How to use the command 'cam' (with examples)

The cam command is a frontend tool for libcamera, a library that allows users to access and control cameras on Linux-based systems. This command provides a convenient way to interact with cameras and perform various operations such as listing available cameras, retrieving control information, capturing frames, and displaying camera feed.

Use case 1: List available cameras

Code:

cam --list

Motivation: This use case is helpful when you want to identify the available cameras on your system. By running this command, you can quickly obtain a list of all the cameras that libcamera can access.

Explanation:

• cam: The command itself.
• --list: An argument that instructs the command to list the available cameras.

Example output:

Camera 0: Integrated Camera (USB: 1.2)
Camera 1: Logitech Webcam C920 HD Pro (USB: 2.1)

Use case 2: List controls of a camera

Code:

cam --camera camera_index --list-controls

Motivation: When working with a specific camera, it is often useful to know what controls it supports. This use case allows you to retrieve a list of controls that can be adjusted on the camera.

Explanation:

• cam: The command itself.
• --camera camera_index: An argument that specifies the index of the camera for which controls need to be listed. Replace camera_index with the actual index (e.g., 0 for the first camera).
• --list-controls: An argument that instructs the command to list the controls of the specified camera.

Example output:

Camera 0: Integrated Camera (USB: 1.2)
=== Controls ===
            Control ID | Type                     | Value       | Flags   | Name
----------------------+--------------------------+-------------+---------+--------
            0x009a0900 | Menu                     | Disabled    | Dynamic | Global
            0x009a0901 | Button                   |             | Dynamic | Global
            0x009a0902 | Power Line Frequency     | 2 (50 Hz)   | Dynamic | Global
            ...

Use case 3: Write frames to a folder

Code:

cam --camera camera_index --capture=frames_to_capture --file

Motivation: If you need to capture a certain number of frames from a camera and save them to a specific folder for later processing, this use case enables you to accomplish that.

Explanation:

• cam: The command itself.
• --camera camera_index: An argument that specifies the index of the camera from which frames should be captured. Replace camera_index with the actual index.
• --capture=frames_to_capture: An argument that sets the number of frames to capture. Replace frames_to_capture with an integer value representing the desired number of frames.
• --file: An argument that instructs the command to save the captured frames to a file.

Example output: No specific output is provided for this use case.

Use case 4: Display camera feed in a window

Code:

cam --camera camera_index --capture --sdl

Motivation: This use case allows you to view the camera feed in a graphical window, making it easy to monitor and assess the video output.

Explanation:

• cam: The command itself.
• --camera camera_index: An argument that specifies the index of the camera whose feed should be displayed. Replace camera_index with the actual index.
• --capture: An argument that instructs the command to continuously capture frames from the camera.
• --sdl: An argument that activates the SDL (Simple DirectMedia Layer) output, allowing the camera feed to be displayed in a window.

Example output: A graphical window displaying the camera feed in real-time.

Conclusion:

The cam command is a powerful tool for interacting with cameras using the libcamera library. With its various use cases, you can easily list available cameras, retrieve control information, capture frames to a folder, and display camera feed in a window. By understanding and utilizing these commands, you can efficiently work with cameras on Linux-based systems.