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

codec A codec is a device or computer program 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 on a signal or ...

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 sou ...

, 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 (1992–2005) headquartered in San Francisco, California, that made products such as Flash and Dreamweaver. It was purchased by its rival Adobe System ...

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 computer software for viewing multimedia contents, executing rich Internet applications, and streaming audio and video content created on the ...

6. (Macromedia is now

Adobe Systems Adobe Inc. ( ), originally called Adobe Systems Incorporated, is an American multinational computer software company incorporated in Delaware and headquartered in San Jose, California. It has historically specialized in software for the cre ...

.) 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 the source code, design documents, or content of the product. The open-source model is a decentralized so ...

Speex Speex is an audio compression codec specifically tuned for the reproduction of human speech and also a free software speech codec that may be used on VoIP applications and podcasts. It is based on the CELP speech coding algorithm.Xiph.OrIntro ...

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 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 I ...

).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, with support from other digital scientists in the United States and elsewhere. Origin ...

/ WAV. In July 2006, they announced that they have not been able to release the FLV/MP3 converter due to restrictions in Nellymoser license agreement. They found that they can 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 Patch or Patches may refer to: Arts, entertainment and media * Patch Johnson, a fictional character from ''Days of Our Lives'' * Patch (''My Little Pony''), a toy * "Patches" (Dickey Lee song), 1962 * "Patches" (Chairmen of the Board song ...

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 of vid ...

multimedia framework A multimedia framework is a software framework that handles media on a computer and through a network. A good multimedia framework offers an intuitive API and a modular architecture to easily add support for new audio, video and container formats ...

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 release with Nellymoser audio support is 0.5, released on March 10, 2009.

References

External links

Nellymoser Inc. website
* {{Compression formats Audio codecs