[vorbis-dev] Can compressed music sound better than uncompressed?

[Greg Mayer]

The idea, I think, is since certain frequencies and sounds are outside of
the range of human hearing, then why bother carrying that information along
in the signal when it can be suppressed with no noticeable effect on the
outcome.  So if you get rid of that information and use the available space
(as Lourens suggested) for higher resolution storage of the information that
you can hear, then the sound quality can be improved.

Developing amplification systems that are linear over all frequencies is an
extremely difficult task, and doesn't make much sense anyway.  So designers
concentrate on the important ~ 20 - 20KHz range and focus their efforts on
the performance between those points.  If you put in a signal that falls
only between that range, then you'll get an output more true to the intended
input.  Plus, the amplifier will actually be somewhat affordable to regular
citizens.

Of course, it's sometimes argued that it is the frequencies outside of this
range, that although they can't be heard, they can be felt by the listener
and these signals add to the "warmth" of the music.  I think it's more of a
mental attitude that these listeners know that something was cut out of the
recording, so they believe that they are "missing" part of the original
sound.  That's my take on it, at least, and I would be interested to hear
other views on that issue.

Greg

-----Original Message-----
From: owner-vorbis-dev at xiph.org [mailto:owner-vorbis-dev at xiph.org]On
Behalf Of Lourens Veen
Sent: Wednesday, May 09, 2001 11:46 AM
To: vorbis-dev at xiph.org
Subject: Re: [vorbis-dev] Can compressed music sound better than
uncompressed?

Robert Voigt wrote:
>
> I quote from "Principles of Digital Audio" by Ken C. Pohlmann:
>
> "Because perceptual coders tailor the coded signal to the ear's acuity,
they
> similarly tailor the required response of the playback system itself. Live
> music does not pass through amplifiers and loudspeakers, it goes directly
to
> the ear. But recorded music must pass through the playback signal chain.
Much
> of the original signal present in a live recording merely degrades the
> playback system's ability to reproduce the audible signal. Because a
> perceptual coder removes inaudible signal content, the playback system's
> ability to convey audible music logically should improve. In short, a
> perceptual coder more properly codes an audio signal for passage through
an
> audio system."
>
> Is this bullshit or an interesting thought?

Interesting thought I think. It's important to remember that
uncompressed does not mean perfect quality. According to the Shannons
sampling theorem any frequencies smaller than 0.5*samplerate (the
Nyquist frequency) are encoded in the signal, higher frequencies are cut
off. Also, samples are quantized representations of the original signal,
and the dynamic range is limited. If we'd send the data compressed, but
at the same data rate, we'd certainly get better quality because the
available bandwidth is allocated to things you can hear, rather than a
simple limited linearly-described portion of the sound.

But I'm not a real expert :).

Lourens

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