Depending on what is lost, this may result in an interpolation (to “guess” the content of the missing data), an error (where data are misread and the erroneous content is rendered in place of the correct content), or a total failure (where the signal may disappear entirely for a period of time). So when digital data are lost, the loss is final. Because these formats are meant to deliver content in real time, however, they can’t employ error correction there’s no time to re-send data packets which aren’t correctly received. One note: it’s often assumed that SPDIF digital audio, or DVI digital video, employ error correction. No matter how much jitter, how much rounding of the shoulders of the square wave, or how much noise, if the bitstream is accurately reconstituted at the receiving end, the result is as though there’d been no degradation of signal at all. While the signal will always degrade to some degree in the cable, if the receiving circuit can actually reconstitute the original bitstream, reception of the signal will be, in the end analysis, perfect. Second, a digital signal, because of the way its information is contained, can be quite robust. The more degradation in the signal, the harder it is for the receiving device to accurately measure the content of the bitstream. This makes it harder for the receiving circuit to accurately identify the transitions and thereby clock the incoming signal (causing the phenomenon known as “jitter”). Depending on the characteristic impedance of the cable, the capacitance of the cable, and the impedance match between the source and load devices, the corners of the square wave will round off to a greater or lesser degree, and the “flat” portions of the wave will become uneven as well. This means that while the signal may originate as a square wave, it never quite arrives as one. But while the alteration of an analog waveform is progressive and continuous–the more noise is introduced, the more noise will come out of our speaker along with the tone–the digital signal suffers alteration quite differently.įirst, a digital signal, because of its sharp transitions, is highly subject to degradation in its waveform those sharp transitions are equivalent to a long–indeed, an infinite–series of harmonics of the base frequency, and the higher the frequency of the signal, the more transmission line effects, such as the characteristic impedance of the cable, and resulting signal reflections (“return loss”) come into play.
Both are electrical signals, carried by a stream of electrons in a wire, and so both are subject to alteration by the electrical characteristics of the cable and by the intrusion of outside electrical noise. One of the interesting distinctions between digital and analog signals is that they degrade in rather different ways. Ideally, these transitions are instantaneous, creating what we call a “square wave.” This is so despite the fact that, when the signal is decoded, the result may be the very same 1000 Hertz tone, with its continuous slopes and lack of sharp transitions, represented by the analog signal described above.
#HOW AN BNC ANALOG TO DIGITAL VIDEO CONVERTER SERIES#
Instead, it consists of a series of “1” and “0” bits, encoded according to some particular standard, and delivered as a series of rapid transitions in voltage. If we could use that electrical signal to drive a speaker cone to physically move in and out in that same pattern, we’d hear the tone come out of the speaker.Ī digital signal, unlike an analog signal, bears no superficial resemblance to the information it seeks to convey. If the information is a 1000 Hertz sine-wave tone, for example, the analog signal is a voltage varying from positive to negative and back again, 1000 times per second, in a sine-wave-shaped pattern. An analog signal represents the information it is intended to convey by presenting a continuous waveform analogous to the information itself.
The first generation of video and audio cables were designed with analog signals in mind. To begin that discussion, let’s first talk about what digital and analog signals are, and how they perform in cables. Many of the best video cables on the market today were designed primarily for use in the digital domain but can a digital cable really perform well as an analog cable? Can an analog cable be used as a digital cable? What’s the difference, anyway, between digital and analog cables? They both move electrons, don’t they? All of these are interesting questions, and bear some discussion.
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