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Topic: Upsampling

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Oversampling

	Upsampling - Wikipedia, the free encyclopedia
		Upsampling is the process of increasing the sampling rate of a signal.
		For example, if compact disc audio is upsampled by a factor of 5/4 then the resulting sampling rate goes from 44,100 Hz to 55,125 Hz, which increases the bit rate from 1,411,200 bit/s to 1,764,000 bit/s.
		Unlike in downsampling which uses a low-pass filter as an anti-aliasing filter, upsampling uses an interpolation filter, which also is a low-pass filter.
	en.wikipedia.org /wiki/Upsampling (332 words)

	The DVD Chroma Upsampling Error (Site not responding. Last check: 2007-10-17)
		The chroma upsampling* error, or "chroma bug", occurs because a DVD (and also the current U.S. digital TV standard) only provides color for every other scan line.
		In other words, for film source material, scan lines 1 and 2 share the same color (it should be the average of the two scan lines), scan lines 3 and 4 share the same color, and so on, although light/dark detail may be unique for each line.
		*Upsampling -- The process of synthesizing additional scan lines or pixels to go between the one that we already have, so as to simulate having gathered more pixels (taken more samples of the original scene) in the first place.
	members.aol.com /ajaynejr/vidbug2.htm (2331 words)

	Theta Digital - Upsampling
		The word "upsampling" was brought to the vocabulary of high-end digital audio by a few companies to describe a digital process that they suggest is unique, and requires a different term from one already in use, "oversampling".
		Upsampling is a term some companies use to describe oversampling when it is done between the CD transport and the separate DAC (figure 6).
		While an upsampling device may help a poor DAC with a poor filter, it will degrade the performance of a superior DAC.
	www.thetadigital.com /upsampling.htm (2044 words)

	Untitled Document
		Upsampling is said to releave the digital signal contained in standard CD’s of its disadvantages, and bring it very close to the sonic qualities that SACD has to offer.
		In the process of explaining the working of the ‘upsampling’ process, we will in the meantime make our point that upsampling is in fact no more than hyped ‘oversampling’;, a 20-year-old technique that is around since the very first days of Compact Disc.
		So yes, upsampling càn sound better then standard oversampling, but it is not a new technique, more a marketing hype that is used to make CD survive in the battle between SACD and DVD-Audio.
	www.kuleuven.ac.be /iccp/2003/iccp13/upsamplingpage.htm (1670 words)

	Upsampling in Photoshop (Site not responding. Last check: 2007-10-17)
		Upsampling is an image-editing process that enlarges your original photo, making up (or interpolating) additional pixels to fill in the gaps.
		There are several upsampling techniques, and professionals are divided as to when and how the method should be used.
		It's important to realize at the outset that upsampling can't increase the detail in a image, and there are limits to its effectiveness.
	facweb.cs.depaul.edu /sgrais/upsampling_in_photoshop.htm (492 words)

	Upsampling vs. Oversampling
		Upsampling cannot increase the amount of information in a signal and the exact mechanism behind the perceived sonic improvements is currently not entirely clear.
		Differences in terminology between upsampling and oversampling may in part be down to semantics, but word-play doesn’t explain differences in perceived sound from ‘mathematically identical’ processes.
		Upsampling is a solely digital domain process where the data stream is also stretched out by interpolation — guessing the points in between, again mathematically — and is typically used to refer to small, non-integer changes, such as from 44.1 kHz to 48kHz.
	www.aslgroup.com /dcs/upandover.htm (1973 words)

	Upsampling CD's. If it can be done in hardware, it can be done in software right? - Topic Powered by eve community (Site not responding. Last check: 2007-10-17)
		There is apparently a plug-in for WinAmp that will upsample on the fly, there is also a program called SSPP (I think, anyway...) that will upsample but really you do NOT want to store upsampled.wavs unless you have a heck of a lot of free hdd space.
		While upsampling probably does allow you to use more relaxed low-pass filters in the DAC chain, these filters are not in place for anti-aliasing.
		CD players have been upsampling since the mid 80's, back then it was dubbed "oversampling." Oversampling or upsampling was first implemented by Phillips to shift digital to analog conversion distortion away from the audible freqency band allowing them to use simpler low pass filters than if they had used a straight 44.1Khz DAC.
	episteme.arstechnica.com /eve/ubb.x/a/tpc/f/67909965/m/5260935775 (3313 words)

	Oversampling vs Upsampling in Digital Audio (Site not responding. Last check: 2007-10-17)
		One major claim that the proponents of upsampling, or sample rate conversion claim is reduction of the effects of this jitter.
		However by upsampling to another rate and using a clock that is asynchronous to our original, the incorrectly sampled data can be somewhat corrected.
		While it is true that upsampling does help us in attenuating the amount of jitter caused by sampling errors and an inaccurate clock, whether this jitter is audible or not is a point of contention.
	audioholics.com /techtips/specsformats/oversamplingvsupsampling2.php (1238 words)

	Upsampling vs. Oversampling for Digital Audio
		Upsampling is on the other hand a rate conversion from one rate to another arbitrary rate.
		Upsampling would give us the same benefits in frequency response that we have gone over, however we can achieve the same effects by sufficiently oversampling our signal both at the DAC and ADC.
		Upsampling has no effect on our digital filter design problem since all our digital filters are FIR (finite impulse response) and all have linear phase.
	www.audioholics.com /techtips/specsformats/upsamplingvsoversampling.php (1393 words)

	SoundStage! Getting Technical Back-Issue Article (11/2003)
		Many authorities argued that oversampling and upsampling were mathematically the same, while others swore there were significant sound improvements with the new process.
		As Thierry explains, "The difference [between oversampling and upsampling] is, to my opinion, more related to the clocking and jitter problem as well as to the statistical distribution of errors or artifacts." Once again, this takes us full circle to the point that oversampling and upsampling occur in different parts of digital audio systems.
		From filters to oversampling to upsampling, the gap between the mathematical "perfect world," whose potential we first glimpsed in 1982, and the "real world with its imperfections," is steadily decreasing.
	www.soundstage.com /gettingtechnical/gettingtechnical200311.htm (2613 words)

	HTGuide Forum - More info on CD upsampling...please
		Upsampling is used to convert lower resolution sources (such as Redbook CD) into bitstreams compatible with modern 96/24 or 192/24 DACs.
		Oversampling was always a power of 2 upconversion, 2x, 4x, 8x, 16x, etc. For 2x oversampling, the DAC simply interpolated a sample (by averaging the two samples) in between two real samples, essentially adding 1 bit of "resolution" to the bitstream.
		Upsampling is a bit more sophisticated, since it isn't a simple doubling of the sample rate.
	www.htguide.com /forum/printthread.php4?t=8680 (474 words)

	DVD Player Benchmark - Chroma Upsampling Error
		The function that does the upsampling is called conver420to422 and it begins on line 467 in store.c.
		The upsampling process essentially fills in the missing scan lines of the image, without regard for the samples from the other field.
		So in the process, detail is left out of each field, and the upsampling process fills it in with what you could call a "best guess." That guess is different for each field, because the two fields have a completely different set of data to work from.
	www.hometheaterhifi.com /volume_8_2/dvd-benchmark-special-report-chroma-bug-4-2001.html (6028 words)

	SFSU Engineering 451 - Laboratory #5 - Upsampling and Downsampling (Site not responding. Last check: 2007-10-17)
		The purpose of this laboratory is to design and implement a routine that will resample (upsample and/or downsample) a sound.
		, you could upsample x[n] by a factor of 3 and then downsample the result by a factor of 2 to form the output sequence, y[n].
		function by upsampling or downsampling a segment of speech.
	robotics.eecs.berkeley.edu /~rvidal/engr451/resample.html#upsample (1011 words)

	onhifi.com -- Features Archives
		I explained upsampling as it had been explained to me and received blank looks of incomprehension from some of the finest digital engineers on the planet.
		"Upsampling almost always makes a difference, and it can make an improvement -- but it's not at all for the reasons most people are saying it is. Upsamplers come in two varieties -- built-in and external.
		Upsampling and oversampling are the very same thing and anybody who tries to tell you differently is misstating the case.
	www.onhifi.com /features/20010301.htm (1250 words)

	Multirate FAQ: Interpolation
		"Upsampling" is the process of inserting zero-valued samples between original samples to increase the sampling rate.
		Upsampling adds undesired spectral images to the signal at multiples of the original sampling rate, so unless you remove those by filtering, the upsampled signal is not "the same" as the original: it's "distorted".
		Compared to the straight-forward implementation of interpolation by upsampling the signal by stuffing it with L-1 zeros, then filtering it, you save memory by a factor of (L-1)/L. In other words, you don't have to store L-1 zero-stuffed "upsamples" per actual input sample.
	www.dspguru.com /info/faqs/multrate/interp.htm (1514 words)

	Winamp Upsampling Output Plugin - Topic Powered by eve community (Site not responding. Last check: 2007-10-17)
		Otherwise there can be no possible advantage to spending millions of CPU clock cycles upsampling an MP3 (or even an APE) to 96KHz when the DAC itself already does this (and more) quite competently.
		For anyone else, however, who has a sound card with a modicum of sanity in its design, such a plugin is complete folly; the DAC itself can handle the job far better, and with zero burden on the CPU.
		And there are the people on avsforum who swear that all their CDs sound better when they upsample them to 24/96 in Sound Forge.
	episteme.arstechnica.com /eve/ubb.x/a/tpc/f/67909965/m/2690918784 (730 words)

	Stereophile: MSB Link DAC III D/A converter
		I have heard upsampling now in three different systems: with the Dodson DA-217 MK2-D digital processor in the listening lair of my friend, Lars; with the dCS Elgar at Dick Sequerra's place; and in my own listening room, with the MSB Link DAC III, equipped with optional upsampling board.
		As with oversampling, one of the aims of upsampling is to push digital noise up to an area of higher frequency, where it can be rolled off by less drastic filters.
		With upsampling, the overall tonality was richer, riper, fuller.
	www.stereophile.com /budgetcomponents/276/index8.html (1932 words)

	chroma upsampling bug - Doom9's Forum (Site not responding. Last check: 2007-10-17)
		The one on the left was upsampled by the XviD decoder and the one on the right was upsampled by the AVISynth filter ConvertToRGB().
		If you use the opposite upsampling method to how the YV12 was downsampled in the first place, then it will look wrong, hence the 'chroma upsampling bug' as described.
		The issue of speed in the upsampling is quaite a aparent to what most ocmputers can handle and a slower version would screw 60% of xvid users.
	forum.doom9.org /showthread.php?t=90306 (1971 words)

	Problems with 96khz upsampling - Hydrogenaudio Forums
		As far as I know, from a technical point of view these upsampling hardware is of no logical use.
		Although, from a theoretical point of view, upsampling can't do anything to improve the signal, there's still the possibility that some DACs perform substantially better at 96 KHz than at 44.1 KHz.
		So in this case high quality upsampling would be good to overcome poorer performance of the DAC at 44.1 KHz.
	www.hydrogenaudio.org /forums/index.php?showtopic=6614 (1341 words)

	Stereophile: Upsampling or Oversampling?
		Editor: In January of the first year of the third millennium, John Atkinson reviewed some new DVD-As that had been originally recorded at 44.1 or 48kHz and then upsampled to 88.2 or 96kHz, and stated that there would be no potential advantage to doing that.
		Of the commercial units you have reviewed, to the best of my knowledge, all of these samplers and upsampling converters, except for the dCS 972 and Purcell models, are based on the Crystal Semiconductor CS 8420.
		Of course, some people may prefer the sound of the asynchronous converter on some recordings, because the vagueness of imaging is aesthetically pleasing (shades of vinyl?).
	www.stereophile.com /asweseeit/344/index1.html (1103 words)

	TNT Readers' corner - April 2005
		Thus using the l2s IC, the 24/192 upsampling in the DAC is bypassed, as you point out.
		Many agree that upsampling the digital stream from PCM 16/44 to 24/192 improves the sonics, and may even create analog-like sonic results.
		Secondly, the upsampling included in the transport allows to fully exploit all the potential of the I2S connection between transport and DAC.
	www.tnt-audio.com /feedback/april05.html (2285 words)

	[audioConnection] gryphon mikado cd player (Site not responding. Last check: 2007-10-17)
		The Gryphon Mikado integrated CD player uniquely embodies the third generation of Gryphon's advanced upsampling technologies, building on major advances made in the development of the world's first upsampling CD player, the Gryphon CDP-1, and further refined in the acclaimed Gryphon Adagio.
		Through upsampling, aliasing noise is shifted upwards in frequency and the upper corner frequency of the digital anti-aliasing filters will be more than doubled compared to the standard 44.1kHz sample rate.
		While extravagant claims are frequently made by manufacturers regarding the ability of upsampling to somehow "guess" at the missing bits in the audio stream and miraculously restore them, Gryphon readily acknowledges that upsampling cannot reconstruct lost information nor generate "new" information.
	www.audioconnection.com.au /product.asp?id=363 (843 words)

	Bel Canto DAC2 Half-Size 24/192 Upsampling D-to-A Converter by John Sunier (Site not responding. Last check: 2007-10-17)
		With major improvements in the basic processor chips resulting in much better sound from entry-level CD and DVD players, plus a number of super high-end all-in-one-expensive-box CD players such as the $20K Linn, it was beginning to appear that separate outboard DACs would become as unpopular as separate FM tuners or cassette decks.
		Unfortunately, none of the less costly upsampling approaches thus far have equaled the often amazing results on some standard CDs with the dCs upsampling processors, but several of them achieve considerably higher fidelity goals than the previous generation of non upsampling DACs.
		A major advantage of the upsampling approach is to avoid time smearing of transient information due to the brick wall high-freq.
	www.enjoythemusic.com /audiophileaudition/0902/belcantodac2.htm (1806 words)

	Systat Software Inc. - AutoSignal - Tutorials
		Click OK to close the upsampling procedure and answer Yes to updating the data table.
		This zero-insertion FFT procedure is fast, but is limited to integer upsampling ratios.
		When data are upsampled by a factor of 5, the Nyquist frequency also increases by a factor of 5.
	www.systat.com /products/AutoSignal/?sec=1042 (2357 words)

	[H]ard\|Forum - Just what is needed for a DVD upsampling HTPC? (Site not responding. Last check: 2007-10-17)
		Unlike a hardware designed to upsample input frames, software resize not handled by resizing 60 frames a second like those people implied, it resizes only the frames that actually exist.
		Really, more than anything else, he just wanted to get one for some deal having to do with some MS thing already and just the principle of the thing as they are a nice thing to have obviously.
		When he found out that practically no DVD players can (and by can I mean just simply refuse to) upsample a copyrighted video through component output, he was pretty dissapointed, and the HTPC idea he'd originally had got a little more interesting.
	www.hardforum.com /showthread.php?t=922271 (4609 words)

	GW Labs DSP Review - APR02 AUDIOPHILE AUDITION
		There is no denying that what it does in upsampling 44.1 digital data to 96K or 192K can bring many standard CDs close to the high resolution levels of many DVD-A or SACDs.
		I had thought that perhaps the upsampling would be more successful on much older CDs that suffered from problems of digititus that have been cleared up in most releases of the last few years.
		It’s enhancement features aside from the upsampling might be similar to what the Superdrives achieve - although the Taddeo works on phase in the analog domain - quite a different approach.
	www.audaud.com /audaud/APR02/EQUIP/equip2APR02.html (1630 words)

	Simaudio Upsampling Article
		The goal of this article is to explain the reality of these technical concepts, leaving all myth aside, and to provide a better understanding of what is really happening with this aspect of digital audio technology.
		This gave rise to the marketing hype with the concepts of upsampling and upconversion, which claims could upsample or upconvert your 16-bit/44.1kHz CD to a 24-bit/96kHz resolution digital signal prior to the digital to analog conversion, resulting in DVD-audio like quality from CD.
		However, the "latest and greatest" upsampling method is not necessarily better than the classic oversampling method.
	www.simaudio.com /upsampling.htm (1448 words)

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