.. SPDX-License-Identifier: GPL-2.0
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The Virtual Video Test Driver (vivid)
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=====================================
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This driver emulates video4linux hardware of various types: video capture, video
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output, vbi capture and output, metadata capture and output, radio receivers and
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transmitters, touch capture and a software defined radio receiver. In addition a
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simple framebuffer device is available for testing capture and output overlays.
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Up to 64 vivid instances can be created, each with up to 16 inputs and 16 outputs.
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Each input can be a webcam, TV capture device, S-Video capture device or an HDMI
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capture device. Each output can be an S-Video output device or an HDMI output
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device.
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These inputs and outputs act exactly as a real hardware device would behave. This
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allows you to use this driver as a test input for application development, since
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you can test the various features without requiring special hardware.
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This document describes the features implemented by this driver:
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- Support for read()/write(), MMAP, USERPTR and DMABUF streaming I/O.
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- A large list of test patterns and variations thereof
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- Working brightness, contrast, saturation and hue controls
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- Support for the alpha color component
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- Full colorspace support, including limited/full RGB range
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- All possible control types are present
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- Support for various pixel aspect ratios and video aspect ratios
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- Error injection to test what happens if errors occur
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- Supports crop/compose/scale in any combination for both input and output
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- Can emulate up to 4K resolutions
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- All Field settings are supported for testing interlaced capturing
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- Supports all standard YUV and RGB formats, including two multiplanar YUV formats
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- Raw and Sliced VBI capture and output support
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- Radio receiver and transmitter support, including RDS support
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- Software defined radio (SDR) support
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- Capture and output overlay support
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- Metadata capture and output support
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- Touch capture support
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These features will be described in more detail below.
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Configuring the driver
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----------------------
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By default the driver will create a single instance that has a video capture
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device with webcam, TV, S-Video and HDMI inputs, a video output device with
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S-Video and HDMI outputs, one vbi capture device, one vbi output device, one
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radio receiver device, one radio transmitter device and one SDR device.
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The number of instances, devices, video inputs and outputs and their types are
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all configurable using the following module options:
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- n_devs:
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number of driver instances to create. By default set to 1. Up to 64
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instances can be created.
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- node_types:
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which devices should each driver instance create. An array of
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hexadecimal values, one for each instance. The default is 0x1d3d.
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Each value is a bitmask with the following meaning:
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- bit 0: Video Capture node
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- bit 2-3: VBI Capture node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both
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- bit 4: Radio Receiver node
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- bit 5: Software Defined Radio Receiver node
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- bit 8: Video Output node
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- bit 10-11: VBI Output node: 0 = none, 1 = raw vbi, 2 = sliced vbi, 3 = both
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- bit 12: Radio Transmitter node
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- bit 16: Framebuffer for testing overlays
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- bit 17: Metadata Capture node
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- bit 18: Metadata Output node
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- bit 19: Touch Capture node
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So to create four instances, the first two with just one video capture
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device, the second two with just one video output device you would pass
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these module options to vivid:
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.. code-block:: none
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n_devs=4 node_types=0x1,0x1,0x100,0x100
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- num_inputs:
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the number of inputs, one for each instance. By default 4 inputs
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are created for each video capture device. At most 16 inputs can be created,
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and there must be at least one.
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- input_types:
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the input types for each instance, the default is 0xe4. This defines
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what the type of each input is when the inputs are created for each driver
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instance. This is a hexadecimal value with up to 16 pairs of bits, each
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pair gives the type and bits 0-1 map to input 0, bits 2-3 map to input 1,
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30-31 map to input 15. Each pair of bits has the following meaning:
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- 00: this is a webcam input
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- 01: this is a TV tuner input
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- 10: this is an S-Video input
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- 11: this is an HDMI input
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So to create a video capture device with 8 inputs where input 0 is a TV
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tuner, inputs 1-3 are S-Video inputs and inputs 4-7 are HDMI inputs you
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would use the following module options:
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.. code-block:: none
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num_inputs=8 input_types=0xffa9
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- num_outputs:
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the number of outputs, one for each instance. By default 2 outputs
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are created for each video output device. At most 16 outputs can be
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created, and there must be at least one.
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- output_types:
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the output types for each instance, the default is 0x02. This defines
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what the type of each output is when the outputs are created for each
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driver instance. This is a hexadecimal value with up to 16 bits, each bit
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gives the type and bit 0 maps to output 0, bit 1 maps to output 1, bit
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15 maps to output 15. The meaning of each bit is as follows:
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- 0: this is an S-Video output
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- 1: this is an HDMI output
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So to create a video output device with 8 outputs where outputs 0-3 are
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S-Video outputs and outputs 4-7 are HDMI outputs you would use the
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following module options:
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.. code-block:: none
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num_outputs=8 output_types=0xf0
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- vid_cap_nr:
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give the desired videoX start number for each video capture device.
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The default is -1 which will just take the first free number. This allows
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you to map capture video nodes to specific videoX device nodes. Example:
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.. code-block:: none
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n_devs=4 vid_cap_nr=2,4,6,8
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This will attempt to assign /dev/video2 for the video capture device of
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the first vivid instance, video4 for the next up to video8 for the last
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instance. If it can't succeed, then it will just take the next free
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number.
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- vid_out_nr:
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give the desired videoX start number for each video output device.
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The default is -1 which will just take the first free number.
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- vbi_cap_nr:
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give the desired vbiX start number for each vbi capture device.
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The default is -1 which will just take the first free number.
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- vbi_out_nr:
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give the desired vbiX start number for each vbi output device.
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The default is -1 which will just take the first free number.
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- radio_rx_nr:
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give the desired radioX start number for each radio receiver device.
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The default is -1 which will just take the first free number.
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- radio_tx_nr:
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give the desired radioX start number for each radio transmitter
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device. The default is -1 which will just take the first free number.
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- sdr_cap_nr:
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give the desired swradioX start number for each SDR capture device.
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The default is -1 which will just take the first free number.
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- meta_cap_nr:
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give the desired videoX start number for each metadata capture device.
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The default is -1 which will just take the first free number.
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- meta_out_nr:
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give the desired videoX start number for each metadata output device.
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The default is -1 which will just take the first free number.
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- touch_cap_nr:
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give the desired v4l-touchX start number for each touch capture device.
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The default is -1 which will just take the first free number.
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- ccs_cap_mode:
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specify the allowed video capture crop/compose/scaling combination
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for each driver instance. Video capture devices can have any combination
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of cropping, composing and scaling capabilities and this will tell the
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vivid driver which of those is should emulate. By default the user can
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select this through controls.
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The value is either -1 (controlled by the user) or a set of three bits,
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each enabling (1) or disabling (0) one of the features:
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- bit 0:
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Enable crop support. Cropping will take only part of the
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incoming picture.
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- bit 1:
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Enable compose support. Composing will copy the incoming
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picture into a larger buffer.
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- bit 2:
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Enable scaling support. Scaling can scale the incoming
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picture. The scaler of the vivid driver can enlarge up
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or down to four times the original size. The scaler is
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very simple and low-quality. Simplicity and speed were
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key, not quality.
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Note that this value is ignored by webcam inputs: those enumerate
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discrete framesizes and that is incompatible with cropping, composing
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or scaling.
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- ccs_out_mode:
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specify the allowed video output crop/compose/scaling combination
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for each driver instance. Video output devices can have any combination
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of cropping, composing and scaling capabilities and this will tell the
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vivid driver which of those is should emulate. By default the user can
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select this through controls.
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The value is either -1 (controlled by the user) or a set of three bits,
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each enabling (1) or disabling (0) one of the features:
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- bit 0:
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Enable crop support. Cropping will take only part of the
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outgoing buffer.
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- bit 1:
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Enable compose support. Composing will copy the incoming
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buffer into a larger picture frame.
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- bit 2:
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Enable scaling support. Scaling can scale the incoming
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buffer. The scaler of the vivid driver can enlarge up
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or down to four times the original size. The scaler is
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very simple and low-quality. Simplicity and speed were
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key, not quality.
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- multiplanar:
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select whether each device instance supports multi-planar formats,
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and thus the V4L2 multi-planar API. By default device instances are
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single-planar.
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This module option can override that for each instance. Values are:
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- 1: this is a single-planar instance.
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- 2: this is a multi-planar instance.
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- vivid_debug:
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enable driver debugging info
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- no_error_inj:
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if set disable the error injecting controls. This option is
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needed in order to run a tool like v4l2-compliance. Tools like that
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exercise all controls including a control like 'Disconnect' which
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emulates a USB disconnect, making the device inaccessible and so
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all tests that v4l2-compliance is doing will fail afterwards.
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There may be other situations as well where you want to disable the
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error injection support of vivid. When this option is set, then the
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controls that select crop, compose and scale behavior are also
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removed. Unless overridden by ccs_cap_mode and/or ccs_out_mode the
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will default to enabling crop, compose and scaling.
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- allocators:
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memory allocator selection, default is 0. It specifies the way buffers
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will be allocated.
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- 0: vmalloc
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- 1: dma-contig
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- cache_hints:
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specifies if the device should set queues' user-space cache and memory
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consistency hint capability (V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS).
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The hints are valid only when using MMAP streaming I/O. Default is 0.
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- 0: forbid hints
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- 1: allow hints
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Taken together, all these module options allow you to precisely customize
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the driver behavior and test your application with all sorts of permutations.
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It is also very suitable to emulate hardware that is not yet available, e.g.
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when developing software for a new upcoming device.
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Video Capture
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-------------
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This is probably the most frequently used feature. The video capture device
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can be configured by using the module options num_inputs, input_types and
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ccs_cap_mode (see section 1 for more detailed information), but by default
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four inputs are configured: a webcam, a TV tuner, an S-Video and an HDMI
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input, one input for each input type. Those are described in more detail
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below.
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Special attention has been given to the rate at which new frames become
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available. The jitter will be around 1 jiffie (that depends on the HZ
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configuration of your kernel, so usually 1/100, 1/250 or 1/1000 of a second),
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but the long-term behavior is exactly following the framerate. So a
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framerate of 59.94 Hz is really different from 60 Hz. If the framerate
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exceeds your kernel's HZ value, then you will get dropped frames, but the
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frame/field sequence counting will keep track of that so the sequence
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count will skip whenever frames are dropped.
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Webcam Input
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~~~~~~~~~~~~
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The webcam input supports three framesizes: 320x180, 640x360 and 1280x720. It
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supports frames per second settings of 10, 15, 25, 30, 50 and 60 fps. Which ones
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are available depends on the chosen framesize: the larger the framesize, the
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lower the maximum frames per second.
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The initially selected colorspace when you switch to the webcam input will be
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sRGB.
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TV and S-Video Inputs
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~~~~~~~~~~~~~~~~~~~~~
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The only difference between the TV and S-Video input is that the TV has a
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tuner. Otherwise they behave identically.
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These inputs support audio inputs as well: one TV and one Line-In. They
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both support all TV standards. If the standard is queried, then the Vivid
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controls 'Standard Signal Mode' and 'Standard' determine what
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the result will be.
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These inputs support all combinations of the field setting. Special care has
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been taken to faithfully reproduce how fields are handled for the different
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TV standards. This is particularly noticeable when generating a horizontally
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moving image so the temporal effect of using interlaced formats becomes clearly
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visible. For 50 Hz standards the top field is the oldest and the bottom field
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is the newest in time. For 60 Hz standards that is reversed: the bottom field
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is the oldest and the top field is the newest in time.
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When you start capturing in V4L2_FIELD_ALTERNATE mode the first buffer will
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contain the top field for 50 Hz standards and the bottom field for 60 Hz
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standards. This is what capture hardware does as well.
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Finally, for PAL/SECAM standards the first half of the top line contains noise.
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This simulates the Wide Screen Signal that is commonly placed there.
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The initially selected colorspace when you switch to the TV or S-Video input
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will be SMPTE-170M.
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The pixel aspect ratio will depend on the TV standard. The video aspect ratio
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can be selected through the 'Standard Aspect Ratio' Vivid control.
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Choices are '4x3', '16x9' which will give letterboxed widescreen video and
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'16x9 Anamorphic' which will give full screen squashed anamorphic widescreen
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video that will need to be scaled accordingly.
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The TV 'tuner' supports a frequency range of 44-958 MHz. Channels are available
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every 6 MHz, starting from 49.25 MHz. For each channel the generated image
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will be in color for the +/- 0.25 MHz around it, and in grayscale for
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+/- 1 MHz around the channel. Beyond that it is just noise. The VIDIOC_G_TUNER
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ioctl will return 100% signal strength for +/- 0.25 MHz and 50% for +/- 1 MHz.
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It will also return correct afc values to show whether the frequency is too
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low or too high.
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The audio subchannels that are returned are MONO for the +/- 1 MHz range around
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a valid channel frequency. When the frequency is within +/- 0.25 MHz of the
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channel it will return either MONO, STEREO, either MONO | SAP (for NTSC) or
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LANG1 | LANG2 (for others), or STEREO | SAP.
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Which one is returned depends on the chosen channel, each next valid channel
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will cycle through the possible audio subchannel combinations. This allows
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you to test the various combinations by just switching channels..
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Finally, for these inputs the v4l2_timecode struct is filled in in the
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dequeued v4l2_buffer struct.
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HDMI Input
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~~~~~~~~~~
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The HDMI inputs supports all CEA-861 and DMT timings, both progressive and
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interlaced, for pixelclock frequencies between 25 and 600 MHz. The field
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mode for interlaced formats is always V4L2_FIELD_ALTERNATE. For HDMI the
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field order is always top field first, and when you start capturing an
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interlaced format you will receive the top field first.
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The initially selected colorspace when you switch to the HDMI input or
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select an HDMI timing is based on the format resolution: for resolutions
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less than or equal to 720x576 the colorspace is set to SMPTE-170M, for
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others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings).
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The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it
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set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV
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standard, and for all others a 1:1 pixel aspect ratio is returned.
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The video aspect ratio can be selected through the 'DV Timings Aspect Ratio'
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Vivid control. Choices are 'Source Width x Height' (just use the
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same ratio as the chosen format), '4x3' or '16x9', either of which can
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result in pillarboxed or letterboxed video.
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For HDMI inputs it is possible to set the EDID. By default a simple EDID
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is provided. You can only set the EDID for HDMI inputs. Internally, however,
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the EDID is shared between all HDMI inputs.
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No interpretation is done of the EDID data with the exception of the
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physical address. See the CEC section for more details.
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There is a maximum of 15 HDMI inputs (if there are more, then they will be
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reduced to 15) since that's the limitation of the EDID physical address.
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Video Output
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------------
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The video output device can be configured by using the module options
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num_outputs, output_types and ccs_out_mode (see section 1 for more detailed
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information), but by default two outputs are configured: an S-Video and an
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HDMI input, one output for each output type. Those are described in more detail
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below.
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Like with video capture the framerate is also exact in the long term.
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S-Video Output
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~~~~~~~~~~~~~~
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This output supports audio outputs as well: "Line-Out 1" and "Line-Out 2".
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The S-Video output supports all TV standards.
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This output supports all combinations of the field setting.
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The initially selected colorspace when you switch to the TV or S-Video input
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will be SMPTE-170M.
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HDMI Output
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~~~~~~~~~~~
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The HDMI output supports all CEA-861 and DMT timings, both progressive and
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interlaced, for pixelclock frequencies between 25 and 600 MHz. The field
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mode for interlaced formats is always V4L2_FIELD_ALTERNATE.
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The initially selected colorspace when you switch to the HDMI output or
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select an HDMI timing is based on the format resolution: for resolutions
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less than or equal to 720x576 the colorspace is set to SMPTE-170M, for
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others it is set to REC-709 (CEA-861 timings) or sRGB (VESA DMT timings).
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The pixel aspect ratio will depend on the HDMI timing: for 720x480 is it
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set as for the NTSC TV standard, for 720x576 it is set as for the PAL TV
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standard, and for all others a 1:1 pixel aspect ratio is returned.
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An HDMI output has a valid EDID which can be obtained through VIDIOC_G_EDID.
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There is a maximum of 15 HDMI outputs (if there are more, then they will be
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reduced to 15) since that's the limitation of the EDID physical address. See
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also the CEC section for more details.
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VBI Capture
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-----------
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There are three types of VBI capture devices: those that only support raw
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(undecoded) VBI, those that only support sliced (decoded) VBI and those that
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support both. This is determined by the node_types module option. In all
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cases the driver will generate valid VBI data: for 60 Hz standards it will
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generate Closed Caption and XDS data. The closed caption stream will
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alternate between "Hello world!" and "Closed captions test" every second.
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The XDS stream will give the current time once a minute. For 50 Hz standards
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it will generate the Wide Screen Signal which is based on the actual Video
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Aspect Ratio control setting and teletext pages 100-159, one page per frame.
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The VBI device will only work for the S-Video and TV inputs, it will give
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back an error if the current input is a webcam or HDMI.
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VBI Output
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----------
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There are three types of VBI output devices: those that only support raw
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(undecoded) VBI, those that only support sliced (decoded) VBI and those that
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support both. This is determined by the node_types module option.
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The sliced VBI output supports the Wide Screen Signal and the teletext signal
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for 50 Hz standards and Closed Captioning + XDS for 60 Hz standards.
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The VBI device will only work for the S-Video output, it will give
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back an error if the current output is HDMI.
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Radio Receiver
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--------------
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The radio receiver emulates an FM/AM/SW receiver. The FM band also supports RDS.
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The frequency ranges are:
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- FM: 64 MHz - 108 MHz
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- AM: 520 kHz - 1710 kHz
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- SW: 2300 kHz - 26.1 MHz
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Valid channels are emulated every 1 MHz for FM and every 100 kHz for AM and SW.
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The signal strength decreases the further the frequency is from the valid
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frequency until it becomes 0% at +/- 50 kHz (FM) or 5 kHz (AM/SW) from the
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ideal frequency. The initial frequency when the driver is loaded is set to
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95 MHz.
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The FM receiver supports RDS as well, both using 'Block I/O' and 'Controls'
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modes. In the 'Controls' mode the RDS information is stored in read-only
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controls. These controls are updated every time the frequency is changed,
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or when the tuner status is requested. The Block I/O method uses the read()
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interface to pass the RDS blocks on to the application for decoding.
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The RDS signal is 'detected' for +/- 12.5 kHz around the channel frequency,
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and the further the frequency is away from the valid frequency the more RDS
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errors are randomly introduced into the block I/O stream, up to 50% of all
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blocks if you are +/- 12.5 kHz from the channel frequency. All four errors
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can occur in equal proportions: blocks marked 'CORRECTED', blocks marked
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'ERROR', blocks marked 'INVALID' and dropped blocks.
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The generated RDS stream contains all the standard fields contained in a
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0B group, and also radio text and the current time.
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The receiver supports HW frequency seek, either in Bounded mode, Wrap Around
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mode or both, which is configurable with the "Radio HW Seek Mode" control.
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Radio Transmitter
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-----------------
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The radio transmitter emulates an FM/AM/SW transmitter. The FM band also supports RDS.
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The frequency ranges are:
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- FM: 64 MHz - 108 MHz
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- AM: 520 kHz - 1710 kHz
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- SW: 2300 kHz - 26.1 MHz
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The initial frequency when the driver is loaded is 95.5 MHz.
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The FM transmitter supports RDS as well, both using 'Block I/O' and 'Controls'
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modes. In the 'Controls' mode the transmitted RDS information is configured
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using controls, and in 'Block I/O' mode the blocks are passed to the driver
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using write().
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Software Defined Radio Receiver
|
-------------------------------
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The SDR receiver has three frequency bands for the ADC tuner:
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- 300 kHz
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- 900 kHz - 2800 kHz
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- 3200 kHz
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The RF tuner supports 50 MHz - 2000 MHz.
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The generated data contains the In-phase and Quadrature components of a
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1 kHz tone that has an amplitude of sqrt(2).
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Metadata Capture
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----------------
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The Metadata capture generates UVC format metadata. The PTS and SCR are
|
transmitted based on the values set in vivid contols.
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|
The Metadata device will only work for the Webcam input, it will give
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back an error for all other inputs.
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Metadata Output
|
---------------
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|
The Metadata output can be used to set brightness, contrast, saturation and hue.
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The Metadata device will only work for the Webcam output, it will give
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back an error for all other outputs.
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Touch Capture
|
-------------
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|
The Touch capture generates touch patterns simulating single tap, double tap,
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triple tap, move from left to right, zoom in, zoom out, palm press (simulating
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a large area being pressed on a touchpad), and simulating 16 simultaneous
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touch points.
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Controls
|
--------
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Different devices support different controls. The sections below will describe
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each control and which devices support them.
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|
User Controls - Test Controls
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
The Button, Boolean, Integer 32 Bits, Integer 64 Bits, Menu, String, Bitmask and
|
Integer Menu are controls that represent all possible control types. The Menu
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control and the Integer Menu control both have 'holes' in their menu list,
|
meaning that one or more menu items return EINVAL when VIDIOC_QUERYMENU is called.
|
Both menu controls also have a non-zero minimum control value. These features
|
allow you to check if your application can handle such things correctly.
|
These controls are supported for every device type.
|
|
|
User Controls - Video Capture
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
The following controls are specific to video capture.
|
|
The Brightness, Contrast, Saturation and Hue controls actually work and are
|
standard. There is one special feature with the Brightness control: each
|
video input has its own brightness value, so changing input will restore
|
the brightness for that input. In addition, each video input uses a different
|
brightness range (minimum and maximum control values). Switching inputs will
|
cause a control event to be sent with the V4L2_EVENT_CTRL_CH_RANGE flag set.
|
This allows you to test controls that can change their range.
|
|
The 'Gain, Automatic' and Gain controls can be used to test volatile controls:
|
if 'Gain, Automatic' is set, then the Gain control is volatile and changes
|
constantly. If 'Gain, Automatic' is cleared, then the Gain control is a normal
|
control.
|
|
The 'Horizontal Flip' and 'Vertical Flip' controls can be used to flip the
|
image. These combine with the 'Sensor Flipped Horizontally/Vertically' Vivid
|
controls.
|
|
The 'Alpha Component' control can be used to set the alpha component for
|
formats containing an alpha channel.
|
|
|
User Controls - Audio
|
~~~~~~~~~~~~~~~~~~~~~
|
|
The following controls are specific to video capture and output and radio
|
receivers and transmitters.
|
|
The 'Volume' and 'Mute' audio controls are typical for such devices to
|
control the volume and mute the audio. They don't actually do anything in
|
the vivid driver.
|
|
|
Vivid Controls
|
~~~~~~~~~~~~~~
|
|
These vivid custom controls control the image generation, error injection, etc.
|
|
|
Test Pattern Controls
|
^^^^^^^^^^^^^^^^^^^^^
|
|
The Test Pattern Controls are all specific to video capture.
|
|
- Test Pattern:
|
|
selects which test pattern to use. Use the CSC Colorbar for
|
testing colorspace conversions: the colors used in that test pattern
|
map to valid colors in all colorspaces. The colorspace conversion
|
is disabled for the other test patterns.
|
|
- OSD Text Mode:
|
|
selects whether the text superimposed on the
|
test pattern should be shown, and if so, whether only counters should
|
be displayed or the full text.
|
|
- Horizontal Movement:
|
|
selects whether the test pattern should
|
move to the left or right and at what speed.
|
|
- Vertical Movement:
|
|
does the same for the vertical direction.
|
|
- Show Border:
|
|
show a two-pixel wide border at the edge of the actual image,
|
excluding letter or pillarboxing.
|
|
- Show Square:
|
|
show a square in the middle of the image. If the image is
|
displayed with the correct pixel and image aspect ratio corrections,
|
then the width and height of the square on the monitor should be
|
the same.
|
|
- Insert SAV Code in Image:
|
|
adds a SAV (Start of Active Video) code to the image.
|
This can be used to check if such codes in the image are inadvertently
|
interpreted instead of being ignored.
|
|
- Insert EAV Code in Image:
|
|
does the same for the EAV (End of Active Video) code.
|
|
|
Capture Feature Selection Controls
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
These controls are all specific to video capture.
|
|
- Sensor Flipped Horizontally:
|
|
the image is flipped horizontally and the
|
V4L2_IN_ST_HFLIP input status flag is set. This emulates the case where
|
a sensor is for example mounted upside down.
|
|
- Sensor Flipped Vertically:
|
|
the image is flipped vertically and the
|
V4L2_IN_ST_VFLIP input status flag is set. This emulates the case where
|
a sensor is for example mounted upside down.
|
|
- Standard Aspect Ratio:
|
|
selects if the image aspect ratio as used for the TV or
|
S-Video input should be 4x3, 16x9 or anamorphic widescreen. This may
|
introduce letterboxing.
|
|
- DV Timings Aspect Ratio:
|
|
selects if the image aspect ratio as used for the HDMI
|
input should be the same as the source width and height ratio, or if
|
it should be 4x3 or 16x9. This may introduce letter or pillarboxing.
|
|
- Timestamp Source:
|
|
selects when the timestamp for each buffer is taken.
|
|
- Colorspace:
|
|
selects which colorspace should be used when generating the image.
|
This only applies if the CSC Colorbar test pattern is selected,
|
otherwise the test pattern will go through unconverted.
|
This behavior is also what you want, since a 75% Colorbar
|
should really have 75% signal intensity and should not be affected
|
by colorspace conversions.
|
|
Changing the colorspace will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates a detected colorspace change.
|
|
- Transfer Function:
|
|
selects which colorspace transfer function should be used when
|
generating an image. This only applies if the CSC Colorbar test pattern is
|
selected, otherwise the test pattern will go through unconverted.
|
This behavior is also what you want, since a 75% Colorbar
|
should really have 75% signal intensity and should not be affected
|
by colorspace conversions.
|
|
Changing the transfer function will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates a detected colorspace change.
|
|
- Y'CbCr Encoding:
|
|
selects which Y'CbCr encoding should be used when generating
|
a Y'CbCr image. This only applies if the format is set to a Y'CbCr format
|
as opposed to an RGB format.
|
|
Changing the Y'CbCr encoding will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates a detected colorspace change.
|
|
- Quantization:
|
|
selects which quantization should be used for the RGB or Y'CbCr
|
encoding when generating the test pattern.
|
|
Changing the quantization will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates a detected colorspace change.
|
|
- Limited RGB Range (16-235):
|
|
selects if the RGB range of the HDMI source should
|
be limited or full range. This combines with the Digital Video 'Rx RGB
|
Quantization Range' control and can be used to test what happens if
|
a source provides you with the wrong quantization range information.
|
See the description of that control for more details.
|
|
- Apply Alpha To Red Only:
|
|
apply the alpha channel as set by the 'Alpha Component'
|
user control to the red color of the test pattern only.
|
|
- Enable Capture Cropping:
|
|
enables crop support. This control is only present if
|
the ccs_cap_mode module option is set to the default value of -1 and if
|
the no_error_inj module option is set to 0 (the default).
|
|
- Enable Capture Composing:
|
|
enables composing support. This control is only
|
present if the ccs_cap_mode module option is set to the default value of
|
-1 and if the no_error_inj module option is set to 0 (the default).
|
|
- Enable Capture Scaler:
|
|
enables support for a scaler (maximum 4 times upscaling
|
and downscaling). This control is only present if the ccs_cap_mode
|
module option is set to the default value of -1 and if the no_error_inj
|
module option is set to 0 (the default).
|
|
- Maximum EDID Blocks:
|
|
determines how many EDID blocks the driver supports.
|
Note that the vivid driver does not actually interpret new EDID
|
data, it just stores it. It allows for up to 256 EDID blocks
|
which is the maximum supported by the standard.
|
|
- Fill Percentage of Frame:
|
|
can be used to draw only the top X percent
|
of the image. Since each frame has to be drawn by the driver, this
|
demands a lot of the CPU. For large resolutions this becomes
|
problematic. By drawing only part of the image this CPU load can
|
be reduced.
|
|
|
Output Feature Selection Controls
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
These controls are all specific to video output.
|
|
- Enable Output Cropping:
|
|
enables crop support. This control is only present if
|
the ccs_out_mode module option is set to the default value of -1 and if
|
the no_error_inj module option is set to 0 (the default).
|
|
- Enable Output Composing:
|
|
enables composing support. This control is only
|
present if the ccs_out_mode module option is set to the default value of
|
-1 and if the no_error_inj module option is set to 0 (the default).
|
|
- Enable Output Scaler:
|
|
enables support for a scaler (maximum 4 times upscaling
|
and downscaling). This control is only present if the ccs_out_mode
|
module option is set to the default value of -1 and if the no_error_inj
|
module option is set to 0 (the default).
|
|
|
Error Injection Controls
|
^^^^^^^^^^^^^^^^^^^^^^^^
|
|
The following two controls are only valid for video and vbi capture.
|
|
- Standard Signal Mode:
|
|
selects the behavior of VIDIOC_QUERYSTD: what should it return?
|
|
Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates a changed input condition (e.g. a cable
|
was plugged in or out).
|
|
- Standard:
|
|
selects the standard that VIDIOC_QUERYSTD should return if the
|
previous control is set to "Selected Standard".
|
|
Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates a changed input standard.
|
|
|
The following two controls are only valid for video capture.
|
|
- DV Timings Signal Mode:
|
|
selects the behavior of VIDIOC_QUERY_DV_TIMINGS: what
|
should it return?
|
|
Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates a changed input condition (e.g. a cable
|
was plugged in or out).
|
|
- DV Timings:
|
|
selects the timings the VIDIOC_QUERY_DV_TIMINGS should return
|
if the previous control is set to "Selected DV Timings".
|
|
Changing this control will result in the V4L2_EVENT_SOURCE_CHANGE
|
to be sent since it emulates changed input timings.
|
|
|
The following controls are only present if the no_error_inj module option
|
is set to 0 (the default). These controls are valid for video and vbi
|
capture and output streams and for the SDR capture device except for the
|
Disconnect control which is valid for all devices.
|
|
- Wrap Sequence Number:
|
|
test what happens when you wrap the sequence number in
|
struct v4l2_buffer around.
|
|
- Wrap Timestamp:
|
|
test what happens when you wrap the timestamp in struct
|
v4l2_buffer around.
|
|
- Percentage of Dropped Buffers:
|
|
sets the percentage of buffers that
|
are never returned by the driver (i.e., they are dropped).
|
|
- Disconnect:
|
|
emulates a USB disconnect. The device will act as if it has
|
been disconnected. Only after all open filehandles to the device
|
node have been closed will the device become 'connected' again.
|
|
- Inject V4L2_BUF_FLAG_ERROR:
|
|
when pressed, the next frame returned by
|
the driver will have the error flag set (i.e. the frame is marked
|
corrupt).
|
|
- Inject VIDIOC_REQBUFS Error:
|
|
when pressed, the next REQBUFS or CREATE_BUFS
|
ioctl call will fail with an error. To be precise: the videobuf2
|
queue_setup() op will return -EINVAL.
|
|
- Inject VIDIOC_QBUF Error:
|
|
when pressed, the next VIDIOC_QBUF or
|
VIDIOC_PREPARE_BUFFER ioctl call will fail with an error. To be
|
precise: the videobuf2 buf_prepare() op will return -EINVAL.
|
|
- Inject VIDIOC_STREAMON Error:
|
|
when pressed, the next VIDIOC_STREAMON ioctl
|
call will fail with an error. To be precise: the videobuf2
|
start_streaming() op will return -EINVAL.
|
|
- Inject Fatal Streaming Error:
|
|
when pressed, the streaming core will be
|
marked as having suffered a fatal error, the only way to recover
|
from that is to stop streaming. To be precise: the videobuf2
|
vb2_queue_error() function is called.
|
|
|
VBI Raw Capture Controls
|
^^^^^^^^^^^^^^^^^^^^^^^^
|
|
- Interlaced VBI Format:
|
|
if set, then the raw VBI data will be interlaced instead
|
of providing it grouped by field.
|
|
|
Digital Video Controls
|
~~~~~~~~~~~~~~~~~~~~~~
|
|
- Rx RGB Quantization Range:
|
|
sets the RGB quantization detection of the HDMI
|
input. This combines with the Vivid 'Limited RGB Range (16-235)'
|
control and can be used to test what happens if a source provides
|
you with the wrong quantization range information. This can be tested
|
by selecting an HDMI input, setting this control to Full or Limited
|
range and selecting the opposite in the 'Limited RGB Range (16-235)'
|
control. The effect is easy to see if the 'Gray Ramp' test pattern
|
is selected.
|
|
- Tx RGB Quantization Range:
|
|
sets the RGB quantization detection of the HDMI
|
output. It is currently not used for anything in vivid, but most HDMI
|
transmitters would typically have this control.
|
|
- Transmit Mode:
|
|
sets the transmit mode of the HDMI output to HDMI or DVI-D. This
|
affects the reported colorspace since DVI_D outputs will always use
|
sRGB.
|
|
- Display Present:
|
|
sets the presence of a "display" on the HDMI output. This affects
|
the tx_edid_present, tx_hotplug and tx_rxsense controls.
|
|
|
FM Radio Receiver Controls
|
~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
- RDS Reception:
|
|
set if the RDS receiver should be enabled.
|
|
- RDS Program Type:
|
|
|
- RDS PS Name:
|
|
|
- RDS Radio Text:
|
|
|
- RDS Traffic Announcement:
|
|
|
- RDS Traffic Program:
|
|
|
- RDS Music:
|
|
these are all read-only controls. If RDS Rx I/O Mode is set to
|
"Block I/O", then they are inactive as well. If RDS Rx I/O Mode is set
|
to "Controls", then these controls report the received RDS data.
|
|
.. note::
|
The vivid implementation of this is pretty basic: they are only
|
updated when you set a new frequency or when you get the tuner status
|
(VIDIOC_G_TUNER).
|
|
- Radio HW Seek Mode:
|
|
can be one of "Bounded", "Wrap Around" or "Both". This
|
determines if VIDIOC_S_HW_FREQ_SEEK will be bounded by the frequency
|
range or wrap-around or if it is selectable by the user.
|
|
- Radio Programmable HW Seek:
|
|
if set, then the user can provide the lower and
|
upper bound of the HW Seek. Otherwise the frequency range boundaries
|
will be used.
|
|
- Generate RBDS Instead of RDS:
|
|
if set, then generate RBDS (the US variant of
|
RDS) data instead of RDS (European-style RDS). This affects only the
|
PICODE and PTY codes.
|
|
- RDS Rx I/O Mode:
|
|
this can be "Block I/O" where the RDS blocks have to be read()
|
by the application, or "Controls" where the RDS data is provided by
|
the RDS controls mentioned above.
|
|
|
FM Radio Modulator Controls
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
- RDS Program ID:
|
|
|
- RDS Program Type:
|
|
|
- RDS PS Name:
|
|
|
- RDS Radio Text:
|
|
|
- RDS Stereo:
|
|
|
- RDS Artificial Head:
|
|
|
- RDS Compressed:
|
|
|
- RDS Dynamic PTY:
|
|
|
- RDS Traffic Announcement:
|
|
|
- RDS Traffic Program:
|
|
|
- RDS Music:
|
|
these are all controls that set the RDS data that is transmitted by
|
the FM modulator.
|
|
- RDS Tx I/O Mode:
|
|
this can be "Block I/O" where the application has to use write()
|
to pass the RDS blocks to the driver, or "Controls" where the RDS data
|
is Provided by the RDS controls mentioned above.
|
|
Metadata Capture Controls
|
~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
- Generate PTS
|
|
if set, then the generated metadata stream contains Presentation timestamp.
|
|
- Generate SCR
|
|
if set, then the generated metadata stream contains Source Clock information.
|
|
Video, VBI and RDS Looping
|
--------------------------
|
|
The vivid driver supports looping of video output to video input, VBI output
|
to VBI input and RDS output to RDS input. For video/VBI looping this emulates
|
as if a cable was hooked up between the output and input connector. So video
|
and VBI looping is only supported between S-Video and HDMI inputs and outputs.
|
VBI is only valid for S-Video as it makes no sense for HDMI.
|
|
Since radio is wireless this looping always happens if the radio receiver
|
frequency is close to the radio transmitter frequency. In that case the radio
|
transmitter will 'override' the emulated radio stations.
|
|
Looping is currently supported only between devices created by the same
|
vivid driver instance.
|
|
|
Video and Sliced VBI looping
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
The way to enable video/VBI looping is currently fairly crude. A 'Loop Video'
|
control is available in the "Vivid" control class of the video
|
capture and VBI capture devices. When checked the video looping will be enabled.
|
Once enabled any video S-Video or HDMI input will show a static test pattern
|
until the video output has started. At that time the video output will be
|
looped to the video input provided that:
|
|
- the input type matches the output type. So the HDMI input cannot receive
|
video from the S-Video output.
|
|
- the video resolution of the video input must match that of the video output.
|
So it is not possible to loop a 50 Hz (720x576) S-Video output to a 60 Hz
|
(720x480) S-Video input, or a 720p60 HDMI output to a 1080p30 input.
|
|
- the pixel formats must be identical on both sides. Otherwise the driver would
|
have to do pixel format conversion as well, and that's taking things too far.
|
|
- the field settings must be identical on both sides. Same reason as above:
|
requiring the driver to convert from one field format to another complicated
|
matters too much. This also prohibits capturing with 'Field Top' or 'Field
|
Bottom' when the output video is set to 'Field Alternate'. This combination,
|
while legal, became too complicated to support. Both sides have to be 'Field
|
Alternate' for this to work. Also note that for this specific case the
|
sequence and field counting in struct v4l2_buffer on the capture side may not
|
be 100% accurate.
|
|
- field settings V4L2_FIELD_SEQ_TB/BT are not supported. While it is possible to
|
implement this, it would mean a lot of work to get this right. Since these
|
field values are rarely used the decision was made not to implement this for
|
now.
|
|
- on the input side the "Standard Signal Mode" for the S-Video input or the
|
"DV Timings Signal Mode" for the HDMI input should be configured so that a
|
valid signal is passed to the video input.
|
|
The framerates do not have to match, although this might change in the future.
|
|
By default you will see the OSD text superimposed on top of the looped video.
|
This can be turned off by changing the "OSD Text Mode" control of the video
|
capture device.
|
|
For VBI looping to work all of the above must be valid and in addition the vbi
|
output must be configured for sliced VBI. The VBI capture side can be configured
|
for either raw or sliced VBI. Note that at the moment only CC/XDS (60 Hz formats)
|
and WSS (50 Hz formats) VBI data is looped. Teletext VBI data is not looped.
|
|
|
Radio & RDS Looping
|
~~~~~~~~~~~~~~~~~~~
|
|
As mentioned in section 6 the radio receiver emulates stations are regular
|
frequency intervals. Depending on the frequency of the radio receiver a
|
signal strength value is calculated (this is returned by VIDIOC_G_TUNER).
|
However, it will also look at the frequency set by the radio transmitter and
|
if that results in a higher signal strength than the settings of the radio
|
transmitter will be used as if it was a valid station. This also includes
|
the RDS data (if any) that the transmitter 'transmits'. This is received
|
faithfully on the receiver side. Note that when the driver is loaded the
|
frequencies of the radio receiver and transmitter are not identical, so
|
initially no looping takes place.
|
|
|
Cropping, Composing, Scaling
|
----------------------------
|
|
This driver supports cropping, composing and scaling in any combination. Normally
|
which features are supported can be selected through the Vivid controls,
|
but it is also possible to hardcode it when the module is loaded through the
|
ccs_cap_mode and ccs_out_mode module options. See section 1 on the details of
|
these module options.
|
|
This allows you to test your application for all these variations.
|
|
Note that the webcam input never supports cropping, composing or scaling. That
|
only applies to the TV/S-Video/HDMI inputs and outputs. The reason is that
|
webcams, including this virtual implementation, normally use
|
VIDIOC_ENUM_FRAMESIZES to list a set of discrete framesizes that it supports.
|
And that does not combine with cropping, composing or scaling. This is
|
primarily a limitation of the V4L2 API which is carefully reproduced here.
|
|
The minimum and maximum resolutions that the scaler can achieve are 16x16 and
|
(4096 * 4) x (2160 x 4), but it can only scale up or down by a factor of 4 or
|
less. So for a source resolution of 1280x720 the minimum the scaler can do is
|
320x180 and the maximum is 5120x2880. You can play around with this using the
|
qv4l2 test tool and you will see these dependencies.
|
|
This driver also supports larger 'bytesperline' settings, something that
|
VIDIOC_S_FMT allows but that few drivers implement.
|
|
The scaler is a simple scaler that uses the Coarse Bresenham algorithm. It's
|
designed for speed and simplicity, not quality.
|
|
If the combination of crop, compose and scaling allows it, then it is possible
|
to change crop and compose rectangles on the fly.
|
|
|
Formats
|
-------
|
|
The driver supports all the regular packed and planar 4:4:4, 4:2:2 and 4:2:0
|
YUYV formats, 8, 16, 24 and 32 RGB packed formats and various multiplanar
|
formats.
|
|
The alpha component can be set through the 'Alpha Component' User control
|
for those formats that support it. If the 'Apply Alpha To Red Only' control
|
is set, then the alpha component is only used for the color red and set to
|
0 otherwise.
|
|
The driver has to be configured to support the multiplanar formats. By default
|
the driver instances are single-planar. This can be changed by setting the
|
multiplanar module option, see section 1 for more details on that option.
|
|
If the driver instance is using the multiplanar formats/API, then the first
|
single planar format (YUYV) and the multiplanar NV16M and NV61M formats the
|
will have a plane that has a non-zero data_offset of 128 bytes. It is rare for
|
data_offset to be non-zero, so this is a useful feature for testing applications.
|
|
Video output will also honor any data_offset that the application set.
|
|
|
Capture Overlay
|
---------------
|
|
Note: capture overlay support is implemented primarily to test the existing
|
V4L2 capture overlay API. In practice few if any GPUs support such overlays
|
anymore, and neither are they generally needed anymore since modern hardware
|
is so much more capable. By setting flag 0x10000 in the node_types module
|
option the vivid driver will create a simple framebuffer device that can be
|
used for testing this API. Whether this API should be used for new drivers is
|
questionable.
|
|
This driver has support for a destructive capture overlay with bitmap clipping
|
and list clipping (up to 16 rectangles) capabilities. Overlays are not
|
supported for multiplanar formats. It also honors the struct v4l2_window field
|
setting: if it is set to FIELD_TOP or FIELD_BOTTOM and the capture setting is
|
FIELD_ALTERNATE, then only the top or bottom fields will be copied to the overlay.
|
|
The overlay only works if you are also capturing at that same time. This is a
|
vivid limitation since it copies from a buffer to the overlay instead of
|
filling the overlay directly. And if you are not capturing, then no buffers
|
are available to fill.
|
|
In addition, the pixelformat of the capture format and that of the framebuffer
|
must be the same for the overlay to work. Otherwise VIDIOC_OVERLAY will return
|
an error.
|
|
In order to really see what it going on you will need to create two vivid
|
instances: the first with a framebuffer enabled. You configure the capture
|
overlay of the second instance to use the framebuffer of the first, then
|
you start capturing in the second instance. For the first instance you setup
|
the output overlay for the video output, turn on video looping and capture
|
to see the blended framebuffer overlay that's being written to by the second
|
instance. This setup would require the following commands:
|
|
.. code-block:: none
|
|
$ sudo modprobe vivid n_devs=2 node_types=0x10101,0x1
|
$ v4l2-ctl -d1 --find-fb
|
/dev/fb1 is the framebuffer associated with base address 0x12800000
|
$ sudo v4l2-ctl -d2 --set-fbuf fb=1
|
$ v4l2-ctl -d1 --set-fbuf fb=1
|
$ v4l2-ctl -d0 --set-fmt-video=pixelformat='AR15'
|
$ v4l2-ctl -d1 --set-fmt-video-out=pixelformat='AR15'
|
$ v4l2-ctl -d2 --set-fmt-video=pixelformat='AR15'
|
$ v4l2-ctl -d0 -i2
|
$ v4l2-ctl -d2 -i2
|
$ v4l2-ctl -d2 -c horizontal_movement=4
|
$ v4l2-ctl -d1 --overlay=1
|
$ v4l2-ctl -d1 -c loop_video=1
|
$ v4l2-ctl -d2 --stream-mmap --overlay=1
|
|
And from another console:
|
|
.. code-block:: none
|
|
$ v4l2-ctl -d1 --stream-out-mmap
|
|
And yet another console:
|
|
.. code-block:: none
|
|
$ qv4l2
|
|
and start streaming.
|
|
As you can see, this is not for the faint of heart...
|
|
|
Output Overlay
|
--------------
|
|
Note: output overlays are primarily implemented in order to test the existing
|
V4L2 output overlay API. Whether this API should be used for new drivers is
|
questionable.
|
|
This driver has support for an output overlay and is capable of:
|
|
- bitmap clipping,
|
- list clipping (up to 16 rectangles)
|
- chromakey
|
- source chromakey
|
- global alpha
|
- local alpha
|
- local inverse alpha
|
|
Output overlays are not supported for multiplanar formats. In addition, the
|
pixelformat of the capture format and that of the framebuffer must be the
|
same for the overlay to work. Otherwise VIDIOC_OVERLAY will return an error.
|
|
Output overlays only work if the driver has been configured to create a
|
framebuffer by setting flag 0x10000 in the node_types module option. The
|
created framebuffer has a size of 720x576 and supports ARGB 1:5:5:5 and
|
RGB 5:6:5.
|
|
In order to see the effects of the various clipping, chromakeying or alpha
|
processing capabilities you need to turn on video looping and see the results
|
on the capture side. The use of the clipping, chromakeying or alpha processing
|
capabilities will slow down the video loop considerably as a lot of checks have
|
to be done per pixel.
|
|
|
CEC (Consumer Electronics Control)
|
----------------------------------
|
|
If there are HDMI inputs then a CEC adapter will be created that has
|
the same number of input ports. This is the equivalent of e.g. a TV that
|
has that number of inputs. Each HDMI output will also create a
|
CEC adapter that is hooked up to the corresponding input port, or (if there
|
are more outputs than inputs) is not hooked up at all. In other words,
|
this is the equivalent of hooking up each output device to an input port of
|
the TV. Any remaining output devices remain unconnected.
|
|
The EDID that each output reads reports a unique CEC physical address that is
|
based on the physical address of the EDID of the input. So if the EDID of the
|
receiver has physical address A.B.0.0, then each output will see an EDID
|
containing physical address A.B.C.0 where C is 1 to the number of inputs. If
|
there are more outputs than inputs then the remaining outputs have a CEC adapter
|
that is disabled and reports an invalid physical address.
|
|
|
Some Future Improvements
|
------------------------
|
|
Just as a reminder and in no particular order:
|
|
- Add a virtual alsa driver to test audio
|
- Add virtual sub-devices and media controller support
|
- Some support for testing compressed video
|
- Add support to loop raw VBI output to raw VBI input
|
- Add support to loop teletext sliced VBI output to VBI input
|
- Fix sequence/field numbering when looping of video with alternate fields
|
- Add support for V4L2_CID_BG_COLOR for video outputs
|
- Add ARGB888 overlay support: better testing of the alpha channel
|
- Improve pixel aspect support in the tpg code by passing a real v4l2_fract
|
- Use per-queue locks and/or per-device locks to improve throughput
|
- Add support to loop from a specific output to a specific input across
|
vivid instances
|
- The SDR radio should use the same 'frequencies' for stations as the normal
|
radio receiver, and give back noise if the frequency doesn't match up with
|
a station frequency
|
- Make a thread for the RDS generation, that would help in particular for the
|
"Controls" RDS Rx I/O Mode as the read-only RDS controls could be updated
|
in real-time.
|
- Changing the EDID should cause hotplug detect emulation to happen.
|
