Re: Apple Computer changes its name

[pausch@saaf.se (Paul Schlyter)]

In article <1168997827.623972.47600@a75g2000cwd.googlegroups.com>,
mdj <mdj.mdj@gmail.com> wrote:

> Matthew T. Russotto wrote:
> 
>> If you use exactly the same codec with exactly the same settings, I'd
>> hope there would be no quality loss.  I don't know if this is the
>> right term, but I call this a "stable" codec -- one where C(D(x)) = x
> 
> Even if that's true (which I doubt)- it's impossible to test, as
> there's no way to know what settings Apple used when encoding the
> tracks that are available on iTunes anyway.

It's impossible in that particular case, but it's not impossible if you're
the one doing the original lossy encoding.  Here's how you do it:

1. Encode some CD track into e.g. an MP3 file

2. Convert the MP3 file back to a wav file containing uncompressed PCM.

3. Re-encode the WAV file back to another MP3 file, using exactly the
same settings as the first encoding to MP3.

4. Take the MD5 of the first and the second MP3 files, to see if their
contents are identical.  Or just compare the binary contents of the
two MP3 files.  Be sure the ID tags of the two MP3 files also contain
exactly the same information before doing the compare.

> Besides, going from iTunes to some other mp3 player guarantees you'll
> be using different codecs.
> 
> Matt
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