bakaid commented on a change in pull request #612: MINIFICPP-854: Capture RTSP
Frame
URL: https://github.com/apache/nifi-minifi-cpp/pull/612#discussion_r304338948
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File path: extensions/opencv/CaptureRTSPFrame.cpp
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@@ -73,6 +73,11 @@ void CaptureRTSPFrame::initialize() {
relationships.insert(Success);
relationships.insert(Failure);
setSupportedRelationships(std::move(relationships));
+ // By default in OpenCV, ffmpeg capture is hardcoded to use TCP and this is
a workaround
+ // also if UDP timeout, ffmpeg will retry with TCP
+ // Note:
+ // 1. OpenCV community are trying to find a better approach than setenv.
+ setenv("OPENCV_FFMPEG_CAPTURE_OPTIONS", "rtsp_transport;udp", 1);
Review comment:
setenv is unfortunately not thread-safe. Not only setting the same
environment variable from two threads is unsafe, but so is setting anything
from two threads at once.
That being said, I know no good solution to this other than a framework for
the global synchronization of setenvs and getenvs, and even that does not
account from potential setenvs/getenvs called by third parties.
I don't think that there is a high probability of this causing issues, but
if we see unexplainable crashes or issues around environment variables, then we
should think of this as a cause.
I would like this comment to be extended with this caveat.
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