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Topic: Audio data compression

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	Encyclopedia at AudioXchange: Audio data compression - Online Store & Product Reviews
		Audio compression is a form of data compression designed to reduce the size of audio data files.
		In contrast to image compression, lossless audio compression algorithms are not nearly as widely used.
		Most lossy audio compression algorithms are based on simple transforms like the modified discrete cosine transform (MDCT), that convert sampled waveforms into their component frequencies.
	www.audioxchange.com /encyclopedia/Audio_compression.shtml (604 words)

	Vorbis Codec by LEAD -Vorbis Audio Compression (Site not responding. Last check: 2007-10-18)
		The LEAD Vorbis Audio Codec is a DirectShow® filter for compressing and decompressing audio data using the Vorbis compression algorithm.
		Vorbis is an audio compression method used to store digital music or any audio data.
		Vorbis is an open and free audio compression (codec) project.
	www.leadcodecs.com /Codecs/LEAD-Vorbis.htm (177 words)

	Datapan.com - Audio Data
		Audio compression is a form of data compression designed to reduce the size of audio data files.
		The primary users of lossless compression are audio engineers, audiophiles and those consumers who want to preserve the full quality of their audio files and who disdain the quality loss from lossy compression techniques such as Vorbis and MP3.
		In contrast to the speed of compression, which is proportional to the number of operations required by the algorithm, here latency refers to the number of samples which must be analysed before a block of audio is processed.
	www.datapan.com /audio.html (954 words)

	Audio data compression - Wikipedia, the free encyclopedia
		Audio compression is a form of data compression designed to reduce the size of audio files.
		Audio compression algorithms are typically referred to as audio codecs.
		Perhaps the earliest algorithms used in speech encoding (and audio data compression in general) were the A-law algorithm and the mu-law algorithm.
	en.wikipedia.org /wiki/Audio_data_compression (2098 words)

	[3.0] MPEG Video & Audio Compression (Site not responding. Last check: 2007-10-18)
		The luminance data for a macroblock is sent as four 8x8 luminance blocks, while the decimated chrominance data for the entire macroblock is sent as one 8x8 chrominance block.
		For example, the audio data on a standard music CD is stored as 16-bit samples taken as a rate of 44.100 kilohertz (kHz), and so in principle the highest frequency in the stored audio is 22.05 kHz.
		In MPEG-1 audio compression, each individual frame is converted from a time-domain signal to a frequency-domain spectrum by an FFT, or more often a DCT; the spectrum is modified according to rules of perceptual coding; and then the spectrum is converted back into a time-domain signal by an inverse FFT or DCT.
	www.vectorsite.net /ttdcmp3.html (5501 words)

	data reduction: Ear damage by MP3, DVD and digital television?
		The danger of this exploitation of human perception flaws is that especially by lossy audio data compression sound portions get destroyed those, although the brain would not pass them to the conscious awareness, are likely necessary for the human hearing's own perpetual calibration.
		The basic principle of modern audio data reduction is, that is to say, to omit during storage exactly those sound portions those an average human being would not consciously perceive.
		The lossy (neuroacoustic) audio data reduction does now basically nothing else than to simulate the interferences of the cochlea and their compensation circuits in the brain.
	infolab.stanford.edu /~nsample/MP3-risk.html (1233 words)

	CUTTING IT FINE
		Compression implies a reversible process (you can expand the compressed material to restore the original) but the majority of data reduction strategies are lossy, meaning that data is thrown away irretrievably.
		They allow audio signals with a wide dynamic range to be stored on a tape medium with a restricted range -- just as we try to squeeze a large amount of digital audio data onto a medium with a restricted data transfer rate.
		Data reduction systems usually only reveal their weaknesses with very complex signals, so you might prefer to record your final mix on a linear PCM format, but data reduction can offer more benefits than drawbacks for the multitrack recorder.
	www.soundonsound.com /sos/aug98/articles/datacompression.html (3386 words)

	MPEG Audio Layer 3 backgrounder (Site not responding. Last check: 2007-10-18)
		Techniques for reducing digital audio data rates were first applied to early digital telephone systems in the 1960s.
		First, analog audio is converted to 16-bit linear data, typically using one of the standard sampling rates of 32, 44.1, or 48 kHz.
		The data rate of a digital audio signal is the product of sampling rate multiplied by the sampling resolution multiplied by the number of audio channels.
	www.audioactive.com /intro/papers/sidebar1.html (562 words)

	Audio Box Inc. - Compression on a Windows PC
		Audio Box Inc. - Compression on a Windows PC Compression on a Windows PC Audio Compression can be one of two categories, lossless or lossy.
		Lossy Audio Compression can yield a variety of different rates of compression based on the ability of your hardware and software to decode and playback the music audio data in real-time.
		There are various compression schemes to achieve different results; for example, many codecs remove portions of the audio signal that human hearing is less sensitive to.
	www.audioboxinc.com /compression.html (1061 words)

	Speech Compression
		With current compression techniques (all of which are lossy), it is possible to reduce the rate to 8 kbps with almost no perceptible loss in quality.
		Further compression is possible at a cost of lower quality.
		ADPCM (32000 bps) This is speech compressed using the Adaptive Differential Pulse Coded Modulation (ADPCM) scheme.
	www.data-compression.com /speech.html (940 words)

	TTA - Biocrawler (Site not responding. Last check: 2007-10-18)
		True Audio (abbreviated TTA) is a free, simple real-time lossless audio codec, based on adaptive prognostic filters which has shown satisfactory results comparing to majority of modern analogs.
		TTA performs lossless compression on multichannel 8, 16 and 24 bit data of uncompressed wav input files.
		The compression ratio of TTA depends on the type of music file being compressed, but after compression the size will generally range between 30% - 70% of the original.
	www.biocrawler.com /encyclopedia/TTA (290 words)

	MPEG Audio Layer 3 backgrounder (Site not responding. Last check: 2007-10-18)
		Audio can also play a primary, rather than a supportive, role by providing a continuous stream of audio that the Web user "tunes into." Most providers of such services are radio stations or networks, who simply put their channels on the Web.
		The audio compression used in applications such as Nevot and VAT was a very primitive pulse-code modulation (PCM) nearly identical to that used in the dial telephone system.
		Special preprocessing techniques such as multiband dynamic range compression and equalization, long used by traditional broadcasters to enhance over-the-air signals, can also be applied to audio signals before digital conversion and data compression, to lessen the audibility of the compression's artifacts.
	www.audioactive.com /intro/papers/archive_papers/webcast.html (3394 words)

	Lossless compression/decompression of digital audio data (US5884269)
		An audio signal compression and decompression method and apparatus that provide lossless, realtime performance.
		Uncompressed audio data samples are first processed by a prediction filter which generates prediction error samples.
		A block structure for the compressed data and a decoder for reconstructing the original audio signal from the compressed data are also disclosed.
	www.delphion.com /details?pn10=US05884269 (348 words)

	TTA - Hydrogenaudio Knowledgebase
		TTA (True Audio) audio codec is a free, simple real-time lossless audio encoder/decoder, based on adaptive prognostic filters which has shown satisfactory results comparing to majority of modern analogs.
		TTA performs lossless compression on multichannel 8, 16 and 24 bit data of the WAV audio files.
		The compression ratios of TTA depend on the type of music file being compressed, but the compression size will generally range between 30% - 70% of the original.
	wiki.hydrogenaudio.org /index.php?title=TTA (131 words)

	TVTechnology - Audio Notes
		As the data rate is lowered, the frequency at which this coupling occurs can be lowered to save additional bits; however, there are certainly audible limits to this technique as the ear does eventually become more discriminating.
		This can be due to many factors, including a data rate that is simply too low to support the desired audio quality, or even audio that is difficult to encode due to noise or other bit-wasting content.
		If you know that the audio will be passed through a subsequent coding generation, make sure to keep the data rates as high as possible at all stages.
	www.tvtechnology.com /features/audio_notes/f_audio_notes-02.18.04.shtml (1400 words)

	DataCompression.info - Audio (Site not responding. Last check: 2007-10-18)
		Compression is one of them, and there is certainly a great deal to learn about compression and media formats at this conference.
		Like other lossless compression schemes the data reduction varies with the source, but it is generally between 25% and 50% for typical popular music and somewhat better than that for classical music and other sources with greater dynamic range.
		It shows up on the data compression radar by virtue of the fact that SoX is able to convert between a wide variety of compressed formats, ranging from MP3 and Ogg to ADPCM and linear PCM.
	www.dogma.net /DataCompression/Audio.shtml (8863 words)

	Digital Compression
		In a lossy compression scheme, as the name implies, some of the original information is discarded when it is compressed.
		One proponent of Lossless Compression is Etree.org a music distribution hub but not for audio that has been compressed in a lossy fashion like MP3 or AAC but for audio that has been compressed in a lossless way.
		Etree.org uses the Shorten (.shn) audio compression format because it creates an exact clone of the original source.
	www.puredigitalaudio.org /digitalcompression/index.shtml (713 words)

	Audio DesignLine \| How audio codecs work - Psycoacoustics
		Lossy audio data compression is based in the principle that some audio information is not perceivable and is therefore discardable.
		Masking is used in audio compression to determine which frequency components can be discarded or more compressed.
		Various audio codecs utilize psychoacoustic models of differing complexity and accuracy to determine what pieces of the audio signal are extraneous.
	www.audiodesignline.com /howto/showArticle.jhtml?articleID=175800470 (1218 words)

	Audio data compression - Article from FactBug.org - the fast Wikipedia mirror site
		Note: This article is about audio data compression, which reduces the data rate of digital audio signals.
		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.
		Useability of lossy audio codecs is determined by:
	www.factbug.org /cgi-bin/a.cgi?a=2318 (981 words)

	TechOnline \| A Fast Algorithm for Computing Two Channel Odd Frequency Transforms with Application to Audio Coding (Site not responding. Last check: 2007-10-18)
		The problem in optimizing this algorithm for real data results from the pre-multiplication step which renders the data complex thus eliminating the symmetry that would have existed in the DFT of data (if it was real).
		For example, an audio disc (CD) stores a stereo audio signal comprised of two 16-bit data words sampled at 44.1 kHz; thus about 1.41 million bits/second of audio data are output from the player.
		Audio compression algorithms or audio codecs are designed to decrease the data rate of audio signals in order to reduce the size of audio files for various applications.
	www.audiodesignline.com /showArticle.jhtml?articleID=192200244 (2848 words)

	Rane Professional Audio Reference (D)
		DCE (Data Communications Equipment) Within the RS-232 standard, the equipment that provides the functions required to establish, maintain, and terminate a connection, as well as the signal conversion, and coding required for communication between data terminal equipment and data circuit -- e.g., a modem or printer.
		DI (digital audio input) AES3 (and IEC 60958-4) abbreviation to be used for panel marking where space is limited and the function of the XLR AES3 connector might be confused with an analog signal connector.
		DO (digital audio output) AES3 (and IEC 60958-4) abbreviation to be used for panel marking where space is limited and the function of the XLR digital AES3 connector might be confused with an analog signal connector.
	www.rane.com /par-d.html (6480 words)

	Windows Media Audio - Biocrawler (Site not responding. Last check: 2007-10-18)
		The resulting file may have the filename suffix "wma" or "asf" with the "wma" suffix being used only if the file is strictly audio.
		Windows Media Audio supports digital rights management using a combination of elliptic curve cryptography key exchange, DES block cipher, a custom block cipher, RC4 stream cipher and the SHA-1 hashing function.
		The most current version of the format is Windows Media Audio 9.1 which includes specific codecs for lossless, multi-channel surround sound and voice encoding in addition to the main lossy codec.
	www.biocrawler.com /encyclopedia/WMA (415 words)

	Audio Box Inc. - Digital Extraction
		PCM WAV data: According to the preset characteristics, the digital data is represented as PCM (Pulse Coded Modulation) data.
		Compression: Audio data can be stored in full quality, full sized form or compressed and stored on the hard drive.
		PCM WAV data: To the preset characteristics, limited by the quality of the sound system, the digital data is represented as PCM (Pulse Coded Modulation) data.
	www.audioboxinc.com /digitalanalog.html (277 words)

	AUDIO OPTIONS FOR DVD-VIDEO
		Uncompressed stereo PCM audio is supported in DVD-Video at resolutions of 16, 20, or 24 bits and sampling rates of 48 or 96 kHz (any combination of these resolutions and sampling rates can be used).
		Stereo audio may also be prepared using data compression.
		The spec states that a stream of either uncompressed linear PCM or data-compressed audio must be included with each track of a disc (there can be up to eight streams), and that if audio is in data-compressed format only, then at least one stream must be AC-3.
	emusician.com /mag/emusic_audio_options_dvdvideo (699 words)

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