双camera同时打开
平台：android5.1
场景：双屏异显设备需求在两个屏上同时打开两个摄像头，确认可行性。
时间：2016.9.28
双camera示例代码：
this.mSurfaceHolder = this.sfv1.getHolder();
this.mSurfaceHolder.addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceDestroyed(SurfaceHolder arg0) {
// TODO Auto-generated method stub
}
@Override
public void surfaceCreated(SurfaceHolder arg0) {
// TODO Auto-generated method stub
Camera mcamera = Camera.open(0);
mcamera.setDisplayOrientation(90);
try {
mcamera.setPreviewDisplay(mSurfaceHolder);
mcamera.startPreview();
return;
} catch (IOException localIOException) {
localIOException.printStackTrace();
}
}
@Override
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
});
this.mSurfaceHolder.setType(3);
this.mSurfaceHolder1 = this.sfv2.getHolder();
this.mSurfaceHolder1.addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceDestroyed(SurfaceHolder arg0) {
// TODO Auto-generated method stub
}
@Override
public void surfaceCreated(SurfaceHolder arg0) {
// TODO Auto-generated method stub
Camera mcamera = Camera.open(1);
mcamera.setDisplayOrientation(90);
try {
mcamera.setPreviewDisplay(mSurfaceHolder1);
mcamera.startPreview();
return;
} catch (IOException localIOException) {
localIOException.printStackTrace();
}
}
@Override
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
});
this.mSurfaceHolder1.setType(3);双Camera同时工作需要硬件设计支持：两路ISP，以及MCLK，I2C是否共用等。
当硬件支持后，如果软件没有支持，则基本上会在Camera.open(1)报错，从此处开始给出调用链：
Camera.java::open()
native_setup()android_hardware_Camera.cpp::android_hardware_Camera_native_setup() //Camera::connect()CameraBase.cpp::connect() //(cs.get()->*fnConnectService)(cl, cameraId, clientPackageName, clientUid,/*out*/ c->mCamera)，此处fnConnectService为connect，即CameraService的connect函数。CameraService.cpp::connect()
//CameraService::onFirstRef()通过hw_get_module(CAMERA_HARDWARE_MODULE_ID, (const hw_module_t **)&mModule)的调用，将module获取。而后在connect()中通过CAMERA_DEVICE_API_VERSION_来创建对应的clinet，KK版本使用的1_0版本，即CameraClient对象。connectFinishUnsafe()
//此函数调用client->initialize(mModule)。CameraClient::initialize()，建立CameraHardwareInterface对象，并调用其initialize()，继而 module->methods->open()，获取到hw_device_t对象。以上对open()调用，已经切入到HAL中。双camera同时工作的判断基本都放在此open()中：
Intel 4.4平台示例：
static int ATOM_OpenCameraHardware(const hw_module_t* module, const char* name,
hw_device_t** device)
{
...
if ((!PlatformData::supportDualVideo() && atom_instances == 1) || atom_instances > MAX_HAL_INSTANCES-1) {
LOGE("error:only support maximum %d instances for front/primary sensor", atom_instances);
return -EINVAL;
}
...
}MTK5.1平台示例：
status_t
CamDeviceManagerBase::
openDeviceLocked(
hw_device_t** device,
hw_module_t const* module,
int32_t const i4OpenId,
uint32_t device_version
)
{
...
if ( OK != (status = validateOpenLocked(i4OpenId, device_version)) )
{
return status;
}
...
}
status_t
CamDeviceManagerImp::
validateOpenLocked(int32_t i4OpenId, uint32_t device_version) const
{
...
#if !defined(MTKCAM_HAVE_NATIVE_PIP) //MTK平台的ProjectConfig.mk中MTK_CAM_NATIVE_PIP_SUPPORT影响这里宏定义
if ( 0 != mOpenMap.size() )
{
MY_LOGE("Not support PIP");
MY_LOGE("[Now] fail to open (deviceId:%d version:0x%x) => failure", i4OpenId, device_version);
MY_LOGE("[Previous] (deviceId:%d version:0x%x) mOpenMap.size:%zu", mOpenMap.keyAt(0), mOpenMap.valueAt(0)->uDeviceVersion, mOpenMap.size());
return -EUSERS;
}
#endif
...
}PS：
关于Camera HAL的结构体和API支持宏定义都申明在hardware/libhardware/include/hardware/camera_common.h和camera.h文件中.