How to get a list of video capture devices (web cameras) on linux ( ubuntu )? (C/C++)

32
votes

So all I need is simple - a list of currently avaliable video capture devices (web cameras). I need it in simple C or C++ console app. By list I mean something like such console output:

1) Asus Web Camera
2) Sony Web Camera

So It seems simple but I have one requirement - use of native OS apis as much as possible - no external libs - after all - all we want is to print out a a list - not to fly onto the moon!)

How to do such thing?

also from this series:

4
c++clinuxwebcamdevice
Can you get it from /proc/bus/input/devices – chrisaycock
The question is how exactly to do it from code? – Rella
Minimal runnable example of how to read the camera, process it on GPU, and show both on a window live: stackoverflow.com/questions/13693946/… – Ciro Santilli 新疆再教育营六四事件法轮功郝海东

4 Answers

47
votes

You can use the following bash command:

v4l2-ctl --list-devices

In order to use the above command, you must install package v4l-utils before. In Ubuntu/Debian you can use the command:

sudo apt-get install v4l-utils
36
votes

It's easy by just traversing sysfs devices by a given class. The following command-line one liner would do so:

for I in /sys/class/video4linux/*; do cat $I/name; done

You can do the same thing in C/C++ application, by just opening up /sys/class/video4linux directory, it will have symlinks to all your web cameras as video4linux devices:

$ ls -al /sys/class/video4linux                          
drwxr-xr-x  2 root root 0 Ноя 27 12:19 ./
drwxr-xr-x 34 root root 0 Ноя 26 00:08 ../
lrwxrwxrwx  1 root root 0 Ноя 27 12:19 video0 -> ../../devices/pci0000:00/0000:00:13.2/usb2/2-5/2-5:1.0/video4linux/video0/

You can follow every symlink to a directory of every device and read full contents of name file in that directory to get the name.

14
votes

This is a code snippet I had laying around. Probably from a book. I guess you could just iterate over all /dev/videoN nodes and get the info.

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/videodev.h>

int main(){
    int fd;
    struct video_capability video_cap;
    struct video_window     video_win;
    struct video_picture   video_pic;

    if((fd = open("/dev/video0", O_RDONLY)) == -1){
        perror("cam_info: Can't open device");
        return 1;
    }

    if(ioctl(fd, VIDIOCGCAP, &video_cap) == -1)
        perror("cam_info: Can't get capabilities");
    else {
        printf("Name:\t\t '%s'\n", video_cap.name);
        printf("Minimum size:\t%d x %d\n", video_cap.minwidth, video_cap.minheight);
        printf("Maximum size:\t%d x %d\n", video_cap.maxwidth, video_cap.maxheight);
    }

    if(ioctl(fd, VIDIOCGWIN, &video_win) == -1)
        perror("cam_info: Can't get window information");
    else
        printf("Current size:\t%d x %d\n", video_win.width, video_win.height);

    if(ioctl(fd, VIDIOCGPICT, &video_pic) == -1)
        perror("cam_info: Can't get picture information");
    else
        printf("Current depth:\t%d\n", video_pic.depth);

    close(fd);
    return 0;
}
0
votes

V4L2 documentation says that there can be 64 allowed devices for each type. For instance for path /dev/video there can be 64 devices addresssed as /dev/video0, /dev/video1, /dev/video2 ...

Iterate over 64 devices until the ioctl retuens ENIVAL which specifies end of the tree.