Android's camera hardware abstraction layer (HAL) connects the higher-levelcamera framework APIs inCamera 2 to your underlying camera driver and hardware. The camera subsystemincludes implementations for camera pipeline components while the camera HALprovides interfaces for use in implementing your version of thesecomponents.
Note: If you are implementing the Camera HAL on Android 8.0 and higher, you must use the HIDL interface. For information on the legacy components, see Legacy HAL components.Architecture
Display analog video using UVC video grabber device on android device.(this device's function is same with Easycap) Also, If your USB camera is UVC type then, you can use the camera with this app.
The following figure and list describe the HAL components.
Figure 1. Camera architecture
- app framework
- At the app framework level is the app's code, which uses the Camera 2 API to interact with the camera hardware. Internally, this code calls corresponding Binder interfaces to access the native code that interacts with the camera.
- AIDL
- The binder interface associated with
CameraService
can be found at frameworks/av/camera/aidl/android/hardware. The generated code calls the lower level native code to obtain access to the physical camera and returns data that is used to create theCameraDevice
and eventuallyCameraCaptureSession
objects at the framework level. - native framework
- This framework residing in
frameworks/av/
provides a native equivalent to theCameraDevice
andCameraCaptureSession
classes. See also NDK camera2 reference. - binder IPC interface
- The IPC binder interface facilitates communication over process boundaries. There are several camera binder classes located in the
frameworks/av/camera/camera/aidl/android/hardware
directory that call into camera service.ICameraService
is the interface to the camera service;ICameraDeviceUser
is the interface to a specific opened camera device; andICameraServiceListener
andICameraDeviceCallbacks
are the respectiveCameraService
andCameraDevice
callbacks to the application framework. - camera service
- The camera service, located in
frameworks/av/services/camera/libcameraservice/CameraService.cpp
, is the actual code that interacts with the HAL. - HAL
- The hardware abstraction layer defines the standard interface that the camera service calls into and that you must implement to have your camera hardware function correctly.
Implementing the HAL
The HAL sits between the camera driver and the higher-level Android frameworkand defines an interface that you must implement so apps can correctly operatethe camera hardware. The HIDLinterfaces for the Camera HAL are defined inhardware/interfaces/camera.
A typical binderized HAL must implement the following HIDL interfaces:
ICameraProvider
: For enumerating individual devices and managing their status.ICameraDevice
: The camera device interface.ICameraDeviceSession
: The active camera device session interface.
Reference HIDL implementations are available for
CameraProvider.cpp
,CameraDevice.cpp
, andCameraDeviceSession.cpp
.The implementation wraps old HALs that still use thelegacy API.Starting with Android 8.0, Camera HAL implementations must use the HIDL API; useof the legacy interface isn't supported.Legacy HAL components
This section describes the architecture of the legacy HAL components and how toimplement the HAL. Camera HAL implementations on Android 8.0 and higher must usethe HIDL API instead, described above.
Architecture (legacy)
The following figure and list describe the legacy camera HAL components.
Figure 2. Legacy camera architecture
- app framework
- At the app framework level is the app's code, which uses the
android.hardware.Camera
API to interact with the camera hardware. Internally, this code calls a corresponding JNI glue class to access the native code that interacts with the camera. - JNI
- The JNI code associated with
android.hardware.Camera
is located inframeworks/base/core/jni/android_hardware_Camera.cpp
. This code calls the lower-level native code to obtain access to the physical camera and returns data that is used to create theandroid.hardware.Camera
object at the framework level. - native framework
- The native framework defined in
frameworks/av/camera/Camera.cpp
provides a native equivalent to theandroid.hardware.Camera
class. This class calls the IPC binder proxies to obtain access to the camera service. - binder IPC proxies
- The IPC binder proxies facilitate communication over process boundaries. There are three camera binder classes that are located in the
frameworks/av/camera
directory that calls into camera service.ICameraService
is the interface to the camera service,ICamera
is the interface to a specific opened camera device, andICameraClient
is the device's interface back to the app framework. - camera service
- The camera service, located in
frameworks/av/services/camera/libcameraservice/CameraService.cpp
, is the actual code that interacts with the HAL. - HAL
- The hardware abstraction layer defines the standard interface that the camera service calls into and that you must implement to have your camera hardware function correctly.
- kernel driver
- The camera's driver interacts with the actual camera hardware and your implementation of the HAL. The camera and driver must support YV12 and NV21 image formats to provide support for previewing the camera image on the display and video recording.
Implementing the HAL (legacy)
The HAL sits between the camera driver and the higher-level Android frameworkand defines an interface that you must implement so apps can correctly operatethe camera hardware. The HAL interface is defined in the
hardware/libhardware/include/hardware/camera.h
andhardware/libhardware/include/hardware/camera_common.h
header files.![Camera Camera](https://www.kayetoncctv.com/wp-content/uploads/01-IMG_4455-5.jpg)
camera_common.h
defines camera_module
, a standardstructure to obtain general information about the camera, such as the camera IDand properties common to all cameras (that is, whether it is a front- orback-facing camera).camera.h
contains code that corresponds toandroid.hardware.Camera
. This header file declares acamera_device
struct that in turn contains acamera_device_ops
struct with pointers to functions that implementthe HAL interface. For documentation on the camera parameters developers canset, refer to frameworks/av/include/camera/CameraParameters.h
.These parameters are set with the function pointed to by int(*set_parameters)(struct camera_device *, const char *parms)
in the HAL.For an example of a HAL implementation, refer to the implementation for theGalaxy Nexus HAL in
hardware/ti/omap4xxx/camera
.Configuring the shared library
Set up the Android build system to correctly package the HAL implementationinto a shared library and copy it to the appropriate location by creating an
Android.mk
file:- Create a
device/<company_name>/<device_name>/camera
directory to contain your library's source files. - Create an
Android.mk
file to build the shared library. Ensurethat the makefile contains the following lines:Your library must be namedcamera.<device_name>
(.so
is appended automatically), so Android can correctly load thelibrary. For an example, see the makefile for the Galaxy Nexus camera located inhardware/ti/omap4xxx/Android.mk
. - Specify your device has camera features by copying the necessary feature XMLfiles in the
frameworks/native/data/etc
directory with yourdevice's makefile. For example, to specify your device has a camera flash andcan autofocus, add the following lines in your device's<device>/<company_name>/<device_name>/device.mk
makefile:For an example of a device makefile, seedevice/samsung/tuna/device.mk
. - Declare your camera’s media codec, format, and resolution capabilities in
device/<company_name>/<device_name>/media_profiles.xml
anddevice/<company_name>/<device_name>/media_codecs.xml
XML files. For details, seeExposing codecs to theframework. - Add the following lines in your device's
device/<company_name>/<device_name>/device.mk
makefileto copy themedia_profiles.xml
andmedia_codecs.xml
files to the appropriate location: - To include the Camera app in your device's system image, specify it in the
PRODUCT_PACKAGES
variable in your device'sdevice/<company>/<device>/device.mk
makefile:
I wish I could post this in the Developer section, but the XDA forum wont allow me to as a new user, so it will have to go here instead. Hopefully it gets viewed by someone that can help.
My question is whether the new upcoming firmware (supposedly being worked on by Mad Catz), or any other unofficial firmware (CM12, Android TV, Remix 2.0) will ever have support for USB webcams to be used for Skype, Facebook Messenger, Camera, etc.
So far, I have had great success at getting apps from the Google Play Store to recognize both the video and audio drivers to be utiliizd in the app for taking pictures/video. However, the Skype app doesn't recognize the webcam because it isn't built-in like it would be on a smartphone.
Would it be possible to trick the firmware into thinking a USB webcam is a built-in camera? Or would something like that require further firmware support? So far, I can't find any apps that will do it.
In addition, I have found information elsewhere that relates to this same subject for other android TV boxes, which seems to prove that this stems from the firmware.
See here: http://www.androydz.com/skype-on-android-mini-pc/
My question is whether the new upcoming firmware (supposedly being worked on by Mad Catz), or any other unofficial firmware (CM12, Android TV, Remix 2.0) will ever have support for USB webcams to be used for Skype, Facebook Messenger, Camera, etc.
So far, I have had great success at getting apps from the Google Play Store to recognize both the video and audio drivers to be utiliizd in the app for taking pictures/video. However, the Skype app doesn't recognize the webcam because it isn't built-in like it would be on a smartphone.
Would it be possible to trick the firmware into thinking a USB webcam is a built-in camera? Or would something like that require further firmware support? So far, I can't find any apps that will do it.
In addition, I have found information elsewhere that relates to this same subject for other android TV boxes, which seems to prove that this stems from the firmware.
See here: http://www.androydz.com/skype-on-android-mini-pc/