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Topic: Audio level compression

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	Audio data compression - Wikipedia, the free encyclopedia
		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 technique.
		As with image compression, both lossy and lossless compression algorithms are used in audio compression.
		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 (2102 words)

	Audio level compression - Wikipedia, the free encyclopedia
		Audio level compression should not be confused with audio data compression, which is used to reduce the size of digital audio files.
		Audio level compression, also called dynamic range compression, compression, or limiting, is a process that manipulates the dynamic range of an audio signal.
		Compression is used extensively in broadcasting to boost the perceived volume of the sound track while keeping it within strict limits (broadcasters in most countries have legal limits on instantaneous peak volume they may broadcast).
	en.wikipedia.org /wiki/Audio_level_compression (1313 words)

	Audio data compression - InfoSearchPoint.com (Site not responding. Last check: 2007-10-21)
		This should not be confused with audio level compression (also known as companding), which reduces the dynamic range of audio signals.
		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.infosearchpoint.com /display/Audio_data_compression (627 words)

	Audio level compression: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-10-21)
		By applying compression followed by gain compensation the overall volume of the track is increased without increasing its peak volume and the sound is perceived as louder.
		A compression artifact is a particular type of data error that is typically the result of quantization in lossy data compression....
		Audio mastering is the process of preparing and transfering recorded audio to a medium for future duplication....
	www.absoluteastronomy.com /encyclopedia/a/au/audio_level_compression.htm (1582 words)

	Compressions (Site not responding. Last check: 2007-10-21)
		For a gas the magnitude of the compressibility depends strongly on whether the process is adiabatic or isothermal, while this difference is small in a solid.
		At low speeds, the compressibility of air is not important for aircraft design, but as the airflow nears and exceeds the speed of sound, a host of new aerodynamic effects become important in the design of aircraft.
		Multimedia compression algorithms, traditionally known as codecs, work in a lossy fashion: #Transform the data according to a model designed to reduce sample-to-sample correlation, concentrating the important signal in a few data values.
	www.wwwtln.com /finance/47/compressions.html (1694 words)

	Audio signal distribution and level measurements
		Audio signals generated by microphones are suitably pre-amplified to line levels and distributed inside broadcast plants or to common carriers for land or satellite transmission.
		Typically, audio equipment designed to handle an SOL of +8 dBm is capable of handling output signal levels in excess of +18 dBm at a total harmonic distortion (THD) not exceeding 1 percent.
		The signal level is expressed in dBu and the SOL in North America is +4 dBu or +8 dBu.
	broadcastengineering.com /mag/broadcasting_audio_signal_distribution (1470 words)

	Compression in Audio Recordings
		Compression ratios of perhaps 2:1 are common, so the output will rise (or fall) by one unit for every two units of input change.
		If the maximum level of a car bomb exploding or a shotgun fired at close range were to be reproduced, and all conversations were at the normal level, no-one in the theatre would hear anything that was said, or would be deafened instantly by the explosions.
		Compression is commonly used in the final mix, and this is where things can go seriously wrong - everything is at the same volume, peak to average ratio is minimal, and the resulting sound is almost always worse than it was before the compression was applied.
	sound.westhost.com /compression.htm (3919 words)

	Chapter 4 MDL's Speaker Phone
		As the level reaches the top of the meter, the green bars turn red, indicating that the current level of input could be excessively high.
		Beneath the level meter is a field that displays the current status of the audio channel, displaying the word "Talking" when you are transmitting, and "Listen" when another conference member is speaking.
		When a conference member changes his audio compression setting, all other conference members are automatically set to the same value.
	www.mdlcorp.com /cusrunix/chap4.htm (1544 words)

	TVTechnology - Inside Audio
		Even more important, among all audio processing types, it is the family of processing that is hardest to "hear out," in the sense of objectively recognizing the compression effect, until it is truly gross.
		Finally, such processing needs to be able to recognize audio behaviors, including transient peaks and noise floors, plus the signal characteristics of such signal types as dialogue, FX and music content, so that its behavior can be altered to cope with these things and their various dynamic range.
		The effect of audio compression is almost always audible, so we can't ever expect our compression to yield a score of "5" on such a scale.
	www.tvtechnology.com /features/Inside-Audio/f_dm_inside_audio.shtml (1070 words)

	Audio level compression - (Site not responding. Last check: 2007-10-21)
		Audio level compression, also called compression or limiting, is a process that manipulates the dynamic range of an audio signal.
		Compression is used in sound recording and live sound reinforcement fields to improve the perceived quality of audio.
		That is, with a ratio of 4:1, if the input level is 4 dB over the threshold, the gain will be reduced so that the output level will only be 1 dB over the threshold.
	psychcentral.com /psypsych/Audio_level_compression (1354 words)

	Harmony Central®: Effects Explained: Compression/Limiting
		The horizontal axis corresponds to the input signal level, and the vertical axis is the output level (both measured in decibels).
		The compressor setting is usually stated as a ratio, such as 2:1, which means that the input level would have to increase by two decibels to create a one decibel increase in the output.
		When the level sensing function is a short time average, the compressor will take a little time before the gain is adjusted to meet the new input level.
	www.harmony-central.com /Effects/Articles/Compression (1713 words)

	Compression (Site not responding. Last check: 2007-10-21)
		The effectiveness of compression is measured by the amount by which the rate is reduced and the loss of quality in the result.
		The codec (the algorithm which compresses and decompresses the signal) uses a model of human perception to deliver a given data rate from a specific input stream.
		Although audio compression level may be chosen independently of video compression, MPEG 1 usually uses either MP1 or MP2 depending on the video data rate to be achieved.
	www.mrichter.com /cdr/primer/compress.htm (465 words)

	Television Production: Wrapping Up Television Audio - Audio Control Devices
		Since they respond to loud noises by quickly pulling down audio levels, this means that words can be lost when an AGC circuit reacts to a loud sound, such as someone bumping the microphone.
		Program audio that has been compressed seems louder to the ear than non-compressed audio, a feature that hasn't escaped the attention of the producers of TV commercials.
		By raising the input level while keeping the output the same, a greater compression is achieved, at least until major distortion becomes evident.
	www.cybercollege.com /tvp045.htm (1020 words)

	streamingmedia.com : business - technology - content
		Keep the audio level as loud as possible without driving the meter into the red -- this is especially critical in DV, where too much level can result in some particularly nasty distortion.
		A compressor consists of a level detector that measures the incoming signal, and an an amplifier whose gain is controlled by the level detector (fig.
		While a compressor can level out a recording, high levels of compression can also introduce artifacts including "pumping", in which there is an audible up and down change in volume of a track, or "breathing", which sounds like someone breathing as the background noise level goes up and down.
	www.streamingmedia.com /tutorials/audioforweb1.asp (1140 words)

	Lossless audio compression
		The question of compressing audio without any loss of quality (including especially without having to even think about how lossy a lossy algorithm is, because the binary bits are fully restored) is obviously important.
		Compression of these 6 second samples will no-doubt produce different ratios then compressing the entire file, due to variations in the sound signal from moment to moment.
		Compressing one section of a test file (03CC.wav) he found that the Windows and Macintosh file sizes were 57.03% and 56.50% respectively.
	www.firstpr.com.au /audiocomp/lossless (8593 words)

	iConference CL Microphone / VoiP Settings (Site not responding. Last check: 2007-10-21)
		To change the volume level at which the sound transmission is triggered, select a Threshold level.
		Select an audio compression level, to control the clarity and resolution of the sound itself.
		Levels 1-5: audio is sent at 8kHz, with increasingly higher compression and resolution.
	www.confhelp.com /voipsettings.htm (878 words)

	VideoHelp.com :: View topic - AC3 Dialogue Normalization in Vegas
		I bypass the Audio FX since I don't need any compression and I don't know how to set the compression, without bypassing it, so that the audio will not be compressed further.
		BJ_M, as far as I understand (being a sound engineer many years back), the audio level compression has nothing to do with bitrate -- it is about reducing the level differences between the loud parts ans soft parts of the audio track(s).
		All I need is a quick and simple way for setting in Vegas the audio level of movies, each captured at different audio level, so that the various movies' audio level will be of similar magnitude -- and similar magnitude to that of commercial DVDs.
	forum.videohelp.com /viewtopic.php?t=297758 (780 words)

	JBIG-KIT lossless image compression library
		JBIG (Joint Bi-level Image experts Group) is the committee that developed this international standard for the lossless compression of images through arithmetic coding.
		About 2 times better compression on typical 300 dpi documents compared to “gzip -9” on raw bitmaps.
		Even much better competitive compression results on computer generated images, which are free of scanning distortions.
	www.cl.cam.ac.uk /~mgk25/jbigkit (885 words)

	dbpowerAMP - some suggestions
		As an audio engineer and all around studio guy, I know that the higher the signal to noise ratio on any recording the better.
		Alternatively, if burning an audio cd, it is acceptable to normalize the wave produced before burning.
		A preset compressor, audio enhancer/ exciter, surround sound simulator plugin would be cool too.
	forum.dbpoweramp.com /showthread.php?t=2704 (1375 words)

	Audio, Books, Shopping and Publications Listing @ LaunchBase.net (Launch Base) (Site not responding. Last check: 2007-10-21)
		Blackstone Audiobooks - Oregon audio book shop with titles available for purchase or rent.
		Hall Graphics - The Sherman Experience Tapes is an audiobook collection of first-hand accounts of British Sherman tank veterans from World War II.
		Scholarly Audio - Bestselling nonfiction audiobooks by leading scholars and experts.
	www.launchbase.net /dir/Shopping/Publications/Books/Audio (295 words)

	W2IHY Dual Band Audio Equalizer and Noise Gate
		Professionals use the signal-shaping power of EQ as both a creative tool to give audio a desired personality and as a corrective tool to overcome frequency response excesses or deficiencies in equipment such as microphones.
		Audio guru Bob Heil recently wrote an article encouraging hams to pay much closer attention to their transmit audio and to not be shy about applying professional audio techniques wherever possible.
		The Noise Gate function is to remove audio signals with energy levels lower than the value established by the threshold.
	w2ihy.com /twoband.asp (2240 words)

	FAQ to Russian Anthems museum
		It is also important that normalizing, audio level compression, equalizer and any other automatic audio adjustment you may have as a feature in your ripper and encoder are all switched OFF.
		Certain educational uses of audio recordings do not requre permission from the rights holder in most countries; for other uses, please check the law.
		Those recordings which I also have on an audio CD or in a lossless format are usually published in the museum at 256 kbps bitrate and above.
	www.hymn.ru /faq-en.html (1704 words)

	W2IHY EQplus
		Art’s audio is a listening treat for everyone on the receiving end.
		Walter’s audio is a thrilling example of what is possible when using W2IHY audio processing on a radio with relatively narrow transmit bandwidth.
		Amateurs interested in the best possible audio from their radio often conclude the speech processor does more harm than good and operate with it turned off.
	w2ihy.com /eqplus.asp (2094 words)

	350008001 Applied Magic Magic Audio, Enhancement Tools to Improve or Change Sound
		Audio enhancement tools which allow you to improve or change the sound of music,voice over or ambient sounds.
		Noise Gate is used to turn off an audio channel except when a signal is present
		Compression audio level controls and balances the soft/loud passages of audio clips
	www.adorama.com /VDAMMA.html (163 words)

	Mobile Game Developer - TTPCom adds enhanced aacPlus audio compression to AJAR platform (Site not responding. Last check: 2007-10-21)
		This optimised implementation of the aacPlus compression technology enables TTPCom’s customers to address the growing music handset market without the need for extensive software development.
		The aacPlus open standard audio codec has been adopted by 3GPP for its ability to deliver superior audio quality at the lowest possible bit rates using limited memory capacity.
		Parametric Stereo from Coding Technologies and Philips again significantly increases the efficiency of audio codecs for stereo signals at low bit rates.
	www.mobilegd.com /article514.html (779 words)

	Streamingmedia.com: Audio for the Web
		Author Steve Cunningham offers insight into basic level-changing and filtering tools you can use in the production process to optimize the file for encoding.
		The downside of normalizing is that it increases the noise as well as the audio, and it may produce distortion in the encoded sound.
		To be notified when this and other tutorials are posted to the streamingmedia.com website, send a blank email to: join-tutorials@ls.streamingmedia.com
	www.streamingmedia.com /article.asp?id=5851 (1168 words)

	Ecamm Network: Conference Recorder - Record Movies From iChat
		Note that these estimates use a 15 frame per second rate.
		Sizes are per minute of recorded video with audio.
		Record Audio Only: Save disk space by recording just audio.
	www.ecamm.com /mac/conferencerecorder/settings.html (416 words)

	Diskwriter->Single file output - Hydrogenaudio Forums
		I have an image of audio CD, stored in APE-CUE (single APE).
		Process goes till first CUE track is finished and then stops and console says:
		INFO (foo_monkey) : Monkey's Audio compression level: Extra High
	www.hydrogenaudio.org /forums/index.php?showtopic=21651 (198 words)

	PodcastUser Magazine: Issue Two at PodcastUser Magazine (Site not responding. Last check: 2007-10-21)
		Great Job Guys, keep up the good work.
		I wish somebody can give a tutorial on audio level compression, this must be the most confusing thing in podcasting.
		Which is better, a software audio level compressor or a hardware audio level compressor?
	podcastusermagazine.com /2006/03/01/podcastuser-magazine-issue-two (412 words)

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