usb_cam::utils

Classes

	Name
struct	usb_cam::utils::buffer

Types

	Name
enum	io_method_t { IO_METHOD_USERPTR, IO_METHOD_UNKNOWN, IO_METHOD_READ, IO_METHOD_MMAP} Read more on IO methods here: https://lwn.net/Articles/240667/.

Functions

	Name
int	xioctl(int fd, uint64_t request, void * arg)
io_method_t	io_method_from_string(const std::string & str)
time_t	get_epoch_time_shift_us() Get epoch time shift in microseconds.
timespec	calc_img_timestamp(const timeval & buffer_time, const time_t & epoch_time_shift_us) Calculate image timestamp from buffer time and epoch time shift. In this, the buffer time is first converted into microseconds before the epoch time shift, which is to be given in microseconds is added to it. Afterwards it is split into seconds and nanoseconds for the image timestamp.
std::map< std::string, v4l2_capability >	available_devices() List currently available valid V4L2 devices Can be used to check if a device string is valid before starting up.

Types Documentation

enum io_method_t

Enumerator	Value	Description
IO_METHOD_USERPTR		memory buffers allocated in the user space
IO_METHOD_UNKNOWN
IO_METHOD_READ		read method copies the video frame between user and kernal space
IO_METHOD_MMAP		memory mapped buffers allocated in kernel space

Read more on IO methods here: https://lwn.net/Articles/240667/.

Functions Documentation

function xioctl

inline int xioctl(
    int fd,
    uint64_t request,
    void * arg
)

function io_method_from_string

inline io_method_t io_method_from_string(
    const std::string & str
)

function get_epoch_time_shift_us

inline time_t get_epoch_time_shift_us()

Get epoch time shift in microseconds.

Run this at start of process to calculate epoch time shift https://stackoverflow.com/questions/10266451/where-does-v4l2-buffer-timestamp-value-starts-counting

function calc_img_timestamp

inline timespec calc_img_timestamp(
    const timeval & buffer_time,
    const time_t & epoch_time_shift_us
)

Calculate image timestamp from buffer time and epoch time shift. In this, the buffer time is first converted into microseconds before the epoch time shift, which is to be given in microseconds is added to it. Afterwards it is split into seconds and nanoseconds for the image timestamp.

function available_devices

inline std::map< std::string, v4l2_capability > available_devices()

List currently available valid V4L2 devices Can be used to check if a device string is valid before starting up.

Inspired by: http://stackoverflow.com/questions/4290834/how-to-get-a-list-of-video-capture-devices-web-cameras-on-linux-ubuntu-c

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Updated on 2024-06-22 at 03:15:44 +0000