Abstract
A Python/OpenCV utility that reads a source video frame by frame, converts each frame to the format expected by pyvirtualcam, and publishes it as a virtual camera device in real time. The non-trivial part is the format and timing bridge between two different video APIs.
1. What This Is
Built in January 2023 to learn real-time video routing in Python. A configured source video is opened with OpenCV, each frame is transformed into the color and shape that pyvirtualcam expects, and the result is published as a virtual camera device that other applications can open as if it were a physical webcam. The loop is paced to the source frame rate rather than running as fast as the CPU allows.
2. How It Works
| # | Stage | Input | Tool | Output |
|---|---|---|---|---|
| 01 | Open source | Video file path | OpenCV VideoCapture | Frame stream |
| 02 | Init virtual cam | Width, height, fps | pyvirtualcam | Virtual device handle |
| 03 | Frame transform | BGR ndarray | NumPy / OpenCV | RGB ndarray, matching shape |
| 04 | Publish and pace | Processed frame | pyvirtualcam + timer | Frame on virtual device |
| 05 | Clean exit | EOF or user stop | Keyboard handler | Device released |
3. Constraints
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File-source only
The reader is a video file; there is no live webcam input path. Swapping the source means rewriting the capture stage.
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No processing pipeline
Frames pass through with only a color and shape conversion. There is no filter or CV-operation stage between read and publish.
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Platform-dependent backend
pyvirtualcam wraps OS-specific virtual-camera drivers. The device name and availability are not portable across systems.
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No mid-stream recovery
If the source file ends or a frame read fails, the stream stops. There is no reconnect or loop-back logic.
4. Next
- a. Add a live webcam input path (OpenCV VideoCapture on a device index) alongside the file-based source.
- b. Insert a pluggable filter stage between read and publish so a single CV operation can be swapped in without touching the loop.
- c. Add a small argparse CLI for source path, output resolution, and target fps so the script is testable without editing constants.
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