{{short description|Audio codec standard}} '''Asao''' (also known as '''Nellymoser''' audio codec) is a proprietary single-channel (mono) codec and compression format optimized for low-bitrate transmission of audio, 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 licensed Nellymoser's Asao speech and audio compression software to be part of FlashMX and Macromedia Flash Player 6.<ref>Nellymoser, Inc. (2002-03-04) {{cite web|url=http://www.nellymoser.com/company/news-macromedia.htm |title=Macromedia Selects Nellymoser's Asao Compression Technology for FlashMX |access-date=2017-04-18 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20030724233145/http://www.nellymoser.com/company/news-macromedia.htm |archive-date=July 24, 2003 }}, Retrieved on 2009-08-12</ref><ref>Adobe Inc. (2008) [http://help.adobe.com/en_US/Flash/9.0/flashforair/help.html?content=legal.html Flash CS3 - Legal Notices], Retrieved on 2009-08-11</ref> (Macromedia is now Adobe Systems.) 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 Speex codec.<ref>AskMeFlash.com (2009-05-10) [https://web.archive.org/web/20090415032211/http://askmeflash.com/article_m.php?p=article&id=2 Speex vs Nellymoser], Retrieved on 2009-08-12</ref>) 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).<ref>MultimediaWiki [http://wiki.multimedia.cx/index.php?title=Nelly_Moser Nelly Moser], Retrieved on 2009-08-11</ref><ref name="lynch-extracting">Mark Lynch (2008-07-23) [https://web.archive.org/web/20091013223924/http://www.lynchconsulting.com.au/blog/index.cfm/2008/7/23/Extracting-from-sound-from-Flash-aka-NellyMoser-codec-sucks Extracting from sound from Flash (aka NellyMoser)], Retrieved on 2009-08-12</ref><ref>(2002-12-27) {{usurped|1=[https://web.archive.org/web/20050108121838/http://www.actionscript.org/forums/showthread.php3?t=20430 NellyMoser Voice Codec]}}, Retrieved on 2009-08-12</ref>

== 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.<ref>Marco Casario (2005-04-14) [http://casario.blogs.com/mmworld/2005/04/flv_created_by_.html FLV created with FCS and nellymoser audio codec], Retrieved on 2009-08-13</ref><ref>FlashComGuru Forum (2006) {{usurped|1=[https://web.archive.org/web/20090823072015/http://www.flashcomguru.com/forum/forum_posts.asp?TID=1842&PN=1&TPN=1 Convert on2 to mp3 / flv to mp3?]}}, Retrieved on 2009-08-12</ref><ref>LiSoG (2006-10-06) [http://www.lisog.org/projekte/supported_projects/bounty-programm/nellymoserasaocodec-bounty.pdf Open Source Tender: Implementation of an Audio Codec Compatible with Nellymoser Asao Codec (PDF)] {{Webarchive|url=https://web.archive.org/web/20061013232714/http://www.lisog.org/projekte/supported_projects/bounty-programm/nellymoserasaocodec-bounty.pdf |date=2006-10-13 }}, Retrieved on 2009-08-12</ref><ref>[http://nellymoser.codec.googlepages.com/ Nellymoser Codec - How many people have run into the same problem?] {{Webarchive|url=https://web.archive.org/web/20090904141803/http://nellymoser.codec.googlepages.com/ |date=2009-09-04 }}, Retrieved on 2009-08-13</ref> Nellymoser Inc. sold a decoder for thousands of US dollars.<ref>Gnash Project Wiki [http://wiki.gnashdev.org/Nellymoser Nellymoser] {{webarchive |url=https://web.archive.org/web/20090818080515/http://wiki.gnashdev.org/Nellymoser |date=August 18, 2009 }}, Retrieved on 2009-08-12</ref><ref>FlashComGuru (2006-07-31) {{usurped|1=[https://archive.today/20130123043508/http://www.flashcomguru.com/index.cfm/2006/7/31/nellymoserlinks Nellymoser Link List]}}, Retrieved on 2009-08-12</ref><ref>Andrew Paul Simmons (2007-05-22) [http://blog.andrewpaulsimmons.com/2007/05/recording-audio-with-flash-player-to.html Recording Audio with Flash Player to MP3, WAV, AVI, etc.] {{webarchive |url=https://web.archive.org/web/20090813161148/http://blog.andrewpaulsimmons.com/2007/05/recording-audio-with-flash-player-to.html |date=August 13, 2009 }}, Retrieved on 2009-08-12</ref><ref>FlashComGuru (2007) {{usurped|1=[https://web.archive.org/web/20071024220839/http://www.flashcomguru.com/forum/forum_posts.asp?TID=1842&PN=1&TPN=13 Convert on2 to mp3 / flv to mp3?]}}, Retrieved on 2009-08-12</ref>

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/WAV.<ref>Steve Wolkoff (2006-03-16) [http://article.gmane.org/gmane.comp.web.flash.server.devel/9685 How to export FLV audio] {{Webarchive|url=https://web.archive.org/web/20090818053259/http://article.gmane.org/gmane.comp.web.flash.server.devel/9685 |date=2009-08-18 }}, Retrieved on 2009-08-13</ref> 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.<ref name="avsguy2">Burak KALAYCI (2006-03-08) [http://www.asvguy.com/2006/03/extracting_flv_.html Extracting FLV Audio (2)] {{Webarchive|url=https://web.archive.org/web/20091001212833/http://www.asvguy.com/2006/03/extracting_flv_.html |date=2009-10-01 }}, ASVGuy SWFBlog, Retrieved on 2009-08-13</ref><ref>FlashComGuru (2006-10-03) {{usurped|1=[https://web.archive.org/web/20061017141818/http://www.flashcomguru.com/index.cfm/2006/10/3/flv2mp3 Adobe comments on FLV to MP3 conversion tool]}}, Retrieved on 2009-08-12</ref>

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.<ref name="lynch-extracting" /><ref>Google Code [https://code.google.com/hosting/takenDown?notice=7281&project=nelly2pcm nelly2pcm - Project Taken Down] {{webarchive |url=https://web.archive.org/web/20100609170331/https://code.google.com/hosting/takenDown?notice=7281&project=nelly2pcm |date=June 9, 2010 }}, Retrieved on 2009-08-12</ref><ref>Audio/video stream recording forums (2008) [http://stream-recorder.com/forum/splitting-nellymoser-flv-extracting-raw-nelly-moser-t2902.html?s=0793436087d882ac2680c320420668cf&amp; Splitting Nellymoser FLV (extracting raw Nellymoser stream from FLV file)], Retrieved on 2009-08-13</ref> There were also some other attempts for creating free Nellymoser decoder.<ref>Moxie Marlinspike (2007-07-03) [https://archive.today/20130415225944/http://www.thoughtcrime.org/software/nellynomore/index.html nellynomore], Retrieved on 2009-08-13</ref> 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.<ref>FlashComGuru Forum (2006) {{usurped|1=[https://web.archive.org/web/20110711005642/http://www.flashcomguru.com/forum/forum_posts.asp?TID=1842&PN=9&TPN=10 Convert on2 to mp3 / flv to mp3?]}}, Page 10, Retrieved on 2009-08-13</ref>

In September 2007, a patch based on "nelly2pcm" was sent to FFmpeg multimedia framework development mailinglist.<ref>(2007-08-11) [http://ffmpeg.org/pipermail/ffmpeg-devel/2007-September/038976.html FFmpeg-devel - PATCH - NellyMoser audio decoder]</ref> In October 2007, a patch for decoding Nellymoser audio was added to FFmpeg SVN.<ref>[http://labs.wichers.nu/2007/10/17/nellymoser-decoding-support-in-ffmpeg/ NellyMoser decoding support in ffmpeg!] {{webarchive |url=https://web.archive.org/web/20090804115952/http://labs.wichers.nu/2007/10/17/nellymoser-decoding-support-in-ffmpeg/ |date=August 4, 2009 }}, Retrieved on 2009-08-12</ref><ref>(2007-10-31) [http://guru.multimedia.cx/2007/10/ Lair Of The Multimedia Guru - FFmpeg weekly news #2 - October 2007], Retrieved on 2009-08-12</ref><ref>(2007-10-15) [http://ffmpeg.org/pipermail/ffmpeg-devel/2007-October/037853.html FFmpeg-devel - PATCH - NellyMoser audio decoder v2]</ref> As of December 3, 2008, the open source FFmpeg project has encoding and decoding support for the Nellymoser Asao codec.<ref>{{ cite web | title = FFmpeg News | url = http://ffmpeg.mplayerhq.hu/ | author = FFmpeg | date = 2008-12-03 | access-date=2009-08-12 | archive-url= https://web.archive.org/web/20090318061009/http://ffmpeg.mplayerhq.hu/| archive-date=March 18, 2009| url-status= live}}</ref><ref>{{ cite web | title = FFmpeg Supported Audio Codecs | url = http://ffmpeg.mplayerhq.hu/general.html#SEC3 | author = FFmpeg | access-date=2009-08-12 }}</ref> Stable version 0.5, with Nellymoser audio support, released on March 10, 2009.

== References == {{reflist}}

== External links == * [https://web.archive.org/web/20030629213736/http://nellymoser.com/products/audio_compression_asao_fst.htm Nellymoser Inc. website] * {{webarchive |url=https://web.archive.org/web/20030629213736/http://nellymoser.com/products/audio_compression_asao_fst.htm |date=June 29, 2003 |title=Nellymoser Asao - historical website from 2003 }}

{{Compression formats}}

Category:Audio codecs