How to configure Wowza Transcoder to encode audio using HE-AAC

This article describes how to configure Wowza Transcoder to encode audio by using HE-AAC (high efficiency AAC). To start, follow the instructions in this article to configure the Wowza Transcoder: How to set up and run Wowza Transcoder.

Notes: Wowza Media Server™ or later is required.

If HE-AAC is used, variable bitrate mode cannot be used.

If HE-AAC is used, the audio sampling rate must NOT be any of the following values: 8000, 11025, 12000, 64000, 88200, or 96000 Hz.


HE-AAC configuration is done in the transcoder template. This example uses the audioonly.xml transcoder template. Edit this template and add the following <Parameter> to the Encode/Audio/Parameters:
Note: Older versions of the example transcoder templates do not include the <Parameters></Parameters> tags for the <Audio> encoding section. Add this set of tags if it is missing from your transcoder template.
Following is an example of the complete audioonly.xml template with the mainconcept.he <Parameter> added:
<!-- Example template for audio only transcoding to AAC from any supported audio codec -->
			<!-- Example Encode block for source, not required unless Member of StreamNameGroup. --> 
					<!-- H.264, PassThru, Disable -->
					<!-- AAC, PassThru, Disable -->
There are three possible values for this parameter:
0: Do not encode using high efficiency (default value).
1: Encode using the high-efficient version 1 (HE-AAC v1).
2: Encode using the high-efficient version 2 (HE-AAC v2).

There is a description of HE-AAC in the following article: High-Efficiency Advanced Audio Coding.

When using either HE-AAC setting, Wowza Media Server should log entries that indicate that the transcoded audio stream is half the sample frequency of the source audio stream. For example, if the source stream is 48000Hz, the transcoded HE-AAC stream will be 24000Hz. This is normal and indicates HE-AAC has been configured properly.

You will see the following log message in the wowzamediaserver_access.log file for a stream named myStream when you use the Wowza transcoder.
 INFO 200 myStream {name:"aac", bitrate:48000, codec:AAC, objectType:LC, sampleRate:22050, channels:2}

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