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Topic: Oversampling

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Upsampling

Undersampling

Sampling frequency

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	Spatial Oversampling: Why HD0 Broadcasting Makes Sense: John Watkinson BSc MSc FAES MBCS (Site not responding. Last check: 2007-10-20)
		In oversampling, the sampling rate is temporarily raised to allow a realizable optical filter to be used prior to digitizing.
		Oversampling may be used with interlaced cameras, but it is heavily sub-optimal, as it doesn't eliminate artifacts.
		Oversampling makes the transmission inherently scalable because the upconverter in the display is optional and lower cost receivers could omit it.
	www.microsoft.com /whdc/archive/ovrsamp.mspx (2980 words)

	15.1 oversampling (Site not responding. Last check: 2007-10-20)
		When we studied oversampling on the input, we learned that in order to bring down the oversample rate, samples are removed.
		Oversampling at the output stage of the digital audio system basically is a process whereby the player reads two samples, and additional values are "interpolated" in between the two.
		Oversampling is used to remove artifacts, which like the input LPF, is usually the job of the output LPF.
	csunix1.lvc.edu /~snyder/ovrsamplng2.html (374 words)

	Audio Allies Definition for: Oversampling
		Oversampling takes two successive (one after the other) samples of the digital data and then splices in additional samples that are interpolated to fall between the two, true originals.
		Oversampling would then add in blocks that are one foot two inches, one foot four inches, one foot six inches, one foot eight inches, and one foot ten inches to create a smoother curve.
		Oversampling helps digital-to-analog converters to operate smoother but it does not compensate for a digital signal with a true higher sampling rate and/or greater word length in bits.
	www.audioallies.com /GetFeatureDesc.asp?Feature=Oversampling (201 words)

	Upsampling vs. Oversampling
		Oversampling is typically used to describe a technique used when transferring beiween the analogue and digital domain, where a signal is sampled many times over and above that actually required by the sampling frequency.
		Oversampling in the context of the D-A process involves multiplying the sampling frequency by a whole number, typically between 4 and 32, or even higher.
		Oversampling, as well as easing the workload of the anti-aliasing filter, which can now operate more gently at a higher frequency, can also reduce distortion created when those analogue signals are first turned from continuous, analogue waveforms into stepped, digital, stair-like curves.
	www.aslgroup.com /dcs/upandover.htm (1973 words)

	NMR Data Oversampling and NUTS
		Oversampling is the act of acquiring data at a faster rate than necessary for the desired spectral window.
		One reason to oversample the data is that audio filters can have their cutoff frequencies set in the spectral region between SW and OSW.
		Oversampling, as discussed above, is acquiring data at a faster rate than necessary for the desired spectral window.
	www.acornnmr.com /appnotes/oversamp.html (627 words)

	[No title]
		Oversampling means that the frequency of the original clock signal is multiplied by a whole number (i.e.
		The idea is that when the converter chip runs at this higher frequency, the low-pass filter after the converter chip can be a simple second-order filter, as opposed to a sixth or higher order filter needed in the case of no oversampling.
		The PCM 1704, in contrast, is a parallel resistor type converter which requires any Oversampling to be done externally by another chip dedicated to this process.
	www.lessloss.com /types.html (1292 words)

	Theta Digital - Upsampling
		In oversampling, the digital data extracted from the CD at 44.1KHz is passed through a "digital filter", a device that performs a mathematical process on the data.
		The desired effect of oversampling is an alteration of the supersonic frequency spectrum.
		As stated previously, oversampling is a mathematical process applied to the digital audio data and is commonly called a "digital filter".
	www.thetadigital.com /upsampling.htm (2044 words)

	SoundStage! Getting Technical Back-Issue Article (11/2003)
		This occurred because oversampling increases the bandwidth from 22.05kHz to 176.4kHz.
		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.
		Oversampling, he says, can allow the use of a "lighter output reconstruction filter with all the benefits it brings, but we are not isolated from clock imperfections that would pass on to the 8 x Fs clock." Upsampling, on the other hand, can help to overcome the clock imperfections.
	www.soundstage.com /gettingtechnical/gettingtechnical200311.htm (2613 words)

	13.1 Oversampling
		Oversampling not only moves the filtering requirements from the analog domain to the digital domain, but also provides a less expensive yet better way to get good quality encoding without the need for expensive analog LPFs.
		In the following example, the sample rate (44.1 kHz) is doubled (2 x oversampled), resulting in a sample rate of 88.2 kHz with a Nyquist level of 44.1 kHz.
		In our example of 14 X oversampling, 13 of the 14 samples are removed leaving 1 sample that still provides the information needed to encode the signal amplitude.
	csunix1.lvc.edu /~snyder/ovrsmplg.html (722 words)

	Upsampling vs Oversampling for Digital Audio (Site not responding. Last check: 2007-10-20)
		Oversampling in the ADC has been around for quite a bit of time, while upsampling of audio that results in a simple rate conversion is relatively newer.
		Oversampling is performed at the ADC and then the signal is sent to the digital processing chain that does the filtering and any DSP operations.
		The key point is that the oversampling in the DAC and the oversampling in the ADC are both important parts of the processing that have been used for a very long time.
	audioholics.com /techtips/specsformats/upsamplingvsoversampling1.php (1383 words)

	The Compact Disc. How does it work?
		Oversampling is a simple, inexpensive device to filter out conversion side effects.
		Oversampling takes the sampling farther away from the audible range (from 44.1 to 176.4 kHz), so that ringing is eliminated.
		By oversampling the digital data four times (at 176.4 kHz instead of 44.1 kHz), the quantisation noise is moved further away from the audible range.
	library.thinkquest.org /26171/gforce.html (3856 words)

	Dr. Dobb's \| Digital Filtering and Oversampling \| July 22, 2001 (Site not responding. Last check: 2007-10-20)
		Oversampling is the technique of sampling a signal at a higher rate than would be required to just preserve the desired signal frequencies.
		Of course, the drawbacks to the oversampling approach are that the ADC must operate at the higher sampling rate and the processor must handle this higher data rate while performing additional processing on the data to implement the digital filter.
		The oversampling multiplier must be selected based on the ability of the ADC and CPU to convert and process the data at higher rates.
	www.ddj.com /184404066?pgno=1 (2835 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		Oversampling and averaging are techniques you can use to boost the resolution and the signal-to-noise (SNR) ratio of A/D conversions.
		Oversampling and averaging are done to accomplish two things: improve the SNR, and increase the effective resolution (i.e., increase the effective number of bits) of an A/D converter measurement.
		To understand the effects of oversampling and averaging on noise, you must first define what the quantization noise will be.
	archive.chipcenter.com /TestandMeasurement/tn034.html (598 words)

	diyAudio Forums - Is this how oversampling works?
		Oversampling is also sometimes called a "digital filter." That is a confusing term.
		Oversampling is only the process of making a DAC convert more samples per unit time than are available in the input stream.
		So if you oversample by 4, you are squeezing an extra 3 samples in the time interval between every two you already have giving you 176.4 kHz sampling frequency for CD audio.
	www.diyaudio.com /forums/showthread.php?postid=56067 (1637 words)

	Oversampling and bitstream methods in audio
		Oversampling and bit reduction techniques are mostly a matter of implementation—in theory, neither of them are needed to build robust, theoretically sound audio processing applications.
		Oversampling combined with digital filtering opens a way to nearly perfect A/D/A conversion and so it is a very important tool to any builder of audio systems.
		DSD is a straight forward application of a multichannel 64 times oversampling delta‐sigma conversion at some two and a half megahertz followed by direct transmission/storage of the resulting bitstreams and low order analog lowpass filtering for reconstruction at the reproduction side.
	www.helsinki.fi /~ssyreeni/texts/bs-over/bs-over.en.html (11379 words)

	OverSampled » About OverSampled (Site not responding. Last check: 2007-10-20)
		OverSampled is a project created by me, Abigail Garner, creator of FamiliesLikeMine.com and author of Families Like Mine: Children of Gay Parents Tell It Like It Is. Oversampled is an extension of the mission of FamiliesLikeMine.com, which is to decrease the invisibility of people with LGBT parents (i.e.
		The word “oversampled” comes from research practices in academia, for which queerspawn are often recruited to determine how we “turn out” which then is supposed to determine if gay people should have the “right” to raise children.
		Media echo this pattern of oversampling, when they are unable to locate kids of gay parents to go on record, and instead opt to approach already-interviewed kids reporters learned about from an earlier report by another media outlet.
	www.oversampled.net /?page_id=243 (297 words)

	soundberry NON oversampling
		When in 8 x oversampling and 20bit, that number would be 1.35ps (diagram 2).
		This means that under an average jitter environment, the oversampling can not operate theoretically, and lowers the accuracy within the operating field.
		Originally, oversampling was developed to allow the use of an analog filter with gentler characteristics as a post-filter, and not to increase the amount of information.
	www.soundberry.com /0-0001fb.html (1543 words)

	Oversampling Filters - Antialising Filters and Reconstruction Filters from Faraday Technology
		The main application of video filters is in the conversion from analogue to digital and digital to analogue for full broadcast standard signals.
		To reduce the complexity of the filter it is possible in many systems to employ oversampling techniques.
		It is usual to include a correction for this in the passband of the reconstruction filter.
	www.faradaytech.co.uk /products/about_oversampling_filters.htm (600 words)

	[No title]
		What an oversampling player does is to take the samples it reads (reading the disk only once) and by use of various 'curve-fitting' types of algorithms, works out intermediate values.
		Introduction: This is a broad and not-very-technical online summary of CD oversampling, antidotal to the lies and nonsense served up in consumer-audio retailing and an alternative to the well-intentioned but misleading or fractional explanations often seen in the popular audio press (including the so-called serious or high-end publications).
		Thumbnail Sketch of Oversampling Signals such as audio, stored digitally, entail a finite sampling rate (44.1 kilosamples/sec for the 12-cm CD) whereas in their natural (analog) form they are continuous-time waveforms (you can think of this usefully as an "infinite" sampling rate).
	archive.cs.uu.nl /pub/MIDI/DOC/oversampling (3458 words)

	Analog Devices: Analog Dialogue: Oversampling ADCs for 16-Bit Resolution
		Analog Devices has introduced two new CMOS high-speed 16-bit oversampling A/D converters for handling wideband signals with wide dynamic range in applications where low power, small footprint, and low-cost monolithic solutions are essential.
		The AD9260, using a 20-MSPS clock in an 8X oversampling mode (Figure 1), can output 16-bit signals at a 2.5-MHz word rate, providing a 1.01-MHz signal passband with 0.004-dB ripple and 100-dB SFDR (spurious-free dynamic range).
		When its throughput is suitable, the AD7723's low cost and special properties are useful in bandpass applications, where a standby condition is necessary, where choice of serial or parallel operation is required, and/or where an oversampling ratio of 16 or more is desirable.
	www.analog.com /library/analogDialogue/archives/32-1/oversampling.html (1230 words)

	Reducing ADC Quantization Noise
		Oversampling is based on the assumption that an ADC's total quantization noise power (variance) is the squared value of the converter's least-significant-bit (LSB) voltage divided by 12:
		Oversampling also assumes that the quantization noise values are truly random; this means that in the frequency domain, quantization noise has a flat spectrum.
		Thus oversampling by a factor of 4 (and filtering), reduces the quantization noise by 1 b.
	www.mwrf.com /Articles/ArticleID/10586/10586.html (1899 words)

	GPS timing receiver using oversampling - Patent 5748144
		Another advantage of the GPS timing receiver of the present invention is that it provides a GPS-derived time signal having a fine incremental time resolution by continuously adjusting a delay of a time signal in increments of the period of a clock signal.
		Another advantage of the GPS timing receiver of the present invention is that it uses oversampling for improving the incremental time resolution of a GPS-derived time signal by decreasing the period of the clock signal.
		The correlation subsystem 22 may optionally include a dither circuit 42 to vary (dither) the code time of arrival and/or frequency of the GPS replica signal according a dither sequence that is random or nearly random.
	www.freepatentsonline.com /5748144.html (3280 words)

	Oversampling UART Reduces RF Noise
		Oversampling at a rate of 10 times the bit rate with sample weighting, for example, will produce a result that is noticeably resistant to noise.
		If one uses the microcontroller interrupt to implement an oversampling, all of the system resources will be at the mercy of the interrupt handler.
		For example, the VHDL source file created for this oversampling project was based on a 20-MHz clock, 200-kbps data transfer rate, 12 B per frame, and a preamble of 8 b (SEE SIDEBAR).
	www.wsdmag.com /Articles/ArticleID/9032/9032.html (1433 words)

	SACD / SUPER AUDIO COMPACT DISC / The Sound of DSD: Oversampling/Upsampling and Noise Shaping.
		By applying an oversampling rate of four times (or a multiple of four times), the brickwall filter is not necessary to act at at 22.050 Hz., the frequency at which the filtering normally should take place.
		The measure of oversampling (4x, 16x, 32x, because designers started applying oversampling in multibit converters first and at a lower rate) determines the accuracy of the signal, especially the accuracy of the high frequencies.
		Through a high rate of oversampling, combined with the noise shaping, the highest frequencies sound friendlier but are less chiseled and less "clean".
	www.soundfountain.com /amb/noisesheng.html (2310 words)

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