Zero-copy video stream for Python
OpenCV-Python is a python library widely used for camera capture and real-time video stream process. However, the pipeline includes many creation and destruction of numpy arrays, which significantly increases the memory consumption. Thus, this article aims at putting forward a paradigm that deals with video stream efficiently and elegantly. The pipeline includes two parts: the python frontend…
OpenCV-Python is a popular Python library utilized for capturing camera input and processing real-time video streams. However, the current pipeline has a drawback - it creates and destroys numerous numpy arrays, leading to substantial memory consumption. This article proposes an alternative approach to handling video streams more efficiently and elegantly.
The proposed pipeline consists of two main components: a Python frontend providing a user-friendly API and a high-performance backend that handles camera data. Both the FFmpeg, OpenCV (C++) and other similar libraries can function as the backend.
The process begins by creating a memory space, specifically a numpy array, which is then provided to the backend. The backend subsequently updates this buffer with the latest frame, eliminating the need for constant array creation and destruction. This architecture proves to be efficient as the memory space is allocated only once, and subsequent updates involve merely modifying the existing data.
To implement this solution, one can initialize a camera (CapCapture) to capture real-time frames. The Mat object, representing the frame data, can be encapsulated into a numpy.ndarray using pybind11. For Python programmers, the process of receiving the array and updating it when necessary is straightforward. Moreover, the array can be set as read-only, and copying should only occur when explicitly instructed by the programmer.
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