[iTunes] Hi Fi quality

[Allan Hise]

On Thu, 3 Apr 2003, Footie wrote:

> Greetings to you all from Prague
>
> I am a very recent convert to I-Tunes, and have never downloaded music
> files. Mainly because we don't have broadband here yet; and I have just
> joined the list. I would appreciate advice regarding the optimisation of
> sound quality when burning CDs, and please assume and forgive my zero
> technical understanding of the issues involved.
>
> I'd be interested to hear from those who burn CD's to play on a decent hi-fi
> system. I have copied a load of my CD's in the MPEG format, and since learnt
> that AIFF format gives much better quality when burning to CD. I have also
> discovered that you can reconvert MPEG files to AIFF. So my question is, in
> terms of sound quality, if you convert a song from MPEG to AIFF, and then
> burn to a CD, will I get the same quality result as if I had stored the song
> in I-tunes initially as an AIFF file.?
>
> Thanks in advance for any advice and sorry if my question sends lots of
> eyebrows raising to heavens!
>
> Richard Hunt

Short answer: No

Longer answer: By making an MP3, you compress the audio file in a lossy
way. That means the file gets smaller by throwing away stuff that the
encoder thinks you won't hear anyway. Some encoders do better than others,
and by specifying a higher bitrate in the encoding, the encoder gets to
keep more stuff, so it sounds better at the cost of a larger file. When
you burn a CD, iTunes or Toast converts it back to an AIFF file (the
natural CD format), but the stuff that got thrown away in the MP3 encoding
process is still gone. So the new AIFF is just an uncompressed copy of the
MP3.

To use a digital picture analogy, an MP3 is like a JPEG and an AIFF is
like a TIFF or a PICT. The JPEG is a smaller picture that can be saved as
a really big TIFF, but the stuff you lost when you made the JPEG is still
gone, and lost forever.

If you want perfect quality, stick with the AIFF. It will take huge
amounts of hard drive space. Most people think an mp3 with a really high
bit rate (256 or 320 or something) will sound just as good with a slightly
smaller file. I suggest experimenting with some of your favorite songs.
Encode at 128, 160, 192, 256, etc. and see what sounds good to you
(everyone is different). Find the smallest bitrate that still sounds good
and you are all set. Consider variable bit rate encoding, which adjusts
the bit rate as needed. For example, a moment of silence can be
represented in far fewer bits than complex orchestral passages. The moment
of silence will drop down to a low bit rate, and as the orchestra jumps in
again the bit rate jumps back up to what it needs to make it sound good.
You can often get a smaller file than constant bit rate. Or a better
sounding file for the same file size.

Allan