Unable to open / write video file / stream on Linux

[kasius75]

The Linux lib is not built using video framework when looking at the cmake.log, resulting no video can be used:

--   Video I/O:
--     DC1394:                      NO
--     GStreamer:                   NO
--     v4l/v4l2:                    YES (linux/videodev2.h)

You should build with ffmpeg, gstreamer and DC1394 support (like this on Ubuntu 18.04):

--   Video I/O:
--     DC1394:                      YES (2.2.5)
--     FFMPEG:                      YES
--       avcodec:                   YES (57.107.100)
--       avformat:                  YES (57.83.100)
--       avutil:                    YES (55.78.100)
--       swscale:                   YES (4.8.100)
--       avresample:                YES (3.7.0)
--     GStreamer:                   YES (1.14.5)
--     v4l/v4l2:                    YES (linux/videodev2.h)

[vonnieda]

See comments in openpnp/openpnp#774. ffmpeg is not included for legal reasons, and because I haven't found a way to statically link it. You can install it manually and it should work.

[kasius75]

FFmpeg is already installed on my system and it does not work. I had to rebuild opencv to be able to use videos with it. I understand the license issue, but at this state, the linux version is almost useless without video support. Maybe you have to warn about it.

[wfaithfull]

👍 I also just discovered this today while trying to port an old OpenCV project to use this. This kills the usefulness of this library because the application revolves around VideoCapture, and without FFMPEG support it can't open anything. I already have FFMPEG installed, of course

[Jotschi]

I think I also ran into the same problem.

The open method always returns false for me.

VideoCapture capture = new VideoCapture();
capture.open(path);

I'm using this version on debian linux (x86_64)

<dependency>
	<groupId>org.openpnp</groupId>
	<artifactId>opencv</artifactId>
	<version>4.3.0-2</version>
</dependency>

[Jotschi]

Short update:

I was able to solve my issue by using the lib from the libopencv4.2-jni debian package.

I load the lib via System.loadLibrary("opencv_java420"); and added -Djava.library.path=/usr/lib/jni/ to my start parameters.

@vonnieda I'm not sure why you did not compile with video support but I think it would be enough to add a hint / note / warning to the readme that informs about this?

[enwi]

I am having the same issue on windows. Is it also not included there?

[peterkronenberg]

I have also not yet been able to find a way to get this to work. Tried -Djava.library.path and -Djna.library.path, but neither seems to work

[deanbrok]

@Jotschi Hi, thank you for sharing your answer, however, are you still using this Maven package in addition to libopencv4.2-jni ? Or did you have to remove the Maven package first and then add libopencv4.2-jni?

[Jotschi]

@deanbrok I have not changed my setup and it works with /usr/lib/jni and debian package opencv4.2-jni (4.2.0+dfsg-6+b4).

[deanbrok]

@Jotschi Thanks for such a quick reply! So you are no longer using Openpnp's Maven package? And I'm planning to deploy the app on a Docker image, I imagine your solution would work fine there too?

[Jotschi]

@deanbrok I'm still using

<dependency>
	<groupId>org.openpnp</groupId>
	<artifactId>opencv</artifactId>
	<version>4.3.0-2</version>
</dependency>

If you provide the same libopencv4.2-jni package in your container image it should work. I'm not aware of any other working solution.

[deanbrok]

@Jotschi Thank you for the help! I will try out your solution.

[vonnieda]

Closing as a duplicate of #74. Please assist with that issue.