Detailed Description

NvJpegEncoder uses the libjpeg APIs for decoding JPEG images.

It supports two methods for encoding:

Encode using a file descriptor (FD) of the MMAP buffer created by a V4L2 element (supports YUV420 and NV12 color formats).
Encode using data pointers in NvBuffer object, i.e., software allocated memory (malloc); supports YUV420 color format.

Note: Only the JCS_YCbCr (YUV420) color space is currently supported.

Definition at line 85 of file NvJpegEncoder.h.

Inheritance diagram for NvJPEGEncoder:

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Collaboration diagram for NvJPEGEncoder:

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Public Member Functions
	~NvJPEGEncoder ()

int	encodeFromFd (int fd, J_COLOR_SPACE color_space, unsigned char **out_buf, unsigned long &out_buf_size, int quality=75)
	Encodes a JPEG image from a file descriptor (FD) of hardware buffer memory. More...

int	encodeFromBuffer (NvBuffer &buffer, J_COLOR_SPACE color_space, unsigned char **out_buf, unsigned long &out_buf_size, int quality=75)
	Encodes a JPEG image from software buffer memory. More...

void	setCropRect (uint32_t left, uint32_t top, uint32_t width, uint32_t height)
	Sets the cropping rectangle used by the JPEG encoder. More...

void	setScaledEncodeParams (uint32_t scale_width, uint32_t scale_height)
	Sets scaling parameters by which image needs to be scaled and encoded. More...

virtual int	isInError ()
	Indicates whether the element encountered an error during its operation. 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...

virtual void	enableProfiling ()
	Enables profiling for the element. More...

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

Static Public Member Functions
static NvJPEGEncoder *	createJPEGEncoder (const char *comp_name)
	Creates a new JPEG encoder named comp_name. More...

Protected Attributes
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

◆ ~NvJPEGEncoder()

NvJPEGEncoder::~NvJPEGEncoder ( )

Member Function Documentation

◆ createJPEGEncoder()

static NvJPEGEncoder* NvJPEGEncoder::createJPEGEncoder ( const char * comp_name )

static

Creates a new JPEG encoder named comp_name.

Returns: Reference to the newly created decoder object, or NULL in case of failure during initialization.

◆ enableProfiling()

virtual void NvElement::enableProfiling ( )

virtualinherited

Enables profiling for the element.

Reimplemented in NvV4l2Element.

◆ encodeFromBuffer()

int NvJPEGEncoder::encodeFromBuffer	(	NvBuffer &	buffer,
		J_COLOR_SPACE	color_space,
		unsigned char **	out_buf,
		unsigned long &	out_buf_size,
		int	quality = `75`
	)

Encodes a JPEG image from software buffer memory.

The application may allocate the memory for storing the JPEG image. If the allocation is less than what is required, libjpeg allocates more memory. The out_buf pointer and out_buf_size are updated accordingly.

The encodeFromBuffer method is slower than NvJPEGEncoder::encodeFromFd because encodeFromBuffer involves conversion from software buffer memory to hardware buffer memory.

Supports the YUV420 format only.

Attention: The application must free the out_buf memory.

Parameters

[out]	buffer	Indicates the NvBuffer object to contain the encoded image.
[out]	color_space	Indicates the color_space to use for encoding.
[in]	out_buf	Specifies a pointer to the memory for the JPEG image.
[in]	out_buf_size	Specifies the size of the output buffer in bytes.
[in]	quality	Sets the image quality.

Returns: 0 for success, -1 otherwise.

◆ encodeFromFd()

int NvJPEGEncoder::encodeFromFd	(	int	fd,
		J_COLOR_SPACE	color_space,
		unsigned char **	out_buf,
		unsigned long &	out_buf_size,
		int	quality = `75`
	)

Encodes a JPEG image from a file descriptor (FD) of hardware buffer memory.

The application may allocate the memory for storing the JPEG image. If the allocation is less than what is required, libjpeg allocates more memory. The out_buf pointer and out_buf_size are updated accordingly.

Supports YUV420 and NV12 formats.

Attention: The application must free the out_buf memory.

Parameters

[out]	fd	Indicates the file descriptor (FD) of the hardware buffer.
[out]	color_space	Indicates the color_space to use for encoding.
[in]	out_buf	Specifies a pointer to the memory for the JPEG image.
[in]	out_buf_size	Specifies the size of the output buffer in bytes.
[in]	quality	Sets the image quality.

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 NvElement::isInError ( )

inlinevirtualinherited

Indicates whether the element encountered an error during its operation.

Returns: 0 if no error was encountered, a non-zero value if an error was encountered.

Reimplemented in NvV4l2Element.

Definition at line 72 of file NvElement.h.

References NvElement::is_in_error.

◆ 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.

◆ setCropRect()

void NvJPEGEncoder::setCropRect	(	uint32_t	left,
		uint32_t	top,
		uint32_t	width,
		uint32_t	height
	)

Sets the cropping rectangle used by the JPEG encoder.

This method must be called before encodeFromFd or encodeFromBuffer for the cropping to take effect.

Attention: The JPEG encoder resets the crop paramaters after each call to jpeg_finish_compress. Therefore, this method must be called before every call to encodeFromFd or encodeFromBuffer.

Parameters

[in]	left	Horizontal offset of the cropping rectangle, in pixels.
[in]	top	Vertical offset of the cropping rectangle, in pixels.
[in]	width	Width of the cropping rectangle, in pixels.
[in]	height	Height of the cropping rectangle, in pixels.

◆ setScaledEncodeParams()

void NvJPEGEncoder::setScaledEncodeParams	(	uint32_t	scale_width,
		uint32_t	scale_height
	)

Sets scaling parameters by which image needs to be scaled and encoded.

This method must be called before encodeFromFd or encodeFromBuffer for scaled encoding to take effect.

Parameters

[in]	scale_width	Specifies width of the scaled image.
[in]	scale_height	Specifies height of the scaled image.

Field Documentation

◆ comp_name

const char* NvElement::comp_name

protectedinherited

Specifies the name of the component, for debugging.

Definition at line 122 of file NvElement.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().

◆ 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/NvJpegEncoder.h

Jetson Linux API Reference

32.7.5 Release

Detailed Description

Public Member Functions

Static Public Member Functions

Protected Attributes

Constructor & Destructor Documentation

◆ ~NvJPEGEncoder()

Member Function Documentation

◆ createJPEGEncoder()

◆ enableProfiling()

◆ encodeFromBuffer()

◆ encodeFromFd()

◆ getProfilingData()

◆ isInError()

◆ isProfilingEnabled()

◆ printProfilingStats()

◆ setCropRect()

◆ setScaledEncodeParams()

Field Documentation

◆ comp_name

◆ is_in_error

◆ profiler