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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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phong
post Aug 22 2003, 16:13
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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.

This is a very good definition of a heuristic. Heuristics are used all the time to get "pretty good" answers to Hard problems. A good example is checking a number for primality. You can do this with 100% certainty by factoring (very slow), or a recently discovered algorithm that takes O(n^12) (still quite slow). There are other algorithms (some of which only work on certain sets of numbers) that when given a number to test and a seed number will tell you if it's prime or not, but get it wrong a certain percentage of the time (for the sake of example, we'll say they guess right 75% of the time). These tests can be run quickly, and changing the seed number results in an independant test. If you test a number with a few dozen seed numbers you can be sure that it's prime within a very small margin of error.

So, it's certainly possible to develop a heuristic to create a close approximation of the original mp3 file from a decoded wav file, and it would be much easier than getting the EXACT mp3 file back. Don't ask me to write it though, it doesn't sound like fun at all. I'd much rather work on graph coloring register allocation.

As far as "image enhancement" algorithms go... Most don't get much additional information from the image. Instead, they make up ficticious image data that looks pretty.


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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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