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mp3 to wav to mp3 to wav same?
gts
post Feb 27 2003, 14:42
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If a file is encoded to mp3, then coverted back to a wav, and then that wav is convered back to mp3, will the both mp3s be the same?
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aggies11
post Aug 22 2003, 05:26
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Sublime:
easiest way to think of it, its like xeroxing a xerox, just never as good as original and if you keep re-encoding same file, it will get worse and worse...

Ideed. And with that in mind, the idea would be to somehow be able to determine the "copiers memory after scanning the original image", from the end resulting copy. Obviously it's not the original, but it would be able to reproduce the copy, at will, without any loss.

But alas, I had thought/feared it was as such. I figured that I couldnt' be the first person to think along those lines, and that if it was possible it'd probably already be done.

With regards to the pigeon hole though, I'd say that one has to take such theories with a grain of salt. Yes, in the most strictist of sense, you can't recreate more information (or recover lost information), from data that has lost/reduced it. In music thats lost fidelity, in images it could be lost resolution/clarity. For the simple reason that the set of input to produce that output is larger than 1. Ie. Theres many starting points to get you to that end state, so there is no way to figure out which one it was. Too many pigeons, not enough holes wink.gif.

However it becomes very difficult to correctly quantify the "amount" of "information" in some item of data. Meaning that you can sometimes "cheat". For example, look at image reconstruction algorithms. They can take a blurry/low resolution picture and enhace it to a a more clear/higher res image. In the strictest sense, that should be impossible. But they use things like light refraction from known light sources, and other such "cheats" to essentially eliminate alot of the possibilities. To reduce the number of pigeons, if you will. Which in actuallity, is that they are increasing the amount of "information" found in the image. They are able to find "more" info in the image. Conventional information theory says that you can't get "more" from "less". But you can get around that in neat ways where you can show that "less" is actually not as little as you had thought.


I've always wondered about the classic NP traveling salesmen problem. Yes it's way above polynomial time to compute all possible routes, to find the best one. But what if you could cheat, eliminating subroutes that were likely not in the solution. So that any master route containing the sub route, would automatically be ignored. Do it enough, you can reduce the complexity of the result set. Sure it's not guaranteed to succeed. But what if you had a probability of sucess of 80%. Than statistically you just run it a bunch of times to guarantee sucess, which still comes in as polynomial. Basically the idea that each possible answer is NOT equally likely to be correct. And so you focus your attentions on the much smaller subset of more likeli answers.

But I digress a bit, heh. If there is indeed uncertainty in the decode process, such that it does not have a well defined inverse, than all hope is lost, heh. Although, that should mean than that it is possible for more than one mp3 datastream to decode to the exact same resulting wav?

Interesting indeed.

Aggies
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- gts   mp3 to wav to mp3 to wav same?   Feb 27 2003, 14:42
- - CiTay   No. MP3 encoding is a lossy process. The WAV that ...   Feb 27 2003, 14:46
- - gts   Well the first conversion from wav to mp3 removes ...   Feb 27 2003, 15:05
- - Xenion   QUOTE (gts @ Feb 27 2003 - 03:05 PM)Well the ...   Feb 27 2003, 15:15
- - X-Fixer   QUOTE (gts @ Feb 27 2003 - 09:05 PM)Well the ...   Feb 27 2003, 15:26
- - gts   QUOTE theoretically this could work this way. (sec...   Feb 27 2003, 23:30
- - gts   QUOTE original wav => mp3 =lossy agreed QUOTE m...   Feb 27 2003, 23:33
- - Messer   Codec does not remove anything. It rounds some val...   Feb 27 2003, 23:39
- - gts   Thank you. What search words will find the topic? ...   Feb 27 2003, 23:43
- - Mac   I'll chip in because it took me a few goes of ...   Feb 27 2003, 23:46
- - Messer   I'd try "reencoding". This is for e...   Feb 27 2003, 23:49
- - gts   Thank you!   Feb 28 2003, 00:01
- - CiTay   QUOTE Codec does not remove anything. It rounds so...   Feb 28 2003, 00:21
- - gts   QUOTE It doesn't care if the WAV was previousl...   Feb 28 2003, 00:30
- - Messer   QUOTE (CiTay @ Feb 28 2003 - 01:21 AM)QUOTE C...   Feb 28 2003, 00:35
- - gts   QUOTE that essential process in lossy compression ...   Feb 28 2003, 00:37
- - fewtch   There's a simple way to test this. Encode a ....   Feb 28 2003, 00:42
- - Artemis3   If you record a CD into a cassette tape, then use ...   Feb 28 2003, 02:14
- - gts   QUOTE If you record a CD into a cassette tape, the...   Feb 28 2003, 02:29
- - rjamorim   QUOTE (gts @ Feb 27 2003 - 08:30 PM)In the jp...   Feb 28 2003, 02:39
- - gts   QUOTE But reducing the amount of colors is only ON...   Feb 28 2003, 02:44
- - rjamorim   QUOTE (gts @ Feb 27 2003 - 10:44 PM)but the p...   Feb 28 2003, 03:05
- - andrew3199   I think we can all agree that there is some loss w...   Feb 28 2003, 04:29
- - rjamorim   QUOTE (andrew3199 @ Feb 28 2003 - 12:29 AM)fo...   Feb 28 2003, 04:36
- - dreamliner77   QUOTE I perceived the decay of plucked notes on an...   Feb 28 2003, 05:19
|- - makarov   An analogy to JPEG lossy image compression was mad...   Jan 30 2005, 07:33
- - NeoRenegade   gts, with regards to your JPEG analogy... you refe...   Mar 2 2003, 23:14
- - kdo   QUOTE (rjamorim @ Feb 28 2003 - 03:05 AM)Code...   Mar 3 2003, 00:37
- - aggies11   Not to resurrect a dead thread or anything, but it...   Aug 21 2003, 02:13
- - Doctor   aggies: no. Lossy sound encoding is not like you ...   Aug 21 2003, 02:54
- - phong   An interesting thought, but probably academic. MP...   Aug 21 2003, 02:58
- - AtaqueEG   QUOTE (dreamliner77 @ Feb 27 2003, 11:19 PM)R...   Aug 21 2003, 03:18
- - 2Bdecided   QUOTE (aggies11 @ Aug 21 2003, 01:13 AM)Could...   Aug 21 2003, 10:33
- - 2Bdecided   In reply to the original question, the simplistic ...   Aug 21 2003, 10:39
- - sld   (Redundant post, sorry)   Aug 21 2003, 10:40
- - Vietwoojagig   I remember long time ago, there was a technology c...   Aug 21 2003, 12:53
- - 2Bdecided   DCC used (what would become) MPEG-1 layer I. You ...   Aug 21 2003, 13:24
- - aggies11   Thanks for the quick replies. Very informative ind...   Aug 21 2003, 17:06
- - phong   The answer to the first question is "no...   Aug 21 2003, 19:29
- - Doctor   Yawn. phong: I think you are wrong on both counts...   Aug 22 2003, 03:29
- - phong   I think I mis-specified which questions I was answ...   Aug 22 2003, 03:46
- - Canar   QUOTE (2Bdecided @ Aug 21 2003, 01:33 AM)I do...   Aug 22 2003, 04:08
- - bexx   Isn't wavpacklossy/hybrid whatever its called ...   Aug 22 2003, 04:29
- - sublimelouie   easiest way to think of it, its like xeroxing a xe...   Aug 22 2003, 04:51
- - aggies11   Sublime: easiest way to think of it, its like xero...   Aug 22 2003, 05:26
- - 2Bdecided   This reply is in response to no one in particular....   Aug 22 2003, 11:05
- - Gabriel   QUOTE IIRC FhG looked at this. You could call it a...   Aug 22 2003, 11:23
- - smg   QUOTE (2Bdecided @ Aug 22 2003, 06:05 AM)This...   Aug 22 2003, 14:46
- - phong   QUOTE Do it enough, you can reduce the complexity ...   Aug 22 2003, 16:13
- - ErikS   QUOTE (Gabriel @ Aug 22 2003, 11:23 AM)Now, t...   Aug 22 2003, 16:50
- - Zilva   Cosine transformation is NOT LOSSY. After transofm...   Sep 10 2003, 10:06
- - tigre   QUOTE (Zilva @ Sep 10 2003, 01:06 AM)Cosine t...   Sep 10 2003, 10:35
- - 2Bdecided   QUOTE (Zilva @ Sep 10 2003, 09:06 AM)Cosine t...   Sep 10 2003, 11:11
- - MugFunky   wow.. old post. ("holy thread resurrection, b...   Jan 31 2005, 04:06
- - h.tuehn   I don't want to correct anything MugFunky or m...   Jan 31 2005, 07:16


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