从AndroidP 开始,高通camera系统全面使用HAL3,之前的HAL1已经被移除,对应HAL3主流的相机开发接口是camera API2 ,但是依然存在大量的使用Camera API 1开发的相机应用,为此Android专门设计了一套兼容API1调用HAL3的中间转换接口,本门主要从几个方面简要介绍下这部分相关的知识。**
- opencamera
- startpreview
- takepicture
- setparameter、getparameter
1. opencamera
相机应用在调用
Camera open(int cameraId)
时, 经过Binder IPC
进入CameraService.cpp
,调用的接口是
CameraService::connectHelper(....){
ALOGI("CameraService::connect call (PID %d \"%s\", camera ID %s) for HAL version %s and "
"Camera API version %d");
ret = makeClient(......))
err = client->initialize(mCameraProviderManager);//重点分析
}
通过makeClient
会创建相应的client
Status CameraService::makeClient(.....) {
......
// Default path: HAL version is unspecified by caller, create CameraClient
// based on device version reported by the HAL.
switch(deviceVersion) {
case CAMERA_DEVICE_API_VERSION_1_0:
//Android P 之后不再存在
if (effectiveApiLevel == API_1) { // Camera1 API route
*client = new CameraClient(....),
} else { // Camera2 API route
}
break;
case CAMERA_DEVICE_API_VERSION_3_0:
case CAMERA_DEVICE_API_VERSION_3_1:
case CAMERA_DEVICE_API_VERSION_3_2:
case CAMERA_DEVICE_API_VERSION_3_3:
case CAMERA_DEVICE_API_VERSION_3_4:
//API1+HAL3 对应的client
if (effectiveApiLevel == API_1) { // Camera1 API route
*client = new Camera2Client(.....);
} else { // Camera2 API route
//API2+HAL3 对应的client
*client = new CameraDeviceClient(.....);
}
break;
default:
// Should not be reachable
ALOGE("Unknown camera device HAL version: %d", deviceVersion);
.....
}
}
通过上述代码分析发现API1+HAL3
对用的client是Camera2Client
其类图如下:
从上边看Camera2Client
继承实现了ICamera
定义的camera API1接口,但是其内部的成员变量mDevice是`Camera3Device 类型,其是针对HAL3设计的,下边分析 openCamera具体流程
从流程图上看,opencamera主要完成了两件事:
- makeclient 创建camera2client对象及Camera3Device对象
- 初始化camera2client,真正完成打开相机的地方
从过程看,Camera2Client
实现的是Camera API1
的接口,并通过
Camera3Device
对象mDevice
完成与Camera HAL3
的对接