 TV standards. This is particularly noticable when generating a horizontally
298 moving image so the temporal effect of using interlaced formats becomes clearly
299 visible. For 50 Hz standards the top field is the oldest and the bottom field
300 is the newest in time. For 60 Hz standards that is reversed: the bottom field
301 is the oldest and the top field is the newest in time.
303 When you start capturing in V4L2_FIELD_ALTERNATE mode the first buffer will
304 contain the top field for 50 Hz standards and the bottom field for 60 Hz
305 standards. This is what capture hardware does as well.
307 Finally, for PAL/SECAM standards the first half of the top line contains noise.
308 This simulates the Wide Screen Signal that is commonly placed there.
310 The initially selected colorspace when you switch to the TV or S-Video input
311 will be SMPTE-170M.
313 The pixel aspect ratio will depend on the TV standard. The video aspect ratio
314 can be selected through the 'Standard Aspect Ratio' Vivid control.
315 Choices are '4x3', '16x9' which will give letterboxed widescreen video and
316 '16x9 Anomorphic' which will give full screen squashed anamorphic widescreen
317 video that will need to be scaled accordingly.
319 The TV 'tuner' supports a frequency range of 44-958 MHz. Channels are available
320 every 6 MHz, starting from 49.25 MHz. For each channel the generated image
321 will be in color for the +/- 0.25 MHz around it, and in grayscale for
322 +/- 1 MHz around the channel. Beyond that it is just noise. The VIDIOC_G_TUNER
323 ioctl will return 100% signal strength for +/- 0.25 MHz and 50% for +/- 1 MHz.
324 It will also return correct afc values to show whether the frequency is too
325 low or too high.
327 The audio subchannels that are returned are MONO for the +/- 1 MHz range around
328 a valid channel frequency. When the frequency is within +/- 0.25 MHz of the
329 channel it will return either MONO, STEREO, either MONO | SAP (for NTSC) or
330 LANG1 | LANG2 (for others), or STEREO | SAP.
332 Which one is returned depends on the chosen channel, each next valid channel
333 will cycle through the possible audio subchannel combinations. This allows
334 you to test the various combinations by just switching channels..
336 Finally, for these inputs the v4l2_timecode struct is filled in in the
337 dequeued v4l2_buffer struct.
340 Section 2.3: HDMI Input
341 -----------------------
343 The HDMI inputs supports all CEA-861 and DMT timings, both progressive and
344 interlaced, for pixelclock frequencies between 25 and 600 MHz. The field
345 mode for interlaced formats is always V4L2_FIELD_ALTERNATE. For HDMI the
346 field order is always top field first, and when you start capturing an
347 interlaced format you will receive the top field first.
349 The initially selected colorspace when you switch to the HDMI input or
350 select an HDMI timing is based on the format resolution: for resolutions
351 less than or equal to 720x576 the colorspace is set to SMPTE-170M, for
352 others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings).
354 The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it
355 set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV
356 standard, and for all others a 1:1 pixel aspect ratio is returned.
358 The video aspect ratio can be selected through the 'DV Timings Aspect Ratio'
359 Vivid control. Choices are 'Source Width x Height' (just use the
360 same ratio as the chosen format), '4x3' or '16x9', either of which can
361 result in pillarboxed or letterboxed video.
363 For HDMI inputs it is possible to set the EDID. By default a simple EDID
364 is provided. You can only set the EDID for HDMI inputs. Internally, however,
365 the EDID is shared between all HDMI inputs.
367 No interpretation is done of the EDID data.
370 Section 3: Video Output
371 -----------------------
373 The video output device can be configured by using the module options
374 num_outputs, output_types and ccs_out_mode (see section 1 for more detailed
375 information), but by default two outputs are configured: an S-Video and an
376 HDMI input, one output for each output type. Those are described in more detail
377 below.
379 Like with video capture the framerate is also exact in the long term.
382 Section 3.1: S-Video Output
383 ---------------------------
385 This output supports audio outputs as well: "Line-Out 1" and "Line-Out 2".
386 The S-Video output supports all TV standards.
388 This output supports all combinations of the field setting.
390 The initially selected colorspace when you switch to the TV or S-Video input
391 will be SMPTE-170M.
394 Section 3.2: HDMI Output
395 ------------------------
397 The HDMI output supports all CEA-861 and DMT timings, both progressive and
398 interlaced, for pixelclock frequencies between 25 and 600 MHz. The field
399 mode for interlaced formats is always V4L2_FIELD_ALTERNATE.
401 The initially selected colorspace when you switch to the HDMI output or
402 select an HDMI timing is based on the format resolution: for resolutions
403 less than or equal to 720x576 the colorspace is set to SMPTE-170M, for
404 others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings).
406 The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it
407 set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV
408 standard, and for all others a 1:1 pixel aspect ratio is returned.
410 An HDMI output has a valid EDID which can be obtained through VIDIOC_G_EDID.
413 Section 4: VBI Capture
414 ----------------------
416 There are three types of VBI capture devices: those that only support raw
417 (undecoded) VBI, those that only support sliced (decoded) VBI and those that
418 support both. This is determined by the node_types module option. In all
419 cases the driver will generate valid VBI data: for 60 Hz standards it will
420 generate Closed Caption and XDS data. The closed caption stream will
421 alternate between "Hello world!" and "Closed captions test" every second.
422 The XDS stream will give the current time once a minute. For 50 Hz standards
423 it will generate the Wide Screen Signal which is based on the actual Video
424 Aspect Ratio control setting and teletext pages 100-159, one page per frame.
426 The VBI device will only work for the S-Video and TV inputs, it will give
427 back an error if the current input is a webcam or HDMI.
430 Section 5: VBI Output
431 ---------------------
433 There are three types of VBI output devices: those that only support raw
434 (undecoded) VBI, those that only support sliced (decoded) VBI and those that
435 support both. This is determined by the node_types module option.
437 The sliced VBI output supports the Wide Screen Signal and the teletext signal
438 for 50 Hz standards and Closed Captioning + XDS for 60 Hz standards.
440 The VBI device will only work for the S-Video output, it will give
441 back an error if the current output is HDMI.
444 Section 6: Radio Receiver
445 -------------------------
447 The radio receiver emulates an FM/AM/SW receiver. The FM band also supports RDS.
448 The frequency ranges are:
450 FM: 64 MHz - 108 MHz
451 AM: 520 kHz - 1710 kHz
452 SW: 2300 kHz - 26.1 MHz
454 Valid channels are emulated every 1 MHz for FM and every 100 kHz for AM and SW.
455 The signal strength decreases the further the frequency is from the valid
456 frequency until it becomes 0% at +/- 50 kHz (FM) or 5 kHz (AM/SW) from the
457 ideal frequency. The initial frequency when the driver is loaded is set to
458 95 MHz.
460 The FM receiver supports RDS as well, both using 'Block I/O' and 'Controls'
461 modes. In the 'Controls' mode the RDS information is stored in read-only
462 controls. These controls are updated every time the frequency is changed,
463 or when the tuner status is requested. The Block I/O method uses the read()
464 interface to pass the RDS blocks on to the application for decoding.
466 The RDS signal is 'detected' for +/- 12.5 kHz around the channel frequency,
467 and the further the frequency is away from the valid frequency the more RDS
468 errors are randomly introduced into the block I/O stream, up to 50% of all
469 blocks if you are +/- 12.5 kHz from the channel frequency. All four errors
470 can occur in equal proportions: blocks marked 'CORRECTED', blocks marked
471 'ERROR', blocks marked 'INVALID' and dropped blocks.
473 The generated RDS stream contains all the standard fields contained in a
474 0B group, and also radio text and the current time.
476 The receiver supports HW frequency seek, either in Bounded mode, Wrap Around
477 mode or both, which is configurable with the "Radio HW Seek Mode" control.
480 Section 7: Radio Transmitter
481 ----------------------------
483 The radio transmitter emulates an FM/AM/SW transmitter. The FM band also supports RDS.
484 The frequency ranges are:
486 FM: 64 MHz - 108 MHz
487 AM: 520 kHz - 1710 kHz
488 SW: 2300 kHz - 26.1 MHz
490 The initial frequency when the driver is loaded is 95.5 MHz.
492 The FM transmitter supports RDS as well, both using 'Block I/O' and 'Controls'
493 modes. In the 'Controls' mode the transmitted RDS information is configured
494 using controls, and in 'Block I/O' mode the blocks are passed to the driver
495 using write().
498 Section 8: Software Defined Radio Receiver
499 ------------------------------------------
501 The SDR receiver has three frequency bands for the ADC tuner:
503 - 300 kHz
504 - 900 kHz - 2800 kHz
505 - 3200 kHz
507 The RF tuner supports 50 MHz - 2000 MHz.
509 The generated data contains the In-phase and Quadrature components of a
510 1 kHz tone that has an amplitude of sqrt(2).
513 Section 9: Controls
514 -------------------
516 Different devices support different controls. The sections below will describe
517 each control and which devices support them.
520 Section 9.1: User Controls - Test Controls
521 ------------------------------------------
523 The Button, Boolean, Integer 32 Bits, Integer 64 Bits, Menu, String, Bitmask and
524 Integer Menu are controls that represent all possible control types. The Menu
525 control and the Integer Menu control both have 'holes' in their menu list,
526 meaning that one or more menu items return EINVAL when VIDIOC_QUERYMENU is called.
527 Both menu controls also have a non-zero minimum control value. These features
528 allow you to check if your application can handle such things correctly.
529 These controls are supported for every device type.
532 Section 9.2: User Controls - Video Capture
533 ------------------------------------------
535 The following controls are specific to video capture.
537 The Brightness, Contrast, Saturation and Hue controls actually work and are
538 standard. There is one special feature with the Brightness control: each
539 video input has its own brightness value, so changing input will restore
540 the brightness for that input. In addition, each video input uses a different
541 brightness range (minimum and maximum control values). Switching inputs will
542 cause a control event to be sent with the V4L2_EVENT_CTRL_CH_RANGE flag set.
543 This allows you to test controls that can change their range.
545 The 'Gain, Automatic' and Gain controls can be used to test volatile controls:
546 if 'Gain, Automatic' is set, then the Gain control is volatile and changes
547 constantly. If 'Gain, Automatic' is cleared, then the Gain control is a normal
548 control.
550 The 'Horizontal Flip' and 'Vertical Flip' controls can be used to flip the
551 image. These combine with the 'Sensor Flipped Horizontally/Vertically' Vivid
552 controls.
554 The 'Alpha Component' control can be used to set the alpha component for
555 formats containing an alpha channel.
558 Section 9.3: User Controls - Audio
559 ----------------------------------
561 The following controls are specific to video capture and output and radio
562 receivers and transmitters.
564 The 'Volume' and 'Mute' audio controls are typical for such devices to
565 control the volume and mute the audio. They don't actually do anything in
566 the vivid driver.
569 Section 9.4: Vivid Controls
570 ---------------------------
572 These vivid custom controls control the image generation, error injection, etc.
575 Section 9.4.1: Test Pattern Controls
576 ------------------------------------
578 The Test Pattern Controls are all specific to video capture.
580 Test Pattern: selects which test pattern to use. Use the CSC Colorbar for
581 testing colorspace conversions: the colors used in that test pattern
582 map to valid colors in all colorspaces. The colorspace conversion
583 is disabled for the other test patterns.
585 OSD Text Mode: selects whether the text superimposed on the
586 test pattern should be shown, and if so, whether only counters should
587 be displayed or the full text.
589 Horizontal Movement: selects whether the test pattern should
590 move to the left or right and at what speed.
592 Vertical Movement: does the same for the vertical direction.
594 Show Border: show a two-pixel wide border at the edge of the actual image,
595 excluding letter or pillarboxing.
597 Show Square: show a square in the middle of the image. If the image is
598 displayed with the correct pixel and image aspect ratio corrections,
599 then the width and height of the square on the monitor should be
600 the same.
602 Insert SAV Code in Image: adds a SAV (Start of Active Video) code to the image.
603 This can be used to check if such codes in the image are inadvertently
604 interpreted instead of being ignored.
606 Insert EAV Code in Image: does the same for the EAV (End of Active Video) code.
609 Section 9.4.2: Capture Feature Selection Controls
610 -------------------------------------------------
612 These controls are all specific to video capture.
614 Sensor Flipped Horizontally: the image is flipped horizontally and the
615 V4L2_IN_ST_HFLIP input status flag is set. This emulates the case where
616 a sensor is for example mounted upside down.
618 Sensor Flipped Vertically: the image is flipped vertically and the
619 V4L2_IN_ST_VFLIP input status flag is set. This emulates the case where
620 a sensor is for example mounted upside down.
622 Standard Aspect Ratio: selects if the image aspect ratio as used for the TV or
623 S-Video input should be 4x3, 16x9 or anamorphic widescreen. This may
624 introduce letterboxing.
626 DV Timings Aspect Ratio: selects if the image aspect ratio as used for the HDMI
627 input should be the same as the source width and height ratio, or if
628 it should be 4x3 or 16x9. This may introduce letter or pillarboxing.
630 Timestamp Source: selects when the timestamp for each buffer is taken.
632 Colorspace: selects which colorspace should be used when generating the image.
633 This only applies if the CSC Colorbar test pattern is selected,
634 otherwise the test pattern will go through unconverted.
635 This behavior is also what you want, since a 75% Colorbar
636 should really have 75% signal intensity and should not be affected
637 by colorspace conversions.
639 Changing the colorspace will result in the V4L2_EVENT_SOURCE_CHANGE
640 to be sent since it emulates a detected colorspace change.
642 Transfer Function: selects which colorspace transfer function should be used when
643 generating an image. This only applies if the CSC Colorbar test pattern is
644 selected, otherwise the test pattern will go through unconverted.
645 This behavior is also what you want, since a 75% Colorbar
646 should really have 75% signal intensity and should not be affected
647 by colorspace conversions.
649 Changing the transfer function will result in the V4L2_EVENT_SOURCE_CHANGE
650 to be sent since it emulates a detected colorspace change.
652 Y'CbCr Encoding: selects which Y'CbCr encoding should be used when generating
653 a Y'CbCr image. This only applies if the format is set to a Y'CbCr format
654 as opposed to an RGB format.
656 Changing the Y'CbCr encoding will result in the V4L2_EVENT_SOURCE_CHANGE
657 to be sent since it emulates a detected colorspace change.
659 Quantization: selects which quantization should be used for the RGB or Y'CbCr
660 encoding when generating the test pattern.
662 Changing the quantization will result in the V4L2_EVENT_SOURCE_CHANGE
663 to be sent since it emulates a detected colorspace change.
665 Limited RGB Range (16-235): selects if the RGB range of the HDMI source should
666 be limited or full range. This combines with the Digital Video 'Rx RGB
667 Quantization Range' control and can be used to test what happens if
668 a source provides you with the wrong quantization range information.
669 See the description of that control for more details.
671 Apply Alpha To Red Only: apply the alpha channel as set by the 'Alpha Component'
672 user control to the red color of the test pattern only.
674 Enable Capture Cropping: enables crop support. This control is only present if
675 the ccs_cap_mode module option is set to the default value of -1 and if
676 the no_error_inj module option is set to 0 (the default).
678 Enable Capture Composing: enables composing support. This control is only
679 present if the ccs_cap_mode module option is set to the default value of
680 -1 and if the no_error_inj module option is set to 0 (the default).
682 Enable Capture Scaler: enables support for a scaler (maximum 4 times upscaling
683 and downscaling). This control is only present if the ccs_cap_mode
684 module option is set to the default value of -1 and if the no_error_inj
685 module option is set to 0 (the default).
687 Maximum EDID Blocks: determines how many EDID blocks the driver supports.
688 Note that the vivid driver does not actually interpret new EDID
689 data, it just stores it. It allows for up to 256 EDID blocks
690 which is the maximum supported by the standard.
692 Fill Percentage of Frame: can be used to draw only the top X percent
693 of the image. Since each frame has to be drawn by the driver, this
694 demands a lot of the CPU. For large resolutions this becomes
695 problematic. By drawing only part of the image this CPU load can
696 be reduced.
699 Section 9.4.3: Output Feature Selection Controls
700 ------------------------------------------------
702 These controls are all specific to video output.
704 Enable Output Cropping: enables crop support. This control is only present if
705 the ccs_out_mode module option is set to the default value of -1 and if
706 the no_error_inj module option is set to 0 (the default).
708 Enable Output Composing: enables composing support. This control is only
709 present if the ccs_out_mode module option is set to the default value of
710 -1 and if the no_error_inj module option is set to 0 (the default).
712 Enable Output Scaler: enables support for a scaler (maximum 4 times upscaling
713 and downscaling). This control is only present if the ccs_out_mode
714 module option is set to the default value of -1 and if the no_error_inj
715 module option is set to 0 (the default).
718 Section 9.4.4: Error Injection Controls
719 ---------------------------------------
721 The following two controls are only valid for video and vbi capture.
723 Standard Signal Mode: selects the behavior of VIDIOC_QUERYSTD: what should
724 it return?
726 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
727 to be sent since it emulates a changed input condition (e.g. a cable
728 was plugged in or out).
730 Standard: selects the standard that VIDIOC_QUERYSTD should return if the
731 previous control is set to "Selected Standard".
733 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
734 to be sent since it emulates a changed input standard.
737 The following two controls are only valid for video capture.
739 DV Timings Signal Mode: selects the behavior of VIDIOC_QUERY_DV_TIMINGS: what
740 should it return?
742 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
743 to be sent since it emulates a changed input condition (e.g. a cable
744 was plugged in or out).
746 DV Timings: selects the timings the VIDIOC_QUERY_DV_TIMINGS should return
747 if the previous control is set to "Selected DV Timings".
749 Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
750 to be sent since it emulates changed input timings.
753 The following controls are only present if the no_error_inj module option
754 is set to 0 (the default). These controls are valid for video and vbi
755 capture and output streams and for the SDR capture device except for the
756 Disconnect control which is valid for all devices.
758 Wrap Sequence Number: test what happens when you wrap the sequence number in
759 struct v4l2_buffer around.
761 Wrap Timestamp: test what happens when you wrap the timestamp in struct
762 v4l2_buffer around.
764 Percentage of Dropped Buffers: sets the percentage of buffers that
765 are never returned by the driver (i.e., they are dropped).
767 Disconnect: emulates a USB disconnect. The device will act as if it has
768 been disconnected. Only after all open filehandles to the device
769 node have been closed will the device become 'connected' again.
771 Inject V4L2_BUF_FLAG_ERROR: when pressed, the next frame returned by
772 the driver will have the error flag set (i.e. the frame is marked
773 corrupt).
775 Inject VIDIOC_REQBUFS Error: when pressed, the next REQBUFS or CREATE_BUFS
776 ioctl call will fail with an error. To be precise: the videobuf2
777 queue_setup() op will return -EINVAL.
779 Inject VIDIOC_QBUF Error: when pressed, the next VIDIOC_QBUF or
780 VIDIOC_PREPARE_BUFFER ioctl call will fail with an error. To be
781 precise: the videobuf2 buf_prepare() op will return -EINVAL.
783 Inject VIDIOC_STREAMON Error: when pressed, the next VIDIOC_STREAMON ioctl
784 call will fail with an error. To be precise: the videobuf2
785 start_streaming() op will return -EINVAL.
787 Inject Fatal Streaming Error: when pressed, the streaming core will be
788 marked as having suffered a fatal error, the only way to recover
789 from that is to stop streaming. To be precise: the videobuf2
790 vb2_queue_error() function is called.
793 Section 9.4.5: VBI Raw Capture Controls
794 ---------------------------------------
796 Interlaced VBI Format: if set, then the raw VBI data will be interlaced instead
797 of providing it grouped by field.
800 Section 9.5: Digital Video Controls
801 -----------------------------------
803 Rx RGB Quantization Range: sets the RGB quantization detection of the HDMI
804 input. This combines with the Vivid 'Limited RGB Range (16-235)'
805 control and can be used to test what happens if a source provides
806 you with the wrong quantization range information. This can be tested
807 by selecting an HDMI input, setting this control to Full or Limited
808 range and selecting the opposite in the 'Limited RGB Range (16-235)'
809 control. The effect is easy to see if the 'Gray Ramp' test pattern
810 is selected.
812 Tx RGB Quantization Range: sets the RGB quantization detection of the HDMI
813 output. It is currently not used for anything in vivid, but most HDMI
814 transmitters would typically have this control.
816 Transmit Mode: sets the transmit mode of the HDMI output to HDMI or DVI-D. This
817 affects the reported colorspace since DVI_D outputs will always use
818 sRGB.
821 Section 9.6: FM Radio Receiver Controls
822 ---------------------------------------
824 RDS Reception: set if the RDS receiver should be enabled.
826 RDS Program Type:
827 RDS PS Name:
828 RDS Radio Text:
829 RDS Traffic Announcement:
830 RDS Traffic Program:
831 RDS Music: these are all read-only controls. If RDS Rx I/O Mode is set to
832 "Block I/O", then they are inactive as well. If RDS Rx I/O Mode is set
833 to "Controls", then these controls report the received RDS data. Note
834 that the vivid implementation of this is pretty basic: they are only
835 updated when you set a new frequency or when you get the tuner status
836 (VIDIOC_G_TUNER).
838 Radio HW Seek Mode: can be one of "Bounded", "Wrap Around" or "Both". This
839 determines if VIDIOC_S_HW_FREQ_SEEK will be bounded by the frequency
840 range or wrap-around or if it is selectable by the user.
842 Radio Programmable HW Seek: if set, then the user can provide the lower and
843 upper bound of the HW Seek. Otherwise the frequency range boundaries
844 will be used.
846 Generate RBDS Instead of RDS: if set, then generate RBDS (the US variant of
847 RDS) data instead of RDS (European-style RDS). This affects only the
848 PICODE and PTY codes.
850 RDS Rx I/O Mode: this can be "Block I/O" where the RDS blocks have to be read()
851 by the application, or "Controls" where the RDS data is provided by
852 the RDS controls mentioned above.
855 Section 9.7: FM Radio Modulator Controls
856 ----------------------------------------
858 RDS Program ID:
859 RDS Program Type:
860 RDS PS Name:
861 RDS Radio Text:
862 RDS Stereo:
863 RDS Artificial Head:
864 RDS Compressed:
865 RDS Dymanic PTY:
866 RDS Traffic Announcement:
867 RDS Traffic Program:
868 RDS Music: these are all controls that set the RDS data that is transmitted by
869 the FM modulator.
871 RDS Tx I/O Mode: this can be "Block I/O" where the application has to use write()
872 to pass the RDS blocks to the driver, or "Controls" where the RDS data is
873 provided by the RDS controls mentioned above.
876 Section 10: Video, VBI and RDS Looping
877 --------------------------------------
879 The vivid driver supports looping of video output to video input, VBI output
880 to VBI input and RDS output to RDS input. For video/VBI looping this emulates
881 as if a cable was hooked up between the output and input connector. So video
882 and VBI looping is only supported between S-Video and HDMI inputs and outputs.
883 VBI is only valid for S-Video as it makes no sense for HDMI.
885 Since radio is wireless this looping always happens if the radio receiver
886 frequency is close to the radio transmitter frequency. In that case the radio
887 transmitter will 'override' the emulated radio stations.
889 Looping is currently supported only between devices created by the same
890 vivid driver instance.
893 Section 10.1: Video and Sliced VBI looping
894 ------------------------------------------
896 The way to enable video/VBI looping is currently fairly crude. A 'Loop Video'
897 control is available in the "Vivid" control class of the video
898 capture and VBI capture devices. When checked the video looping will be enabled.
899 Once enabled any video S-Video or HDMI input will show a static test pattern
900 until the video output has started. At that time the video output will be
901 looped to the video input provided that:
903 - the input type matches the output type. So the HDMI input cannot receive
904 video from the S-Video output.
906 - the video resolution of the video input must match that of the video output.
907 So it is not possible to loop a 50 Hz (720x576) S-Video output to a 60 Hz
908 (720x480) S-Video input, or a 720p60 HDMI output to a 1080p30 input.
910 - the pixel formats must be identical on both sides. Otherwise the driver would
911 have to do pixel format conversion as well, and that's taking things too far.
913 - the field settings must be identical on both sides. Same reason as above:
914 requiring the driver to convert from one field format to another complicated
915 matters too much. This also prohibits capturing with 'Field Top' or 'Field
916 Bottom' when the output video is set to 'Field Alternate'. This combination,
917 while legal, became too complicated to support. Both sides have to be 'Field
918 Alternate' for this to work. Also note that for this specific case the
919 sequence and field counting in struct v4l2_buffer on the capture side may not
920 be 100% accurate.
922 - field settings V4L2_FIELD_SEQ_TB/BT are not supported. While it is possible to
923 implement this, it would mean a lot of work to get this right. Since these
924 field values are rarely used the decision was made not to implement this for
925 now.
927 - on the input side the "Standard Signal Mode" for the S-Video input or the
928 "DV Timings Signal Mode" for the HDMI input should be configured so that a
929 valid signal is passed to the video input.
931 The framerates do not have to match, although this might change in the future.
933 By default you will see the OSD text superimposed on top of the looped video.
934 This can be turned off by changing the "OSD Text Mode" control of the video
935 capture device.
937 For VBI looping to work all of the above must be valid and in addition the vbi
938 output must be configured for sliced VBI. The VBI capture side can be configured
939 for either raw or sliced VBI. Note that at the moment only CC/XDS (60 Hz formats)
940 and WSS (50 Hz formats) VBI data is looped. Teletext VBI data is not looped.
943 Section 10.2: Radio & RDS Looping
944 ---------------------------------
946 As mentioned in section 6 the radio receiver emulates stations are regular
947 frequency intervals. Depending on the frequency of the radio receiver a
948 signal strength value is calculated (this is returned by VIDIOC_G_TUNER).
949 However, it will also look at the frequency set by the radio transmitter and
950 if that results in a higher signal strength than the settings of the radio
951 transmitter will be used as if it was a valid station. This also includes
952 the RDS data (if any) that the transmitter 'transmits'. This is received
953 faithfully on the receiver side. Note that when the driver is loaded the
954 frequencies of the radio receiver and transmitter are not identical, so
955 initially no looping takes place.
958 Section 11: Cropping, Composing, Scaling
959 ----------------------------------------
961 This driver supports cropping, composing and scaling in any combination. Normally
962 which features are supported can be selected through the Vivid controls,
963 but it is also possible to hardcode it when the module is loaded through the
964 ccs_cap_mode and ccs_out_mode module options. See section 1 on the details of
965 these module options.
967 This allows you to test your application for all these variations.
969 Note that the webcam input never supports cropping, composing or scaling. That
970 only applies to the TV/S-Video/HDMI inputs and outputs. The reason is that
971 webcams, including this virtual implementation, normally use
972 VIDIOC_ENUM_FRAMESIZES to list a set of discrete framesizes that it supports.
973 And that does not combine with cropping, composing or scaling. This is
974 primarily a limitation of the V4L2 API which is carefully reproduced here.
976 The minimum and maximum resolutions that the scaler can achieve are 16x16 and
977 (4096 * 4) x (2160 x 4), but it can only scale up or down by a factor of 4 or
978 less. So for a source resolution of 1280x720 the minimum the scaler can do is
979 320x180 and the maximum is 5120x2880. You can play around with this using the
980 qv4l2 test tool and you will see these dependencies.
982 This driver also supports larger 'bytesperline' settings, something that
983 VIDIOC_S_FMT allows but that few drivers implement.
985 The scaler is a simple scaler that uses the Coarse Bresenham algorithm. It's
986 designed for speed and simplicity, not quality.
988 If the combination of crop, compose and scaling allows it, then it is possible
989 to change crop and compose rectangles on the fly.
992 Section 12: Formats
993 -------------------
995 The driver supports all the regular packed and planar 4:4:4, 4:2:2 and 4:2:0
996 YUYV formats, 8, 16, 24 and 32 RGB packed formats and various multiplanar
997 formats.
999 The alpha component can be set through the 'Alpha Component' User control
1000 for those formats that support it. If the 'Apply Alpha To Red Only' control
1001 is set, then the alpha component is only used for the color red and set to
1002 0 otherwise.
1004 The driver has to be configured to support the multiplanar formats. By default
1005 the driver instances are single-planar. This can be changed by setting the
1006 multiplanar module option, see section 1 for more details on that option.
1008 If the driver instance is using the multiplanar formats/API, then the first
1009 single planar format (YUYV) and the multiplanar NV16M and NV61M formats the
1010 will have a plane that has a non-zero data_offset of 128 bytes. It is rare for
1011 data_offset to be non-zero, so this is a useful feature for testing applications.
1013 Video output will also honor any data_offset that the application set.
1016 Section 13: Capture Overlay
1017 ---------------------------
1019 Note: capture overlay support is implemented primarily to test the existing
1020 V4L2 capture overlay API. In practice few if any GPUs support such overlays
1021 anymore, and neither are they generally needed anymore since modern hardware
1022 is so much more capable. By setting flag 0x10000 in the node_types module
1023 option the vivid driver will create a simple framebuffer device that can be
1024 used for testing this API. Whether this API should be used for new drivers is
1025 questionable.
1027 This driver has support for a destructive capture overlay with bitmap clipping
1028 and list clipping (up to 16 rectangles) capabilities. Overlays are not
1029 supported for multiplanar formats. It also honors the struct v4l2_window field
1030 setting: if it is set to FIELD_TOP or FIELD_BOTTOM and the capture setting is
1031 FIELD_ALTERNATE, then only the top or bottom fields will be copied to the overlay.
1033 The overlay only works if you are also capturing at that same time. This is a
1034 vivid limitation since it copies from a buffer to the overlay instead of
1035 filling the overlay directly. And if you are not capturing, then no buffers
1036 are available to fill.
1038 In addition, the pixelformat of the capture format and that of the framebuffer
1039 must be the same for the overlay to work. Otherwise VIDIOC_OVERLAY will return
1040 an error.
1042 In order to really see what it going on you will need to create two vivid
1043 instances: the first with a framebuffer enabled. You configure the capture
1044 overlay of the second instance to use the framebuffer of the first, then
1045 you start capturing in the second instance. For the first instance you setup
1046 the output overlay for the video output, turn on video looping and capture
1047 to see the blended framebuffer overlay that's being written to by the second
1048 instance. This setup would require the following commands:
1050 $ sudo modprobe vivid n_devs=2 node_types=0x10101,0x1
1051 $ v4l2-ctl -d1 --find-fb
1052 /dev/fb1 is the framebuffer associated with base address 0x12800000
1053 $ sudo v4l2-ctl -d2 --set-fbuf fb=1
1054 $ v4l2-ctl -d1 --set-fbuf fb=1
1055 $ v4l2-ctl -d0 --set-fmt-video=pixelformat='AR15'
1056 $ v4l2-ctl -d1 --set-fmt-video-out=pixelformat='AR15'
1057 $ v4l2-ctl -d2 --set-fmt-video=pixelformat='AR15'
1058 $ v4l2-ctl -d0 -i2
1059 $ v4l2-ctl -d2 -i2
1060 $ v4l2-ctl -d2 -c horizontal_movement=4
1061 $ v4l2-ctl -d1 --overlay=1
1062 $ v4l2-ctl -d1 -c loop_video=1
1063 $ v4l2-ctl -d2 --stream-mmap --overlay=1
1065 And from another console:
1067 $ v4l2-ctl -d1 --stream-out-mmap
1069 And yet another console:
1071 $ qv4l2
1073 and start streaming.
1075 As you can see, this is not for the faint of heart...
1078 Section 14: Output Overlay
1079 --------------------------
1081 Note: output overlays are primarily implemented in order to test the existing
1082 V4L2 output overlay API. Whether this API should be used for new drivers is
1083 questionable.
1085 This driver has support for an output overlay and is capable of:
1087 - bitmap clipping,
1088 - list clipping (up to 16 rectangles)
1089 - chromakey
1090 - source chromakey
1091 - global alpha
1092 - local alpha
1093 - local inverse alpha
1095 Output overlays are not supported for multiplanar formats. In addition, the
1096 pixelformat of the capture format and that of the framebuffer must be the
1097 same for the overlay to work. Otherwise VIDIOC_OVERLAY will return an error.
1099 Output overlays only work if the driver has been configured to create a
1100 framebuffer by setting flag 0x10000 in the node_types module option. The
1101 created framebuffer has a size of 720x576 and supports ARGB 1:5:5:5 and
1102 RGB 5:6:5.
1104 In order to see the effects of the various clipping, chromakeying or alpha
1105 processing capabilities you need to turn on video looping and see the results
1106 on the capture side. The use of the clipping, chromakeying or alpha processing
1107 capabilities will slow down the video loop considerably as a lot of checks have
1108 to be done per pixel.
1111 Section 15: Some Future Improvements
1112 ------------------------------------
1114 Just as a reminder and in no particular order:
1116 - Add a virtual alsa driver to test audio
1117 - Add virtual sub-devices and media controller support
1118 - Some support for testing compressed video
1119 - Add support to loop raw VBI output to raw VBI input
1120 - Add support to loop teletext sliced VBI output to VBI input
1121 - Fix sequence/field numbering when looping of video with alternate fields
1122 - Add support for V4L2_CID_BG_COLOR for video outputs
1123 - Add ARGB888 overlay support: better testing of the alpha channel
1124 - Add custom DV timings support
1125 - Add support for V4L2_DV_FL_REDUCED_FPS
1126 - Improve pixel aspect support in the tpg code by passing a real v4l2_fract
1127 - Use per-queue locks and/or per-device locks to improve throughput
1128 - Add support to loop from a specific output to a specific input across
1129 vivid instances
1130 - The SDR radio should use the same 'frequencies' for stations as the normal
1131 radio receiver, and give back noise if the frequency doesn't match up with
1132 a station frequency
1133 - Make a thread for the RDS generation, that would help in particular for the
1134 "Controls" RDS Rx I/O Mode as the read-only RDS controls could be updated
1135 in real-time.