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1、| 2012 Aptina Imaging Corporation 1 2012 Aptina Imaging Corporation. All rights reserved. Products are warranted only to meet Aptinas production data sheet specifications. Information, products, and/or specifications are subject to change without notice. All information is provided on an “AS IS” bas
2、is without warranties of any kind. Dates are estimates only. Drawings not to scale. Aptina and the Aptina logo are trademarks of Aptina Imaging Corporation. All other trademarks are the property of their respective owners. Exposing the Android Camera Stack Balwinder Kaur, Principal Software Architec
3、t Joe Rickson, Principal Software Engineer The San Francisco Android User Group 8.28.2012 | 2012 Aptina Imaging Corporation 2 Agenda Camera APIs Overview of android.hardware.Camera Whats new in Jelly Bean ? Prominent Camera Use Cases Android Media Framework Camera Native Camera service Whats new in
4、Jelly Bean ? Media Subsystem Interactions Its all about the Camera hardware ! Camera Hardware Abstraction Layer Camera Device Driver Camera Hardware Architecture Future Trends Q get(“your_param_string”); Auto White Balance, Scene Modes, Focus Modes, Preview Sizes, Picture Sizes, Thumbnail Sizes, Pre
5、view Format, Picture Format, Anti-Banding | 2012 Aptina Imaging Corporation 7 the rest of the Camera Classes Camera.CameraInfo For each camera, front or back facing, orientation of the camera image Camera.Size width and height of the image Camera.Face face-id, co-ordinates for left eye, right eye, m
6、outh, outer bounds of the face Camera.Area Rectangular bounds with a weight Metering Regions for 3A : Auto Focus, Auto White Balance, Auto Exposure | 2012 Aptina Imaging Corporation 8 Whats new in Jelly Bean ? APIs Camera.AutoFocusMoveCallback FOCUS_MODE_CONTINUOUS_PICTURE and FOCUS_MODE_CONTINUOUS_
7、VIDEO allows you to listen for changes to the auto focus movement starting if (p.getMaxNumDetectedFaces() 0 ) mCamera.startFaceDetection(); Face Information is available through the Camera.FaceDetectionListener void onFaceDetection (Face faces, Camera camera) / Overlay Green, White or your favorite
8、color squares / on the Preview Surface Some of the ISPs will overlay these on the Preview stream directly | 2012 Aptina Imaging Corporation 15 Other Applications ZXing: Open Source Library for 1D/2D image processing library uses the Camera.setOneShotPreviewCallback Processing the live Preview Stream
9、 w/o a display In API level 11 (HoneyComb), Camera.setPreviewTexture() call was introduced. With this call, Camera Streams can be processed w/o necessarily needing a display GPU Processing: Need an OpenGL context. SurfaceTexture.updateTexImage will update SurfaceTexture to the latest preview frame f
10、rom the camera CPU Processing: Dont call updateTexImage. The SurfaceTexture will simply discard all data passed into it by the camera. Set up preview callbacks using setPreviewCallback, and use that data (typically in a YUV format) for CPU processing. Less efficient than GPU processing. No knowledge
11、 of OpenGL is needed. OpenCV sample code uses this pattern a lot. Google IO 2011 : http:/ | 2012 Aptina Imaging Corporation 16 Section II Android Media Framework - Camera | 2012 Aptina Imaging Corporation 17 High Level Architecture | 2012 Aptina Imaging Corporation 18 Source: Android Anatomy and Phy
12、siology, Google IO 2008 Android High Level Architecture | 2012 Aptina Imaging Corporation 19 Source: Android Anatomy and Physiology, Google IO 2008 Hardware Abstraction Layer Hardware Abstraction Layer Camera | 2012 Aptina Imaging Corporation 20 Camera Subsystem Application Application framework Cam
13、era Service Camera HAL Implementation Camera Device Driver Hardware Independent Hardware Dependent Camera Hardware HAL = Hardware Abstraction Layer | 2012 Aptina Imaging Corporation 21 Process View App App App Binder IPC ICamera Media server Camera Service Back Facing Camera Hardware Object Front Fa
14、cing Camera Hardware Object Kernel Driver Kernel Driver System Call System Call Binder IPC ISurface Surfaceflinger | 2012 Aptina Imaging Corporation 22 Inside the Camera App Media server Camera Service libcameraservice.so Camera HAL implementation Application Code android framework code Camera.java
15、JNI android_hardware_Camera.cpp | 2012 Aptina Imaging Corporation 23 JNI Layer | 2012 Aptina Imaging Corporation 24 JNI Layer Media server Camera Service libcameraservice.so Camera HAL implementation Application Code android framework code Camera.java JNI android_hardware_Camera.cpp | 2012 Aptina Imaging Corporation 25 android_hardware_Camera Creates a persistent context for callbacks from native code to Java (JNICameraContext) Holds references to the Java Camera, Face and Area objects. If a Copy of the Preview Frame is requested by the app, then the copy f
