Nellymoser Asao Codec
Encyclopedia
Asao is a proprietary single-channel (mono) codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

 and compression format optimized for low-bitrate
Bitrate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....

 transmission of audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

, developed by Nellymoser Inc.
Nellymoser
Nellymoser, Inc. is a privately held company that specializes in mobile computing. Its main products include the Nellymoser Platform and Media On-Demand, Music Companion & Infotainment On-Demand Mobile Advantage Packs.- Corporate history:...



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
Macromedia was an American graphics and web development software company headquartered in San Francisco, California that produced such products as Flash and Dreamweaver. Its rival, Adobe Systems, acquired Macromedia on December 3, 2005 and controls the line of Macromedia...

 licensed Nellymoser's Asao speech and audio compression software to be part of FlashMX
Adobe Flash
Adobe Flash is a multimedia platform used to add animation, video, and interactivity to web pages. Flash is frequently used for advertisements, games and flash animations for broadcast...

 and Macromedia Flash Player 6. (Macromedia is now Adobe Systems
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...

.) 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
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

 Speex
Speex
Speex is a patent-free audio compression format designed for 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. Speex claims to be free of any patent restrictions and is licensed under the revised BSD...

 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
Real Time Messaging Protocol
Real Time Messaging Protocol was initially a proprietary protocol developed by Macromedia for streaming audio, video and data over the Internet, between a Flash player and a server...

 protocol to an RTMP server (Flash Media Server, Wowza Media Server
Wowza Media Server
Wowza Media Server is unified server software developed by Wowza Media Systems. The server is used for streaming of live and on-demand video, audio, and RIAs over public and private IP networks to desktop, laptop, and tablet computers, mobile devices, IPTV set-top boxes, internet-connected TV...

).

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. sell 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
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...

/WAV
WAV
Waveform Audio File Format , is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs...

. 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.

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
Digital Millennium Copyright Act
The Digital Millennium Copyright Act is a United States copyright law that implements two 1996 treaties of the World Intellectual Property Organization . It criminalizes production and dissemination of technology, devices, or services intended to circumvent measures that control access to...

. 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 Nelly Moser codec.

In September 2007, a patch
Patch (computing)
A patch is a piece of software designed to fix problems with, or update a computer program or its supporting data. This includes fixing security vulnerabilities and other bugs, and improving the usability or performance...

 based on "nelly2pcm" was sent to FFmpeg
FFmpeg
FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...

 multimedia framework
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 and transmission protocols...

 development mailinglist. In October 2007, a patch for decoding Nellymoser audio was added to FFmpeg SVN. As of December 3, 2008, the open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

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.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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