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Noob questions, how would you explain tech to a newbie?
SacRat
post Apr 8 2004, 17:55
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Several times I've been asked to explain people principles of lossy music coding. This was especially hard as those, who asked knew nothing about psychoacoustics and has troubles with math.
Just wondering: what would you do on my place? For example, how could you explain technical differences between MP3 and AAC to your friend while sitting in the bar and drinking beer?


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sven_Bent
post Apr 8 2004, 18:49
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the same way you would talk about the difference on a red and a green car to a blind :-)
impossible

you cannot explain technical details un technical..because then they would be untechnical and not tecnical details...


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SebastianG
post Apr 8 2004, 19:28
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I once compared it to dolby's noise reduction system.

digital <-> analog
--------------------
transmitting digital audio samples with fewer bits <-> noisy analog channel
sophisticated noise shaping (mp3/aac) <-> multi-band compressor / noisy transmission / expander

in the end bitrate reduction is achieved by
- removing "impercible" informations (introduces noise)
- entropy coding (lossless stage like ZIP and stuff)

This is already a VERY simple explanation of the idea behind the magic (without going deeper into psychoaccoustics and "how-to-do-it-actually")

I guess, a comparison between MP3 and AAC would be impossible without getting technical. wink.gif

bye,
Sebi

This post has been edited by SebastianG: Apr 8 2004, 19:35
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Steve
post Apr 8 2004, 19:35
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Had to rewrite a paper in non-technical language for a composition class at the professor's request. I basically did these things:

Relate what is happening to things they do in every day life, using analogies and metaphors
Show how this relates to them in particular, by explaining possible uses, etc
Break it down into bite-sized pieces, to decrease the intimidation of a new concept
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Sebastian Mares
post Apr 8 2004, 20:04
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Example of the difference between lossy and lossless:

Image being in a forest and hearing the beautiful sound of the birds, of the trees, while suddenly an airplane flighs above you. During the airplane's flight, the sound of the birds and of the forest seems to be gone, while instead, the sound of the plane's engines can be heard.

Now, storing this situation losslessly would require you to include the sound of the birds, of the forest and of the engines (although you can actually only hear the engines, everything must be saved).
Lossy compression methods will analyze which parts of the sound can be heard and which not. It will then discard the parts which are not relevant and only include the parts which are significant.

This post has been edited by Sebastian Mares: Apr 8 2004, 20:07


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Pio2001
post Apr 9 2004, 21:52
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Lossy encoders make little files from big ones.
In order to acheive this, they remove as much sounds as possible, but they try to choose sounds that are inaudible, so that it doesn't matter if they are missing.
But when we want to compress very much, there is a point after which there is nothing more inaudible to remove. The encoder then starts to remove audible sounds, so as to make the file even smaller. In technical terms, we would say that we are "below the threshold of perceptual transparency".
Different encoders, like MP3 and AAC, choose then different sounds to remove, so the result is different.
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URMEL
post Apr 10 2004, 00:11
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QUOTE (Sebastian Mares @ Apr 8 2004, 11:04 AM)
Example of the difference between lossy and lossless:

Image being in a forest and hearing the beautiful sound of the birds, of the trees, while suddenly an airplane flighs above you. During the airplane's flight, the sound of the birds and of the forest seems to be gone, while instead, the sound of the plane's engines can be heard.

Now, storing this situation losslessly would require you to include the sound of the birds, of the forest and of the engines (although you can actually only hear the engines, everything must be saved).
Lossy compression methods will analyze which parts of the sound can be heard and which not. It will then discard the parts which are not relevant and only include the parts which are significant.

you hit the point ^^
the thing is, that you have to compare the complicated technical stuff to things the person you talk to knows already, like the birds vs. airplane.
In most cases, you have to drop certain aspects, but that should be worth it.
In lossy and lossless encoding, drop the psychoacoustic stuff, only say "sounds you can not hear", that will make it easy to understand. And don't use any foreign words ^^
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