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Topic: Perceptual Audio Coding

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	[No title] (Site not responding. Last check: 2007-10-08)
		Perceptual audio coding systems attempt to encode an audio signal into an encoded signal that has lower information capacity requirements than the original audio signal, and then subsequently decode the encoded signal to provide an output that is perceptually indistinguishable from the original audio signal.
		In these two coding systems, as well as in many other perceptual coding systems, a split-band transmitter applies an analysis filterbank to an audio signal to obtain spectral components that are arranged in groups or frequency bands, and encodes the spectral components according to psychoacoustic principles to generate an encoded signal.
		Perceptual coding systems can be used to reduce the information capacity requirements of an audio signal while preserving a subjective or perceived measure of audio quality so that an encoded representation of the audio signal can be conveyed through a communication channel using less bandwidth or stored on a recording medium using less space.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=03/107329.031224&ELEMENT_SET=DECL (4630 words)

	Advanced Audio Coding - Wikipedia, the free encyclopedia
		AAC is a wideband audio coding algorithm that exploits two primary coding strategies to dramatically reduce the amount of data needed to convey high-quality digital audio.
		MPEG-4 audio standard does not require a single or small set of highly efficient compression schemes but rather a complex toolbox to perform a wide range of operations from low-bit-rate speech coding to high-quality audio coding and music synthesis.
		The MPEG-4 audio coding algorithm family spans the range from low bit-rate speech coding (down to 2 kbit/s) to high-quality audio coding (at 64 kbit/s per channel and higher).
	en.wikipedia.org /wiki/Advanced_Audio_Coding (1318 words)

	MPEG-1 Audio Layer 3 - Hutchinson encyclopedia article about MPEG-1 Audio Layer 3 (Site not responding. Last check: 2007-10-08)
		Audio compression format that uses perceptual audio coding and psychoacoustic compression to strip inaudible and unnecessary information from sound signals.
		The two competitors are MP4, which is a proprietary format based on MPEG-2 ACC technology, and Microsoft's Windows Media Audio (WMA), which is capable of producing a similar sound quality to MP3, but with half the file size.
		This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional.
	encyclopedia.farlex.com /MPEG-1+audio+layer+3 (185 words)

	Perceptual Audio Coding (Site not responding. Last check: 2007-10-08)
		Perceptual Audio Coding (PAC) is an algorithm, like MPEG 's MP3 standard, used to compress digital audio by removing extraneous information not perceived by most people.
		The Coding Institute Specialty-specific coding, reimbursement, and compliance publications, teleconferences, audio tapes and seminars, and continung education courses.
		Perceptual Science Group Part of the Department of Brain and Cognitive Sciences at MIT, researching human visual perception, machine vision, and image processing.
	www.serebella.com /encyclopedia/article-Perceptual_Audio_Coding.html (383 words)

	Electrical and Computer Engineering - Drexel University
		Perceptual audio coding is the method used in MP3, MPEG-2 AAC, computer audio distribution, movie audio codecs, DVD movie audio, and digital audio radio methods to reduce the bit rate of a PCM audio signal to something that the channel, storage methods, and/or media can support.
		Perceptual audio coding is the use of knowledge of the destination (the human auditory system) in order to discard irrelevant parts of a digital audio signal.
		The talk will cover basic coding methods, basics of the human auditory system relevant to coding, perceptual masking models, rate loops, noiseless compression methods, and stereo and multichannel coding at a tutorial level.
	www.ece.drexel.edu /calendar/seminars/Johnston.html (276 words)

	ipedia.com: Audio data compression Article (Site not responding. Last check: 2007-10-08)
		This should not be confused with audio level compression which reduces the dynamic range of audio signals, or companding, which uses both compression and complementary dynamic range expansion as a noise reduction techique for analog audio systems.
		Audio compression is a form of data compression designed to reduce the size of audio data files.
		The second reason is that values of audio sampless change very quickly, so generic data compression algorithms don't work well for audio, and strings of consecutive bytes don't generally appear very often.
	www.ipedia.com /audio_data_compression.html (744 words)

	TechOnLine - Introduction to Audio Codecs
		When there is a pause in the audio, you can save bits by replacing the samples of silence with a code that indicates the duration of the silence, then reinserting the missing samples during decoding.
		In direct audio coding, the main tradeoff is between bit rate and audio bandwidth.
		While perceptual coding goes a long way to reducing data rates for music and other wideband audio, it still falls short of the compression levels needed for wireless telephony applications.
	www.techonline.com /community/ed_resource/feature_article/36563 (2016 words)

	AES Releases Tutorial CD-ROM on Coding Artifacts (Site not responding. Last check: 2007-10-08)
		New York City--The Audio Engineering Society's (AES) Technical Council has launched a tutorial project on CD-ROM, "Perceptual Audio Coders: What to Listen For." Developed by the Technical Committee on Coding of Audio Signals, and produced by Dr. Markus Erne, the CD-ROM is the first of its kind to be produced by the AES.
		Perceptual audio coding is a relatively new field and exhibits completely different types of artifacts.
		"Perceptual Audio Coders: What to Listen For" will be especially helpful to audio professionals, including engineers, designers and students who are presented with audio material that has undergone audio compression, in which the process of coding artifacts takes place.
	www.prosoundnews.com /stories/2002/january/0116/0116.1.shtml (377 words)

	Basics about MPEG Perceptual Audio Coding
		Modern perceptual audio coding techniques (like MPEG Layer-3 or MPEG-2 AAC) exploit the properties of the human ear (the perception of sound) to achieve a size reduction by a factor of 12 with little or no perceptible loss of quality.
		Highest coding efficiency is achieved with algorithms exploiting signal redundancies and irrelevancies in the frequency domain based on a model of the human auditory system.
		For the audio quality of a coded and decoded audio signal the quality of the psychoacoustics model used by an audio encoder is of prime importance.
	www.harmoniccycle.com /harmonicweb/music-mp3-info-fraubasic.htm (804 words)

	Perceptual Audio Coders: Tutorial CD-ROM On Coding Artifacts (Site not responding. Last check: 2007-10-08)
		New York, January 11, 2002-The Audio Engineering Society's Technical Council has launched a tutorial project on CD-ROM, "Perceptual Audio Coders: What to Listen For." Developed by the Technical Committee on Coding of Audio Signals, and produced by Dr. Markus Erne, the unique CD-ROM is the first of its kind to be produced by the AES.
		In addition to the CD-ROM's inclusion of 8 different chapters on audio coding artifacts, there are 3 tutorials on audio coding principles designed to familiarize the reader with the underlying technology.
		"Perceptual Audio Coders: What to Listen For," is available for purchase at special introductory prices of $20.00 for nonmembers, $15.00 for members, $15.00 for student nonmembers, and $10.00 for student members.
	www.aes.org /publications/AudioCoding.cfm (428 words)

	Speech and Audio Coding (Site not responding. Last check: 2007-10-08)
		Audio coding is a technique sometimes referred to as perceptually lossless coding.
		The concept of perceptual audio coding eventually lead to the first transparent audio coder commonly referred to as PAC.
		Digital Audio Broadcasting (DAB) in the general sense means delivery of high quality digital audio from a single source (broadcast station) to many end users.
	www.bell-labs.com /org/1133/Research/SpeechAudioCoding/audio.html (758 words)

	ITU - DTTB Tutorial - Video & Audio Source Coding Pt4
		The "Audio Subgroup" of MPEG had the responsibility for developing a standard for coding of PCM audio signals with sampling rates of 32, 44.1 and 48 kHz at bit rates in a range of 32 to 192 kbit/s per mono and 64 to 384 kbit/s per stereo audio channel.
		For multichannel audio, the composite coding technique is very efficient, because there are a lot of correlation, both in the signal by itself, and in the binaural perception of such a signal.
		In the composite coding mode the irrelevant and redundant portions of the stereophonic signals are eliminated as consequently as possible.
	happy.emu.id.au /lab/tut/dttb/dtbtut3d.htm (1666 words)

	Method and apparatus for coding audio signals based on perceptual model (US5481614)
		Coding of high quality stereophonic audio signals is accomplished in a perceptual filterbank coder which exploits the interchannel redundancies and psychoacoustic.
		Using perceptual principles, switching between a normal and short window of input samples improve output signal quality for certain input signals, particularly those having a rapid attack.
		Switching is also accomplished between coding of left and right channels and so-called sum and difference channels in response to particular signal conditions.
	www.delphion.com /details?pn=US05481614__ (596 words)

	Advanced Audio Coding -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-08)
		Advanced Audio Coding (AAC) is a (additional info and facts about lossy data compression) lossy data compression scheme intended for audio streams.
		Although the AAC codec specified in (additional info and facts about MPEG-2) MPEG-2 Part 7 and the AAC specified in (additional info and facts about MPEG-4) MPEG-4 Part 3 are somewhat different, they are both informally known as AAC (for clarity it is best to refer specifically either to MPEG-2 AAC or to MPEG-4 AAC).
		These technologies significantly improve the performance of AAC at lower bitrates, and are used, for example, in (additional info and facts about Digital Radio Mondiale) Digital Radio Mondiale.
	www.absoluteastronomy.com /encyclopedia/a/ad/advanced_audio_coding.htm (452 words)

	Frequently Asked Questions about MPEG Audio Layer-3
		Therefore, audio on the Internet calls for an audio coding scheme that maintains sound quality as far as possible and allows real-time decoding on a large number of computer platforms without special add-on hardware.
		IS-13818-3 ("Audio") describes a backward compatible extension of MPEG-1 for multichannel audio coding ("surround sound", "multilingual sound") and a non-backward compatible extension to lower sample rates, to support sound applications with limited audio bandwidth requirements.
		For around 10 years, perceptual audio coding is a permanent topic at various scientific conferences; e.g., the AES (Audio Engineering Society) organizes two conventions per year.
	www.vishalkaranwal.8m.com /mp31.htm (5988 words)

	Overview of MPEG-2 AAC Audio Coding
		Applying perceptual coding methods, it is possible to pass studio-quality 15 or 20 kHz bandwidth audio over ISDN channels.
		When audio in a particular band falls below the masking threshold, few or no bits are devoted to encoding that signal, resulting in a conservation of bits that can then be used for the bands where they are needed.
		Its audio coding scheme is used in a wide variety of broadcasting, storage, and telecommunications applications.
	www.telos-systems.com /techtalk/mpeg (1044 words)

	Lucent Digital Radio announces new product line based on the Lucent Perceptual Audio Coder (PAC ^TM) (Site not responding. Last check: 2007-10-08)
		The new PAC coders, which offer transparent CD quality at 128 kilobits per second (Kb/s) and CD-like quality at 96 Kb/s, are available at a wide range of bit rates, from 16 Kb/s to 128 Kb/s.
		The PAC coders will be available to customers developing applications for transmission of digital audio over a variety of wireless and wireline channels.
		PAC Version 1.0 is optimized for low bit-rate transmission of voice and music with up to 8.0 kHz audio bandwidth.
	www.lucent.com /press/0499/990412.cob.html (692 words)

	Bibliography for J. D. Johnston (jj) (Site not responding. Last check: 2007-10-08)
		Kuo, S. and Johnston, J. ``A study of why cross channel prediction is not applicable to perceptual audio coding,'' 111 AES Convention, New York, NY, 21-24 September 2001.
		Johnston, J. ``Audio coding with filter banks'' in Subband and Wavelet Transforms, Akansu, A. and Smith, M. (Ed.), Kluwer, 1996.
		Princen, J. and Johnston, J. ``Audio coding with signal adaptive filterbanks,'' IEEE ICASSP, 1995, pp.
	www.research.att.com /resources/biblios/jj.html (1107 words)

	MPEG-4 AAC Standard (Site not responding. Last check: 2007-10-08)
		Advanced Audio Coding (AAC) is a wideband audio coding algorithm that exploits two primary coding strategies to dramatically reduce the amount of data needed to convey high-quality digital audio.
		First, signal components that are "perceptually irrelevant" and can be discarded without a perceived loss of audio quality are removed.
		Efficient audio compression is achieved by a variety of perceptual audio coding and data compression tools, which are combined in the MPEG-4 AAC specification.
	www.vialicensing.com /products/mpeg4aac/standard.html (185 words)

	MPEG Summary (Site not responding. Last check: 2007-10-08)
		Modern perceptual audio coding techniques (like MPEG Layer-III or MPEG-2 AAC) exploit the properties of the human ear (the perception of sound) to achieve a size reduction by a factor of 12 with little or no perceptible loss of quality.
		A perceptual subband audio encoder constantly analyses the incoming audio signal and determines the so-called masking curve, the threshold under which additional noise will not be audible by the human auditory system.
		It is a perfect complement to the perceptual coding: During big polyphonys, the perceptual coding is very efficient because many sounds are masked or lessened, but few information being identical, the Huffmann algorithm is very few efficient.
	www.delysid.org /alien/sound/mpeg/mpeg.html (5070 words)

	AudioVideo101.com - Audio/Video Dictionary - Perceptual Coding
		Method of reducing the amount of data in an audio or video signal by eliminating or reducing the data that human senses cannot perceive or cannot perceive well in a specific circumstance.
		Perceptual coding takes this into account and allocates more data storage to the areas where we will notice it and less to those where we will not.
		Perceptual coding uses the human senses to its advantage in order to use only what data storage is necessary in order to produce a signal that will appear the same as a non-encoded signal and thus use much less data.
	www.audiovideo101.com /dictionary/dictionary.asp?dictionaryid=340 (421 words)

	The Banff Centre Programs -CCRMA@Banff Summer Workshops: Perceptual Audio Coding
		Perceptual audio coders are currently used in many applications including Digital Radio and Television, Digital Sound on Film, Multimedia/Internet Audio, Portable Devices, and Electronic Music Distribution (EMD).
		The first part of the workshop addresses the basic principles of perceptual audio coding.
		In-class demonstrations will allow students to hear the quality of state-of-the-art implementations at varying data rates and they will be required to program their own simple perceptual audio coder during the workshop.
	www.banffcentre.ca /programs/program.aspx?id=153 (291 words)

	AUDIO CODING
		To appreciate the importance of coding digital audio efficiently and with quality which is essentially indistinguishable from that of an original CD, consider the bit rate that current CD's use to code audio.
		Current state-of-the-art coding algorithms, such as the Perceptual Audio Coder or PAC developed at ATandT Bell Labs, are capable of coding 2 channels of digital audio at a total bit rate of 128 kbps with essentially no loss in quality from that of the original CD coding [6,2].
		Such coders provide sufficient dynamic range for audio coding, but they do not reduce bit rates efficiently since they neither exploit statistical dependence between samples nor auditory masking effects [3].
	www.umiacs.umd.edu /users/desin/Speech/node13.html (575 words)

	Multiple Description Perceptual Audio Coding with Correlating Transforms - Arean, Kova, Goyal (ResearchIndex) (Site not responding. Last check: 2007-10-08)
		Abstract: In audio communication over a lossy packet network, concealment techniques are used to mitigate the effects of lost packets.
		A perceptual audio coder employing multiple description correlating transforms demonstrates this phenomenon.
		30 Transform coding of audio signals using perceptual noise cri..
	citeseer.ist.psu.edu /arean00multiple.html (455 words)

	Speech and Audio Coding, Processing and Recognition
		Shihua Wang and A. Gersho, "Interframe Coding of LPC Parameters with Band-Splitting VQ," Conf.
		Kenneth Zeger and A. Gersho, "Real-Time Vector Predictive Coding of Speech," Proceedings IEEE Inter.
		Cuperman and A. Gersho, "Vector Predictive Coding of Speech at 16 Kb/s," IEEE Trans.
	scl.ece.ucsb.edu /html/papers_E.htm (4031 words)

	AES 17th Conference in Florence - Tutorials (Site not responding. Last check: 2007-10-08)
		In this tutoral session we will present an overview of the basics of perceptual coding, including the usual blocks in a coder, for later reference during the rest of the tutorial sessions.
		This paper presents an overview of the filter-bank technologies used in the time to frequency mapping of perceptual audio coders.
		Perceptual audio coding has become an important key technology for many types of multimedia services these days.
	www.iis.fraunhofer.de /aes17/tutorial.html (357 words)

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