src/devices/media.jd

page.title=Media
@jd:body

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  <div id="qv">
    <h2>In this document</h2>
    <ol id="auto-toc">
    </ol>
  </div>
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<img style="float: right; margin: 0px 15px 15px 0px;" src="images/ape_fwk_hal_media.png" alt="Android Media HAL icon" width="175" />

<p>
  Android provides a media playback engine at the native level called Stagefright that comes built-in with software-based codecs for several popular media formats. Stagefright features for audio and video playback include integration with OpenMAX codecs, session management, time-synchronized rendering, transport control, and DRM.</p>
  <p>In addition, Stagefright supports integration with custom hardware codecs that you provide.
  There actually isn't a HAL to implement for custom codecs, but to provide a hardware path to encode and decode media, you must implement your hardware-based codec as an OpenMax IL (Integration Layer) component.</p>


<h2 id="architecture">Architecture</h2>
<p>The following diagram shows how media applications interact with the Android native multimedia framework.</p>
  <img src="images/ape_fwk_media.png" alt="Android media architecture" id="figure1" />
<p class="img-caption">
  <strong>Figure 1.</strong> Media 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/media/package-summary.html">android.media</a>
  APIs to interact with the multimedia hardware.</dd>
  <dt>Binder IPC</dt>
  <dd>The Binder IPC proxies facilitate communication over process boundaries. They are located in 
    the <code>frameworks/av/media/libmedia</code> directory and begin with the letter "I".</dd>
  <dt>Native Multimedia Framework</dt>
  <dd>At the native level, Android provides a multimedia framework that utilizes the Stagefright engine for
  audio and video recording and playback. Stagefright comes with a default list of supported software codecs
  and you can implement your own hardware codec by using the OpenMax integration layer standard. For more
  implementation details, see the various MediaPlayer and Stagefright components located in
  <code>frameworks/av/media</code>.
  </dd>
  <dt>OpenMAX Integration Layer (IL)</dt>
  <dd>The OpenMAX IL provides a standardized way for Stagefright to recognize and use custom hardware-based
  multimedia codecs called components. You must provide an OpenMAX plugin in the form of a shared library
  named <code>libstagefrighthw.so</code>. This plugin links your custom codec components to Stagefright.
  Your custom codecs must be implemented according to the OpenMAX IL component standard.
   </dd>
</dl>


<h2 id="codecs">
Implementing Custom Codecs
</h2>
<p>Stagefright comes with built-in software codecs for common media formats, but you can also add your
  own custom hardware codecs as OpenMAX components. To do this, you need to create OMX components and also an
  OMX plugin that hooks together your custom codecs with the Stagefright framework. For an example, see
  the <code>hardware/ti/omap4xxx/domx/</code> for example components and <code>hardware/ti/omap4xx/libstagefrighthw</code>
  for an example plugin for the Galaxy Nexus.
</p>
  <p>To add your own codecs:</p>
<ol>
<li>Create your components according to the OpenMAX IL component standard. The component interface is located in the
  <code>frameworks/native/include/media/OpenMAX/OMX_Component.h</code> file. To learn more about the
  OpenMAX IL specification, see the <a href="http://www.khronos.org/openmax/">OpenMAX website</a>.</li>
<li>Create a OpenMAX plugin that links your components with the Stagefright service.
  See the <code>frameworks/native/include/media/hardware/OMXPluginBase.h</code> and <code>HardwareAPI.h</code> header
  files for the interfaces to create the plugin.
</li>
<li>Build your plugin as a shared library with the name <code>libstagefrighthw.so</code> in your product Makefile. For example:
<pre>LOCAL_MODULE := libstagefrighthw</pre>

<p>In your device's Makefile, ensure that you declare the module as a product package:</p>
<pre>
PRODUCT_PACKAGES += \
  libstagefrighthw \
  ...
</pre>
</li>
</ol>

<h2 id="expose">Exposing Codecs to the Framework</h2>
<p>The Stagefright service parses the <code>system/etc/media_codecs.xml</code> and <code>system/etc/media_profiles.xml</code>
  to expose the supported codecs and profiles on the device to app developers via the <code>android.media.MediaCodecList</code> and
  <code>android.media.CamcorderProfile</code> classes. You need to create both files in the
  <code>device/&lt;company_name&gt;/&lt;device_name&gt;/</code> directory
 and copy this over to the system image's <code>system/etc</code> directory in your device's Makefile.
 For example:</p>

 <pre>
PRODUCT_COPY_FILES += \
  device/samsung/tuna/media_profiles.xml:system/etc/media_profiles.xml \
  device/samsung/tuna/media_codecs.xml:system/etc/media_codecs.xml \
</pre>

<p>See the <code>device/samsung/tuna/media_codecs.xml</code> and
  <code>device/samsung/tuna/media_profiles.xml</code> file for complete examples.</p>

<p class="note"><strong>Note:</strong> The <code>&lt;Quirk&gt;</code> element for media codecs is no longer supported
  by Android starting in Jelly Bean.</p>