Android includes Stagefright, a media playback engine at the native level that has built-in software-based codecs for popular media formats.
Stagefright audio and video playback features include integration with OpenMAX codecs, session management, time-synchronized rendering, transport control, and DRM.
Stagefright also supports integration with custom hardware codecs provided by you. To set a hardware path to encode and decode media, you must implement a hardware-based codec as an OpenMax IL (Integration Layer) component.
Note: Stagefright updates can occur through the Android monthly security update process and as part of an Android OS release.
Architecture
Media applications interact with the Android native multimedia framework according to the following architecture.
Figure 1. Media architecture
- Application Framework
- At the application framework level is application code that utilizes android.media APIs to interact with the multimedia hardware.
- Binder IPC
- The Binder IPC proxies facilitate communication over process boundaries.
They are located in the
frameworks/av/media/libmediadirectory and begin with the letter "I". - Native Multimedia Framework
- 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 MediaPlayer and Stagefright components
located in
frameworks/av/media. - OpenMAX Integration Layer (IL)
- 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
libstagefrighthw.so. This plugin links Stagefright with your custom codec components, which must be implemented according to the OpenMAX IL component standard.
Implementing custom codecs
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 must create the OMX components and an OMX plugin that hooks together
your custom codecs with the Stagefright framework. For example components, see
the hardware/ti/omap4xxx/domx/; for an example plugin for the
Galaxy Nexus, see hardware/ti/omap4xx/libstagefrighthw.
To add your own codecs:
- Create your components according to the OpenMAX IL component standard. The
component interface is located in the
frameworks/native/include/media/OpenMAX/OMX_Component.hfile. To learn more about the OpenMAX IL specification, refer to the OpenMAX website. - Create a OpenMAX plugin that links your components with the Stagefright
service. For the interfaces to create the plugin, see
frameworks/native/include/media/hardware/OMXPluginBase.handHardwareAPI.hheader files. - Build your plugin as a shared library with the name
libstagefrighthw.soin your product Makefile. For example:
LOCAL_MODULE := libstagefrighthw
In your device's Makefile, ensure you declare the module as a product package:
PRODUCT_PACKAGES += \ libstagefrighthw \ ...
Exposing codecs to the framework
The Stagefright service parses the system/etc/media_codecs.xml
and system/etc/media_profiles.xml to expose the supported codecs
and profiles on the device to app developers via the
android.media.MediaCodecList and
android.media.CamcorderProfile classes. You must create both files
in the device/<company>/<device>/ directory
and copy this over to the system image's system/etc directory in
your device's Makefile. For example:
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 \
For complete examples, see device/samsung/tuna/media_codecs.xml
and device/samsung/tuna/media_profiles.xml .
Note: As of Android 4.1, the
<Quirk> element for media codecs is no longer supported.