I like scrambled eggs, not scrambled files.

December 15, 2008 8:45 PM

Through a long series of circumstances, I need to reencode my entire .mp3 music collection. I would like to reencode them at the same bitrate, but am getting very strange results when I do. Please help!

I am using Easy CD-DA Extractor for this, and am confused on two points:

First and foremost, when I click to "Properties>Summary>Details" on Windows Explorer, a significant portion of my .mp3s are showing up as in bitrates not supported by Easy CD-DA Extractor, such as "194 kbits/s" rather than 192. Is this some weirdness on the part of my .mp3s, or do I simply need to get a better program than the free trial version of Easy CD-DA?

Secondly, when I reencode at these lower rates, the audio is completely scrambled, or sometimes sped up. I know that reencoding at a lower or higher rate affects quality, but I didn't think it had such drastic effects.

In other words, what am I doing wrong, how do I fix it, and is it even possible to reencode these files at the same bitrate?

posted by WidgetAlley to Technology (10 answers total)

I'm not familiar with the software you've mentioned here but do want to ask... are these mp3s encoded with VBR (Variable Bit Rate)? That could be part of the problem.

Also, I don't mean to be presumptuous about your project but your reencoding from mp3 TO mp3 (again)? Can you list three brief reasons why you're doing this?
posted by ezekieldas at 9:24 PM on December 15, 2008

If the audio is sped up it may be that you're re-encoding them at a higher sample rate. CD quality audio is 41.1kHz, mp3 is usually less than that. As I understand it, changing the sample rate of digital audio is going to affect the pitch of the audio. Changing the bit rate is going to affect the relative volume of the audio

I've never used Easy CD-DA Extractor but try tweaking the settings for the sample rate, if possible, to match the sample rate of the original mp3s.
posted by robotot at 9:31 PM on December 15, 2008

Are you re-encoding existing mp3s, or are you ripping your CD collection?
posted by Jairus at 9:53 PM on December 15, 2008

Do you just need to edit the ID3 tags or do you actually have to change something about the audio?
posted by PueExMachina at 10:19 PM on December 15, 2008

1. If you are re-encoding mp3s - don't do that :)
2. If you are ripping from a cd and get a strange bitrate in the resulting mp3, you have VBR encoding enabled.
posted by devnull at 11:48 PM on December 15, 2008

What everyone else says.
As for better software, I prefer Exact Audio Copy. Lots of options, and it does lots of things to ensure that you get a very accurate copy.
posted by le morte de bea arthur at 1:30 AM on December 16, 2008

iTunes can also do this: Go to Preferences and select the encoding parameters you want, and then select all the songs you want to reencode, right-click, and select "Create MP3 Version".

Then you can sort the songs by date created and do what you want with the new versions.
posted by dunkadunc at 1:59 AM on December 16, 2008

Response by poster: Hullo all,

Thanks for the advice, and for those of you who are asking WHY I have to do this, it's because a spy-ware program rewrote all my .mp3s, adding containers to them with a bunch of spyware crap on there. There is no way to remove the container, because the extension is still .mp3, without re-encoding only the audio information (i.e., re-encoding mp3 to mp3.)

I know this because every time I play an .mp3, my browser gets hijacked instantaneously.

So to answer Jairus' question, I am literally re-encoding existing MP3s.
posted by WidgetAlley at 8:47 AM on December 16, 2008

Assuming your diagnosis is right, you might just be able to copy all the compressed audio data to new files without suffering the quality degredation of re-encoding. I'm not sure what would do the trick, but I bet if you asked over at Hydrogenaudio.org, you'd get answers.
posted by Good Brain at 10:41 AM on December 16, 2008

I don't know what OS you use, but I think the best way to fix your files (without losing quality) would be to compile this program:

http://id3v2.sourceforge.net/

Then write a script which calls this program with the --delete-all option for every mp3 in your library.

Finally, download the musicbrainz tagger (musicbrainz.org) and let it process and re-add all of your tags.
posted by helios at 7:18 PM on December 16, 2008