Vorbis dev - May 2001 - 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?
It's exactly what Microsoft audio does, it massages the audio to make it
sound 'better' to people. This is basically signal compression - nothign
to do with compressing the data, just cmpacting the dynamic range and
boosting frequencies that people listen to to make it sound better and
hide the places that are flawed.


-- 
Scott Manley (AKA Szyzyg)
Streaming Media Hacker
www.myplay.com

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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?

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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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Robert Voigt <f1k@gmx.de> writes:
> Is this bullshit or an interesting thought?
My vote is for "interesting bullshit".  Pushing audio through a codec
is
arguably like pushing it through a very complicated dynamic filter.  The
result, like the result of any filter, might sound subjectively better to
someone, or even most people, but I can't see it sounding better to everyone
for all kinds of input.  (There are probably still audiophiles out there that
think vinyl sounds better than 44kHz digital.)

As for the arguments about bandwidth, if you *knew* that every signal your
amplifier (and the rest of your analog path) was going to come from the output
of a certain codec, you might be able to take that fact into account to design
an analog path that sounded better for the price, or whatever.

--Mike

P.S.  I am not a EE, etc.


-- 
Mike Coleman, mkc@mathdogs.com
  http://www.mathdogs.com -- problem solving, expert software development

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Robert Voigt (f1k@gmx.de) wrote :
> On Wednesday 09 May 2001 22:24, Greg Mayer wrote: 
> > Consider this: 
> > 
> > With digital encoding, we are limited to discrete values for signal 
> > representation. So if we increase the number of bits available to us
in
> > the encoding, then we can get a more accurate representation of the 
> > original analog signal. How can we increase the number of bits
available?
> > We free up bits that would have been used to store audio signals
outside of
> > the normal range of hearing or that were masked by other sounds. 
> > 
> > You are absolutely right that you cannot increase resolution beyond
that of
> > the original recording. But if you have a high quality analog
recording,
> > then you can more closely represent the analog signal digitally with
more
> > bits available to you. Although, in practice, this increase may not be
> > perceivable to the listener. 
> 
> Ok, you mean feeding a high quality 24 bit PCM to a perceptual encoder may 
> sound better than 16 bit PCM. I agree, but I think the author of that book 
> means comparing 16 bit PCM to compressed music where the input to the
encoder
> was also 16 bit. 
Did you read the book ?

The piece mailed here doesn't mention PCM or even digital audio.
It mentions "perceptual coder" but the tranforms could be done
in a pure analog domain.
>  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.
How does it degrade ?
Is the level of degradation noticable or even measurable ?
> Because a
>    perceptual coder removes inaudible signal content, the playback
system's
>    ability to convey audible music logically should improve.
He says "should improve", not "will improve".
> In short, a
>    perceptual coder more properly codes an audio signal for passage through
an
>    audio system."
He doesn't say that any audio quality improvement should or does happen.
Maybe it only reduces the power consumption of the amplifier , now that sounds
logical ( less audio, less energy , less power )
 
>    Is this bullshit or an interesting thought?

-- 
David Balazic
--------------
"Be excellent to each other." - Bill & Ted
- - - - - - - - - - - - - - - - - - - - - -

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