What is life cycle of CoreMediaIO DAL Plugin?

Question

The CoreMediaIO Device Abstraction Layer (DAL) is analogous to CoreAudio’s Hardware Abstraction Layer (HAL). Just as the HAL deals with audio streams from audio hardware, the DAL handles video (and muxed) streams from video devices.

DAL Pludins resides at /Library/CoreMediaIO/Plug-Ins/DAL/

What is life cycle of these DAL Plugins?

• When they get started running?
• When they get stopped?
• When they get paused?
• Where can I see their logs?
• What happens when they are not in use?
• How can I see their performance if they are efficient or not?

One of the famous example of CoreMediaIO DAL Plugin is OBS Virtual Camera if someone does not know.

Note: This question should not be marked too broad. I am not asking multiple questions. It's only one question to know the life cycle of CoreMediaIO DAL Plugin.

Answer 1

Life cycle of these DAL Plugins

When they get started running?

• Consider OBS Virtual camera, whenever you select the virtual camera the DAL Plugin will be loaded into the memory of the application in which you selected the camera. For Example, In Google Chrome browser you are starting the google meet and selecting the OBS Virtual camera as your video device. The OBS Virtual camera DAL Plugin will be loaded into the Google chrome application memory and will be initiated

When they get stopped?

• As in the above example assume you have selected OBS Virtual camera (DAL Plugin) in the Google Meet on Google Chrome browser. When you change the camera selection in the video source from OBS Virtual camera to some other camera, the OBS Virtual camera (DAL Plugin) will be stopped. If you close the browser/tab the camera DAL plugin will be stopped and unloaded

When they get paused?

NA

Where can I see their logs?

• If you are using nslogs you can see them in Console

What happens when they are not in use?

• Nothing will happen. The DAL plugin will be like just another file in your machine. It won't be active.

How can I see their performance if they are efficient or not?

• If you consider the OBS Virtual camera, the performance camera performance shall be based on How smooth it is and how close (resolution, color ...) it is to the actual camera which is getting used by OBS Virtual Camera.