本文基于Android 4.2.2+Linux3.6.9+SAMA5D3 SoC从源码的角度审视Android Camera子系统。

应用层

Androd原生Camera应用

/system/app/LegacyCamera.apk

http://androidxref.com/4.2.2_r1/xref/packages/apps/LegacyCamera/

Camera应用调用Android应用框架提供的Camera API

import android.hardware.Camera;

import android.hardware.Camera.Area;

import android.hardware.Camera.CameraInfo;

import android.hardware.Camera.Face;

import android.hardware.Camera.FaceDetectionListener;

import android.hardware.Camera.Parameters;

import android.hardware.Camera.PictureCallback;

import android.hardware.Camera.Size;

应用框架层

/system/framework/framework.jar

http://androidxref.com/4.2.2_r1/xref/frameworks/base/core/java/android/hardware/Camera.java

JNI

/system/lib/libandroid_runtime.so

http://androidxref.com/4.2.2_r1/xref/frameworks/base/core/jni/android_hardware_Camera.cpp

Camera Service
Binder Proxy

Camera Service
Binder Proxy是Camera Client和Camera Service之间通信的统一通道。Camera Client和Camera
Service都会调用Camera Service Binder Proxy。

/system/lib/libcamera_client.so

头文件文件夹

http://androidxref.com/4.2.2_r1/xref/frameworks/av/include/camera/

源文件文件夹

http://androidxref.com/4.2.2_r1/xref/frameworks/av/camera/

Camera Service

Camera Service与Camera HAL交互，通过Binder Service的方式为Camera
Client提供服务。

/system/lib/libcameraservice.so

http://androidxref.com/4.2.2_r1/xref/frameworks/av/services/camera/libcameraservice/

HAL

Camera硬件抽象层定义并实现供Camera Service调用的标准接口，保证Camera硬件的功能可以正常发挥。

/system/lib/hw/camera.sama5d3-ek.so

头文件

http://androidxref.com/4.2.2_r1/xref/hardware/libhardware/include/hardware/camera.h

源文件文件夹

https://github.com/Android4SAM/platform_hardware_atmel/tree/master/sama5d3/camera

Kernel
Driver

Camera驱动程序与Camera硬件和HAL交互。Camera硬件和驱动程序必须支持YV12和NV21图像格式以支持预览和录像。

The V4L2driver for Atmel Linux

https://github.com/Android4SAM/linux-at91/blob/android4sam_v4.0/drivers/media/video/atmel-isi.c

SoC Cameradriver for Omni Vision 2640 sensor

https://github.com/Android4SAM/linux-at91/blob/android4sam_v4.0/drivers/media/video/ov2640.c