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opencv / opencv

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Android NDK camera support #19597

Merged

alalek merged 4 commits into opencv:master from komakai:android-ndk-camera

Feb 25, 2021

+749 −3

Contributor

komakai commented Feb 22, 2021 •

edited by alalek

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

I agree to contribute to the project under Apache 2 License.
To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
The PR is proposed to proper branch
There is reference to original bug report and related work

This PR fixes #11952

Add an Android native camera capture backend to the videoio module.
Based loosely on https://github.com/android/ndk-samples/tree/main/camera
Requires Android native API level 24 or above (in order to access NDK camera APIs)

android_pack_config=ndk-18-api-level-24.config.py

komakai added 4 commits


          Add native camera video backend for Android

e2022d1


          In the event of a "No buffer available error" wait for the appropriat…

18317a1

…e callback and retry


          Fix stale context when creating a new AndroidCameraCapture

d1cf432


          Add property handling

2e2df44

alalek added feature platform: android category: videoio labels

alalek added this to the 4.5.2 milestone

alalek self-requested a review

alalek approved these changes

Contributor

alalek left a comment

Well done! Thank you for contribution 👍

alalek self-assigned this

alalek merged commit 0553543 into opencv:master

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jumpy88 commented Feb 26, 2021

So, should now with this update cv::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 cameras https://source.android.com/devices/camera/external-usb-cameras)

Contributor Author

komakai commented Feb 27, 2021

@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 cameras https://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 OpenCV videoio module is written in C++)

jumpy88 commented Mar 5, 2021

@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.

jumpy88 commented Mar 25, 2021 •

edited

Hi, I've just done some experiments with 2e2df44 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 here https://github.com/jumpy88/godot_ocv-camera-reader
Thank you for the great job @komakai

alalek reviewed

modules/videoio/src/cap_android_camera.cpp

  
                        }

                        return true;

                    case CV_CAP_PROP_CONVERT_RGB:

                        convertToRgb = (value != 0);

alalek Mar 25, 2021
Contributor

`cv::cvtColor(yuv, out, convertToRgb ? cv::COLOR_YUV2RGB_YV12 : cv::COLOR_YUV2BGR_YV12);`

BTW, meaning of this property is different (name misleads unfortunately, it is not BGR / RGB switch):

CV_CAP_PROP_CONVERT_RGB = 1 (default): VideoCapture returns frames as "BGR" 8UC3 cv::Mat.

CV_CAP_PROP_CONVERT_RGB = 0: VideoCapture returns frames in other formats, like NV12, Y8, etc (format is retrieved and/or sometimes specified through `CAP_PROP_FOURCC`)

komakai Mar 26, 2021
Author Contributor

@alalek OK thanks for the explanation - will prepare a fix for this when I get a minute.

splinterwhatever Mar 26, 2021

Is there a space in the api to allow for the BGR/RGB switch in addition to the correct convertToRGB behaviour?

cheers, Jeff

komakai mentioned this pull request

Fix Android NDK camera's color format conversions #19855

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