So, should now with this updatecv::VideoCapture.open(0) succeed and return an handle to accede a camera on Android? Does it only work for internal cameras or also for USB cameras? (Camera2 API I understand this patch is based on should support USB camerashttps://source.android.com/devices/camera/external-usb-cameras)

@jumpy88 it will work for any device that is accessible to the Android NDK Camera API (https://developer.android.com/ndk/reference/group/camera)

(Camera2 API I understand this patch is based on should support USB camerashttps://source.android.com/devices/camera/external-usb-cameras)

This link is aimed at device manufacturers who are building the Android OS itself, not general Android app developers. (Also note: Camera2 is a Java API whereas the OpenCVvideoio module is written in C++)

@komakai Ops, sorry, I thought Camera2 was an API for developers and it was accessible in Android NDK. My knowledge about Android is still very poor. Ok, I'll give it a try with your code and will post the result.
Thank you for your contribution and support.

Hi, I've just done some experiments with2e2df44 commit in a Godot Engine proof of concept. It works with built-in cameras but doesn't seem to recognize external USB cameras. The only weird thing is sometimes the visualized frame appears having blue and red channels swapped, but I don't have enough information to open an issue (I don't know if it's due to OpenCV itself or is my fault). You can find the sample code herehttps://github.com/jumpy88/godot_ocv-camera-reader
Thank you for the great job@komakai

Hello,

I am using opencv 4.5.4. python reports on android: after calling

cam = cv2.VideoCapture(0)
cam.isOpened(): True.

but i can't get a frame from the video stream. If i call

retval, frame = cam.read()

retval is returned as False and Frame is None. Do i miss something? The code works on windows.

@komakai Do you know what i am missing here?

@Ay-De running OpenCv Python on Android is not something I have tested. I would suggest to look in the Logcat output to see if there are any error messages there

@Ay-De running OpenCv Python on Android is not something I have tested. I would suggest to look in the Logcat output to see if there are any error messages there

Hello, i am using kivy to run python code on android. OpenCV is being imported, videocapture(0) (or 1) works also. As i said, the isOpened() function also returns true, but if i try to read a frame, with read(), that returns nothing. No error is thrown according to logcat, but the variable for frame says it is None.

@Ay-De Do you have an APK file you can share?

@Ay-De Do you have an APK file you can share?

Yes, here:
https://github.com/Ay-De/Kivy_Python_Camera_Demo/releases/tag/0.0.17

There is also the source code (See the main.py in develop branch. sorry it is still quite messy). The APK is compiled with debug mode enabled. If you execute the main.py on a windows computer with a webcam, it will work without errors (i tested it on a Surface Pro 7).

OK - so I tried your APK and saw lots of output like this:

2022-02-14 21:30:53.148 26028-26132/org.ayde.kivycamera V/NativeCamera: session 0x7bce246ba0 capture completed
2022-02-14 21:30:53.149 26028-26066/org.ayde.kivycameraE/NativeCamera: Unsupported format

Ok sorry i somehow missed that part. I think the problem lies in returned image format from the sensor? Is there a way to specify it in OpenCV? OpenCV has a flag CAP_PROP_FORMAT to fetch undecoded RAW video streams, but unfortunatly, the android camera seems to support different ones and i can't currently find a way to set it on the Android side. Would it maybe be possible to set the camera format after opening the image stream by making direct API calls?
https://developer.android.com/reference/android/graphics/ImageFormat

I am sorry if i am derailing this thread here!

@Ay-De The error message is coming from this line:
https://github.com/opencv/opencv/blob/4.x/modules/videoio/src/cap_android_camera.cpp#L324

There were some bug fixes recently in that area of the code:
68667d6
fa222b0
21d0f40
So my guess would be the build you have is missing one or more of these fixes.

So, first of all, thanks for your help. I really appreciate it.

I updated my files to include opencv in version 4.5.5, which include the above mentioned fixes, but it still doesn't work. May i ask you, which tools you are using to get the above mentioned logs?

2022-02-14 21:30:53.148 26028-26132/org.ayde.kivycamera V/NativeCamera: session 0x7bce246ba0 capture completed
2022-02-14 21:30:53.149 26028-26066/org.ayde.kivycamera E/NativeCamera: Unsupported format

I am using logcat for debugging but i am not seeing this errors, i guess i am maybe filtering out to much? I would like to understand the problems myself better instead of just asking and for that i think i need a better insight.

I am currently only seeing these logs:

02-15 16:48:55.923 10556 10748 I python : Run user program, change dir and execute entrypoint
02-15 16:48:55.966 10556 10748 I python : [WARNING] [Config ] Older configuration version detected (0 instead of 21)
02-15 16:48:55.966 10556 10748 I python : [WARNING] [Config ] Upgrading configuration in progress.
02-15 16:48:55.970 10556 10748 I python : [INFO ] [Logger ] Record log in /data/user/0/org.ayde.kivycamera/files/app/.kivy/logs/kivy_22-02-15_0.txt
02-15 16:48:55.970 10556 10748 I python : [INFO ] [Kivy ] v2.0.0
02-15 16:48:55.970 10556 10748 I python : [INFO ] [Kivy ] Installed at "/data/user/0/org.ayde.kivycamera/files/app/_python_bundle/site-packages/kivy/init.pyc"
02-15 16:48:55.970 10556 10748 I python : [INFO ] [Python ] v3.8.9 (default, Feb 15 2022, 16:29:31)
02-15 16:48:55.970 10556 10748 I python : [Clang 9.0.9 (https://android.googlesource.com/toolchain/llvm-project a2a1e703c
02-15 16:48:55.970 10556 10748 I python : [INFO ] [Python ] Interpreter at ""
02-15 16:48:56.256 10556 10748 I python : [INFO ] [Factory ] 186 symbols loaded
02-15 16:48:56.341 10556 10748 I python : [INFO ] [Image ] Providers: img_tex, img_dds, img_sdl2 (img_pil, img_ffpyplayer ignored)
02-15 16:48:56.517 10556 10748 I python : OpenCV version: 4.5.5
02-15 16:48:56.597 10556 10748 I python : [INFO ] [Window ] Provider: sdl2
02-15 16:48:56.611 10556 10748 I python : [INFO ] [GL ] Using the "OpenGL ES 2" graphics system
02-15 16:48:56.611 10556 10748 I python : [INFO ] [GL ] Backend used
02-15 16:48:56.612 10556 10748 I python : [INFO ] [GL ] OpenGL version <b'OpenGL ES 3.2 V@0530.0 (GIT@5a9022f91f, Ib11adbd47c, 1627309424) (Date:07/26/21)'>
02-15 16:48:56.612 10556 10748 I python : [INFO ] [GL ] OpenGL vendor <b'Qualcomm'>
02-15 16:48:56.612 10556 10748 I python : [INFO ] [GL ] OpenGL renderer <b'Adreno (TM) 660'>
02-15 16:48:56.613 10556 10748 I python : [INFO ] [GL ] OpenGL parsed version: 3, 2
02-15 16:48:56.613 10556 10748 I python : [INFO ] [GL ] Texture max size <16384>
02-15 16:48:56.613 10556 10748 I python : [INFO ] [GL ] Texture max units <16>
02-15 16:48:56.631 10556 10748 I python : [INFO ] [Window ] auto add sdl2 input provider
02-15 16:48:56.632 10556 10748 I python : [INFO ] [Window ] virtual keyboard not allowed, single mode, not docked
02-15 16:48:56.633 10556 10748 I python : [INFO ] [GL ] NPOT texture support is available
02-15 16:48:57.073 10556 10748 I python : Camera connected Status: True
02-15 16:48:57.478 10556 10748 I python : Frame returned: False
02-15 16:48:57.478 10556 10748 I python : Frame data: None
02-15 16:48:57.704 10556 10748 I python : [INFO ] [Text ] Provider: sdl2
02-15 16:48:57.746 10556 10748 I python : [WARNING] [Base ] Unknown provider
02-15 16:48:57.746 10556 10748 I python : [INFO ] [Base ] Start application main loop

Sorry for all these probably easy to fix questions.^^

May i ask you, which tools you are using to get the above mentioned logs?
In Android Studio look for a tab along the bottom called "Logcat"

There is an Android/Java sample here:
https://github.com/komakai/NdkCamtest/blob/master/app/src/main/java/net/telepathix/ndkcam/MainActivity.java#L97
If you copy the same logic into Python it should work 🤞

I finally got it to work. Thanks@komakai.

Hi, I've just done some experiments with2e2df44 commit in a Godot Engine proof of concept. It works with built-in cameras but doesn't seem to recognize external USB cameras. The only weird thing is sometimes the visualized frame appears having blue and red channels swapped, but I don't have enough information to open an issue (I don't know if it's due to OpenCV itself or is my fault). You can find the sample code herehttps://github.com/jumpy88/godot_ocv-camera-reader Thank you for the great job@komakai

Let us know any further improvements committed for external USB camera access? For external camera to support we need to enable below feature. My understanding is for some android mobile manufactures, USB Webcam access support is available, in that mobile CAMERA2 API will work. ie,. external camera will be detected in CameraManager API.