Live Audio Broadcast Using
Wowza Media Server

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Wowza for Live Audio Broadcast : A Brief Overview
• Wowza Media Server is a popular, Java-based streaming server used for streaming live
and on-demand audio and video content for consumption on various client platforms like
PC, iPhone, Android, etc.
• Wowza provides a lot of features out of the box. Its written in Java and can be extended
by writing components in Java
• In order to stream live radio, Neev uses a Flex based client that captures the audio input
from user’s microphone and sends the same to Wowza Server for broadcasting
• This needs knowledge of Flex API and ActionScript
• For listening to the live stream, one can use JWPlayer (for Flash-based browsers) or
HTML5 for iPhone/iPAD browsers

Setting up Wowza Media Server
Setting up Wowza Media Server comprises a few simple steps :
• Assuming we have a Wowza Media Server already installed, we need to
setup an application under Wowza Media Server. Let’s call this liveradio.
• To do this:
1. Create a folder named liveradio under Wowza
installation’s application directory
2. Create a folder named liveradio under Wowza installation’s conf directory
3. Create a file named Application.xml by copying an existing file
from conf directory
4. Open the newly created Application.xml and modify the value
of /Root/Streams/StreamType node to live
5. Restart Wowza server

Coding the Flex Client for Broadcasting
• Coding the Flex Client for an audio broadcast would need very good
understanding of Flex API and ActionScript (AS).
• You will need to setup an ActionScript project.
• An IDE like FlashDevelop can be used for the same.
• The typical steps you need to follow to capture audio and send to Wowza are
given in the next few slides.

Setting up the Microphone
•
The screenshot below links to AS code for setting up the microphone.
•
Please click on it to view it on the respective blog page.

Setting up the Network Connection
•
We need to set up the Network Connection to send captured audio data to
Wowza server.
(The screenshot below links to relevant code. Please click on it to view it.)

Creating a Page for Playing to the Live Broadcast
• The broadcasted audio can be played by using a flash
based player or HTML5 audio-tag based on the
browser.
• One can also use a player like JWPlayer that can
embed audio/video in Flash format with HTML5
fallback.
• Any other flv player that supports RTMP streaming can
also be used.
• The code has two configurations viz RTMP and HTML5.
• RTMP is supported in browsers that allow content in
flash.
• Since both iPhone and iPad do not support Flash
content therefore one must fall back on HTML5 and
use the Cupertino streaming support for iPAD and
iPhone.
(Please click on the code below to reach our blog which
contains the code)

Challenges and How They Were Overcome
• The streams published from the flex based client is in RTMP format and it can be streamed to a
RTMP/Flash based player only
• SPEEX, which is the audio codec used, needs to be converted to an H.264 compatible codec
like AAC . This can then be played on an iPhone/iPAD
• There are two ways to do the same
• Firstly, one could use an AddOn like Wowza Transcoder or a tool like FFMPEG
• The Wowza Transcoder works on only 64-bit machines with 64-bit Java, whereas FFMPEG is OpenSource and could be used on 32-bit machines

Wowza Transcoder AddOn
• The Wowza Transcoder AddOn can transcode any configured incoming stream from one
format to another.
• Here we encoded our live audio format codec from SPEEX to AAC.
• Here’s how to do this:
1. Setup Wowza Transcoder AddOn. The AddOn works only on 64-bit machines.
2. Create a transcoder template audio_speex.xml in Wowza’s transcoder/templates folder
as shown in the linked content below. (Please click on it to reach the blog which contains
the code)
3. Edit Application.xml and
set /Root/Transcoder/Templates to ${SourceStreamName}_speex.xml, transrate.xml
4. The Wowza Transcoder Add-on is quite powerful and can transcode the incoming
streams to multiple formats and bit rates for consumption on different types of players
and devices with varying bandwidths.

FFMPEG : Simple Command Line Tool for Transcoding
• FFmpeg is a set of tools to record, play and convert audio and video from/to various
formats
• It can be used with Wowza Media Server to encode the live audio stream from our
application from SPEEX to AAC codec
• Below are the steps to get it working with Wowza:
1. Install FFmpeg for the respective platform. This is a challenging task as FFmpeg has a
lot of dependencies. It will usually get installed using yum on CentOS or aptitude get
install on Ubuntu. Make sure FFmpeg is configured with –enable-librtmp and –
enable-libfaac. Run ffmpeg command without any arguments if these are enabled.
2. Start broadcasting the audio from the flex client
3. Run the below command to transcode the live stream called ‘audio’ from Wowza and
make it available as another stream called ‘audio_ios’ for playing on iPhone/iPAD
ffmpeg -i rtmp:///liveradio/audio -acodec libfaac -vcodec copy -f flv
rtmp:///liveradio/audio_ios

Extending Current Setup to Include Video
This setup can be extended easily to stream live video along with audio.
This can be done as follows:
1. In your flex client, the Camera will be setup just like the Microphone was in the above
example and the same will be attached to the flash NetStream
2. The JWPlayer code is modified so that the provider for html2 is video instead of sound

Wowza Use Cases at Neev
• We at Neev Technologies have successfully used Wowza Media Server for
applications involving on-demand streaming of movies/TV programs, live
audio/video streaming.
• In addition there are other use cases like live re-streaming/recording of IP
camera streams, live video/chat where we see Wowza as a great fit.
• Some applications were deployed on a single node and some used OriginEdge cluster for high load and scalability.
• Using the Java API we were also able to customize Wowza to add additional
security features like time based expiry of stream URLs.
Click here to read this blog post on the Neevtech blog.

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