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

The cam command is a frontend tool for interacting with libcamera, a library that offers a comprehensive framework for supporting camera devices in Linux. This tool simplifies the process of accessing, controlling, and capturing data from cameras, making it particularly useful for developers and engineers working with camera imaging systems. The command provides a straightforward interface to perform various tasks such as listing cameras, controlling camera settings, capturing frames, and displaying live feeds.

Use case 1: Listing Available Cameras

Code:

cam --list

Motivation:

Listing available cameras is an essential step in any camera-related task. Before any operations such as capturing images or adjusting settings can be performed, it is important to identify which cameras are connected to the system and are available for use. This is particularly useful in systems with multiple cameras, where selecting the correct camera for specific purposes ensures proper functionality and avoids conflicts.

Explanation:

• cam: The base command to initiate the frontend tool for libcamera.
• --list: An option that instructs the command to list all the available cameras on the system. This option does not require any additional arguments.

Example Output:

When executed, this command will return a list of all cameras connected to the system:

Available cameras: 
0: /dev/video0
1: /dev/video1

Use case 2: Listing Controls of a Camera

Code:

cam --camera 0 --list-controls

Motivation:

Understanding the controls available for a camera is crucial for adjusting and fine-tuning camera settings, such as exposure, focus, and brightness. This is particularly valuable for applications that require specific configurations to achieve optimal image quality or for developing automated systems that adjust settings based on environmental conditions.

Explanation:

• cam: The base command for using the frontend tool.
• --camera 0: Specifies the camera to be queried, where 0 is the index of the camera as identified from the list of available cameras.
• --list-controls: An option to list all the controls that can be modified for the specified camera. This helps users understand configurable parameters for better control.

Example Output:

The output will display a list of controls available for the chosen camera:

Available controls for camera 0:
1. Exposure Time
2. White Balance
3. Brightness

Use case 3: Writing Frames to a Folder

Code:

cam --camera 0 --capture=10 --file

Motivation:

Capturing frames and writing them to a folder is a vital functionality for applications that require storing image data for later analysis, editing, or sharing. This is particularly useful in surveillance systems, content creation, and any scenario where capturing a set number of frames at defined intervals is needed for subsequent processing.

Explanation:

• cam: Initiates the command line tool.
• --camera 0: Selects the camera with index 0.
• --capture=10: Specifies the number of frames to be captured, in this case, 10 frames.
• --file: Directs the command to write the captured frames to the filesystem rather than displaying them or processing them in-memory.

Example Output:

Captured images will be written to the current folder, possibly named like:

frame0001.jpg
frame0002.jpg
...
frame0010.jpg

Use case 4: Displaying Camera Feed in a Window

Code:

cam --camera 0 --capture --sdl

Motivation:

Real-time monitoring of a camera feed in a window is essential for live applications such as video conferencing, live streaming, or visual inspection systems. Displaying a feed directly on the screen allows users to view and assess the real-time output from the camera easily.

Explanation:

• cam: The initial command.
• --camera 0: Specifies the camera device to capture from.
• --capture: Indicates that frames should be continuously captured from the camera.
• --sdl: Instructs the command to display the camera feed in a window using SDL (Simple DirectMedia Layer), which is a cross-platform library designed to provide hardware-accelerated graphics rendering.

Example Output:

A GUI window will open displaying the live feed from the selected camera. This window will continue showing real-time footage until closed by the user.

Conclusion

The cam command provides a versatile set of functionalities for interacting with cameras on Linux using libcamera. Whether listing and controlling available cameras, capturing and saving frames, or displaying live feeds, this tool is instrumental for developers and users who need to manage camera operations effectively and efficiently. Each use case highlighted above illustrates the practical applications of the command and how these can be leveraged in real-world situations.