How to Address Video Capture Lag Caused by a Full Capture Buffer in OpenCV?

Delay in Video Capture Due to Capture Buffer

Issue

Capturing mjpeg video streams from a webcam using OpenCV's VideoCapture can result in a significant lag if the capture thread reads frames at a lower rate than the webcam feed's frame rate. This is caused by the accumulation of frames in the capture buffer until the buffer is flushed.

OpenCV Solution

To manually flush the capture buffer, you can set the CV_CAP_PROP_BUFFERSIZE property of the VideoCapture object. This will limit the number of frames stored in the internal buffer. However, this option is only supported for certain backend hardware.

Hackaround 1

If setting the buffer size does not resolve the issue, you can use a hackaround technique. It involves repeatedly querying frames until the time taken to retrieve a frame exceeds a certain threshold. If the retrieval time is unusually low, it indicates that the frame was obtained from the buffer and should be discarded.

Hackaround 2

Another hackaround solution is to create a separate thread that continuously grabs frames at a high speed to keep the capture buffer empty. This thread should use the cv::VideoCapture.grab() function to avoid overhead while grabbing frames. You can use synchronization techniques to ensure that the worker thread reads frames from the buffer in a controlled manner.

The above is the detailed content of How to Address Video Capture Lag Caused by a Full Capture Buffer in OpenCV?. For more information, please follow other related articles on the PHP Chinese website!