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Analogue vs. Digital and MPEG4

  1. Dec 11, 2003 #1

    jimmy p

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    Ok, i learned yesterday that Digital was old fashioned, which does in a way make sense because the waves are very basic (compared to analogue. Also i learned that Digital TV cut out around 95% of the information that would appear on an analogue wave. Instead of focusing on expanding digital processes, why cant they research improvements on analogue? I know that analogue waves are are subject to interference and when signals are picked up, there is a lot of background noise, so why cant we une UHF (ultra high frequency...if that exists) waves to counteract the wavelengths of background noise? It seems like a step backwards to have to use digital technology.

    Which leads me to my next question what is going to be different between MPEG2 and MPEG4, is it just gonna be minor tweaks to quality or are there gonna be radical changes?
  2. jcsd
  3. Dec 11, 2003 #2
    how does a discussion on analogue techniques lead you to MPEG???
    MPEG4 and MPEG 2 are different compression algorithms. see for yourself:

    PS: I feel so old fashioned
  4. Dec 11, 2003 #3


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    UHF is in common use, it is broadcast TV channels 14 and up.
    The trouble with noise on analog signals is that it is usually "white" which means it is comprised of a wide range of frequencies, to filter it out means that you must also filter out portions of your signal, thus losing fidelity. There are many difficuties inherent in analog transmissions that are not present in digital. A key one would be band width, a high defintion analog signal will require a very high band width, our broadcast bands are already crowded this increase in band width would shove many stations off the air. (Simply not enough room for them!) The higher your bandwidth the more expensive the electronic to reproduce it, the list continues. Why fight these fundamental problems when digital is avialble?
    You might explore the other forums on this board to find a more fitting place to post this question. (Technology would be a good start)
  5. Dec 11, 2003 #4
    well, two quick things that come to mind:

    - error detection/correction is extremely easy with digital signals.

    - filtering is also easy for digital signals. While a analogue filter is made of a lot of components and must be carefully designed, a digital filter can be made with DSPs in less than a day's work

    but don't worry, there will always be need for analogue design...
  6. Dec 11, 2003 #5
    Analogue is always superior to digital in picture quality. Why? Consider the light coming at you from any given object. It's a full wave. Digitising it means sampling it at various points of that wave, and sending the data about those sampled points only. So digital is always lower quality than analogue. But the nifty thing about digital is its ability to be manipulated and used by computers.
  7. Dec 11, 2003 #6


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    Actually, digital information is not inherently lower-quality than analog information.

    First, consider the fact that most compression standards (like mp3 and mpeg) remove information that is not psychologically important. In other words, as far as your ear or eye are concerned, the picture and sound are exactly the same. A lot of audiophiles (the sort of people who pay $100 per foot for premium speaker wire) claim to be able to distinguish CD audio from phonograph audio. When pushed into actually testing these claims in laboratories, the audiophiles can't do it.

    Second, consider the fact that the digital audio or picture information is reconstructed into an analog signal before it sent to the picture tube or the loudspeaker. With proper filtering, the quantization noise of the digital-to-analog converter can be virtually eliminated, allowing a digital receiver to produce a final signal that is not measurably different from an analog receiver.

    With high sample rates and good processing technology, the outputs of a digital and analog receiver are virtually indistinguishable. Your brain simply doesn't need all the "infinite" frequency content of an analog signal.

    Digital transmission, of course, means a longer range on your cell phone, no static or interference on your TV, no tape or vinyl record degradation for your audio and video entertainment, and so on. In addition, as has been mentioned, extremely high performance digital receivers can be built in software quite easily. An analog receiver with similar specifications would cost a fortune, take forever to build, and would require frequent tune-ups.

    - Warren
  8. Dec 11, 2003 #7
    Reconstructed signals are NOT the same as the original. They attempt to interpolate the data supplied, but can not rebuild exactly the original signal.

    Now, as for psychology, the thing is, human perceptions have thresholds which cut off data outside certain ranges from conscious perception. However, that does not mean the data outside those ranges does not enter our subconscious perceptions. Digital sampling techniques will take data from the range we consciously percieve, since that is what is tested for when people are developing the methods.

    There is a reason why HDTV and digitcal TV were having a Beta/VHS-style conflict for supremacy a while ago. Analogue (HDTV) is better picture quality, while digital allows more options for playing with the images.

    Once again, reconstructed signals using interpolation are NOT the same as original signals.
  9. Dec 11, 2003 #8


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    I didn't say they were exactly the same. I said they were not measurably different. This is subtle -- I just mean it can be very difficult to build measurement equipment sensitive enough to detect the differences. Your brain, by the way, is not a very accurate measuring device.
    I doubt you can provide any evidence that peoples' subconscious minds absorb the infinite spectral content in an analog signal, and that somehow it means an analog video or audio recording is somehow more pleasing. Give me a break, dude. That's just silly.
    Hint: HDTV is digital.
    Once again, if you have buy a $50,000 instrument just to be able to detect the difference between the two, that difference is totally irrelevant. In any event, your choice of speakers, enclosures, and acoustic environment, or your choice of display technology and room lighting are much more important.

    - Warren
  10. Dec 11, 2003 #9
    No, the senses don't take in EVERYTHING, But they do take in more than we consciously perceive.

    There have been Analogue and Digital HDTV systems. However, "HDTV" generally refers to the Analogue type since the battle was between high definition analogue (mostly from Europe), and digital (pushed mainly from America). The FCC in the USA basically sealed the deal and went with a high definition digital standard.
  11. Dec 11, 2003 #10


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    Prove it. Besides, if you can't consciously perceive it, why does it matter?

    Realize this: an analog signal contains an infinite amount of information. It contains some spectral information at every frequency, from dc to infinity. Unless you'd like to try to convince me your brain can receive (and process, and store) an infinite amount of information, your argument is moot. You can digitize a signal at a sample rate that will satisfy your conscious mind's apetite for information -- and your subconscious mind's, also, if you'd like to believe it somehow matters.

    - Warren
  12. Dec 11, 2003 #11


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    Along the same lines, the final analog signal is also never the same as the original. There is ALWAYS a loss in the transmission of an analog signal. This does not happen with digital - the final digital signal is identical to the original.

    There are technologies that make a sound signal digital from where it leaves the microphone, right into the speaker. These virtually eliminate losses associated with analog signals, as wherever the signal is digital, there is no loss.
  13. Dec 11, 2003 #12
    WTF have you been smoking? It's called sensory gating. First year psychology.

    Absolutely. Unless you discount as irrelevent the entire subconscious.

    I realise an analogue signal contains infinite data. And no, it is not moot, unless, as stated, you wish to discount entirely the whole of the subconscious mind. We perceive more than we know, and those perceptions do have effects on us. Does this mean analogue is better than digital? It depends what you wish to do with the signal. Digital is better for repeating and for doing funky things on the screen. Analogue is a better picture quality.

    No, you can't. Maybe some day we will have the ability to digitise and reproduce images with such high definition that there is absolutely no consciously or subconsciously discernible difference between analogue and digital, but that day has yet to arrive. Not in mass media, anyway.
  14. Dec 11, 2003 #13
  15. Dec 11, 2003 #14


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    I'll go look it up!
    The increase in quality is not, in general, measurable either by human perception or by machine.
    Follow this argument carefully.

    1) The brain does not have infinite storage.

    2) The brain does not have infinite processing capability.

    3) When presented with an analog signal with infinite spectral content, the brain must throw away some of it. See (1) and (2).

    4) The amount of the information NOT thrown away by the brain is finite.

    5) A high enough sample rate can encode any finite amount of data.

    6) A digital signal can thus carry all of the information your brain can handle.

    7) If both an analog signal and a digital signal utilize all of your brain's information-handling bandwidth, then the digital signal cannot be regarded as inferior psychologically.

    Which part of this do you disagree with?

    - Warren
  16. Dec 11, 2003 #15
    I've never seen any computer monitor with resolution as great as that of the human eye.

    It doesn't? Wow. That's news to me. I was under the impression that the precise mechnism for human memory is as yet unknown.

    It does, however, have far greater processing capacity than any computer on Earth.

    Reliant upon 1 and 2 being correct.


    Yes. But that does not equal the system encoding the entire analogue signal.

    Only if the brain's memory if finite, the digital system is superior in processing, and the sampling is of finer definition than can be detected even subconsciously by humans.

    True. IF.
  17. Dec 11, 2003 #16


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    Stand far enough away from it.

    I'm not talking about devices that have been built. I'm not talking about devices that we will be able to build soon. I'm talking about the very principles of digital versus analog implementation. As sample rate goes to infinity, the two descriptions become indistinguishable.
    No matter what mechanism it is, it's packed inside that three-pound lump of wet stuff you carry around. That lump of wet stuff still has to obey the laws of physics. You can't store an infinite amount of information in a finite space -- not in this universe anyway.
    I'm not sure I'd say that either. Especially, since, as you've said, the precise mechanisms used by the brain are not entirely known yet. I would be more inclined to say the brain is just a different type of computer altogether than man-made ones.
    Exactly. There's nothing fundamentally inferior about digital communication over analog communication. Thanks for being logical.

    - Warren
  18. Dec 11, 2003 #17
    by this argument, you have yourself disproved the notion of "an infinite amount of information". just as the brain must obey the laws of physics, so too must the medium carrying your analogue signal. it cannot carry an infinite amount of energy or information.

    so even in principle, an analogue signal cannot have information at all frequencies. they must have some cutoff. there is a limit to the resolution that, e.g. air can have for carrying sound waves.

    you can t have sound waves with wavelengths on the order of the size of an atom.

    all you must do is match this resolution with your digital sampling, and your digital signal will contain all the information of your analogue signal.
  19. Dec 11, 2003 #18
    its funny that on the one hand you claim that analogue contains an infinite amount of information, while digital contains a finite amount, but on the other hand, claim that digital is not inherently inferior quality.

    clearly, there is some limit in measurement, so perhaps digital is not measurably inferior to a pure mathematical analogue signal, but inherently the signals are as different as night and day.
  20. Dec 11, 2003 #19


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    A good point -- thanks for strengthening my argument. I was speaking in purely mathematical terms.

    - Warren
  21. Dec 11, 2003 #20
    From a practical view analog systems don’t deliver what your eye could see anyway. There are many reasons for this; limitations of the recording media, bandwidth limitations on broadcast signals necessitating compression of the analog signal, analog RF transmissions converted to digital by intermediate systems, the number of lines and pixels on the monitor you’re viewing with, etc, etc.
    Looking at a simple case such as an analog cassette tape, for example, it is immediately recognizable that the frequency response is lacking, and therefore not on par with what human ears can hear. It took high density tapes and noise reduction to yank the sound above the noise floor, and audio reproduction is much less demanding than video.
    The bottom line is engineering and economics, that is; what can we build, and who can afford it? Digital media is acceptable to hear and to view and I do not foresee it going away.
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