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Electronic signals -- as they originate in microphones and cameras -- are analog (or analogue) in form.

This means the equipment detects signals in terms of continuing variations in relative strength oramplitude.

In audio, this translates into the relative volume orloudness of the sound; in video, it's the relative

brightness of different areas of the picture.

As illustrated above, we can change these analog signals (on the left) into digital data (on theright). The latter is computer zeros and ones (0s and 1s, or binary computer code). The digital signal isthen sent to subsequent electronic equipment.

Backing up a bit, we need toexplain how the analog-to-digital

process works. The top part of theillustration below shows how an analogsignal can rise and fall over time toreflect changes in the original audio or

video source.

In order to change an analog signal todigital, that wave pattern is sampled ata high rate of speed. The amplitude ateach of those sampled moments (shownin blue-green on the left) is convertedinto a number equivalent.

These numbers are simply thecombinations of the 0s and 1s used incomputer language.

Since we are dealing with numericalquantities, this conversion process isappropriately called quantizing.

Once the information isconverted into numbers, we can do some interesting things (generally, visual effects) by adding,subtracting, multiplying, and dividing the numbers.

The faster all this is done, the better the audio and video quality. But this means that as the qualityincreases the technical requirements become more demanding.

Thus, we are frequently dealing with the difference between high-quality equipment that can handleultra high-speed data rates and lower-level (less expensive) consumer equipment that relies on areduced sampling rate. This, in part, answers the question about why some video recorders cost $300and others cost $100,000.

What's the Advantage of Digital Data?

Compared to the digital signal, an analog signal would seem to be the most accurate and idealrepresentation of the original signal.

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While this may initially be true, theproblem arises in the need for constantamplification and re-amplification of thesignal throughout every stage ofthe audio and video process.

Whenever an analog signal isreproduced or amplified noise isinevitably introduced, which degradesthe signal.

In audio, this can take the form of ahissing sound; in video, it appears as a subtle background "snow" effect. This is exaggerated in the

photo below.

By converting the original analog signalinto digital form, we can eliminate this noise buildup, even though the signal is amplified or "copied"

dozens of times.

Because digital signals are limited to the form of 0s and 1s, no "in-between" information (spuriousnoise) can creep in to degrade the signal.

We'll delve more deeply into some of these issues when we focus ondigital audio.

Today's digital audio and video equipment has borrowed heavily from developments incomputer technology -- so heavily, in fact, that the two areas are now merging.

Satellite services such as DISH and Direct TV make use of digital receivers that are, in effect,specialized computers. And you probably listen to music recorded on a pocket-sized device capable of

storing several hours of digitized music.

We discuss some of the advantages of digital electronics in video production

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