VideoCapture with the FFMpeg backend has a lock in VideoCapture::open() which means that only one open can happen in any thread at any one time. See below for more details
opened 03:39PM - 18 May 21 UTC
category: videoio
category: 3rdparty
On windows when opening up RTSP streams with VideoCapture::open() and the FFMPEG… back end, there is normally a delay, say 2000ms while the stream is setup, which is to be expected.
While this is happening any additional calls to VideoCapture::open() and VideoWriter.open() in other threads are blocked.
Is this blocking/queuing part of OpenCV or FFMPEG and can it be removed?
##### System information (version)
- OpenCV => 4.5.2
- Operating System / Platform => Windows 64 Bit
- Compiler => Visual Studio 2019
##### Steps to reproduce
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With rtsp streams this is more apparent because each stream can take a number of seconds to open. Try with a video file to see if the situation improves.
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