Getting started with multimedia

Introduction

This document has been reviewed for maemo 4.x.

This document explains how to get started developing multimedia applications and plugins in the maemo SDK.

This assumes you are familiar with the maemo SDK, if you are not, then read maemo tutorial.

Also it's recommended to read GStreamer's documentation.

Here is a diagram of the multimedia architecture from the device's Media Player point of view. It's important if you plan to develop GStreamer plugins that can be used by the Media Player.

Application development

This example demonstrates how to use GStreamer's API to play PCM audio.

You can fetch the code from the maemo-examples package:

apt-get source maemo-examples

The source code is here example_wavlaunch.c.

Building and running

cd maemo-examples-2.0
make
af-sb-init.sh start
run-standalone.sh ./example_wavlaunch

You need Xephyr running as mentioned in the Maemo tutorial

To use simply:

Click Open to open the File Chooser.
Browse to a wav file and select Open.
Play to start playing.

Screenshot:

Many aspects of GStreamer's application development are described in the Application Developer Manual.

For more information about how to use GStreamer's API see the Core API Reference.

Plugin development

To have support for the new media format in the maemo SDK you need to compile a codec for that format and compile GStreamer plug-in supporting that codec.

Codecs are libraries that enable the use of compression for digital audio and video. GStreamer plugins are loadable libraries that provide GStreamer elements that process video and audio streams. Some plugins have the codec embedded and therefore do not need an additional library.

To play some formats one usually needs a demuxer GStreamer plugin as well. More information about the internals of GStreamer plugins can be found in the Plugin Writers Guide.

The list of plugins for GStreamer is available here.

To add support for the new media format, you need:

Codec from the codec's manufacturer.
GStreamer plugins from the GStreamer website.
Extract packages to the Scratchbox environment and follow the compiling instructions for the codec and the GStreamer plugins package

Install OGG Vorbis

To enable playback for ogg-vorbis audio files on the platform, take the following steps:

Get the integer-only implementation from here.
```
svn co http://svn.xiph.org/trunk/Tremor/
```
Build and install in Scratchbox.
```
./autogen.sh --prefix=/usr
make install
```
Get gst-plugins-bad-0.10.5.

Build and install in Scratchbox:

./configure --prefix=/usr
make -C ext/ivorbis install

Check that it's there (if you have gstreamer-tools):
```
gst-inspect-0.10 tremor
```

If you want to try it:

gst-launch-0.10 filesrc location=test.ogg ! application/ogg ! tremor ! alsasink

Deployment

Copy files from scratchbox to the device (into the same directory):

/usr/lib/libvorbisidec.so* -> /usr/lib/
/usr/lib/gstreamer-0.10/libgstivorbis.so -> /usr/lib/gstreamer-0.10

If you want to try it:

gst-launch-0.10 filesrc location=test.ogg ! application/ogg ! tremor ! dsppcmsink

The next step is to tell the file-manager and the media-player about the new format.

Edit /usr/share/mime/packages/ogg-vorbis.xml:

<?xml version="1.0" encoding="UTF-8"?>
 <mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
  <mime-type type="audio/x-vorbis">
   <glob pattern="*.ogg"/>
   <magic priority="50">
    <match type="string" value="OggS" offset="0"/>
   </magic>
   <comment>OGG Vorbis audio</comment>
 </mime-type>
</mime-info>

Note that the mime-type needs to start with "audio/" to be properly recognized. The same applies to video codecs ("video/").

Update the MIME database:

update-mime-database /usr/share/mime

Add "audio/x-vorbis" to /usr/share/applications/hildon/mp_ui.desktop

Update the Desktop database:
```
update-desktop-database
```
Add ogg to the libmetalayer configuration /usr/share/libmetalayer/metadata_lib.conf
```
ogg libmtext_gst
```
Reload metalayer crawler
```
/etc/init.d/metalayer-crawler0 restart
```

That's it!

This information may contain references to third-party information, software and/or services. Such third-party references in this document do not imply endorsement by Nokia of the third party in any way. Your use of third party software shall be governed by and subject to you agreeing to the terms of separate software licenses and Nokia shall not be responsible or liable for any part of such dealings.

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