Capture images from a V4L2 device (Video for Linux 2) More...

#include <linux/v4l2-subdev.h>
#include <pthread.h>
#include <sys/time.h>
#include "std.h"
#include "modules/computer_vision/lib/vision/image.h"

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Go to the source code of this file.

Data Structures
struct	v4l2_img_buf

struct	v4l2_device

Macros
#define	V4L2_IMG_NONE 255
	There currently no image available. More...

Functions
bool	v4l2_init_subdev (char *subdev_name, uint8_t pad, uint16_t code, struct img_size_t size)
	Initialize a V4L2 subdevice. More...

struct v4l2_device *	v4l2_init (char *device_name, struct img_size_t size, struct crop_t crop, uint8_t buffers_cnt, uint32_t _pixelformat)
	Initialize a V4L2(Video for Linux 2) device. More...

void	v4l2_image_get (struct v4l2_device dev, struct image_t img)
	Get the latest image buffer and lock it (Thread safe, BLOCKING) This functions blocks until image access is granted. More...

bool	v4l2_image_get_nonblock (struct v4l2_device dev, struct image_t img)
	Get the latest image and lock it (Thread safe, NON BLOCKING) This function returns NULL if it can't get access to the current image. More...

void	v4l2_image_free (struct v4l2_device dev, struct image_t img)
	Free the image and enqueue the buffer (Thread safe) This must be done after processing the image, because else all buffers are locked. More...

bool	v4l2_start_capture (struct v4l2_device *dev)
	Start capturing images in streaming mode (Thread safe) More...

bool	v4l2_stop_capture (struct v4l2_device *dev)
	Stop capturing of the image stream (Thread safe) This function is blocking until capturing thread is closed. More...

void	v4l2_close (struct v4l2_device *dev)
	Close the V4L2 device (Thread safe) This needs to be preformed to clean up all the buffers and close the device. More...

Detailed Description

Capture images from a V4L2 device (Video for Linux 2)

Definition in file v4l2.h.

Data Structure Documentation

◆ v4l2_img_buf

struct v4l2_img_buf

Definition at line 41 of file v4l2.h.

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Data Fields
void *	buf	Pointer to the memory mapped buffer.
size_t	length	The size of the buffer.
uint32_t	physp	Physical address pointer.
uint32_t	pprz_timestamp	The time of the image in us since system startup.
struct timeval	timestamp	The time value of the image.

◆ v4l2_device

struct v4l2_device

Definition at line 50 of file v4l2.h.

Collaboration diagram for v4l2_device:

Data Fields
struct v4l2_img_buf *	buffers	The memory mapped image buffers.
uint8_t	buffers_cnt	The number of image buffers.
volatile uint8_t	buffers_deq_idx	The current dequeued index.
int	fd	The file pointer to the device.
uint16_t	h	The height of the image.
pthread_mutex_t	mutex	Mutex lock for enqueue/dequeue of buffers (change the deq_idx)
char *	name	The name of the device.
pthread_t	thread	The thread that handles the images.
uint16_t	w	The width of the image.

Macro Definition Documentation

◆ V4L2_IMG_NONE

#define V4L2_IMG_NONE 255

There currently no image available.

Definition at line 38 of file v4l2.h.

Function Documentation

◆ v4l2_close()

void v4l2_close ( struct v4l2_device * dev )

Close the V4L2 device (Thread safe) This needs to be preformed to clean up all the buffers and close the device.

Note that this also stops the capturing if it is still capturing.

Parameters

[in] *dev The video for linux device to close(cleanup)

Definition at line 537 of file v4l2.c.

References dev, and v4l2_stop_capture().

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◆ v4l2_image_free()

void v4l2_image_free	(	struct v4l2_device *	dev,
		struct image_t *	img
	)

Free the image and enqueue the buffer (Thread safe) This must be done after processing the image, because else all buffers are locked.

Parameters

[in]	*dev	The video for linux device which the image is from
[in]	*img	The image to free

Definition at line 418 of file v4l2.c.

References image_t::buf_idx, CLEAR, and dev.

Referenced by video_thread_function().

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◆ v4l2_image_get()

void v4l2_image_get	(	struct v4l2_device *	dev,
		struct image_t *	img
	)

Get the latest image buffer and lock it (Thread safe, BLOCKING) This functions blocks until image access is granted.

This should not take that long, because it is only locked while enqueueing an image. Make sure you free the image after processing with v4l2_image_free()!

Parameters

[in]	*dev	The V4L2 video device we want to get an image from
[out]	*img	The image that we got from the video device

Definition at line 344 of file v4l2.c.

References image_t::buf, image_t::buf_idx, image_t::buf_size, dev, image_t::h, IMAGE_YUV422, image_t::pprz_ts, image_t::ts, image_t::type, V4L2_IMG_NONE, and image_t::w.

Referenced by video_thread_function().

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◆ v4l2_image_get_nonblock()

bool v4l2_image_get_nonblock	(	struct v4l2_device *	dev,
		struct image_t *	img
	)

Get the latest image and lock it (Thread safe, NON BLOCKING) This function returns NULL if it can't get access to the current image.

Make sure you free the image after processing with v4l2_image_free())!

Parameters

[in]	*dev	The V4L2 video device we want to get an image from
[out]	*img	The image that we got from the video device

Returns: Whether we got an image or not

Definition at line 383 of file v4l2.c.

References image_t::buf, image_t::buf_idx, image_t::buf_size, dev, image_t::h, IMAGE_YUV422, image_t::pprz_ts, image_t::ts, image_t::type, V4L2_IMG_NONE, and image_t::w.

◆ v4l2_init()

struct v4l2_device* v4l2_init	(	char *	device_name,
		struct img_size_t	size,
		struct crop_t	crop,
		uint8_t	buffers_cnt,
		uint32_t	_pixelformat
	)

Initialize a V4L2(Video for Linux 2) device.

Note that the device must be closed with v4l2_close(dev) at the end.

Parameters

[in]	device_name	The video device name (like /dev/video1)
[in]	width,height	The width and height of the images
[in]	buffers_cnt	The amount of buffers used for mapping

Returns: The newly create V4L2 device

Definition at line 184 of file v4l2.c.

References v4l2_img_buf::buf, v4l2_device::buffers, check_contiguity(), CLEAR, dev, fd, img_size_t::h, crop_t::h, v4l2_img_buf::length, physmem::paddr, v4l2_img_buf::physp, physmem::size, img_size_t::w, crop_t::w, crop_t::x, and crop_t::y.

Referenced by initialize_camera().

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◆ v4l2_init_subdev()

bool v4l2_init_subdev	(	char *	subdev_name,
		uint8_t	pad,
		uint16_t	code,
		struct img_size_t	size
	)

Initialize a V4L2 subdevice.

Parameters

[in]	*subdev_name	The subdevice name (like /dev/v4l-subdev0)
[in]	pad,which	The way the subdevice should comminicate and be connected to the real device.
[in]	code	The encoding the subdevice uses (like V4L2_MBUS_FMT_UYVY8_2X8, see the V4L2 manual for available encodings)
[in]	width,height	The width and height of the images