Cisco Support Community
Community Member

Changing audio format for messages?

Is there a way to change the compression rate or something similiar for messages and prompts? <br><br>


Re: Changing audio format for messages?

yes, you can set the default WAV format to one of four different codecs.

The system ships with MuLaw 8K/sec setup as the default WAV format. We use this as the default since it sounds the best, of course, and it's also natively supported by all versions of Windows and Mac OSes. As such if you send a voice mail to someone who does not have VMO installed, they can always open the email and just play the WAV attachment.

The system also supports ALaw (also 8K/sec), and 3K/sec ADPCM and 4K/sec ADPCM formats. Be aware, however, if you change the default to one of the ADPCM formats, users who get a voice mail in their inbox and don't have VMO installed will not be able to play the attached WAV file unless they've installed the Windows ADPCM codec (I don't believe there is an ADPCM code for Mac). You can get this off AVs web site at ""

Just for reference, a 60 second message in MuLaw takes up around 480K of storage space, where as 4K ADPCM is around 240K. There's some space for message headers and the like but you'll find that formula holds true.

If you want to change the default WAV format, it changes it system wide for all messages and voice names. To change it does require a registry edit, and as usual proceed with extreme caution when editing anything in the registry.

Open your favorite registry editor and head to "HKLM|Software\Active Voice\MIU\1.0\Initialization". You'll see a key there called "Default WAV Format". It'll be set to "3" for MuLaw. For 3K ADPCM set it to 1, for 4K ADPCM set it to 2. This will require a restart of Unity before it takes affect.

BTW, other WAV formats are coming soon (i.e. G.729a and the like). Stay tuned.

Jeff Lindborg
Unity Product Architect
Active Voice Corp

CreatePlease to create content