android camera flow and V4L2 in linux kernel--------android 调用流程

最新推荐文章于 2024-04-27 09:35:01 发布

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最新推荐文章于 2024-04-27 09:35:01 发布 · 2.4k 阅读

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#Android #camera #v4l2

本文详述了Android系统中调用相机的流程，从硬件/camera.java开始，经由libs/camera.camera.cpp、ICamera.cpp，直至CameraHal.cpp，涉及setParameters和startPreview的过程。在MX53平台上，通过V4L2接口与摄像头驱动进行交互，包括VIDIOC_G_CTRL和VIDIOC_S_CTRL操作来获取和设置camera control状态。

记录自己的学习过程。。。。。。。

注：1. surfaceflinger暂时不完全懂，后续研究

2. 平台mx53

android 中文件调用流程： hardware/camera.java -----> libs/camera.camera.cpp ------> cameraservice.cpp ------> CameraHal.cpp

hardware/camera.java -----> libs/camera.camera.cpp ------> ICamera.cpp ------> cameraservice.cpp ------> CameraHal.cpp

android 中打开摄像头驱动的基本流程：

打开camera，函数调用流程：

a) 调用framework/base/core/java/android/hardware/carema.java 中的camera.open函数

    public static Camera open() {
        int numberOfCameras = getNumberOfCameras();                           //获取camera数量
        CameraInfo cameraInfo = new CameraInfo();
        for (int i = 0; i < numberOfCameras; i++) {
            getCameraInfo(i, cameraInfo);
            if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK) {         //看注释，好像是判断是前置摄像头，还是后置摄像头
                return new Camera(i);
            }
        }
        return null;
    }

    Camera(int cameraId) {
        mShutterCallback = null;
        mRawImageCallback = null;
        mJpegCallback = null;
        mPreviewCallback = null;
        mPostviewCallback = null;
        mZoomListener = null;

        Looper looper;
        if ((looper = Looper.myLooper()) != null) {
            mEventHandler = new EventHandler(this, looper);
        } else if ((looper = Looper.getMainLooper()) != null) {
            mEventHandler = new EventHandler(this, looper);
        } else {
            mEventHandler = null;
        }

        native_setup(new WeakReference<Camera>(this), cameraId);              //connect to camera service
    }

b) native_setup会调用到android_hardware_camera.cpp文件中的android_hardware_camera_native_setup（）函数

static void android_hardware_Camera_native_setup(JNIEnv *env, jobject thiz,
    jobject weak_this, jint cameraId)
{
    sp<Camera> camera = Camera::connect(cameraId);                            //framework/base/libs/camera/camera.cpp中的connect函数，如下

    if (camera == NULL) {
        jniThrowException(env, "java/lang/RuntimeException",
                          "Fail to connect to camera service");
        return;
    }

    // make sure camera hardware is alive
    if (camera->getStatus() != NO_E

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