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Saving modified mp3 file - quality question

 
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tenant13



Joined: 12 Aug 2008
Posts: 3

PostPosted: Tue Aug 12, 2008 4:45 pm    Post subject: Saving modified mp3 file - quality question Reply with quote

I used Amadeus to clean up a small digital pop in a mp3 file. Am I correct thinking that Amadeus re-encodes the file back to mp3 instead of just saving the original with the applied edit? Should I be concerned about the loss of quality? The original is 128 so it's not that great sounding to begin with. Are there some settings in the Save dialogue box that are recommended in such case?
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CDJonah_alt



Joined: 15 Mar 2007
Posts: 378

PostPosted: Tue Aug 12, 2008 7:38 pm    Post subject: Saving modified mp3 file - quality question Reply with quote

I think the answer is yes -- it will re-encode and no, it almost
certainly won't make an appreciable difference.

Chuck

tenant13 wrote:
Quote:
I used Amadeus to clean up a small digital pop in a mp3 file. Am I correct thinking that Amadeus re-encodes the file back to mp3 instead of just saving the original with the applied edit? Should I be concerned about the loss of quality? The original is 128 so it's not that great sounding to begin with. Are there some settings in the Save dialogue box that are recommended in such case?




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tenant13



Joined: 12 Aug 2008
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PostPosted: Tue Aug 12, 2008 7:44 pm    Post subject: Reply with quote

To follow up: does it re-encode while splitting according to markers?
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Martin Hairer
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Joined: 08 Nov 2006
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PostPosted: Tue Aug 12, 2008 7:52 pm    Post subject: Saving modified mp3 file - quality question Reply with quote

Quote:
To follow up: does it re-encode while splitting according to markers?

Yes, it does. Regards,

Martin

HairerSoft
http://www.hairersoft.com/


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CDJonah_alt



Joined: 15 Mar 2007
Posts: 378

PostPosted: Tue Aug 12, 2008 7:54 pm    Post subject: Saving modified mp3 file - quality question Reply with quote

Not sure where you are going.

My understanding (and it could be wrong) is that the file is read and
turned into what one might call an aiff file (i.e. a non-compressed file
that maps sound) When you save the file, it will have to be converted
into whatever form you need -- if it is a simple sound file, it will add
headers and go, if it is going to mp3, it will then be encoded. So, if
it is being saved to mp3, it will convert. So if you are splitting
according to markers, it will take each hunk, encode it and save it.

Of course I could be wrong.

Chuck

tenant13 wrote:
Quote:
To follow up: does it re-encode while splitting according to markers?




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tenant13



Joined: 12 Aug 2008
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PostPosted: Tue Aug 12, 2008 8:14 pm    Post subject: Reply with quote

I was using Amadeus to insert markers into en existing mp3 mixed file in order to split it into separate tracks. So I guess in such case it's better to just export markers as a cue file and use different utility to split the original mp3.
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robert_theory



Joined: 29 Nov 2006
Posts: 35

PostPosted: Tue Aug 12, 2008 8:27 pm    Post subject: Saving modified mp3 file - quality question Reply with quote

Quote:
To follow up: does it re-encode while splitting according to markers?

It always re-encodes. It's an audio editor, not an MP3 editor.

-- Robert
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CDJonah_alt



Joined: 15 Mar 2007
Posts: 378

PostPosted: Wed Aug 13, 2008 3:58 am    Post subject: Saving modified mp3 file - quality question Reply with quote

I don't think you will gain much unless you have some very strange
sounds. Also, remember that there are only a limited number of things
you can do with mp3s without decoding and recoding.

Chuck

tenant13 wrote:
Quote:
I was using Amadeus to insert markers into en existing mp3 mixed file in order to split it into separate tracks. So I guess in such case it's better to just export markers as a cue file and use different utility to split the original mp3.




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Martin Hairer
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Joined: 08 Nov 2006
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PostPosted: Wed Aug 13, 2008 9:28 am    Post subject: Saving modified mp3 file - quality question Reply with quote

Quote:
Also, remember that there are only a limited number of things you
can do with mp3s without decoding and recoding.

Be aware also of the fact that the splitting will be less precise
since it can only split on frame boundaries without reencoding. (If
the program is very smart, it may decode and reencode only the last
frame in order to get a split at exactly the right location. I
wouldn't know whether this is the case for a particular program.)
Regards,

Martin

HairerSoft
http://www.hairersoft.com/


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Lou Kash



Joined: 16 Jul 2008
Posts: 87

PostPosted: Tue Aug 19, 2008 12:38 pm    Post subject: Reply with quote

MP3 Trimmer can edit and repair MP3 without reencoding. It's not expensive at all.
http://deepniner.net/mp3trimmer
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rfwilmut



Joined: 17 Nov 2006
Posts: 255

PostPosted: Wed Aug 20, 2008 10:19 am    Post subject: Reply with quote

Basically MP3 encoding works by leaving out bits of the audio which you can't hear anyway because of what's called 'perceptual masking' - loud sounds masking quieter sounds at nearby frequencies. Decoding and then re-encoding a file in the same format and settings doesn't usually make much difference (at least at the higher bitrates) because the selected parts of the audio have already been left out. The problem arises when mixing compression systems - like opening a WMA and then re-encoding as MP3.
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Lou Kash



Joined: 16 Jul 2008
Posts: 87

PostPosted: Wed Aug 20, 2008 12:45 pm    Post subject: Reply with quote

Slightly "off topic":
Speaking of encoding, just recently I compared various lossy compression formats against each other on an average but well produced pop song (Steely Dan's "Peg" from the CD) by importing them into Amadeus and using the Sonogram function. I didn't test what happens if I re-encode an already compressed file, though.

- MP3 cuts off almost anything above 16 kHz, regardless of bit rate - i.e. also at 320 kbps.

- OGG at 256 kbps (and higher) looks visually nearly identical to uncompressed audio.

- AAC at 256 kbps (and higher) doesn't look bad either, although there are visual differences to AIFF in the higher frequency range.

As for audible differences:
I can definitely tell a difference between a 128 kbps MP3 and the original AIFF file. But being an active musician and DJ, now in my forties, there's only silence above 15 kHz for me anyway. :) In that sense: I can't tell a difference between a 192 kbps MP3 (or any other format of such quality) and an AIFF file anymore.

The conclusion from my testing is, that encoding audio as MP3 at 320 kbps while expecting significantly better sound than at 192 kbps is quite a waste of megabytes. 192 kbps MP3 will do for most parts. Other than that you better use another format, where AAC is quite obviously the format of choice on a Mac. (You can load OGG files into iTunes when you install the appropriate 3rd party QT plugin, but not all metadata fields are supported in iTunes.)

For those interested:
http://external.loukash.com/steelydan_peg_sonograms_linear.pdf (3.1 MB)

(Speaking of Sonogram export from Amadeus, there appears to be a bug or two, but that's another topic again...)
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