gstreamer/sdk-installing-for-android-development.md

Installing for Android development

All versions starting from 2.3.1 Gingerbread are supported

Prerequisites

The development machine is where you will develop your Android application, which then you will deploy on the target machine, which should obviously be an Android device.

The development machine can either be a Linux, Mac OS X or Windows, and needs to have installed:

• The latest version of the Android SDK
• The latest version of the Android NDK
• GStreamer for Android is targeted at API version 9 (Android 2.3.1, Gingerbread) or higher. Use the SDK Manager tool to make sure you have at least one Android SDK platform installed with API version 9 or higher.

Before continuing, make sure you can compile and run the samples included in the Android NDK, and that you understand how the integration of C and Java works via the Java Native Interface (JNI). Besides the Android NDK documentation, you can find some useful Android JNI tips here.

Download and install GStreamer binaries

The GStreamer project provides prebuilt binaries you should download the latest version and unzip it into any folder of your choice.

In the process of building GStreamer-enabled Android applications, some tools will need to know where you installed the GStreamer binaries. You must define an environment variable called GSTREAMER_ROOT_ANDROID and point it to the folder where you extracted the GStreamer binaries. This environment variable must be available at build time, so maybe you want to make it available system-wide by adding it to your ~/.profile file (on Linux and Mac) or to the Environment Variables in the System Properties dialog (on Windows).

Point GSTREAMER_ROOT_ANDROID to the folder where you unzipped the binaries.

If you plan to use Android Studio and do not want to define this environment variable globally, you can set it inside the build.gradle.

If you plan to use Eclipse, and do not want to define this environment variable globally, you can set it inside Eclipse. Go to Window → Preferences → C/C++ → Build → Build Variables and define GSTREAMER_ROOT_ANDROID there.

The NDK support in the Gradle build system used by Android Studio is still in beta, so the recommended way to build using the GStreamer SDK is still to use "ndk-build".

Configure your development environment

There are two routes to use GStreamer in an Android application: Either writing your GStreamer code in Java or in C.

Android applications are mainly written in Java, so adding GStreamer code to them in the same language is a huge advantage. However, this requires using language bindings for the GStreamer API which are not complete yet. In the meantime, this documentation will use Java for the User Interface (UI) part and C for the GStreamer code. Both parts interact through JNI.

Building the tutorials

There are a few Android-specific tutorials in the $GSTREAMER_ROOT_ANDROID/share/gst-sdk/tutorials folder. Each tutorial is a folder containing source code (in Java and C) and the resource files required to build a complete Android application.

The rest of the GStreamer tutorials (basic and playback tutorials) cannot be run on Android without modification.

Android projects with GStreamer support are built like conventional Android NDK projects, so the instructions at the Android NDK home can be followed:

Using Eclipse

Make sure you have installed the ADT and NDK plugins listed in the prerequisites section, and that they are both aware of the location of the Android SDK and NDK respectively.

Import a tutorial into the Eclipse workspace: File → New → Project… → Android Project from Existing Code, and select the folder called android-tutorial-1.

After reading in the project and generating some extra files and folders, Eclipse might complain about missing files. This is normal, we are not finished yet.

Provide native development support by activating the NDK plugin: Right-click on the project in the Project Explorer (this should be the top-most folder, called com.gst_sdk_tutorials.tutorial_1.Tutorial1) → Android tools → Add Native Support… Here the NDK plugin asks for a library name. This is irrelevant and any valid file name will do. Accept.

Eclipse will still complain about errors in the code. This is normal. Some files are missing because they are generated during the first build run.

Build the project: Project → Build Project. If you bring up the Eclipse Console, you should see some progress messages. Once finished, the missing files will appear and all error messages should be gone. The project is now ready to run. Hit Run → Run.

A new application called “Android tutorial 1” should now be available on your device, with the GStreamer logo. If you want to run the tutorial in an Android Virtual Device (AVD), make sure to create the device with support for audio playback and GPU Emulation (to enable OpenGL ES).

Using the command line

Note that, on Windows, this procedure requires a working Cygwin shell, as explained in the Android NDK System Requirements

For each tutorial, move to its folder and run:

android update project -p . -s --target X

Where X is one of the targets available in your system (the ones you installed with the SDK manager). Make sure to use a target with at least API level 9.

To get a list of all available targets in your system issue this command:

android list

The “update project” command generates the build.xml file needed by the build system. You only need to perform this action once per project.

To build the C part, just call:

ndk-build

A few lines in the Android.mk file (reviewed later) pull up the necessary machinery to compile the GStreamer bits and generate the Shared Object libraries (.so) that the Java code can use as native methods.

Finally, compile the Java code with:

ant debug

And install on the device with:

adb install -r bin/Tutorial1-debug.apk

The -r switch allows the installer to overwrite previous versions. Otherwise, you need to manually uninstall previous versions of your application.

A new application called “Android tutorial 1” should now be available on your device, with the GStreamer logo. If you want to run the tutorial in an Android Virtual Device (AVD), make sure to create the device with support for audio playback and GPU Emulation (to enable OpenGL ES).

Windows linkage problems

Due to problems related to the standard linker, Google’s Gold Linker is used to build GStreamer applications.  Unfortunately, the Android NDK toolchain for Windows does not include the gold linker and the standard one has to be used.

If you observe linkage problems, you can replace the linker in your Android NDK with the gold one from this project. Download the android-ndk-r8b-ma-windows.7z file, extract \android-ndk-r8b\toolchains\arm-linux-androideabi-4.6\prebuilt\windows\arm-linux-androideabi\bin\ld.exe (only this file is needed) and overwrite the one in the same folder in your Android NDK installation. You might need the free 7-Zip archiving utility

Creating new projects

Create a normal NDK project, either from the command line as described in the Android NDK home, or use Eclipse: File → New → Project… → Android Application Project, and, once the wizard is complete, right click on the project → Android Tools → Add Native Support …

To add GStreamer support you only need to modify the jni/Android.mk file. This file describes the native files in your project, and its barebones structure (as auto-generated by Eclipse) is:

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := NativeApplication
LOCAL_SRC_FILES := NativeApplication.c

include $(BUILD_SHARED_LIBRARY)

Where line 5 specifies the name of the .so file that will contain your native code and line 6 states all source files that compose your native code, separated by spaces.

Adding GStreamer support only requires adding these lines:

Android.mk with GStreamer support

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := NativeApplication
LOCAL_SRC_FILES := NativeApplication.c
LOCAL_SHARED_LIBRARIES := gstreamer_android
LOCAL_LDLIBS := -landroid

include $(BUILD_SHARED_LIBRARY)

ifndef GSTREAMER_ROOT
ifndef GSTREAMER_ROOT_ANDROID
$(error GSTREAMER_ROOT_ANDROID is not defined!)
endif
GSTREAMER_ROOT            := $(GSTREAMER_ROOT_ANDROID)
endif

GSTREAMER_NDK_BUILD_PATH  := $(GSTREAMER_ROOT)/share/gst-android/ndk-build/
GSTREAMER_PLUGINS         := coreelements ogg theora vorbis videoconvert audioconvert audioresample playback glimagesink soup opensles
G_IO_MODULES              := gnutls
GSTREAMER_EXTRA_DEPS      := gstreamer-video-1.0

include $(GSTREAMER_NDK_BUILD_PATH)/gstreamer.mk

Where line 7 specifies an extra library to be included in the project: libgstreamer_android.so. This library contains all GStreamer code, tailored for your application’s needs, as shown below.

Line 8 specifies additional system libraries, in this case, in order to access android-specific functionality.

Lines 12 and 13 simply define some convenient macros.

Line 20 lists the plugins you want statically linked into libgstreamer_android.so. Listing only the ones you need makes your application smaller.

Line 21 is required to have HTTPS/TLS support from GStreamer, through the souphttpsrc element.

Line 22 defines which GStreamer libraries your application requires.

Finally, line 24 includes the make files which perform the rest of the magic.

Listing all desired plugins can be cumbersome, so they have been grouped into categories, which can be used by including the plugins.mk file, and used as follows:

include $(GSTREAMER_NDK_BUILD_PATH)/plugins.mk
GSTREAMER_PLUGINS  := $(GSTREAMER_PLUGINS_CORE) $(GSTREAMER_PLUGINS_CODECS) playbin souphttpsrc

List of categories and included plugins

Category	Included plugins
GSTREAMER_PLUGINS_CORE	coreelements coreindexers adder app audioconvert audiorate audioresample audiotestsrc videoconvert gdp gio pango typefindfunctions videorate videoscale videotestsrc volume autodetect videofilter
GSTREAMER_PLUGINS_PLAYBACK	decodebin playbin
GSTREAMER_PLUGINS_CODECS	subparse ogg theora vorbis alaw annodex apetag audioparsers auparse avi flac flv flxdec icydemux id3demux isomp4 jpeg matroska mulaw multipart png speex taglib wavenc wavpack wavparse y4menc adpcmdec adpcmenc aiff cdxaparse dtmf dvbsuboverlay dvdspu fragmented hdvparse id3tag ivfparse jp2k kate mve mxf nsf nuvdemux opus pcapparse pnm schro siren subenc tta videoparsersbad vmnc vp8 y4mdec
GSTREAMER_PLUGINS_VIS	libvisual goom goom2k1 audiovisualizers
GSTREAMER_PLUGINS_EFFECTS	alpha alphacolor audiofx cutter debug deinterlace effectv equalizer gdkpixbuf imagefreeze interleave level multifile replaygain shapewipe smpte spectrum videobox videocrop videomixer autoconvert bayer coloreffects faceoverlay fieldanalysis freeverb frei0r gaudieffects geometrictransform interlace jp2kdecimator liveadder rawparse removesilence scaletempoplugin segmentclip smooth speed stereo videofiltersbad videomeasure videosignal
GSTREAMER_PLUGINS_NET	rtsp rtp rtpmanager souphttpsrc udp dataurisrc rtpmux rtpvp8 sdpelem
GSTREAMER_PLUGINS_CODECS_GPL	assrender
GSTREAMER_PLUGINS_SYS	glimagesink opensles amc

Build and run your application as explained in the Building the tutorial section.