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Hi berak. Yes, I can explain :) Some months ago, I 'wrapped' the openCV320 for Android 'official' SDK so that it could b

Hi berak. Yes, I can explain :) Some months ago, I 'wrapped' the openCV320 for Android 'official' SDK so that it could b

Thanks! Just to try (I was desperate), I just had edited it manually doing the same (adding Java in cmakelists) and 'bin

Can't get Facerecognizer Java bindings building OpenCV3.30 for Android I am trying to build OpenCV 3.30 for Android with

Solved. I post the solution here in case someone faces the same issue.

My fault, I had installed Simplicity Studio which also had Make and ARM utilities. Even if it was at a lower position in my path, somehow it was affecting. I cleant it and worked normally as expected.

I could successfully build OpenCV320 for android under Windows10 using cmake, targeting armeabi-v7a and arm64-v8a abis

Now I am trying to build it with "armeabi-v7a with NEON" to check performance differences. Build process works ok, but when I try to run, it crashes at the first JNI call (SISEGV error...).

So my question is if this is a known issue, or on the contrary perhaps there is some other cmake option that "must go together" with -DANDROID_ABI="armeabi-v7a with NEON" so that it can work correctly, or just I did something wrong.

Any input will be welcome :)

--edit-- Also a good starting point would be to find wich cmake options can be used to build the officially released 3.20 from master.

( I don't know if it is the right place to post it, so please point me in the right direction if not so.)

Has anyone succeeded to build openCV for android in Windows 10 with cmake/make in a clean manner? My goal is to generate libopencv_java3.so and the java classes.

I succeeded with the official 3.20 package, but only after some errors here and there, having to figure how to prevent the error shown, sometimes in source code, ... So it is ok since now I have it working, but in the future I will need to customize quite often the C code, and build the libs again. I would like to be able to do this process without intermediate errors.

On the other hand, I read posts of people that have been able to build it totally "clean" just following the same process than me (build opencv from trunk)

For instance, one of the errors I am getting now in the make process is (after git cloning opencv and trying with different commits)

• C:\Develop\git\opencv_320\build4>cmake -G "Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=..\platforms\android\android.toolchain.cmake .. (this works ok)
• C:\Develop\git\opencv_320\build4>make (always stops at about 85%, with this error)

....
[ 85%] Generating jni/photo.cpp
[ 85%] Generating jni/video.cpp
[ 85%] Generating jni/imgcodecs.cpp
[ 85%] Generating jni/videoio.cpp
[ 86%] Generating jni/features2d.cpp
[ 86%] Generating OpenCV Android library project. SDK target: android-23
make[2]: * [build.xml] Error 2
make[1]: [modules/java/CMakeFiles/opencv_java.dir/all] Error 2
make: ** [all] Error 2

In short, is it possible that the success of the cmake/make process (in Windows 10) could depend on the versions of the installed tools (cmake, make, NDK, ...., and the ENV variables)? It would be of great help, in order to be able to compare and have a known starting point, to have a checklist of a "working set" of tools (cmake, make, ndk, whatever...) I mean its versions, System environment variables, and whatever can affect the build process.

Thanks a lot for answering. Will test and report back results in case I achieve something useful :)

Thanks berak for your answer! Do you know if building with ffmeg support (through cmake compilation switches) will directly make the other codes available for videowriter?

OpenCv3.20 for Android only allows (for what I have tried and seen in some posts) videowriter to encode .AVI files with fourcc "MJPG" code. Any other options that I have tried result in .isOpened() returning false.

I am confused as I don't know if the official 3.20 version for android is built with 3rd party libs as ffmpeg. I see that there are options in build process to include this and other 3rd party libs.

My question is: Assuming that it is not included in the official release, if I get to rebuild opencv3.2 with ffmpeg, does it mean that videowriter will internally be able to use them? Or it will be just be just an extension of the lib with its own API but not tied internally to OpenCv? Any hint will be welcome since I am quite lost.

I prefer to ask because instead of trying directly because I am not agile in this (building process) and would like to be sure before spending time with trial and errors