Capturing video from camera device under Linux

Uses the video4linux2 (or simply v4l2) input device to capture live input such as from a webcam.

To list the supported, connected capture devices you can use the v4l-ctl tool. This example shows two connected webcams: /dev/video0 and /dev/video1.

$ v4l2-ctl --list-devices

Acer Crystal Eye webcam (usb-0000:00:1a.7-1):
/dev/video0

PATHPARTNER 5MP-OV-1 CAMERA (usb-0000:00:1d.7-1):
/dev/video1

Adjusting camera functions

Brightness, zoom, focus, etc, can be adjusted with v4l2-ctl. Display all controls and their menus:

$ v4l2-ctl -L
                     brightness (int)    : min=-64 max=64 step=1 default=-20 value=20
                       contrast (int)    : min=0 max=95 step=1 default=0 value=0
                     saturation (int)    : min=0 max=128 step=1 default=60 value=60
                            hue (int)    : min=-40 max=40 step=1 default=-5 value=-5
   white_balance_component_auto (bool)   : default=1 value=1
    white_balance_red_component (int)    : min=1 max=500 step=1 default=100 value=100
   white_balance_blue_component (int)    : min=1 max=500 step=1 default=100 value=100
                          gamma (int)    : min=72 max=500 step=1 default=110 value=110
           power_line_frequency (menu)   : min=0 max=2 default=2 value=2
    0: Disabled
    1: 50 Hz
    2: 60 Hz
                      sharpness (int)    : min=0 max=7 step=1 default=2 value=2
         backlight_compensation (int)    : min=0 max=1 step=1 default=0 value=0

Then adjust the value:
v4l2-ctl -c == 

asvkarthick@asvkarthick:~$ v4l2-ctl --list-formats
ioctl: VIDIOC_ENUM_FMT
Index       : 0
Type        : Video Capture
Pixel Format: 'YUYV'
Name        : YUV 4:2:2 (YUYV)

asvkarthick@asvkarthick:~$ cat /dev/video
video0  video1
asvkarthick@asvkarthick:~$ v4l2-ctl --all
Driver Info (not using libv4l2):
Driver name   : uvcvideo
Card type     : Acer Crystal Eye webcam
Bus info      : usb-0000:00:1a.7-1
Driver version: 3.2.55
Capabilities  : 0x04000001
Video Capture
Streaming
Format Video Capture:
Width/Height  : 640/480
Pixel Format  : 'YUYV'
Field         : None
Bytes per Line: 1280
Size Image    : 614400
Colorspace    : SRGB
Crop Capability Video Capture:
Bounds      : Left 0, Top 0, Width 640, Height 480
Default     : Left 0, Top 0, Width 640, Height 480
Pixel Aspect: 1/1
Video input : 0 (Camera 1: ok)
Streaming Parameters Video Capture:
Capabilities     : timeperframe
Frames per second: 25.000 (25/1)
Read buffers     : 0

  avconv -f video4linux2 -i /dev/video0 video0.avi

Records the captured video frame into the file