V4L2 Video Capture

Capture video from USB camera using V4L2

• Library:

• Simulink Coder Support Package for BeagleBone Blue Hardware / Video

• 

Description

Capture live video from a USB video camera, using the V4L2 (Video for Linux Two API) driver framework. The output is in row major format. During simulation, the model outputs a moving colorbar image.

The Ubuntu Linux image used on the target hardware supports video capture from USB cameras listed as Universal Video Class (UVC). In addition to being a UVC class camera, the camera itself must support data acquisition in YUYV mode.

The following cameras have been tested:

• Logitech QuickCam Pro 9000

• Logitech QuickCam Pro 3000

• Logitech Webcam C600

• Logitech HD Webcam C310

Ports

Output

R — Red component of pixel

matrix

This port outputs the red component of each pixel.

Dependencies

This port appears only when you select the RGB from Pixel format.

Data Types: uint8

G — Green component of pixel

matrix

This port outputs the green component of each pixel.

Dependencies

This port appears only when you select the RGB from Pixel format.

Data Types: uint8

B — Blue component of pixel

matrix

This port outputs the blue component of each pixel.

Dependencies

This port appears only when you select the RGB from Pixel format.

Data Types: uint8

Y — Luma component of pixel

matrix

This port outputs the luma component of each pixel.

Dependencies

This port appears only when you select the YCbCr 4:2:2 from Pixel format.

Data Types: uint8

Cb — Blue difference component of pixel

matrix

This port outputs the blue difference component of each pixel.

Dependencies

This port appears only when you select the YCbCr 4:2:2 from Pixel format.

Data Types: uint8

Cr — Red difference component of pixel

matrix

This port outputs the red difference component of each pixel.

Dependencies

This port appears only when you select the YCbCr 4:2:2 from Pixel format.

Data Types: uint8

Parameters

Device name — Name of connected video device

'/dev/video0' (default)

Enter the path and name of the video device.

The Linux kernel creates a video device file when you connect a supported USB video camera to the target hardware. By default, the Linux kernel supports all USB video class (UVC) devices.

To see the list of video device files, open a command line session with the target hardware and enter: ls -al /dev/video*.

Image size — Display resolution

320x240 (default) | 160x120 | Custom

Specify the display resolution of the image to be captured, in pixels.

Image size ([width, height]) — Size of the image to be captured

[640,480] (default)

Specify the width in pixels and height in lines of the image to be captured.

Dependencies

This parameter appears only when you select Custom from Image Size.

Pixel format — Format of output video stream

RGB (default)

Select the video format of the video device, RGB or YCbCr 4:2:2.

RGB represents the red, green, and blue components of a pixel using an 8-bit value. RGB color space is device-dependent.

YCbCr 4:2:2 uses three channels to represent color image data for each pixel:

• Y is the luma component (essentially a grayscale signal).

• Cb is the blue-difference chroma component.

• Cr is the red-difference chroma component.

The Cb and Cr components are sampled at half the sample rate of Y.

Sample time — Frequency at which a new image is captured

1/10 (default)

Select the sample time of the video device.

Smaller values require the processor to complete the same number of instructions in less time, which can cause task overruns.