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Analog vs digital

Introduction

You often hear argued that a particular technology is so much better now that it is digital; when cassettes were replaced by CD's, when VHS was replaced by DVD, when NTSC television was replaced by ATSC digital television and so on. But is digital really better than analog? And, if so, why?

The truth is, the answer is a little more complicated that one type being flat out superior to another. However, for the people marketing a product, it is much simpler to propagate the illusion that digital is absolutely better than analog. Rather than making an intelligent argument for why one is better than another. If they can convince you it's better by mass marketing and commercialization, then all they have to do is put a digital sticker on it and they get people to buy it. Can you say, "Bah'ah'ah'!"

But for those interested in understanding the difference, here is a quick, albeit, highly simplified explanation. To start, you must understand what the goal is in any Analog or Digital systems. With regard to audio and video, it is a reference to a transmission system. In other words, how do they get the original performance, audio and/or visual from the point where it was captured to the point where it is delivered to your senses. So, everything from how they record the performance, store it, transfer it from one medium to another or one device to another to the point where it is reproduced in front of you can be done through analog means, digital means or as is often the case, a combination of both.

The nature of sound and sight is analog.

So what factors affect the quality of the performance as it passes through these phases? One thing you should understand is that that both sound and vision is, in its natural state, analog. Both the creation and reception is an analog process. Analog systems are based on a wav or pulse. For sound, whether it is coming from an instrument, a speaker or your vocal cords, the thing that is making the sound is making vibrations in the air which passes through the atmosphere to your eardrums which absorb the vibrations and send the message to your brain. With vision, the particles of energy that form light travel in a wave that are perceived by our eyes and formed into pictures in our brains. Sound is a result of accoustic waves and all sight is a reflection of light waves.

An analog system records these waves by getting an impression of them or converting them into a representational wav of proportional matching frequency and amplitude in another form such as electricity. However, the problem with analog recording systems is that the quality of the medium which captures it or through which the signal passes can affect the reproduction on the other end.

For instance, with a simple analog system like on old vinyl records, the record is made by cutting grooves into the vinyl surface. These grooves are not smooth, instead they have rough edges that will cause the needle (stylus) of the record player to vibrate, creating pulses, that reproduce the sound of the recording. This is then amplified and brought back to a listening level. However, imperfections on the surface of the vinyl and the quality of the vinyl itself affect the reproduction of the sound. You will get a low level hiss and pops along with other anomalies that were not a part of the original performance. The sounds waves have been distorted or "colored" by the medium.

The best analog recordings will be recorded onto a medium of high quality with few imperfections inherent to the media itself.

You can have the same effect on electrical waves passing through a copper wire. Poor conductive materials in a wire or fluctuations in density can color the resulting output. Because of this, better quality cables will affect the quality of the reproduction. But it is important to remember, better is not necessarily equal to more expensive, especially when it comes to cables. You should know what more money buys you in terms of cable quality and understand that there is a practical cap to what should be considered a reasonable price.

The digital solution.

Digital attempts to correct the problem of analog recordings and transmissions by plotting out the points of the wave that make up sound and vision through a set of binary instructions and connecting the dots. By converting to a set of instructions instead of a representational copy of the wave, distortion is eliminated because the instructions for the distortion is not encoded into the instructions. Where digital fails in comparison to analog is that, while points on a contiguous line are infinite, that is between any two distinct points on a line, there is always a point half way between them, digital instruction sets can only account for a fixed number of set points and must interpolate all other points in between. So while in theory, analog recordings represent the smooth linear transition from every infinite point on the line to the next, digital has gaps.

Increasing the digital bit rate (or sample rate) of a recording will increase the number of times different points are calculated, increasing the number of points plotted on the line, however, it will also increase file size. And no matter how high the bit rate is, it will never be infinite.

The reason that digital is still acceptable and can still reproduce performances that are nearly indistinguishable from the original is because of the limits of human perception. For audio, perfect human audible acuity is estimated to be between 20 Hz and 20,000 Hz. For vision, the bands lie between the spectrum of light visible to the human eye. Bands beyond our limits, such as infrared exist and are measureable, but can not be seen by the naked eye.

So bit rate is increased to provide a better digital capture of the original performance, however, extended bitrates create files that are too large to manage. So the next step in the digital process is compression. Compression removes details from the original file. It uses algorithms to filter data which is considered unnecessary from the digital instruction set. So, for audio, frequencies below and above 20 Hz and 20kHz respectively are removed. For video, bands of color beyond human vision and resolution that is not perceivable is removed. However, depending on the codec being used, compression can also remove, less perceivable, yet still perceived data such as dynamic range, contrast, gradation from one level to the next and so on.

The best digital files will have more bitrate and less compression.

Transmission of digital files across cables is not affected the same way analog signals are. Though the signal may suffer corruption in transmission, error correction can correct for some of it. If the transmission is overly distorted, the signal generally gets dropped completely. In this way, digital signal transmissions tend to be all or nothing. However, if the transmission is successful, the reproduction of the information will be perfect and true to its originally recorded quality. If the recording was originally done well, i.e., high bitrate, low compression, the recreation will be the same.

Conclusion.

So to answer which is better, the truth is there is a compromise between both. In a perfect world without the possibility of distortion, analog systems would already be perfect. But the nature of all things in our world is distortion. That is, music itself is a rhythmic blend of notes distorted to different degrees to produce pleasant sounds. The alternative being single notes without variation. Imagine if pianos where made without the sharp or flat keys, without pedals and each note had to be played as a quarter note. Many visual effects are the filmmakers abilities to distort the perception of what we see in order to effectively tell a story. So though distortion can be manipulated in some ways to give us what we want, it is also inherent in areas where they are not wanted and very difficult to remove. Digital attempts to replicate the natural world without the distortion, but will inherently fall short of perfection. All fall short of the glory of God.

As technology improves, so will our ability to replicate the natural world. However, there will never be a complete match to a live performance. Some audiophiles will say, I'm willing to live with the imperfections of an analog recording, amplified through analog tubes, so long as you deny me as little of every nuance of every note. The rest of us will probably say, I like the sound coming through my media player and the only thing I hear missing is the low level noise that shouldn't be there. To each his own. Realize, however, most system today are a blend that passes analog to digital back to analog and maybe converted several times again before getting to its destination.

One final note, some company's like to market a system as being all digital in order to imply there is less distortion due to conversion from analog to digital. However, while fewer conversions is better, conversion from one digital format to another digital format can be just as bad as analog/digital conversion and as stated earlier, all sound and vision must start and end as analog.