Detailed Description

Defines a helper class for V4L2 based components.

This derived class provides common functionality for V4L2 components. V4L2-based components such as encoder/decoder extend from this class.

This class is modeled on V4L2 M2M devices. It includes the file descriptor (FD) of the device opened using v4l2_open, two planes (NvV4l2ElementPlane), output plane, capture plane, and other helper methods, such as setting/getting controls, subscribing/dequeueing events, etc.

Definition at line 65 of file NvV4l2Element.h.

Inheritance diagram for NvV4l2Element:

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Collaboration diagram for NvV4l2Element:

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Public Member Functions
virtual	~NvV4l2Element ()

int	subscribeEvent (uint32_t type, uint32_t id, uint32_t flags)
	Subscribes to an V4L2 event. More...

int	dqEvent (struct v4l2_event &event, uint32_t max_wait_ms)
	Dequeues an event from the element. More...

int	setControl (uint32_t id, int32_t value)
	Sets the value of a control. More...

int	getControl (uint32_t id, int32_t &value)
	Gets the value of a control. More...

int	setExtControls (struct v4l2_ext_controls &ctl)
	Sets the value of several controls. More...

int	getExtControls (struct v4l2_ext_controls &ctl)
	Gets the value of several controls. More...

virtual int	isInError ()

int	abort ()
	Terminates processing of queued buffers immediately. More...

virtual int	waitForIdle (uint32_t max_wait_ms)
	Waits until the element processes all the output plane buffers. More...

void	enableProfiling ()
	Enables profiling for the V4l2Element. More...

void	getProfilingData (NvElementProfiler::NvElementProfilerData &data)
	Gets profiling data for the element. More...

void	printProfilingStats (std::ostream &out_stream=std::cout)
	Prints profiling data for the element to an output stream. More...

bool	isProfilingEnabled ()
	Checks whether profiling is enabled for the element. More...

Data Fields
NvV4l2ElementPlane	output_plane
	Sets the output plane. More...

NvV4l2ElementPlane	capture_plane
	Sets the capture plane. More...

void *	app_data
	A pointer to the application-specific data. More...

Protected Member Functions
	NvV4l2Element (const char comp_name, const char dev_node, int flags, NvElementProfiler::ProfilerField fields)
	Creates a new V4l2Element named name. More...

Protected Attributes
int	fd
	Specifies the FD of the device opened using `v4l2_open`. More...

uint32_t	output_plane_pixfmt
	Pixel format of output plane buffers. More...

uint32_t	capture_plane_pixfmt
	Pixel format of capture plane buffers. More...

int	is_in_error
	Indicates if an error was encountered during the operation of the element. More...

const char *	comp_name
	Specifies the name of the component, for debugging. More...

NvElementProfiler	profiler
	Profiler for the element. More...

Constructor & Destructor Documentation

◆ ~NvV4l2Element()

virtual NvV4l2Element::~NvV4l2Element ( )

virtual

◆ NvV4l2Element()

NvV4l2Element::NvV4l2Element	(	const char *	comp_name,
		const char *	dev_node,
		int	flags,
		NvElementProfiler::ProfilerField	fields
	)

protected

Creates a new V4l2Element named name.

This constructor calls v4l2_open on the dev_node. It sets an error if v4l2_open fails.

This function also checks if the device supports V4L2_CAP_VIDEO_M2M_MPLANE capability.

Parameters

[in]	comp_name	A pointer to the unique name to identity the element instance.
[in]	dev_node	A pointer to /dev/ * node of the device.
[in]	flags	Flags with which to open the device.
[in]	fields	Profiler fields that are valid for the element.

Member Function Documentation

◆ abort()

int NvV4l2Element::abort ( )

Terminates processing of queued buffers immediately.

All the buffers are returned to the application.

Calls VIDIOC_STREAMOFF IOCTL on both of the planes internally.

Returns: 0 for success, -1 otherwise.

◆ dqEvent()

int NvV4l2Element::dqEvent	(	struct v4l2_event &	event,
		uint32_t	max_wait_ms
	)

Dequeues an event from the element.

Calls VIDIOC_DQEVENT IOCTL internally. The caller can specify the maximum time to wait for dequeuing the event. The call blocks until an event is dequeued successfully or timeout is reached.

Parameters

[in,out]	event	A reference to the `v4l2_event` structure to fill.
[in]	max_wait_ms	Specifies the max wait time for dequeuing an event, in milliseconds.

Returns: 0 for success, -1 otherwise.

◆ enableProfiling()

void NvV4l2Element::enableProfiling ( )

virtual

Enables profiling for the V4l2Element.

Must be called before setting either plane formats.

Reimplemented from NvElement.

◆ getControl()

int NvV4l2Element::getControl	(	uint32_t	id,
		int32_t &	value
	)

Gets the value of a control.

Calls VIDIOC_G_CTRL IOCTL internally.

Parameters

[in]	id	ID of the control to get.
[out]	value	A reference to the variable into which the control value is read.

Returns: 0 for success, -1 otherwise.

◆ getExtControls()

int NvV4l2Element::getExtControls ( struct v4l2_ext_controls & ctl )

Gets the value of several controls.

Calls VIDIOC_G_EXT_CTRLS IOCTL internally.

Parameters

[in,out] ctl A pointer to the controls to get.

Returns: 0 for success, -1 otherwise.

◆ getProfilingData()

void NvElement::getProfilingData ( NvElementProfiler::NvElementProfilerData & data )

inherited

Gets profiling data for the element.

Returns: A constant reference to the element's profiling data.

◆ isInError()

virtual int NvV4l2Element::isInError ( )

virtual

Reimplemented from NvElement.

◆ isProfilingEnabled()

bool NvElement::isProfilingEnabled ( )

inherited

Checks whether profiling is enabled for the element.

Returns: Boolean value indicating if profiling is enabled.

◆ printProfilingStats()

void NvElement::printProfilingStats ( std::ostream & out_stream = std::cout )

inherited

Prints profiling data for the element to an output stream.

Parameters

[in] out_stream Output stream of type std::ostream to print the data to. It takes the default value std::cout if not specified.

◆ setControl()

int NvV4l2Element::setControl	(	uint32_t	id,
		int32_t	value
	)

Sets the value of a control.

Calls VIDIOC_S_CTRL IOCTL internally.

Parameters

[in]	id	ID of the control to be set.
[in]	value	Value to be set on the control.

Returns: 0 for success, -1 otherwise.

◆ setExtControls()

int NvV4l2Element::setExtControls ( struct v4l2_ext_controls & ctl )

Sets the value of several controls.

Calls VIDIOC_S_EXT_CTRLS IOCTL internally.

Parameters

[in] ctl A pointer to the controls to set.

Returns: 0 for success, -1 otherwise.

◆ subscribeEvent()

int NvV4l2Element::subscribeEvent	(	uint32_t	type,
		uint32_t	id,
		uint32_t	flags
	)

Subscribes to an V4L2 event.

Calls VIDIOC_SUBSCRIBE_EVENT IOCTL internally.

Parameters

[in]	type	Type of the event.
[in]	id	ID of the event source.
[in]	flags	Event flags.

Returns: 0 for success, -1 otherwise.

◆ waitForIdle()

virtual int NvV4l2Element::waitForIdle ( uint32_t max_wait_ms )

virtual

Waits until the element processes all the output plane buffers.

Objects extending V4l2Element must implement this because the idle condition is component-specific.

Parameters

[in] max_wait_ms Max time to wait in milliseconds.

Returns: 0 for success, -1 otherwise.

Field Documentation

◆ app_data

void* NvV4l2Element::app_data

A pointer to the application-specific data.

Definition at line 169 of file NvV4l2Element.h.

◆ capture_plane

NvV4l2ElementPlane NvV4l2Element::capture_plane

Sets the capture plane.

Capture plane of the element

Definition at line 145 of file NvV4l2Element.h.

◆ capture_plane_pixfmt

uint32_t NvV4l2Element::capture_plane_pixfmt

protected

Pixel format of capture plane buffers.

Definition at line 182 of file NvV4l2Element.h.

◆ comp_name

const char* NvElement::comp_name

protectedinherited

Specifies the name of the component, for debugging.

Definition at line 122 of file NvElement.h.

◆ fd

int NvV4l2Element::fd

protected

Specifies the FD of the device opened using v4l2_open.

Definition at line 179 of file NvV4l2Element.h.

◆ is_in_error

int NvElement::is_in_error

protectedinherited

Indicates if an error was encountered during the operation of the element.

Definition at line 120 of file NvElement.h.

Referenced by NvElement::isInError().

◆ output_plane

NvV4l2ElementPlane NvV4l2Element::output_plane

Sets the output plane.

Output plane of the element

Definition at line 141 of file NvV4l2Element.h.

◆ output_plane_pixfmt

uint32_t NvV4l2Element::output_plane_pixfmt

protected

Pixel format of output plane buffers.

Definition at line 181 of file NvV4l2Element.h.

◆ profiler

NvElementProfiler NvElement::profiler

protectedinherited

Profiler for the element.

Definition at line 124 of file NvElement.h.

The documentation for this class was generated from the following file:

multimedia_api/ll_samples/include/NvV4l2Element.h

Jetson Linux API Reference

36.2 Release

Detailed Description

Public Member Functions

Data Fields

Protected Member Functions

Protected Attributes

Constructor & Destructor Documentation

◆ ~NvV4l2Element()

◆ NvV4l2Element()

Member Function Documentation

◆ abort()

◆ dqEvent()

◆ enableProfiling()

◆ getControl()

◆ getExtControls()

◆ getProfilingData()

◆ isInError()

◆ isProfilingEnabled()

◆ printProfilingStats()

◆ setControl()

◆ setExtControls()

◆ subscribeEvent()

◆ waitForIdle()

Field Documentation

◆ app_data

◆ capture_plane

◆ capture_plane_pixfmt

◆ comp_name

◆ fd

◆ is_in_error

◆ output_plane

◆ output_plane_pixfmt

◆ profiler