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Re-encoding...mp3-to-mp3 question....
Rickkins
post Jul 31 2002, 14:38
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Hello all. Here's my question.
I've dl'd reams of mp3's and I'd like to bring
them all to the same quality level. Some are
different bitrates, some are encoded differently etc (lame. frau, etc)
What would be the best way to bring them all equal, to a
good quality level.
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verloren
post Jul 31 2002, 15:00
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There isn't a way - any re-encoding you do will reduce their quality level, so you should leave them as they are. They may not all be good, but they're all as good as they're going to get!

Cheers, Paul
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Rickkins
post Jul 31 2002, 15:02
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Really ???? That sucks.
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Rickkins
post Aug 4 2002, 19:09
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So, is that the final word on that question ???
I had hoped for more opinions...
(of course, I was hopin' someone would say it is possible... biggrin.gif
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NickSD
post Aug 4 2002, 19:31
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Once an MP3 is created, you can't improve the quality after the fact. You can only make it worse.

This analogy might help:

When you photocopy a piece of paper, and then photocopy that photocopy, the quality will degrade. Same idea with MP3 or any lossy codec. Think of the MP3 encoder as a photocopier, in a sense -- It produces a usable result, but it's not quite as good as the original.

Nick
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Artemis3
post Aug 4 2002, 19:35
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Well, certainly, the only thing you can do is to make them all sound much worse, but i guess they will have the same bad quality wink.gif

Transcoding is a no no. If you have the audio discs and can rip them again, then sure, otherwise, donīt touch.

Example:

Transcoding a 128kbps file to 320kbps. The 128kbps file will have better quality.

You canīt make a copy of a copy better quality, only worse quality. Think of VHS copies, then you will get it.

This rule applies to all kinds of lossy compression, be it mpeg video, jpeg pictures, or mpeg audio.


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sven_Bent
post Aug 4 2002, 21:42
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its logical reencoding will onlu hurt

if you could increase quality be reencoding, every player would do it before playing.

and therefor you could compress to 8kbits without loosing quality (playback would jsut reencode in mem to 320kbits before playback)


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kennedyb4
post Aug 4 2002, 22:41
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QUOTE
Originally posted by Rickkins
So, is that the final word on that question ???
I had hoped for more opinions...
(of course, I was hopin' someone would say it is possible... biggrin.gif


Its possible. Lots of people take their aps files and encode with --alt-preset 128 for use on their portables or car stereos. Less critical listening environments allow for this. The files have increased artifact but for the most part sound OK for this type of application.

But to chuck the original is a big mistake.

Sometime somewhere it was decided that xing and blade 128 files re-encoded to blade 320 sounded better than the original.

As a result, there are a whole bunch of bogus blade 320 files floating around out there that sound like shit. You can pick them up by ear then do a frequency sweep on them to confirm.

So with your stuff it would be best to just leave them be.biggrin.gif
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celafon
post Feb 12 2004, 18:41
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I was thinking:

maybe it's possible for encoder to use the existing mp3 srtucture (whatever it is like... - i dont know the tech stuff) and reencode the file in lower bitrate? let's say I have a 320 kbits file and I'd like to have it in something like VBR 240...????

What I mean is - dont decode it to wav, try to use the existing mp3 and cut it a bit.

What do you think?
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Sebastian Mares
post Feb 12 2004, 19:28
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You mean something like a bitrate peeling application? I don't think that the MP3 layout allows that.


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celafon
post Feb 15 2004, 19:52
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AFAIK in jpeg it would be ok to do it. And mp3 is based on same mathematic transformation. Someone who knows this small important details should reply now dry.gif .

Anyway - even IF it's possible - is there any software? I doubt it...


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ChangFest
post Feb 16 2004, 16:58
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Bitrate peeling is simply not possible with mp3. The only format that I know of that "has" a bitrate peeling option is Vorbis. That option has failed to be developed though. Your only option would be to transcode, which will result in large quality degradation. This will allow you to lower the bitrates of your files though.
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Moguta
post Feb 17 2004, 20:28
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It would indeed be possible to cut bits off of every MP3 frame, and reduce the filesize in that manner.

However, doing this will result in worse quality than simply re-encoding that MP3 to another MP3. That's why there are no bitrate-peeling applications, and also why Ogg Vorbis (which was made with the sweet-sounding promise of bitrate-peeling support) does not have such a function.
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