The terms "analog" and "digital" are used when it comes to store or transmit the representation of a signal (audio, video, etc...). A signal lives in the real world in an analog form. For a while now, humans have been looking for ways to transmit and store such signals. Transmissions use mediums such as electrical wires or waves in the atmosphere. Storage typically involved magnetic media or engraving a vinyl disk.

Digital? Digital is different than analog storage/transmission in that it is discrete. Let me take an example:

I want to measure a temperature.

• I can read my mercury thermometer. That's the analog way of representing a temperature. Pro: Given good tools, you can be very accurate. In fact, this level is in one unique place that no one would be able to fully measure. Absolute precision. Drawback: Two people coming to read the temperature might read slightly different numbers depending on their mood...
• Or I can just read the temperature from my digital thermometer. That's the digital way. Pro: As long as the text is readable, no one will doubt the temperature written. 25.3 is it (for example). Drawback: This is just an approximation of the real temperature. An infinite number of digits would be needed to represent the real temperature.

And there you go: Here is the real theoretical difference between digital information over analog information:

1. Digital information can be - in theory, and assuming it can be read at all - cloned without loss.
2. The drawback is that it is always an approximation of the measurement.

A side effect of the benefit of digital vs. analog is that the information stored on a medium will age differently:

• With analog storage, the information will loose definition over time, but given that the medium is still readable (as opposed to a broken LP for example) the core of the information will still be there after a while, with reduced quality. The perfect example is photos printouts from our grandparents. A lot of the color information is lost, but the picture is still there.
• With digital storage, the information will not degrade over time. For as long as the medium is still readable, the data stored onto it will be readable in the exact form it was stored. When the medium start being only partially readable, chunks of data becomes unreadable. For example, if you store pictures on a CD-ROM and scratch the CD in one place, you will have probably lost some of your pictures entirely and the rest will still be intact.

To conclude, here are the pros and cons of digital:

1. Digital information can be cloned without loss.
2. If the medium remains readable, there is no quality loss over time.
3. But the data stored is an approximation of its analog representation.

And if you hear someone talking about "The Digital Quality", you will know that digital doesn't imply quality. Proof: a cinema movie is of greater quality than a DVD, and yet the DVD is digital and the film is analog. In both worlds, the quality of restitution is dependant on the storage type and how it was designed and engineered, not the medium itself.

So, "The Digital Quality" doesn't mean anything. It just assert the digital nature of the information.

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Posted by pieroxy on February 13, 2005 5:48:00 AM PST #