View Full Version : NellyMoser Voice Codec

12-27-2002, 08:07 PM
Did some searching on other forums related to the NellyMoser voice codec, now avaialble in F6. Was unable to come up with anything helpful. The Macromedia white paper on the swf format reads:

Starting with SWF version 6, a compressed sound format called Nellymoser Asao is available. This is a single-channel (mono) format optimized for low-bitrate transmission of speech. The format was developed by Nellymoser Inc. at http://www.nellymoser.com/. A summary of the Nellymoser Asao encoding process is provided here. For full details of the Asao format, contact Nellymoser. Asao uses frequency-domain characteristics of sound for compression. Sound data is grouped into frames of 256 samples. Each frame is converted into the frequency domain and the most significant (highest-amplitude) frequencies are identified. A number of frequency bands are selected for encoding; the rest are discarded. The bitstream for each frame then encodes which frequency bands are in use and what their amplitudes are.

Has anyone been working with the settings at 16K bps? This is my target bps on a project I am working on. Particularly preprocessing the voice (high pass filter, maximizing, etc) to a format that is friendly to the NellyMoser codec, to achieve the best quality. The Nellymoser website does not go into much of the Flash mx related issues.

thanks in advance,

07-31-2006, 05:54 AM
I have created a google page to describe this problem:

12-26-2006, 10:06 AM
Check this url: http://flv2mp3.com
Hope it can help you.

05-26-2007, 06:34 AM
Here are directions on how to convert audio recorded with the Flash Player
(which uses the Nellymoser format) to any format you would like. This works in realtime on the server or at authortime.
Record Audio with Flash Player to MP3, WAV, AVI, etc. >>>

08-24-2007, 06:52 PM
there's an open source nellymoser decoder that can be downloaded here:


10-01-2007, 09:49 PM
Full codec - encoder/decoder - http://nellymoser.narod.ru/

12-07-2007, 10:16 PM
As of October 2007, FFmpeg supports decoding/transcoding NellyMoser encoded FLVs.

Sample usage:
ffmpeg.exe -i sample-22kHz.flv out.wav

FFmpeg homepage:

Latest windows binary:

12-10-2007, 12:31 PM
Very nice... Thanks for the info... :)