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Olivier Crête
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# Android tutorial 4: A basic media player
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### Goal
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## Goal
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![screenshot]
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@ -19,7 +19,7 @@ It also uses the knowledge gathered in the [](sdk-basic-tutorials.md) regarding:
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- How to use `playbin` to play any kind of media
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- How to handle network resilience problems
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### Introduction
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## Introduction
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From the previous tutorials, we already have almost all necessary pieces
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to build a media player. The most complex part is assembling a pipeline
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@ -41,7 +41,7 @@ the video sink is not forced to draw black borders around the clip.
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media content. You can still force the video surface to have a specific
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size if you really want to.
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### A basic media player \[Java code\]
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## A basic media player \[Java code\]
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**src/com/gst\_sdk\_tutorials/tutorial\_4/Tutorial4.java**
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@ -298,7 +298,7 @@ public class Tutorial4 extends Activity implements SurfaceHolder.Callback, OnSee
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}
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```
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#### Supporting arbitrary media URIs
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### Supporting arbitrary media URIs
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The C code provides the `nativeSetUri()` method so we can indicate the
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URI of the media to play. Since `playbin` will be taking care of
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@ -319,7 +319,7 @@ private void setMediaUri() {
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We call `setMediaUri()` in the `onGStreamerInitialized()` callback, once
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the pipeline is ready to accept commands.
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#### Reporting media size
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### Reporting media size
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Every time the size of the media changes (which could happen mid-stream,
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for some kind of streams), or when it is first detected, C code calls
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@ -349,7 +349,7 @@ the UI must be called from the main thread, and we are now in a
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callback from some GStreamer internal thread. Hence, the usage of
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[runOnUiThread()](http://developer.android.com/reference/android/app/Activity.html#runOnUiThread\(java.lang.Runnable\)).
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#### Refreshing the Seek Bar
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### Refreshing the Seek Bar
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[](sdk-basic-tutorial-toolkit-integration.md)
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has already shown how to implement a [Seek
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@ -404,7 +404,7 @@ private void updateTimeWidget () {
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}
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```
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#### Seeking with the Seek Bar
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### Seeking with the Seek Bar
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To perform the second function of the [Seek
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Bar](http://developer.android.com/reference/android/widget/SeekBar.html) (allowing
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@ -479,7 +479,7 @@ desired playing state.
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This concludes the User interface part of this tutorial. Let’s review
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now the under-the-hood C code that allows this to work.
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### A basic media player \[C code\]
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## A basic media player \[C code\]
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**jni/tutorial-4.c**
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@ -1054,7 +1054,7 @@ jint JNI_OnLoad(JavaVM *vm, void *reserved) {
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}
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```
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#### Supporting arbitrary media URIs
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### Supporting arbitrary media URIs
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Java code will call `gst_native_set_uri()` whenever it wants to change
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the playing URI (in this tutorial the URI never changes, but it could):
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@ -1100,7 +1100,7 @@ not. Live sources must not use buffering (otherwise latency is
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introduced which is inacceptable for them), so we keep track of this
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information in the `is_live` variable.
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#### Reporting media size
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### Reporting media size
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Some codecs allow the media size (width and height of the video) to
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change during playback. For simplicity, this tutorial assumes that they
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@ -1152,7 +1152,7 @@ The helper functions `gst_video_format_parse_caps()` and
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manageable integers, which we pass to Java through
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its `onMediaSizeChanged()` callback.
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#### Refreshing the Seek Bar
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### Refreshing the Seek Bar
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To keep the UI updated, a GLib timer is installed in the
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`app_function()` that fires 4 times per second (or every 250ms), right
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@ -1201,7 +1201,7 @@ Bear in mind that all time-related measures returned by GStreamer are in
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nanoseconds, whereas, for simplicity, we decided to make the UI code
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work in milliseconds.
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#### Seeking with the Seek Bar
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### Seeking with the Seek Bar
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The Java UI code already takes care of most of the complexity of seeking
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by dragging the thumb of the Seek Bar. From C code, we just need to
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@ -1215,7 +1215,7 @@ Bar can generate a very high number of seek requests in a short period
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of time, which is visually useless and will impair responsiveness. Let’s
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see how to overcome these problems.
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##### Delayed seeks
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#### Delayed seeks
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In
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`gst_native_set_position()`:
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@ -1255,7 +1255,7 @@ Once the pipeline moves from the READY to the PAUSED state, we check if
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there is a pending seek operation and execute it. The
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`desired_position` variable is reset inside `execute_seek()`.
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##### Seek throttling
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#### Seek throttling
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A seek is potentially a lengthy operation. The demuxer (the element
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typically in charge of seeking) needs to estimate the appropriate byte
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@ -1331,7 +1331,7 @@ The one-shot timer calls `delayed_seek_cb()`, which simply calls
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>
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> This is not a complete solution: the scheduled seek will still be executed, even though a more-recent seek has already been executed that should have cancelled it. However, it is a good tradeoff between functionality and simplicity.
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#### Network resilience
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### Network resilience
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[](sdk-basic-tutorial-streaming.md) has already
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shown how to adapt to the variable nature of the network bandwidth by
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@ -1373,7 +1373,7 @@ pipeline, which might be different to the current state, because
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buffering forces us to go to PAUSED. Once buffering is complete we set
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the pipeline to the `target_state`.
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### A basic media player \[Android.mk\]
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## A basic media player \[Android.mk\]
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The only line worth mentioning in the makefile
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is `GSTREAMER_PLUGINS`:
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@ -1388,7 +1388,7 @@ In which all plugins required for playback are loaded, because it is not
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known at build time what would be needed for an unspecified URI (again,
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in this tutorial the URI does not change, but it will in the next one).
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### Conclusion
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## Conclusion
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This tutorial has shown how to embed a `playbin` pipeline into an
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Android application. This, effectively, turns such application into a
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@ -104,11 +104,11 @@ and on an aggregate basis only.
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## Frequently Asked Questions
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##### What licenses are there?
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#### What licenses are there?
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GStreamer binaries containst software under various licenses. See above.
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##### How does this relate to the packaging system?
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#### How does this relate to the packaging system?
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The packaging is only a more convenient way to install software and
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decide what's good for you. GStreamer is meant to be modular, making use
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@ -128,7 +128,7 @@ reference, but we cannot guarantee that our selection is 100% correct,
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so it is up to the user to verify the actual licensing conditions before
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distributing works that utilize GStreamer.
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##### Can I / must I distribute GStreamer along with my application?
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#### Can I / must I distribute GStreamer along with my application?
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You surely can. All software is Free/Open Source software, and can be
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distributed freely. You are not **required** to distribute it. Only,
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@ -142,7 +142,7 @@ entire source code, you might want to include it (or the directories
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containing the source code) with your application as a safe way to
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comply with this requirement of the license.
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##### What happens when I modify the GStreamer's source code?
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#### What happens when I modify the GStreamer's source code?
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You are invited to do so, as the licenses (unless you are dealing with
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proprietary bits, but in that case you will not find the corresponding
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@ -157,7 +157,7 @@ to fork the code, if at all possible. he Cerbero build system has a
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containing all of the complete corresponding machine readable source
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code that you are required to provide.
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##### How does licensing relate to software patents? What about software patents in general?
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#### How does licensing relate to software patents? What about software patents in general?
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This is a tricky question. We believe software patents should not exist,
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so that by distributing and using software on a general purpose machine
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@ -185,7 +185,7 @@ This is why GStreamer has taken a modular approach, so that you can use
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a Free plugins or a proprietary, patent royalty bearing, plugin for a
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given standard.
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##### What about static vs. dynamic linking and copyleft?
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#### What about static vs. dynamic linking and copyleft?
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We cannot provide one single answer to that question. Since copyright in
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software works as copyright in literature, static linking means
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