Re: MP3 files for Classical - What are the issues?
- From: Kimba W Lion <KimbaWLion>
- Date: Fri, 04 May 2007 10:28:31 -0400
"Peter Greenstein" <pgreenst@xxxxxxxxxxx> wrote:
What are the issues with mp3? I've heard it referred to as a "compression"
format. I know this doesn't mean the dynamic range is compressed and these
files don't sound that way. They sound good enough but is this format of
transfer (or "recording") comparable to taping?
In terms of a digital file, compression means reducing the size of the
file. This can be lossless, using algorithms that are exactly reversible,
or lossy, using algorithms based on measurements of human perception to
throw away data that is considered imperceptible. This audio data is gone
forever.
Aside from bouts of nostalgia (like when I edited a three-hour program on
open reel just because I missed the art of razor blades and sticky tape),
I use MP3 for backup copies of the CDs I make. I would never consider
using cassettes for new recordings. Record to WAV (lossless), then when
you have a finished product, burn to CD from WAV and make a backup copy
that I will probably never use again as high-quality MP3.
How comparable is this format to the old way of taping a record with a
cassette recorder? Is it as good as a decent cassette recorder? Is it not as
good as a top quality tape recorder?
When the settings are chosen properly, MP3 is far better than any cassette
recorder. Even the seductively beautiful sound of my open reel machine is
subject to glitches that will never happen with a digital file. But if the
settings are chosen poorly, an MP3 file can be worse than your first
portable recorder with the cheapest tape ever was.
With tape recording we got an increase in background noise, and though dolby
reduced this the process itself introduced sometimes noticeable effects.
What about mp3?
Throwing away data can have audible consequences, so it is a good idea to
avoid repeatedly doing that to any one recording (i.e. re-encoding it to a
new lossy file). Most people won't notice any ill effects with a file
encoded at a sampling rate of 44.1kHz, and a bit rate of 192k bps. Some
encoders can do well at a lower bit rate, but some popular ones start to
sound swishy (phasey) at 128k bps.
With tape we got some high frequency loss. How about mp3?
Lower sampling rates will lower the top end of the frequency response.
Sampling at 22.05kHz will limit the frequency response to 10kHz.
What about distortion (harmonic)? Are there measurable or audible increases
with mp3 conversion?
Not harmonic distortion, but there is definitely a unique kind of
distortion apparent on poorly-encoded files (the swishy or phasey sound I
mentioned). Also, up-sampling (i.e., going from 22.05 to 44.1kHz) will
introduce a very unpleasant distortion that fortunately is very easy to
filter out, even though a lot of people don't seem to know that. You can't
regain the higher frequencies by upsampling.
.
- References:
- MP3 files for Classical - What are the issues?
- From: Peter Greenstein
- MP3 files for Classical - What are the issues?
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