Asao (also known as Nellymoser audio codec) is a proprietary single-channel (mono)

codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...

and compression format optimized for low-

bitrate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...

transmission of

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...

, developed by Nellymoser Inc.

Technical details

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. This codec does not take into consideration actual sample rate, and has fixed ratio between input samples amount and output packet size (2 bits per input sample).

Use in Flash technology

On March 4, 2002 Nellymoser Inc. announced that

Macromedia Macromedia, Inc. was an American graphics, multimedia, and web development software company headquartered in San Francisco, California, that made products such as Adobe Flash, Flash and Adobe Dreamweaver, Dreamweaver. It was purchased by its riv ...

licensed Nellymoser's Asao speech and audio compression software to be part of FlashMX and Macromedia

Flash Player Adobe Flash Player (known in Internet Explorer, Firefox, and Google Chrome as Shockwave Flash) is a discontinuedExcept in China, where it continues to be used, as well as Harman for enterprise users. computer program for viewing multimedia c ...

6. (Macromedia is now

Adobe Systems Adobe Inc. ( ), formerly Adobe Systems Incorporated, is an American software, computer software company based in San Jose, California. It offers a wide range of programs from web design tools, photo manipulation and vector creation, through to ...

.) The Nellymoser Asao codec is an integral part of the Flash-plugin since Flash version 6, released in 2003. The codec is optimized for real-time and low-latency encoding of audio. Flash Player clients, when recording audio from a user's microphone, can use the Nellymoser Asao codec. (Flash Player 10 released in 2008 also supports the

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

Speex {{More citations needed, date=May 2025 The Speex project is an attempt to create a free software speech codec, unencumbered by patent restrictions. Speex is licensed under the BSD License and is used with the Xiph.org Foundation's Ogg containe ...

codec.) The sampling rate of the audio capture can be controlled by the Flash programmer to increase and decrease encoding bitrate and quality. Encoding is done on the client host, and compressed data is then sent using Adobe's

RTMP RTMP may refer to: * Real-Time Messaging Protocol, a multimedia streaming and remote procedure call protocol primarily used in Adobe Flash * Routing Table Maintenance Protocol, part of the AppleTalk network stack * Royal Tyrrell Museum of Palaeon ...

protocol to an RTMP server ( Flash Media Server,

Wowza Media Server Wowza Streaming Engine (known as Wowza Media Server prior to version 4) is a unified streaming media server software developed by Wowza. The server is used for streaming of live and on-demand video, audio, and rich Internet applications over ...

).Mark Lynch (2008-07-23
Extracting from sound from Flash (aka NellyMoser)
Retrieved on 2009-08-12

Use in other technology

At the time of the release of Flash Player 6 in 2003, there was no free or open source software for encoding and decoding Nellymoser audio. Nellymoser Inc. sold a decoder for thousands of US dollars. In March 2006, Adobe Systems' people posted to ''Flash Server development newsgroup'' information about an on-coming new tool for FLV audio (including Nellymoser audio) conversion to

MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany under the lead of Karlheinz Brandenburg. It was designed to greatly reduce the amount ...

WAV Waveform Audio File Format (WAVE, or WAV due to its filename extension; pronounced or ) is an audio file format standard for storing an audio bitstream on personal computers. The format was developed and published for the first time in 1991 ...

. In July 2006, they announced that they have not been able to release the FLV/MP3 converter due to restrictions in their license agreement with Nellymoser. They found that they could only distribute this tool to be used with licensed copies of Flash Media Server.Burak KALAYCI (2006-03-08
Extracting FLV Audio (2)
, ASVGuy SWFBlog, Retrieved on 2009-08-13 In 2007, a project called "nelly2pcm" was created. In 2008, this project was removed from Google Code in response to a complaint under the U.S.

Digital Millennium Copyright Act The Digital Millennium Copyright Act (DMCA) is a 1998 United States copyright law that implements two 1996 treaties of the World Intellectual Property Organization (WIPO). It criminalizes production and dissemination of technology, devices, or ...

. There were also some other attempts for creating free Nellymoser decoder. Some apparently use a "wrapper" to force the flash ocx to play audio faster (e.g. 1:4 ratio), which redirects and grabs the audio output (wave) and then encodes it to MP3. This method does not use a licensed Nellymoser codec. In September 2007, a patch based on "nelly2pcm" was sent to

FFmpeg FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing vide ...

multimedia framework A multimedia framework is a software framework that handles Electronic media, media on a computer and through a network. A good multimedia framework offers an intuitive Application programming interface, API and a modular architecture to easily a ...

development mailinglist. In October 2007, a patch for decoding Nellymoser audio was added to FFmpeg SVN. As of December 3, 2008, the

FFmpeg project has encoding and decoding support for the Nellymoser Asao codec. Stable version 0.5, with Nellymoser audio support, released on March 10, 2009.

References

External links

Nellymoser Inc. website
* {{Compression formats Audio codecs