src/devices/camera/index.jd - platform/docs/source.android.com - Git at Google


            
            page.title=Camera

            
            @jd:body


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            <div id="qv-wrapper">

            
              <div id="qv">

            
                <h2>In this document</h2>

            
                <ol id="auto-toc">

            
                </ol>

            
              </div>

            
            </div>


            <img style="float: right; margin: 0px 15px 15px 15px;" src="images/ape_fwk_hal_camera.png" alt="Android Camera HAL icon"/>


            <p>Android's camera Hardware Abstraction Layer (HAL) connects the higher level

            
            camera framework APIs in <a href="http://developer.android.com/reference/android/hardware/package-summary.html">android.hardware</a> to your underlying camera driver and hardware. The camera subsystem includes implementations for camera pipeline components while the camera HAL provides interfaces for use in implementing your version of these components.</p>


            <h2 id="architecture">Architecture</h2>

            
            <p>The following figure and list describe the components involved and where to find the source for each:

            
            </p>


            <img src="images/ape_fwk_camera.png" alt="Android camera architecture" id="figure1" />

            
            <p class="img-caption">

            
              <strong>Figure 1.</strong> Camera architecture

            
            </p>


            <dl>


              <dt>Application framework</dt>

            
              <dd>At the application framework level is the app's code, which utilizes the <a

            
              href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a>

            
              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.</dd>


              <dt>JNI</dt>

            
              <dd>The JNI code associated with <a

            
              href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a> is located in

            
              <code>frameworks/base/core/jni/android_hardware_Camera.cpp</code>. This code calls the lower level

            
              native code to obtain access to the physical camera and returns data that is used to create the

            
             <a href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a> object at the framework level.</dd>


              <dt>Native framework<dt>

            
              <dd>The native framework defined in <code>frameworks/av/camera/Camera.cpp</code> provides a native equivalent

            
              to the <a href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a> class.

            
              This class calls the IPC binder proxies to obtain access to the camera service.</dd>


              <dt>Binder IPC proxies</dt>

            
              <dd>The IPC binder proxies facilitate communication over process boundaries. There are three camera binder

            
              classes that are located in the <code>frameworks/av/camera</code> directory that calls into

            
              camera service.  ICameraService is the interface to the camera service, ICamera is the interface

            
              to a specific opened camera device, and ICameraClient is the device's interface back to the application framework.</dd>


              <dt>Camera service</dt>

            
              <dd>The camera service, located in <code>frameworks/av/services/camera/libcameraservice/CameraService.cpp</code>, is  the actual code that interacts with the HAL.</p>


              <dt>HAL</dt>

            
              <dd>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.

            
              </dd>


              <dt>Kernel driver</dt>

            
              <dd>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.</dd>

            
              </dl>


            <h2 id="implementing">Implementing the HAL</h2>

            
            <p>The HAL sits between the camera driver and the higher level Android framework

            
            and defines an interface that you must implement so that apps can

            
            correctly operate the camera hardware. The HAL interface is defined in the

            
            <code>hardware/libhardware/include/hardware/camera.h</code> and

            
            <code>hardware/libhardware/include/hardware/camera_common.h</code> header files.

            
            </p>


            <p>

            
            <code>camera_common.h</code> defines an important struct, <code>camera_module</code>, which defines a standard

            
            structure to obtain general information about the camera, such as its ID and properties

            
            that are common to all cameras such as whether or not it is a front or back-facing camera.

            
            </p>


            <p>

            
            <code>camera.h</code> contains the code that corresponds mainly with

            
            <a href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a>. This header file declares a <code>camera_device</code>

            
            struct that contains a <code>camera_device_ops</code> struct with function pointers

            
            that point to functions that implement the HAL interface. For documentation on the

            
            different types of camera parameters that a developer can set,

            
            see the <code>frameworks/av/include/camera/CameraParameters.h</code> file.

            
            These parameters are set with the function pointed to by

            
            <code>int (*set_parameters)(struct camera_device *, const char *parms)</code> in the HAL.

            
            </p>


            <p>For an example of a HAL implementation, see the implementation for the Galaxy Nexus HAL in

            
            <code>hardware/ti/omap4xxx/camera</code>.</p>


            <h2 id="configuring">Configuring the Shared Library</h2>

            
            <p>You need to set up the Android build system to

            
              correctly package the HAL implementation into a shared library and copy it to the

            
              appropriate location by creating an <code>Android.mk</code> file:


            <ol>

            
              <li>Create a <code>device/&lt;company_name&gt;/&lt;device_name&gt;/camera</code> directory to contain your

            
              library's source files.</li>

            
              <li>Create an <code>Android.mk</code> file to build the shared library. Ensure that the Makefile contains the following lines:

            
            <pre>

            
            LOCAL_MODULE := camera.&lt;device_name&gt;

            
            LOCAL_MODULE_RELATIVE_PATH := hw

            
            </pre>

            
            <p>Notice that your library must be named <code>camera.&lt;device_name&gt;</code> (<code>.so</code> is appended automatically),

            
            so that Android can correctly load the library. For an example, see the Makefile

            
            for the Galaxy Nexus camera located in <code>hardware/ti/omap4xxx/Android.mk</code>.</p>


            </li>

            
            <li>Specify that your device has camera features by copying the necessary feature XML files in the

            
            <code>frameworks/native/data/etc</code> directory with your

            
            device's Makefile. For example, to specify that your device has a camera flash and can autofocus,

            
            add the following lines in your device's

            
            <code>&lt;device&gt;/&lt;company_name&gt;/&lt;device_name&gt;/device.mk</code> Makefile:


            <pre class="no-pretty-print">

            
            PRODUCT_COPY_FILES := \ ...


            PRODUCT_COPY_FILES += \

            
            frameworks/native/data/etc/android.hardware.camera.flash-autofocus.xml:system/etc/permissions/android.hardware.camera.flash-autofocus.xml \

            
            </pre>


            <p>For an example of a device Makefile, see <code>device/samsung/tuna/device.mk</code>.</p>

            
            </li>


            <li>Declare your camera’s media codec, format, and resolution capabilities in

            
            <code>device/&lt;company_name&gt;/&lt;device_name&gt;/media_profiles.xml</code> and

            
            <code>device/&lt;company_name&gt;/&lt;device_name&gt;/media_codecs.xml</code> XML files.

            
             For more information, see <a href="{@docRoot}devices/media.html#expose"> Exposing

            
             Codecs and Profiles to the Framework</a> for information on how to do this.

            
            </p></code>


            </li>


            <li>Add the following lines in your device's

            
               <code>device/&lt;company_name&gt;/&lt;device_name&gt;/device.mk</code>

            
              Makefile to copy the <code>media_profiles.xml</code>

            
            and <code>media_codecs.xml</code> files to the appropriate location:

            
            <pre>

            
            # media config xml file

            
            PRODUCT_COPY_FILES += \

            
                &lt;device&gt;/&lt;company_name&gt;/&lt;device_name&gt;/media_profiles.xml:system/etc/media_profiles.xml


            # media codec config xml file

            
            PRODUCT_COPY_FILES += \

            
                &lt;device&gt;/&lt;company_name&gt;/&lt;device_name&gt;/media_codecs.xml:system/etc/media_codecs.xml

            
            </pre>

            
            </li>


            <li>

            
            <p>Declare that you want to include the Camera app in your device's system image by

            
            specifying it in the <code>PRODUCT_PACKAGES</code> variable in your device's

            
               <code>device/&lt;company_name&gt;/&lt;device_name&gt;/device.mk</code>

            
              Makefile:</p>

            
            <pre>

            
            PRODUCT_PACKAGES := \

            
            Gallery2 \

            
            ...

            
            </pre>

            
            </li>


            </ol>
	page.title=Camera
	@jd:body

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	Copyright 2015 The Android Open Source Project

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
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	<div id="qv-wrapper">
	<div id="qv">
	<h2>In this document</h2>
	<ol id="auto-toc">
	</ol>
	</div>
	</div>

	<img style="float: right; margin: 0px 15px 15px 15px;" src="images/ape_fwk_hal_camera.png" alt="Android Camera HAL icon"/>

	<p>Android's camera Hardware Abstraction Layer (HAL) connects the higher level
	camera framework APIs in <a href="http://developer.android.com/reference/android/hardware/package-summary.html">android.hardware</a> to your underlying camera driver and hardware. The camera subsystem includes implementations for camera pipeline components while the camera HAL provides interfaces for use in implementing your version of these components.</p>

	<h2 id="architecture">Architecture</h2>
	<p>The following figure and list describe the components involved and where to find the source for each:
	</p>

	<img src="images/ape_fwk_camera.png" alt="Android camera architecture" id="figure1" />
	<p class="img-caption">
	<strong>Figure 1.</strong> Camera architecture
	</p>

	<dl>

	<dt>Application framework</dt>
	<dd>At the application framework level is the app's code, which utilizes the <a
	href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a>
	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.</dd>

	<dt>JNI</dt>
	<dd>The JNI code associated with <a
	href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a> is located in
	<code>frameworks/base/core/jni/android_hardware_Camera.cpp</code>. This code calls the lower level
	native code to obtain access to the physical camera and returns data that is used to create the
	<a href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a> object at the framework level.</dd>

	<dt>Native framework<dt>
	<dd>The native framework defined in <code>frameworks/av/camera/Camera.cpp</code> provides a native equivalent
	to the <a href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a> class.
	This class calls the IPC binder proxies to obtain access to the camera service.</dd>

	<dt>Binder IPC proxies</dt>
	<dd>The IPC binder proxies facilitate communication over process boundaries. There are three camera binder
	classes that are located in the <code>frameworks/av/camera</code> directory that calls into
	camera service. ICameraService is the interface to the camera service, ICamera is the interface
	to a specific opened camera device, and ICameraClient is the device's interface back to the application framework.</dd>

	<dt>Camera service</dt>
	<dd>The camera service, located in <code>frameworks/av/services/camera/libcameraservice/CameraService.cpp</code>, is the actual code that interacts with the HAL.</p>

	<dt>HAL</dt>
	<dd>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.
	</dd>

	<dt>Kernel driver</dt>
	<dd>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.</dd>
	</dl>


	<h2 id="implementing">Implementing the HAL</h2>
	<p>The HAL sits between the camera driver and the higher level Android framework
	and defines an interface that you must implement so that apps can
	correctly operate the camera hardware. The HAL interface is defined in the
	<code>hardware/libhardware/include/hardware/camera.h</code> and
	<code>hardware/libhardware/include/hardware/camera_common.h</code> header files.
	</p>

	<p>
	<code>camera_common.h</code> defines an important struct, <code>camera_module</code>, which defines a standard
	structure to obtain general information about the camera, such as its ID and properties
	that are common to all cameras such as whether or not it is a front or back-facing camera.
	</p>

	<p>
	<code>camera.h</code> contains the code that corresponds mainly with
	<a href="http://developer.android.com/reference/android/hardware/Camera.html">android.hardware.Camera</a>. This header file declares a <code>camera_device</code>
	struct that contains a <code>camera_device_ops</code> struct with function pointers
	that point to functions that implement the HAL interface. For documentation on the
	different types of camera parameters that a developer can set,
	see the <code>frameworks/av/include/camera/CameraParameters.h</code> file.
	These parameters are set with the function pointed to by
	<code>int (set_parameters)(struct camera_device , const char *parms)</code> in the HAL.
	</p>

	<p>For an example of a HAL implementation, see the implementation for the Galaxy Nexus HAL in
	<code>hardware/ti/omap4xxx/camera</code>.</p>


	<h2 id="configuring">Configuring the Shared Library</h2>
	<p>You need to set up the Android build system to
	correctly package the HAL implementation into a shared library and copy it to the
	appropriate location by creating an <code>Android.mk</code> file:

	<ol>
	<li>Create a <code>device/<company_name>/<device_name>/camera</code> directory to contain your
	library's source files.</li>
	<li>Create an <code>Android.mk</code> file to build the shared library. Ensure that the Makefile contains the following lines:
	<pre>
	LOCAL_MODULE := camera.<device_name>
	LOCAL_MODULE_RELATIVE_PATH := hw
	</pre>
	<p>Notice that your library must be named <code>camera.<device_name></code> (<code>.so</code> is appended automatically),
	so that Android can correctly load the library. For an example, see the Makefile
	for the Galaxy Nexus camera located in <code>hardware/ti/omap4xxx/Android.mk</code>.</p>

	</li>
	<li>Specify that your device has camera features by copying the necessary feature XML files in the
	<code>frameworks/native/data/etc</code> directory with your
	device's Makefile. For example, to specify that your device has a camera flash and can autofocus,
	add the following lines in your device's
	<code><device>/<company_name>/<device_name>/device.mk</code> Makefile:

	<pre class="no-pretty-print">
	PRODUCT_COPY_FILES := \ ...

	PRODUCT_COPY_FILES += \
	frameworks/native/data/etc/android.hardware.camera.flash-autofocus.xml:system/etc/permissions/android.hardware.camera.flash-autofocus.xml \
	</pre>

	<p>For an example of a device Makefile, see <code>device/samsung/tuna/device.mk</code>.</p>
	</li>

	<li>Declare your camera’s media codec, format, and resolution capabilities in
	<code>device/<company_name>/<device_name>/media_profiles.xml</code> and
	<code>device/<company_name>/<device_name>/media_codecs.xml</code> XML files.
	For more information, see <a href="{@docRoot}devices/media.html#expose"> Exposing
	Codecs and Profiles to the Framework</a> for information on how to do this.
	</p></code>

	</li>

	<li>Add the following lines in your device's
	<code>device/<company_name>/<device_name>/device.mk</code>
	Makefile to copy the <code>media_profiles.xml</code>
	and <code>media_codecs.xml</code> files to the appropriate location:
	<pre>
	# media config xml file
	PRODUCT_COPY_FILES += \
	<device>/<company_name>/<device_name>/media_profiles.xml:system/etc/media_profiles.xml

	# media codec config xml file
	PRODUCT_COPY_FILES += \
	<device>/<company_name>/<device_name>/media_codecs.xml:system/etc/media_codecs.xml
	</pre>
	</li>

	<li>
	<p>Declare that you want to include the Camera app in your device's system image by
	specifying it in the <code>PRODUCT_PACKAGES</code> variable in your device's
	<code>device/<company_name>/<device_name>/device.mk</code>
	Makefile:</p>
	<pre>
	PRODUCT_PACKAGES := \
	Gallery2 \
	...
	</pre>
	</li>

	</ol>