Puzzled WHY compressing music damages the sound.,

Christopher Burke

Christopher Burke

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Jun 21, 2018
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Dear Anyone.

OK, I'm not a professional, I'm a wannabe who wants to learn and has a bunch of STOOOPID questions he doesn't understand. Here's one of them!

Sound on a computer is 1's and 0's. As is text. But I've discovered the hard way that if you compress a sound to an MP3 you lose definition that you DON'T get back by re-opening it as a .WAV. But I don't understand WHY. I mean if I compressed a book to a .RAR file (or .PDF or whatever) and then reopened it as a text file, I wouldn't lose any of the book, would I? The text all looks the same quality to me, I've tried it. I could compress and uncompress (decompress?) it all day long and it would stay the same.

So why if I do the same thing to a soundfile, compress it and decompress it, does it make any difference to the quality of the sound? Is it just nobody's bothered to get the algorithms right? And if I compress it to a .RAR instead of a .MP3, would it keep the original qualities that way so when decompressed, it would sound like the original .WAV file? What puzzles me even more is that it can't be an inherent property of the soundfile because I've discovered something called FLAC, Free Lossless Audio Codec, that shrinks a file AND keeps all the audio quality (that's what it says on the package anyway!)

So what's the problem with .MP3s? If .RAR can keep things lossless (though you'll have to tell me if that includes audio) and FLAC keeps sound lossless (again, if that's not correct you'll have to tell me) why can't .MP3 keep things lossless?

Beginning to think it's going to be one of those 'why do graphics always have white backgrounds you can't get rid of' type questions where the answer is 'because nobody's bothered designing a graphic filetype that doesn't have a white background!' (I know you've got GIFs but they're strange, they DO degrade the original picture and I dunno why, maybe they're designed by the .MP3 guy!)

Hope someone chooses to answer. Sorry I'm not an expert like you guys, but I do want to learn.

Yours respectfully

Chris.
 
hey

Simply, its because MP3's are designed specifically to BE lossy, to give up information.

Yes, it's possible to compress a file without losing any data. The examples you give of FLAC and RAR are such, and they compress the information as much as they can while still keeping the data intact, and then the audio is decompressed back exactly the same as it was when played.

However there is only so far that you can go, so much you can compress, while still keeping things lossless. Back in the very early days of transferring music over the internet, people's bandwidth was so small that transferring big lossless files was very impractical at best. The needed a format that was able to discard some information to make the file even smaller, with as little impact as possible to the audio. the original MP3 format used the best known strategies at the time based on psycho-acoustics and how your brain perceives audio to discard some of the audio while still keeping it as close to listenable and unnoticeable as possible (depending on exactly what bitrate etc you chose etc of course).
 
Hi Chris-

You conflate data compression (RAR, ZIP) with CODECs that compress data as part of the transcoding.

Fraunhofer IIS developed a number of audio CODECs including MP3. You might want to start with them... :D

MP3 is a "lossy" CODEC - whatever it doesn't keep is discarded (which is why re-coding the stream doesn't improve anything; once it's gone, it's gone). Higher bit rates mean less is thrown away but there are still bits that don't make the cut. Fraunhofer compensates for these losses in a couple of clever ways but at lower bit rates the losses are apparent to those who know what to listen for.
 
Dear Everyone.

Thanks very much for your excellent replies, I now understand everything (to a point!!)

One wonders, now there's more bandwidth floating around, why everyone still uses lossy MP3s and not lossLESS FLAC to listen to everything with. You'd've thought MP3s would have been discarded with the advent of more bandwidth as standard and FLAC taken over (or a similar lossless format, I know WAV's the best but they CAN get big!!)

Wonder why MP3s stayed around?

Yours respectfully

Chris.
 
Christopher Burke said:
Dear Everyone.

Thanks very much for your excellent replies, I now understand everything (to a point!!)

One wonders, now there's more bandwidth floating around, why everyone still uses lossy MP3s and not lossLESS FLAC to listen to everything with. You'd've thought MP3s would have been discarded with the advent of more bandwidth as standard and FLAC taken over (or a similar lossless format, I know WAV's the best but they CAN get big!!)

Wonder why MP3s stayed around?

Yours respectfully

Chris.
Click to expand...

They stay because they are small and everywhere.



 
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Christopher Burke said:
Dear Everyone.

Thanks very much for your excellent replies, I now understand everything (to a point!!)

One wonders, now there's more bandwidth floating around, why everyone still uses lossy MP3s and not lossLESS FLAC to listen to everything with. You'd've thought MP3s would have been discarded with the advent of more bandwidth as standard and FLAC taken over (or a similar lossless format, I know WAV's the best but they CAN get big!!)

Wonder why MP3s stayed around?

Yours respectfully

Chris.
Click to expand...

Ubiquity for one, and the propensity of the public to use one noun for multiple, different things that *appear to the public* to be the same. Think "Xerox" and how it became a verb "Xeroxing 25 copies for your presentation" and how to the public any form of photocopying was called Xerox.

But unlike photocopies if you ask for an MP3, that's what you'll get.

The other reason is that consumers don't know, don't care and certainly will not be driving any form of "change" regarding music reproduction quality. Why? Because they don't know how music is supposed to sound. With "mastered for stuffing in your earbuds", there is precious little dynamic range in pop music forms as delivered to the consumer. They don't listen to music on a sophisticated audio system at home, in a controlled environment - only from the $5 buds that come with their phones. Since they've never heard reverb tales or the natural decay of an instrument sound or vocal they won't hear the CODEC doing its loss-based work.
 
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