This presentation shows the Android Camera Architecture for who want to know the detail of the camera implementation on Android.

1. Android Camera Architecture Author: Picker

2. Architecture

4. Architecture Path of the Source Code frameworks/base/core/java/android/hardware/ frameworks/base/core/jni/ frameworks/base/libs/camera/ frameworks/base/services/camera/libcameraservice/ vendor/nvidia/tegra/hal/libnvomxcamera/

5. Proxy Pattern

6. Reference to: Design Patterns by Gamma, Helm, Johnson, Vlissides

7. A Possible Object Diagram of Proxy Structure at Run-Time Proxy Structure Reference to: Design Patterns by Gamma, Helm, Johnson, Vlissides

8. Implementation - Design a Abstract Class for Proxy and Server to Extend it. - Give an RealObject Instance for Proxy. Execute these Methods by Proxy. - The Client just Need to Face the Proxy.

9. Singleton Pattern

10. Reference to: Design Patterns by Gamma, Helm, Johnson, Vlissides Singleton Structure

11. Reference to: Design Patterns by Gamma, Helm, Johnson, Vlissides Singleton* Singleton::_instance = 0; Singleton* Singleton::Instance () { if (_instance == 0) { _instance = new Singleton; } return _instance; } Implementation

12. Architecture Diagram

13. Proxy Pattern Singleton Pattern

14. 33 // client singleton for camera service binder interface 34 Mutex Camera::mLock; 35 sp<ICameraService> Camera::mCameraService; 36 sp<Camera::DeathNotifier> Camera::mDeathNotifier; Singleton Pattern Camera.cpp frameworks/base/libs/camera/

15. 38 // establish binder interface to camera service 39 const sp<ICameraService>& Camera::getCameraService() 40 { 41 Mutex::Autolock _l(mLock); 42 if (mCameraService.get() == 0) { 43 sp<IServiceManager> sm = defaultServiceManager(); 44 sp<IBinder> binder; 45 do { 46 binder = sm->getService(String16(&quot;media.camera&quot;)); 47 if (binder != 0) 48 break; 49 LOGW(&quot;CameraService not published, waiting...&quot;); 50 usleep(500000); // 0.5 s 51 } while(true); 52 if (mDeathNotifier == NULL) { 53 mDeathNotifier = new DeathNotifier(); 54 } 55 binder->linkToDeath(mDeathNotifier); 56 mCameraService = interface_cast<ICameraService>(binder); 57 } 58 LOGE_IF(mCameraService==0, &quot;no CameraService!?&quot;); 59 return mCameraService; 60 } Camera.cpp frameworks/base/libs/camera/

16. 53 class BpCamera: public BpInterface<ICamera> 54 { 55 public: 56 BpCamera(const sp<IBinder>& impl) 57 : BpInterface<ICamera>(impl) 58 { 59 } 60 61 // disconnect from camera service 62 void disconnect() 63 { 64 LOGV(&quot;disconnect&quot;); 65 Parcel data, reply; 66 data.writeInterfaceToken(ICamera::getInterfaceDescriptor()); 67 remote()->transact(DISCONNECT, data, &reply); 68 } ICamera.cpp frameworks/base/libs/camera/ Proxy Pattern - Sender

17. 34 class CameraService : 35 public BinderService<CameraService>, 36 public BnCameraService 37 { 38 class Client; 39 friend class BinderService<CameraService>; 82 class Client : public BnCamera 83 { 84 public: 85 // ICamera interface (see ICamera for details) 86 virtual void disconnect(); 87 virtual status_t connect(const sp<ICameraClient>& client); 88 virtual status_t lock(); 89 virtual status_t unlock(); … … … 206 } Proxy Pattern - Receiver CameraService.h frameworks/base/services/camera/libcameraservice/

18. A Simple Workflow of Starting the Camera Preview

20. An Example: Set the Preview Display

21. 349 public final void setPreviewDisplay (SurfaceHolder holder) throws IOException { 350 if (holder != null) { 351 setPreviewDisplay (holder.getSurface()); 352 } else { 353 setPreviewDisplay ((Surface)null); 354 } 355 } Camera.java frameworks/base/core/java/android/hardware/

22. android_hardware_Camera.cpp 381 static void android_hardware_Camera_setPreviewDisplay ( JNIEnv *env, jobject thiz, jobject jSurface) 382 { 383 LOGV(&quot;setPreviewDisplay&quot;); 384 sp<Camera> camera = get_native_camera(env, thiz, NULL); 385 if (camera == 0) return; 386 387 sp<Surface> surface = NULL; 388 if (jSurface != NULL) { 389 surface = reinterpret_cast<Surface*>( env->GetIntField(jSurface, fields.surface)); 390 } 391 if ( camera->setPreviewDisplay (surface) != NO_ERROR) { 392 jniThrowException(env, &quot;java/io/IOException&quot;, &quot;setPreviewDisplay failed&quot;); 393 } 394 } frameworks/base/core/jni/

23. Camera.cpp frameworks/base/libs/camera/ 171 // pass the buffered ISurface to the camera service 172 status_t Camera::setPreviewDisplay (const sp<Surface>& surface) 173 { 174 LOGV(&quot;setPreviewDisplay&quot;); 175 sp <ICamera> c = mCamera; 176 if (c == 0) return NO_INIT; 177 if (surface != 0) { 178 return c->setPreviewDisplay (surface->getISurface()); 179 } else { 180 LOGD(&quot;app passed NULL surface&quot;); 181 return c->setPreviewDisplay (0); 182 } 183 }

24. ICamera.cpp 70 // pass the buffered ISurface to the camera service 71 status_t setPreviewDisplay (const sp<ISurface>& surface) 72 { 73 LOGV(&quot;setPreviewDisplay&quot;); 74 Parcel data, reply; 75 data.writeInterfaceToken(ICamera::getInterfaceDescriptor()); 76 data.writeStrongBinder(surface->asBinder()); 77 remote()->transact (SET_PREVIEW_DISPLAY, data, &reply); 78 return reply.readInt32(); 79 } frameworks/base/libs/camera/

25. CameraService.cpp frameworks/base/libs/camera/ 485 status_t CameraService::Client::setPreviewDisplay (const sp<ISurface>& surface) { 486 LOG1(&quot;setPreviewDisplay(%p) (pid %d)&quot;, surface.get(), getCallingPid()); … … … 510 mSurface = surface; 511 mOverlayRef = 0; 512 // If preview has been already started, set overlay or register preview 513 // buffers now. 514 if ( mHardware->previewEnabled() ) { 515 if (mUseOverlay) { 516 result = setOverlay(); 517 } else if (mSurface != 0) { 518 result = registerPreviewBuffers(); 519 } 520 }

26. frameworks/base/libs/camera/ CameraService.cpp 525 status_t CameraService::Client::registerPreviewBuffers () { 526 int w, h; 527 CameraParameters params(mHardware->getParameters()); 528 params.getPreviewSize(&w, &h); 529 530 // FIXME: don't use a hardcoded format here. 531 ISurface::BufferHeap buffers(w, h, w, h, 532 HAL_PIXEL_FORMAT_YCrCb_420_SP, 533 mOrientation, 534 0, 535 mHardware->getPreviewHeap ()); 536 537 status_t result = mSurface->registerBuffers(buffers); 538 if (result != NO_ERROR) { 539 LOGE(&quot;registerBuffers failed with status %d&quot;, result); 540 } 541 return result; 542 }

27. frameworks/base/libs/camera/ CameraHardwareStub.cpp 104 sp<IMemoryHeap> CameraHardwareStub::getPreviewHeap() const 105 { 106 return mPreviewHeap; 107 }