Update

subprojects/gst-docs/markdown/tutorials/android/a-complete-media-player.md

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+# Android tutorial 5: A Complete media player
+
+## Goal!
+
+![screenshot]
+
+This tutorial wants to be the “demo application” that showcases what can
+be done with GStreamer in the Android platform.
+
+It is intended to be downloaded in final, compiled, form rather than
+analyzed for its pedagogical value, since it adds very little GStreamer
+knowledge over what has already been shown in [](tutorials/android/media-player.md).
+
+
+**FIXME: Do we want to provide a binary of the app?**
+
+## Introduction
+
+The previous tutorial already implemented a basic media player. This one
+simply adds a few finishing touches. In particular, it adds the
+capability to choose the media to play, and disables the screensaver
+during media playback.
+
+These are not features directly related to GStreamer, and are therefore
+outside the scope of these tutorials. Only a few implementation pointers
+are given here.
+
+## Registering as a media player
+
+The `AndroidManifest.xml` tells the Android system the capabilities of
+the application. By specifying in the `intent-filter` of the activity
+that it understands the `audio/*`, `video/*` and `image/*` MIME types,
+the tutorial will be offered as an option whenever an application
+requires such medias to be viewed.
+
+“Unfortunately”, GStreamer knows more file formats than Android does,
+so, for some files, Android will not provide a MIME type. For these
+cases, a new `intent-filter` has to be provided which ignores MIME types
+and focuses only in the filename extension. This is inconvenient because
+the list of extensions can be large, but there does not seem to be
+another option. In this tutorial, only a very short list of extensions
+is provided, for simplicity.
+
+Finally, GStreamer can also playback remote files, so URI schemes like
+`http` are supported in another `intent-filter`. Android does not
+provide MIME types for remote files, so the filename extension list has
+to be provided again.
+
+Once we have informed the system of our capabilities, it will start
+sending
+[Intents](http://developer.android.com/reference/android/content/Intent.html)
+to invoke our activity, which will contain the desired URI to play. In
+the `onCreate()` method the intent that invoked the activity is
+retrieved and checked for such URI.
+
+## Implementing a file chooser dialog
+
+The UI includes a new button ![media-next) which
+was not present in [](tutorials/android/media-player.md). It
+invokes a file chooser dialog (based on the [Android File
+Dialog](http://code.google.com/p/android-file-dialog/) project) that
+allows you to choose a local media file, no matter what extension or
+MIME type it has.
+
+If a new media is selected, it is passed onto the native code (which
+will set the pipeline to READY, pass the URI onto `playbin`, and bring
+the pipeline back to the previous state). The current position is also
+reset, so the new clip does not start in the previous position.
+
+## Preventing the screen from turning off
+
+While watching a movie, there is typically no user activity. After a
+short period of such inactivity, Android will dim the screen, and then
+turn it off completely. To prevent this, a [Wake
+Lock](http://developer.android.com/reference/android/os/PowerManager.WakeLock.html)
+is used. The application acquires the lock when the Play button is
+pressed, so the screen is never turned off, and releases it when the
+Pause button is pressed.
+
+## Conclusion
+
+This finishes the series of Android tutorials. Each one of the
+preceding tutorials has evolved on top of the previous one, showing
+how to implement a particular set of features, and concluding in this
+tutorial 5. The goal of tutorial 5 is to build a complete media player
+which can already be used to showcase the integration of GStreamer and
+Android.
+
+It has been a pleasure having you here, and see you soon!
+
+ [screenshot]: images/tutorials/android-a-complete-media-player-screenshot.png
+ [media-next]: images/media-next.png

subprojects/gst-docs/markdown/tutorials/android/index.md

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+# Android tutorials
+
+## Welcome to the GStreamer Android tutorials
+
+These tutorials describe Android-specific topics. General GStreamer
+concepts will not be explained in these tutorials, so the
+[](tutorials/basic/index.md) should be reviewed first. The reader should
+also be familiar with basic Android programming techniques.
+
+Each Android tutorial builds on top of the previous one and adds
+progressively more functionality, until a working media player
+application is obtained in [](tutorials/android/a-complete-media-player.md).
+This is the same media player application used to advertise
+GStreamer on Android, and the download link can be found in
+the [](tutorials/android/a-complete-media-player.md) page.
+
+Make sure to have read the instructions in
+[](installing/for-android-development.md) before jumping into the
+Android tutorials.
+
+### A note on the documentation
+
+All Java methods, both Android-specific and generic, are documented in
+the [Android reference
+site](http://developer.android.com/reference/packages.html).
+
+Unfortunately, there is no official online documentation for the NDK.
+The header files, though, are well commented. If you installed the
+Android NDK in the `$(ANDROID_NDK_ROOT)` folder, you can find the header
+files
+in `$(ANDROID_NDK_ROOT)\platforms\android-9\arch-arm\usr\include\android`.

subprojects/gst-docs/markdown/tutorials/android/link-against-gstreamer.md

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+# Android tutorial 1: Link against GStreamer
+
+## Goal!
+
+![screenshot]
+
+This first Android tutorial is extremely simple: it just retrieves the
+GStreamer version and displays it on the screen. It exemplifies how to
+access GStreamer C code from Java and verifies that there have been no
+linkage problems.
+
+## Hello GStreamer \[Java code\]
+
+The tutorial code is in the [gst-docs subdirectory](https://gitlab.freedesktop.org/gstreamer/gstreamer/-/tree/main/subprojects/gst-docs/examples/tutorials/android/android-tutorial-1).
+This directory contains the usual Android NDK structure: a `src` folder for the Java code,
+a `jni` folder for the C code and a `res` folder for UI resources.
+
+We recommend that you open this project in Eclipse (as explained
+in [](installing/for-android-development.md)) so you can
+easily see how all the pieces fit together.
+
+Let’s first introduce the Java code, then the C code and finally the
+makefile that allows GStreamer integration.
+
+**src/org/freedesktop/gstreamer/tutorials/tutorial_1/Tutorial1.java**
+
+``` java
+package org.freedesktop.gstreamer.tutorials.tutorial_1;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import org.freedesktop.gstreamer.GStreamer;
+
+public class Tutorial1 extends Activity {
+    private native String nativeGetGStreamerInfo();
+
+    // Called when the activity is first created.
+    @Override
+    public void onCreate(Bundle savedInstanceState)
+    {
+        super.onCreate(savedInstanceState);
+
+        try {
+            GStreamer.init(this);
+        } catch (Exception e) {
+            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();
+            finish();
+            return;
+        }
+
+        setContentView(R.layout.main);
+
+        TextView tv = (TextView)findViewById(R.id.textview_info);
+        tv.setText("Welcome to " + nativeGetGStreamerInfo() + " !");
+    }
+
+    static {
+        System.loadLibrary("gstreamer_android");
+        System.loadLibrary("tutorial-1");
+    }
+
+}
+```
+
+Calls from Java to C happen through native methods, like the one
+declared here:
+
+``` java
+private native String nativeGetGStreamerInfo();
+```
+
+This tells Java that there exists a method with this signature somewhere
+so it compiles happily. It is your responsibility to ensure that, **at
+runtime**, this method is accessible. This is accomplished by the C code
+shown later.
+
+The first bit of code that gets actually executed is the static
+initializer of the class:
+
+``` java
+static {
+    System.loadLibrary("gstreamer_android");
+    System.loadLibrary("tutorial-1");
+}
+```
+
+It loads `libgstreamer_android.so`, which contains all GStreamer
+methods, and `libtutorial-1.so`, which contains the C part of this
+tutorial, explained below.
+
+Upon loading, each of these libraries’ `JNI_OnLoad()` method is
+executed. It basically registers the native methods that these libraries
+expose. The GStreamer library only exposes a `init()` method, which
+initializes GStreamer and registers all plugins (The tutorial library is
+explained later below).
+
+``` java
+try {
+    GStreamer.init(this);
+} catch (Exception e) {
+    Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();
+    finish();
+    return;
+}
+```
+
+Next, in the `OnCreate()` method of the
+[Activity](http://developer.android.com/reference/android/app/Activity.html)
+we actually initialize GStreamer by calling `GStreamer.init()`. This
+method requires a
+[Context](http://developer.android.com/reference/android/content/Context.html)
+so it cannot be called from the static initializer, but there is no
+danger in calling it multiple times, as all but the first time the calls
+will be ignored.
+
+Should initialization fail, the `init()` method would throw an
+[Exception](http://developer.android.com/reference/java/lang/Exception.html)
+with the details provided by the GStreamer library.
+
+``` java
+TextView tv = (TextView)findViewById(R.id.textview_info);
+tv.setText("Welcome to " + nativeGetGStreamerInfo() + " !");
+```
+
+Then, the native method `nativeGetGStreamerInfo()` is called and a
+string is retrieved, which is used to format the content of the
+[TextView](http://developer.android.com/reference/android/widget/TextView.html)
+in the UI.
+
+This finishes the UI part of this tutorial. Let’s take a look at the C
+code:
+
+## Hello GStreamer \[C code\]
+
+**jni/tutorial-1.c**
+
+``` c
+#include <string.h>
+#include <jni.h>
+#include <android/log.h>
+#include <gst/gst.h>
+
+/*
+ * Java Bindings
+ */
+static jstring gst_native_get_gstreamer_info (JNIEnv* env, jobject thiz) {
+  char *version_utf8 = gst_version_string();
+  jstring *version_jstring = (*env)->NewStringUTF(env, version_utf8);
+  g_free (version_utf8);
+  return version_jstring;
+}
+
+static JNINativeMethod native_methods[] = {
+  { "nativeGetGStreamerInfo", "()Ljava/lang/String;", (void *) gst_native_get_gstreamer_info}
+};
+
+jint JNI_OnLoad(JavaVM *vm, void *reserved) {
+  JNIEnv *env = NULL;
+
+  if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
+    __android_log_print (ANDROID_LOG_ERROR, "tutorial-1", "Could not retrieve JNIEnv");
+    return 0;
+  }
+  jclass klass = (*env)->FindClass (env, "org/freedesktop/gstreamer/tutorials/tutorial_1/Tutorial1");
+  (*env)->RegisterNatives (env, klass, native_methods, G_N_ELEMENTS(native_methods));
+
+  return JNI_VERSION_1_4;
+}
+```
+
+The `JNI_OnLoad()` method is executed every time the Java Virtual
+Machine (VM) loads a library.
+
+Here, we retrieve the JNI environment needed to make calls that interact
+with Java:
+
+``` c
+JNIEnv *env = NULL;
+
+if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
+  __android_log_print (ANDROID_LOG_ERROR, "tutorial-1", "Could not retrieve JNIEnv");
+  return 0;
+}
+```
+
+And then locate the class containing the UI part of this tutorial using
+`
+FindClass()`:
+
+``` c
+jclass klass = (*env)->FindClass (env, "org/freedesktop/gstreamer/tutorials/tutorial_1/Tutorial1");
+```
+
+Finally, we register our native methods with `RegisterNatives()`, this
+is, we provide the code for the methods we advertised in Java using the
+**`native`**
+ keyword:
+
+``` c
+(*env)->RegisterNatives (env, klass, native_methods, G_N_ELEMENTS(native_methods));
+```
+
+The `native_methods` array describes each one of the methods to register
+(only one in this tutorial).  For each method, it provides its Java
+name, its [type
+signature](http://docs.oracle.com/javase/1.5.0/docs/guide/jni/spec/types.html#wp276)
+and a pointer to the C function implementing it:
+
+``` c
+static JNINativeMethod native_methods[] = {
+  { "nativeGetGStreamerInfo", "()Ljava/lang/String;", (void *) gst_native_get_gstreamer_info}
+};
+```
+
+The only native method used in this tutorial
+is `nativeGetGStreamerInfo()`:
+
+``` c
+jstring gst_native_get_gstreamer_info (JNIEnv* env, jobject thiz) {
+  char *version_utf8 = gst_version_string();
+  jstring *version_jstring = (*env)->NewStringUTF(env, version_utf8);
+  g_free (version_utf8);
+  return version_jstring;
+}
+```
+
+It simply calls `gst_version_string()` to obtain a string describing
+this version of GStreamer. This [Modified
+UTF8](http://en.wikipedia.org/wiki/UTF-8#Modified_UTF-8) string is then
+converted to [UTF16](http://en.wikipedia.org/wiki/UTF-16) by `
+NewStringUTF()` as required by Java and returned. Java will be
+responsible for freeing the memory used by the new UTF16 String, but we
+must free the `char *` returned by `gst_version_string()`.
+
+## Hello GStreamer \[Android.mk\]
+
+**jni/Android.mk**
+
+``` ruby
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+
+LOCAL_MODULE    := tutorial-1
+LOCAL_SRC_FILES := tutorial-1.c
+LOCAL_SHARED_LIBRARIES := gstreamer_android
+LOCAL_LDLIBS := -llog
+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
+include $(GSTREAMER_NDK_BUILD_PATH)/gstreamer-1.0.mk
+```
+
+This is a barebones makefile for a project with GStreamer support. It
+simply states that it depends on the `libgstreamer_android.so` library
+(line 7), and requires the `coreelements` plugin (line 18). More complex
+applications will probably add more libraries and plugins
+to `Android.mk`
+
+## Conclusion
+
+This ends the first Android tutorial. It has shown that, besides the
+interconnection between Java and C (which abides to the standard JNI
+procedure), adding GStreamer support to an Android application is not
+any more complicated than adding it to a desktop application.
+
+The following tutorials detail the few places in which care has to be
+taken when developing specifically for the Android platform.
+
+As usual, it has been a pleasure having you here, and see you soon\!
+
+  [screenshot]: images/tutorials/android-link-against-gstreamer-screenshot.png

subprojects/gst-docs/markdown/tutorials/android/video.md

@@ -0,0 +1,913 @@
+# Android tutorial 3: Video
+
+### Goal
+
+![screenshot]
+
+Except for [](tutorials/basic/toolkit-integration.md),
+which embedded a video window on a GTK application, all tutorials so far
+relied on GStreamer video sinks to create a window to display their
+contents. The video sink on Android is not capable of creating its own
+window, so a drawing surface always needs to be provided. This tutorial
+shows:
+
+  - How to allocate a drawing surface on the Android layout and pass it
+    to GStreamer
+  - How to keep GStreamer posted on changes to the surface
+
+### Introduction
+
+Since Android does not provide a windowing system, a GStreamer video
+sink cannot create pop-up windows as it would do on a Desktop platform.
+Fortunately, the `VideoOverlay` interface allows providing video sinks with
+an already created window onto which they can draw, as we have seen in
+[](tutorials/basic/toolkit-integration.md).
+
+In this tutorial, a
+[SurfaceView](http://developer.android.com/reference/android/view/SurfaceView.html)
+widget (actually, a subclass of it) is placed on the main layout. When
+Android informs the application that a surface has been created for this
+widget, we pass it to the C code which stores it. The
+`check_initialization_complete()` method explained in the previous
+tutorial is extended so that GStreamer is not considered initialized
+until a main loop is running and a drawing surface has been received.
+
+### A video surface on Android \[Java code\]
+
+**src/org/freedesktop/gstreamer/tutorials/tutorial\_3/Tutorial3.java**
+
+``` java
+package org.freedesktop.gstreamer.tutorials.tutorial_3;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.util.Log;
+import android.view.SurfaceHolder;
+import android.view.SurfaceView;
+import android.view.View;
+import android.view.View.OnClickListener;
+import android.widget.ImageButton;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import org.freedesktop.gstreamer.GStreamer;
+
+public class Tutorial3 extends Activity implements SurfaceHolder.Callback {
+    private native void nativeInit();     // Initialize native code, build pipeline, etc
+    private native void nativeFinalize(); // Destroy pipeline and shutdown native code
+    private native void nativePlay();     // Set pipeline to PLAYING
+    private native void nativePause();    // Set pipeline to PAUSED
+    private static native boolean nativeClassInit(); // Initialize native class: cache Method IDs for callbacks
+    private native void nativeSurfaceInit(Object surface);
+    private native void nativeSurfaceFinalize();
+    private long native_custom_data;      // Native code will use this to keep private data
+
+    private boolean is_playing_desired;   // Whether the user asked to go to PLAYING
+
+    // Called when the activity is first created.
+    @Override
+    public void onCreate(Bundle savedInstanceState)
+    {
+        super.onCreate(savedInstanceState);
+
+        // Initialize GStreamer and warn if it fails
+        try {
+            GStreamer.init(this);
+        } catch (Exception e) {
+            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();
+            finish();
+            return;
+        }
+
+        setContentView(R.layout.main);
+
+        ImageButton play = (ImageButton) this.findViewById(R.id.button_play);
+        play.setOnClickListener(new OnClickListener() {
+            public void onClick(View v) {
+                is_playing_desired = true;
+                nativePlay();
+            }
+        });
+
+        ImageButton pause = (ImageButton) this.findViewById(R.id.button_stop);
+        pause.setOnClickListener(new OnClickListener() {
+            public void onClick(View v) {
+                is_playing_desired = false;
+                nativePause();
+            }
+        });
+
+        SurfaceView sv = (SurfaceView) this.findViewById(R.id.surface_video);
+        SurfaceHolder sh = sv.getHolder();
+        sh.addCallback(this);
+
+        if (savedInstanceState != null) {
+            is_playing_desired = savedInstanceState.getBoolean("playing");
+            Log.i ("GStreamer", "Activity created. Saved state is playing:" + is_playing_desired);
+        } else {
+            is_playing_desired = false;
+            Log.i ("GStreamer", "Activity created. There is no saved state, playing: false");
+        }
+
+        // Start with disabled buttons, until native code is initialized
+        this.findViewById(R.id.button_play).setEnabled(false);
+        this.findViewById(R.id.button_stop).setEnabled(false);
+
+        nativeInit();
+    }
+
+    protected void onSaveInstanceState (Bundle outState) {
+        Log.d ("GStreamer", "Saving state, playing:" + is_playing_desired);
+        outState.putBoolean("playing", is_playing_desired);
+    }
+
+    protected void onDestroy() {
+        nativeFinalize();
+        super.onDestroy();
+    }
+
+    // Called from native code. This sets the content of the TextView from the UI thread.
+    private void setMessage(final String message) {
+        final TextView tv = (TextView) this.findViewById(R.id.textview_message);
+        runOnUiThread (new Runnable() {
+          public void run() {
+            tv.setText(message);
+          }
+        });
+    }
+
+    // Called from native code. Native code calls this once it has created its pipeline and
+    // the main loop is running, so it is ready to accept commands.
+    private void onGStreamerInitialized () {
+        Log.i ("GStreamer", "Gst initialized. Restoring state, playing:" + is_playing_desired);
+        // Restore previous playing state
+        if (is_playing_desired) {
+            nativePlay();
+        } else {
+            nativePause();
+        }
+
+        // Re-enable buttons, now that GStreamer is initialized
+        final Activity activity = this;
+        runOnUiThread(new Runnable() {
+            public void run() {
+                activity.findViewById(R.id.button_play).setEnabled(true);
+                activity.findViewById(R.id.button_stop).setEnabled(true);
+            }
+        });
+    }
+
+    static {
+        System.loadLibrary("gstreamer_android");
+        System.loadLibrary("tutorial-3");
+        nativeClassInit();
+    }
+
+    public void surfaceChanged(SurfaceHolder holder, int format, int width,
+            int height) {
+        Log.d("GStreamer", "Surface changed to format " + format + " width "
+                + width + " height " + height);
+        nativeSurfaceInit (holder.getSurface());
+    }
+
+    public void surfaceCreated(SurfaceHolder holder) {
+        Log.d("GStreamer", "Surface created: " + holder.getSurface());
+    }
+
+    public void surfaceDestroyed(SurfaceHolder holder) {
+        Log.d("GStreamer", "Surface destroyed");
+        nativeSurfaceFinalize ();
+    }
+
+}
+```
+
+This tutorial continues where the previous one left, adding a video
+surface to the layout and changing the GStreamer pipeline to produce
+video instead of audio. Only the parts of the code that are new will be
+discussed.
+
+``` java
+private native void nativeSurfaceInit(Object surface);
+private native void nativeSurfaceFinalize();
+```
+
+Two new entry points to the C code are defined,
+`nativeSurfaceInit()` and `nativeSurfaceFinalize()`, which we will call
+when the video surface becomes available and when it is about to be
+destroyed, respectively.
+
+``` java
+SurfaceView sv = (SurfaceView) this.findViewById(R.id.surface_video);
+SurfaceHolder sh = sv.getHolder();
+sh.addCallback(this);
+```
+
+In `onCreate()`, we retrieve the
+[SurfaceView](http://developer.android.com/reference/android/view/SurfaceView.html),
+and then register ourselves to receive notifications about the surface
+state through the
+[SurfaceHolder](http://developer.android.com/reference/android/view/SurfaceHolder.html)
+interface. This is why we declared this Activity as implementing the
+[SurfaceHolder.Callback](http://developer.android.com/reference/android/view/SurfaceHolder.Callback.html)
+interface in line 16.
+
+``` java
+public void surfaceChanged(SurfaceHolder holder, int format, int width,
+        int height) {
+    Log.d("GStreamer", "Surface changed to format " + format + " width "
+            + width + " height " + height);
+    nativeSurfaceInit (holder.getSurface());
+}
+
+public void surfaceCreated(SurfaceHolder holder) {
+    Log.d("GStreamer", "Surface created: " + holder.getSurface());
+}
+
+public void surfaceDestroyed(SurfaceHolder holder) {
+    Log.d("GStreamer", "Surface destroyed");
+    nativeSurfaceFinalize ();
+}
+```
+
+This interface is composed of the three methods above, which get called
+when the geometry of the surface changes, when the surface is created
+and when it is about to be destroyed. `surfaceChanged()` always gets
+called at least once, right after `surfaceCreated()`, so we will use it
+to notify GStreamer about the new surface. We use
+`surfaceDestroyed()` to tell GStreamer to stop using this surface.
+
+Let’s review the C code to see what these functions do.
+
+### A video surface on Android \[C code\]
+
+**jni/tutorial-3.c**
+
+``` c
+#include <string.h>
+#include <stdint.h>
+#include <jni.h>
+#include <android/log.h>
+#include <android/native_window.h>
+#include <android/native_window_jni.h>
+#include <gst/gst.h>
+#include <gst/video/video.h>
+#include <pthread.h>
+
+GST_DEBUG_CATEGORY_STATIC (debug_category);
+#define GST_CAT_DEFAULT debug_category
+
+/*
+ * These macros provide a way to store the native pointer to CustomData, which might be 32 or 64 bits, into
+ * a jlong, which is always 64 bits, without warnings.
+ */
+#if GLIB_SIZEOF_VOID_P == 8
+## define GET_CUSTOM_DATA(env, thiz, fieldID) (CustomData *)(*env)->GetLongField (env, thiz, fieldID)
+## define SET_CUSTOM_DATA(env, thiz, fieldID, data) (*env)->SetLongField (env, thiz, fieldID, (jlong)data)
+#else
+## define GET_CUSTOM_DATA(env, thiz, fieldID) (CustomData *)(jint)(*env)->GetLongField (env, thiz, fieldID)
+## define SET_CUSTOM_DATA(env, thiz, fieldID, data) (*env)->SetLongField (env, thiz, fieldID, (jlong)(jint)data)
+#endif
+
+/* Structure to contain all our information, so we can pass it to callbacks */
+typedef struct _CustomData {
+  jobject app;            /* Application instance, used to call its methods. A global reference is kept. */
+  GstElement *pipeline;   /* The running pipeline */
+  GMainContext *context;  /* GLib context used to run the main loop */
+  GMainLoop *main_loop;   /* GLib main loop */
+  gboolean initialized;   /* To avoid informing the UI multiple times about the initialization */
+  GstElement *video_sink; /* The video sink element which receives VideoOverlay commands */
+  ANativeWindow *native_window; /* The Android native window where video will be rendered */
+} CustomData;
+
+/* These global variables cache values which are not changing during execution */
+static pthread_t gst_app_thread;
+static pthread_key_t current_jni_env;
+static JavaVM *java_vm;
+static jfieldID custom_data_field_id;
+static jmethodID set_message_method_id;
+static jmethodID on_gstreamer_initialized_method_id;
+
+/*
+ * Private methods
+ */
+
+/* Register this thread with the VM */
+static JNIEnv *attach_current_thread (void) {
+  JNIEnv *env;
+  JavaVMAttachArgs args;
+
+  GST_DEBUG ("Attaching thread %p", g_thread_self ());
+  args.version = JNI_VERSION_1_4;
+  args.name = NULL;
+  args.group = NULL;
+
+  if ((*java_vm)->AttachCurrentThread (java_vm, &env, &args) < 0) {
+    GST_ERROR ("Failed to attach current thread");
+    return NULL;
+  }
+
+  return env;
+}
+
+/* Unregister this thread from the VM */
+static void detach_current_thread (void *env) {
+  GST_DEBUG ("Detaching thread %p", g_thread_self ());
+  (*java_vm)->DetachCurrentThread (java_vm);
+}
+
+/* Retrieve the JNI environment for this thread */
+static JNIEnv *get_jni_env (void) {
+  JNIEnv *env;
+
+  if ((env = pthread_getspecific (current_jni_env)) == NULL) {
+    env = attach_current_thread ();
+    pthread_setspecific (current_jni_env, env);
+  }
+
+  return env;
+}
+
+/* Change the content of the UI's TextView */
+static void set_ui_message (const gchar *message, CustomData *data) {
+  JNIEnv *env = get_jni_env ();
+  GST_DEBUG ("Setting message to: %s", message);
+  jstring jmessage = (*env)->NewStringUTF(env, message);
+  (*env)->CallVoidMethod (env, data->app, set_message_method_id, jmessage);
+  if ((*env)->ExceptionCheck (env)) {
+    GST_ERROR ("Failed to call Java method");
+    (*env)->ExceptionClear (env);
+  }
+  (*env)->DeleteLocalRef (env, jmessage);
+}
+
+/* Retrieve errors from the bus and show them on the UI */
+static void error_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
+  GError *err;
+  gchar *debug_info;
+  gchar *message_string;
+
+  gst_message_parse_error (msg, &err, &debug_info);
+  message_string = g_strdup_printf ("Error received from element %s: %s", GST_OBJECT_NAME (msg->src), err->message);
+  g_clear_error (&err);
+  g_free (debug_info);
+  set_ui_message (message_string, data);
+  g_free (message_string);
+  gst_element_set_state (data->pipeline, GST_STATE_NULL);
+}
+
+/* Notify UI about pipeline state changes */
+static void state_changed_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
+  GstState old_state, new_state, pending_state;
+  gst_message_parse_state_changed (msg, &old_state, &new_state, &pending_state);
+  /* Only pay attention to messages coming from the pipeline, not its children */
+  if (GST_MESSAGE_SRC (msg) == GST_OBJECT (data->pipeline)) {
+    gchar *message = g_strdup_printf("State changed to %s", gst_element_state_get_name(new_state));
+    set_ui_message(message, data);
+    g_free (message);
+  }
+}
+
+/* Check if all conditions are met to report GStreamer as initialized.
+ * These conditions will change depending on the application */
+static void check_initialization_complete (CustomData *data) {
+  JNIEnv *env = get_jni_env ();
+  if (!data->initialized && data->native_window && data->main_loop) {
+    GST_DEBUG ("Initialization complete, notifying application. native_window:%p main_loop:%p", data->native_window, data->main_loop);
+
+    /* The main loop is running and we received a native window, inform the sink about it */
+    gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (data->video_sink), (guintptr)data->native_window);
+
+    (*env)->CallVoidMethod (env, data->app, on_gstreamer_initialized_method_id);
+    if ((*env)->ExceptionCheck (env)) {
+      GST_ERROR ("Failed to call Java method");
+      (*env)->ExceptionClear (env);
+    }
+    data->initialized = TRUE;
+  }
+}
+
+/* Main method for the native code. This is executed on its own thread. */
+static void *app_function (void *userdata) {
+  JavaVMAttachArgs args;
+  GstBus *bus;
+  CustomData *data = (CustomData *)userdata;
+  GSource *bus_source;
+  GError *error = NULL;
+
+  GST_DEBUG ("Creating pipeline in CustomData at %p", data);
+
+  /* Create our own GLib Main Context and make it the default one */
+  data->context = g_main_context_new ();
+  g_main_context_push_thread_default(data->context);
+
+  /* Build pipeline */
+  data->pipeline = gst_parse_launch("videotestsrc ! warptv ! videoconvert ! autovideosink", &error);
+  if (error) {
+    gchar *message = g_strdup_printf("Unable to build pipeline: %s", error->message);
+    g_clear_error (&error);
+    set_ui_message(message, data);
+    g_free (message);
+    return NULL;
+  }
+
+  /* Set the pipeline to READY, so it can already accept a window handle, if we have one */
+  gst_element_set_state(data->pipeline, GST_STATE_READY);
+
+  data->video_sink = gst_bin_get_by_interface(GST_BIN(data->pipeline), GST_TYPE_VIDEO_OVERLAY);
+  if (!data->video_sink) {
+    GST_ERROR ("Could not retrieve video sink");
+    return NULL;
+  }
+
+  /* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
+  bus = gst_element_get_bus (data->pipeline);
+  bus_source = gst_bus_create_watch (bus);
+  g_source_set_callback (bus_source, (GSourceFunc) gst_bus_async_signal_func, NULL, NULL);
+  g_source_attach (bus_source, data->context);
+  g_source_unref (bus_source);
+  g_signal_connect (G_OBJECT (bus), "message::error", (GCallback)error_cb, data);
+  g_signal_connect (G_OBJECT (bus), "message::state-changed", (GCallback)state_changed_cb, data);
+  gst_object_unref (bus);
+
+  /* Create a GLib Main Loop and set it to run */
+  GST_DEBUG ("Entering main loop... (CustomData:%p)", data);
+  data->main_loop = g_main_loop_new (data->context, FALSE);
+  check_initialization_complete (data);
+  g_main_loop_run (data->main_loop);
+  GST_DEBUG ("Exited main loop");
+  g_main_loop_unref (data->main_loop);
+  data->main_loop = NULL;
+
+  /* Free resources */
+  g_main_context_pop_thread_default(data->context);
+  g_main_context_unref (data->context);
+  gst_element_set_state (data->pipeline, GST_STATE_NULL);
+  gst_object_unref (data->video_sink);
+  gst_object_unref (data->pipeline);
+
+  return NULL;
+}
+
+/*
+ * Java Bindings
+ */
+
+/* Instruct the native code to create its internal data structure, pipeline and thread */
+static void gst_native_init (JNIEnv* env, jobject thiz) {
+  CustomData *data = g_new0 (CustomData, 1);
+  SET_CUSTOM_DATA (env, thiz, custom_data_field_id, data);
+  GST_DEBUG_CATEGORY_INIT (debug_category, "tutorial-3", 0, "Android tutorial 3");
+  gst_debug_set_threshold_for_name("tutorial-3", GST_LEVEL_DEBUG);
+  GST_DEBUG ("Created CustomData at %p", data);
+  data->app = (*env)->NewGlobalRef (env, thiz);
+  GST_DEBUG ("Created GlobalRef for app object at %p", data->app);
+  pthread_create (&gst_app_thread, NULL, &app_function, data);
+}
+
+/* Quit the main loop, remove the native thread and free resources */
+static void gst_native_finalize (JNIEnv* env, jobject thiz) {
+  CustomData *data = GET_CUSTOM_DATA (env, thiz, custom_data_field_id);
+  if (!data) return;
+  GST_DEBUG ("Quitting main loop...");
+  g_main_loop_quit (data->main_loop);
+  GST_DEBUG ("Waiting for thread to finish...");
+  pthread_join (gst_app_thread, NULL);
+  GST_DEBUG ("Deleting GlobalRef for app object at %p", data->app);
+  (*env)->DeleteGlobalRef (env, data->app);
+  GST_DEBUG ("Freeing CustomData at %p", data);
+  g_free (data);
+  SET_CUSTOM_DATA (env, thiz, custom_data_field_id, NULL);
+  GST_DEBUG ("Done finalizing");
+}
+
+/* Set pipeline to PLAYING state */
+static void gst_native_play (JNIEnv* env, jobject thiz) {
+  CustomData *data = GET_CUSTOM_DATA (env, thiz, custom_data_field_id);
+  if (!data) return;
+  GST_DEBUG ("Setting state to PLAYING");
+  gst_element_set_state (data->pipeline, GST_STATE_PLAYING);
+}
+
+/* Set pipeline to PAUSED state */
+static void gst_native_pause (JNIEnv* env, jobject thiz) {
+  CustomData *data = GET_CUSTOM_DATA (env, thiz, custom_data_field_id);
+  if (!data) return;
+  GST_DEBUG ("Setting state to PAUSED");
+  gst_element_set_state (data->pipeline, GST_STATE_PAUSED);
+}
+
+/* Static class initializer: retrieve method and field IDs */
+static jboolean gst_native_class_init (JNIEnv* env, jclass klass) {
+  custom_data_field_id = (*env)->GetFieldID (env, klass, "native_custom_data", "J");
+  set_message_method_id = (*env)->GetMethodID (env, klass, "setMessage", "(Ljava/lang/String;)V");
+  on_gstreamer_initialized_method_id = (*env)->GetMethodID (env, klass, "onGStreamerInitialized", "()V");
+
+  if (!custom_data_field_id || !set_message_method_id || !on_gstreamer_initialized_method_id) {
+    /* We emit this message through the Android log instead of the GStreamer log because the later
+     * has not been initialized yet.
+     */
+    __android_log_print (ANDROID_LOG_ERROR, "tutorial-3", "The calling class does not implement all necessary interface methods");
+    return JNI_FALSE;
+  }
+  return JNI_TRUE;
+}
+
+static void gst_native_surface_init (JNIEnv *env, jobject thiz, jobject surface) {
+  CustomData *data = GET_CUSTOM_DATA (env, thiz, custom_data_field_id);
+  if (!data) return;
+  ANativeWindow *new_native_window = ANativeWindow_fromSurface(env, surface);
+  GST_DEBUG ("Received surface %p (native window %p)", surface, new_native_window);
+
+  if (data->native_window) {
+    ANativeWindow_release (data->native_window);
+    if (data->native_window == new_native_window) {
+      GST_DEBUG ("New native window is the same as the previous one", data->native_window);
+      if (data->video_sink) {
+        gst_video_overlay_expose(GST_VIDEO_OVERLAY (data->video_sink));
+        gst_video_overlay_expose(GST_VIDEO_OVERLAY (data->video_sink));
+      }
+      return;
+    } else {
+      GST_DEBUG ("Released previous native window %p", data->native_window);
+      data->initialized = FALSE;
+    }
+  }
+  data->native_window = new_native_window;
+
+  check_initialization_complete (data);
+}
+
+static void gst_native_surface_finalize (JNIEnv *env, jobject thiz) {
+  CustomData *data = GET_CUSTOM_DATA (env, thiz, custom_data_field_id);
+  if (!data) return;
+  GST_DEBUG ("Releasing Native Window %p", data->native_window);
+
+  if (data->video_sink) {
+    gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (data->video_sink), (guintptr)NULL);
+    gst_element_set_state (data->pipeline, GST_STATE_READY);
+  }
+
+  ANativeWindow_release (data->native_window);
+  data->native_window = NULL;
+  data->initialized = FALSE;
+}
+
+/* List of implemented native methods */
+static JNINativeMethod native_methods[] = {
+  { "nativeInit", "()V", (void *) gst_native_init},
+  { "nativeFinalize", "()V", (void *) gst_native_finalize},
+  { "nativePlay", "()V", (void *) gst_native_play},
+  { "nativePause", "()V", (void *) gst_native_pause},
+  { "nativeSurfaceInit", "(Ljava/lang/Object;)V", (void *) gst_native_surface_init},
+  { "nativeSurfaceFinalize", "()V", (void *) gst_native_surface_finalize},
+  { "nativeClassInit", "()Z", (void *) gst_native_class_init}
+};
+
+/* Library initializer */
+jint JNI_OnLoad(JavaVM *vm, void *reserved) {
+  JNIEnv *env = NULL;
+
+  java_vm = vm;
+
+  if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
+    __android_log_print (ANDROID_LOG_ERROR, "tutorial-3", "Could not retrieve JNIEnv");
+    return 0;
+  }
+  jclass klass = (*env)->FindClass (env, "org/freedesktop/gstreamer/tutorials/tutorial_3/Tutorial3");
+  (*env)->RegisterNatives (env, klass, native_methods, G_N_ELEMENTS(native_methods));
+
+  pthread_key_create (&current_jni_env, detach_current_thread);
+
+  return JNI_VERSION_1_4;
+}
+```
+
+First, our `CustomData` structure is augmented to keep a pointer to the
+video sink element and the native window
+handle:
+
+``` c
+GstElement *video_sink; /* The video sink element which receives VideoOverlay commands */
+ANativeWindow *native_window; /* The Android native window where video will be rendered */
+```
+
+The `check_initialization_complete()` method is also augmented so that
+it requires a native window before considering GStreamer to be
+initialized:
+
+``` c
+static void check_initialization_complete (CustomData *data) {
+  JNIEnv *env = get_jni_env ();
+  if (!data->initialized && data->native_window && data->main_loop) {
+    GST_DEBUG ("Initialization complete, notifying application. native_window:%p main_loop:%p", data->native_window, data->main_loop);
+
+    /* The main loop is running and we received a native window, inform the sink about it */
+    gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (data->video_sink), (guintptr)data->native_window);
+
+    (*env)->CallVoidMethod (env, data->app, on_gstreamer_initialized_method_id);
+    if ((*env)->ExceptionCheck (env)) {
+      GST_ERROR ("Failed to call Java method");
+      (*env)->ExceptionClear (env);
+    }
+    data->initialized = TRUE;
+  }
+}
+```
+
+Also, once the pipeline has been built and a native window has been
+received, we inform the video sink of the window handle to use via the
+`gst_video_overlay_set_window_handle()` method.
+
+The GStreamer pipeline for this tutorial involves a `videotestsrc`, a
+`warptv` psychedelic distorter effect (check out other cool video
+effects in the `GSTREAMER_PLUGINS_EFFECTS` package), and an
+`autovideosink` which will instantiate the adequate video sink for the
+platform:
+
+``` c
+data->pipeline = gst_parse_launch("videotestsrc ! warptv ! videoconvert ! autovideosink ", &error);
+```
+
+Here things start to get more
+interesting:
+
+``` c
+/* Set the pipeline to READY, so it can already accept a window handle, if we have one */
+gst_element_set_state(data->pipeline, GST_STATE_READY);
+
+data->video_sink = gst_bin_get_by_interface(GST_BIN(data->pipeline), GST_TYPE_VIDEO_OVERLAY);
+if (!data->video_sink) {
+  GST_ERROR ("Could not retrieve video sink");
+  return NULL;
+}
+```
+
+We start by setting the pipeline to the READY state. No data flow occurs
+yet, but the `autovideosink` will instantiate the actual sink so we can
+ask for it immediately.
+
+The `gst_bin_get_by_interface()` method will examine the whole pipeline
+and return a pointer to an element which supports the requested
+interface. We are asking for the `VideoOverlay` interface, explained in
+[](tutorials/basic/toolkit-integration.md),
+which controls how to perform rendering into foreign (non-GStreamer)
+windows. The internal video sink instantiated by `autovideosink` is the
+only element in this pipeline implementing it, so it will be returned.
+
+Now we will implement the two native functions called by the Java code
+when the drawing surface becomes available or is about to be
+destroyed:
+
+``` c
+static void gst_native_surface_init (JNIEnv *env, jobject thiz, jobject surface) {
+  CustomData *data = GET_CUSTOM_DATA (env, thiz, custom_data_field_id);
+  if (!data) return;
+  ANativeWindow *new_native_window = ANativeWindow_fromSurface(env, surface);
+  GST_DEBUG ("Received surface %p (native window %p)", surface, new_native_window);
+
+  if (data->native_window) {
+    ANativeWindow_release (data->native_window);
+    if (data->native_window == new_native_window) {
+      GST_DEBUG ("New native window is the same as the previous one", data->native_window);
+      if (data->video_sink) {
+        gst_video_overlay_expose(GST_VIDEO_OVERLAY (data->video_sink));
+        gst_video_overlay_expose(GST_VIDEO_OVERLAY (data->video_sink));
+      }
+      return;
+    } else {
+      GST_DEBUG ("Released previous native window %p", data->native_window);
+      data->initialized = FALSE;
+    }
+  }
+  data->native_window = new_native_window;
+
+  check_initialization_complete (data);
+}
+```
+
+This method is responsible for providing the video sink with the window
+handle coming from the Java code. We are passed a
+[Surface](http://developer.android.com/reference/android/view/Surface.html)
+object, and we use `ANativeWindow_fromSurface()` to obtain the
+underlying native window pointer. There is no official online
+documentation for the NDK, but fortunately the header files are well
+commented. Native window management functions can be found in
+`$(ANDROID_NDK_ROOT)\platforms\android-9\arch-arm\usr\include\android\native_window.h` and `native_window_jni.h`
+
+If we had already stored a native window, the one we just received can
+either be a new one, or just an update of the one we have. If the
+pointers are the same, we assume the geometry of the surface has
+changed, and simply instruct the video sink to redraw itself, via the
+`gst_video_overlay_expose()` method. The video sink will recover the new
+size from the surface itself, so we do not need to bother about it
+here. We need to call `gst_video_overlay_expose()` twice because of the way
+the surface changes propagate down the OpenGL ES / EGL pipeline (The
+only video sink available for Android in GStreamer uses OpenGL
+ES). By the time we call the first expose, the surface that the sink
+will pick up still contains the old size.
+
+On the other hand, if the pointers are different, we mark GStreamer as
+not being initialized. Next time we call
+`check_initialization_complete()`, the video sink will be informed of
+the new window handle.
+
+We finally store the new window handle and call
+`check_initialization_complete()` to inform the Java code that
+everything is set up, if that is the case.
+
+``` c
+static void gst_native_surface_finalize (JNIEnv *env, jobject thiz) {
+  CustomData *data = GET_CUSTOM_DATA (env, thiz, custom_data_field_id);
+  if (!data) return;
+  GST_DEBUG ("Releasing Native Window %p", data->native_window);
+
+  if (data->video_sink) {
+    gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (data->video_sink), (guintptr)NULL);
+    gst_element_set_state (data->pipeline, GST_STATE_READY);
+  }
+
+  ANativeWindow_release (data->native_window);
+  data->native_window = NULL;
+  data->initialized = FALSE;
+}
+```
+
+The complementary function, `gst_native_surface_finalize()` is called
+when a surface is about to be destroyed and should not be used anymore.
+Here, we simply instruct the video sink to stop using the window handle
+and set the pipeline to READY so no rendering occurs. We release the
+window pointer we had stored with `ANativeWindow_release()`, and mark
+GStreamer as not being initialized anymore.
+
+And this is all there is to it, regarding the main code. Only a couple
+of details remain, the subclass we made for SurfaceView and the
+`Android.mk` file.
+
+### GStreamerSurfaceView, a convenient SurfaceView wrapper \[Java code\]
+
+By default,
+[SurfaceView](http://developer.android.com/reference/android/view/SurfaceView.html) does
+not have any particular size, so it expands to use all the space the
+layout can give it. While this might be convenient sometimes, it does
+not allow a great deal of control. In particular, when the surface does
+not have the same aspect ratio as the media, the sink will add black
+borders (the known “letterbox” or “pillarbox” effect), which is an
+unnecessary work (and a waste of battery).
+
+The subclass of
+[SurfaceView](http://developer.android.com/reference/android/view/SurfaceView.html) presented
+here overrides the
+[onMeasure()](http://developer.android.com/reference/android/view/SurfaceView.html#onMeasure\(int,%20int\)) method
+to report the actual media size, so the surface can adapt to any layout
+while preserving the media aspect ratio.
+
+Since in this tutorial the media size is known beforehand, it is
+hardcoded in the GStreamerSurfaceView class for simplicity. The next
+tutorial shows how it can be recovered at runtime and passed onto the
+surface.
+
+**src/org/freedesktop/gstreamer/tutorials/tutorial\_3/GStreamerSurfaceView.java**
+
+``` java
+package org.freedesktop.gstreamer.tutorials.tutorial_3;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.util.Log;
+import android.view.SurfaceView;
+import android.view.View;
+
+// A simple SurfaceView whose width and height can be set from the outside
+public class GStreamerSurfaceView extends SurfaceView {
+    public int media_width = 320;
+    public int media_height = 240;
+
+    // Mandatory constructors, they do not do much
+    public GStreamerSurfaceView(Context context, AttributeSet attrs,
+            int defStyle) {
+        super(context, attrs, defStyle);
+    }
+
+    public GStreamerSurfaceView(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public GStreamerSurfaceView (Context context) {
+        super(context);
+    }
+
+    // Called by the layout manager to find out our size and give us some rules.
+    // We will try to maximize our size, and preserve the media's aspect ratio if
+    // we are given the freedom to do so.
+    @Override
+    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+        int width = 0, height = 0;
+        int wmode = View.MeasureSpec.getMode(widthMeasureSpec);
+        int hmode = View.MeasureSpec.getMode(heightMeasureSpec);
+        int wsize = View.MeasureSpec.getSize(widthMeasureSpec);
+        int hsize = View.MeasureSpec.getSize(heightMeasureSpec);
+
+        Log.i ("GStreamer", "onMeasure called with " + media_width + "x" + media_height);
+        // Obey width rules
+        switch (wmode) {
+        case View.MeasureSpec.AT_MOST:
+            if (hmode == View.MeasureSpec.EXACTLY) {
+                width = Math.min(hsize * media_width / media_height, wsize);
+                break;
+            }
+        case View.MeasureSpec.EXACTLY:
+            width = wsize;
+            break;
+        case View.MeasureSpec.UNSPECIFIED:
+            width = media_width;
+        }
+
+        // Obey height rules
+        switch (hmode) {
+        case View.MeasureSpec.AT_MOST:
+            if (wmode == View.MeasureSpec.EXACTLY) {
+                height = Math.min(wsize * media_height / media_width, hsize);
+                break;
+            }
+        case View.MeasureSpec.EXACTLY:
+            height = hsize;
+            break;
+        case View.MeasureSpec.UNSPECIFIED:
+            height = media_height;
+        }
+
+        // Finally, calculate best size when both axis are free
+        if (hmode == View.MeasureSpec.AT_MOST && wmode == View.MeasureSpec.AT_MOST) {
+            int correct_height = width * media_height / media_width;
+            int correct_width = height * media_width / media_height;
+
+            if (correct_height < height)
+                height = correct_height;
+            else
+                width = correct_width;
+        }
+
+        // Obey minimum size
+        width = Math.max (getSuggestedMinimumWidth(), width);
+        height = Math.max (getSuggestedMinimumHeight(), height);
+        setMeasuredDimension(width, height);
+    }
+
+}
+```
+
+### A video surface on Android \[Android.mk\]
+
+**/jni/Android.mk**
+
+``` ruby
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+
+LOCAL_MODULE    := tutorial-3
+LOCAL_SRC_FILES := tutorial-3.c
+LOCAL_SHARED_LIBRARIES := gstreamer_android
+LOCAL_LDLIBS := -llog -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/
+include $(GSTREAMER_NDK_BUILD_PATH)/plugins.mk
+GSTREAMER_PLUGINS         := $(GSTREAMER_PLUGINS_CORE) $(GSTREAMER_PLUGINS_SYS) $(GSTREAMER_PLUGINS_EFFECTS)
+GSTREAMER_EXTRA_DEPS      := gstreamer-video-1.0
+include $(GSTREAMER_NDK_BUILD_PATH)/gstreamer.mk
+```
+
+Worth mentioning is the `-landroid` library being used to allow
+interaction with the native windows, and the different plugin
+packages: `GSTREAMER_PLUGINS_SYS` for the system-dependent video sink
+and `GSTREAMER_PLUGINS_EFFECTS` for the `warptv` element. This tutorial
+requires the `gstreamer-video` library to use the
+`VideoOverlay` interface and the video helper methods.
+
+### Conclusion
+
+This tutorial has shown:
+
+  - How to display video on Android using a
+    [SurfaceView](http://developer.android.com/reference/android/view/SurfaceView.html) and
+    the `VideoOverlay` interface.
+  - How to be aware of changes in the surface’s size using
+    [SurfaceView](http://developer.android.com/reference/android/view/SurfaceView.html)’s
+    callbacks.
+  - How to report the media size to the Android layout engine.
+
+The following tutorial plays an actual clip and adds a few more controls
+to this tutorial in order to build a simple media player.
+
+It has been a pleasure having you here, and see you soon\!
+
+
+ [screenshot]: images/tutorials/android-video-screenshot.png