Timeout on VideoCapture.open(0)?

asked 2014-11-09 17:48:28 -0600

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I am calling VideoCapture.open(0) and everything works like a charm if I have a device at ID 0. Problem is if I don't have a openable device there, OpenCV will continue trying to establish a connection afaik - FOREVER. This occurs for example when I run the code on my laptop which has a facetime HD camera in the lid. if i run the computer from an external monitor and I have the lid down then it just hangs forever. As soon as I open the lid it springs to life. Is there any way to specify a timeout for trying? If it will never stop trying to connect then constructs like ...

if (!cap.isOpened()) // check if we succeeded

make no sense, because it will never report that it did not succeed. any solutions? I am using OpenCV 2.4.10 on Mac OSX 10.10 with Java 1.8.0_25. Thanks,

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Please try to use more recent version, like 3.4.3

mshabunin ( 2018-11-16 14:21:02 -0600 )edit

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answered 2018-11-16 10:35:24 -0600

oyyablokov
11 ●1 ●1

updated 2018-11-16 10:44:09 -0600

First of all, if you use ffmpeg as a backend for VideoCapture, cap.open() will actually return after some time (more specifically, the timeout is defined in ffmpeg somewhere in source):

#define LIBAVFORMAT_INTERRUPT_OPEN_TIMEOUT_MS 30000
#define LIBAVFORMAT_INTERRUPT_READ_TIMEOUT_MS 30000

If you are unsatisfied with these timeout values, I see two options. First - compile ffmpeg with changed constants and link against it, and second - try to use another backend (the list is here) like this:

cap.open(0, cv::CAP_XIAPI); // or cv::CAP_<something else>

Update: this example is valid in C++, but maybe there is a similar workaround in Java.

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Timeout on VideoCapture.open(0)?

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Timeout on VideoCapture.open(0)?