From: d88-jwa@dront.nada.kth.se (Jon W{tte)
Newsgroups: comp.compression
Subject: Re: Too much lossy encoding?
Date: 10 Apr 92 13:05:08 GMT
	<1992Apr8.160300.5981@tc.fluke.COM>
	<1992Apr10.072719.28885@rp.CSIRO.AU>
Organization: Royal Institute of Technology, Stockholm, Sweden
Originator: d88-jwa@dront.nada.kth.se

.CSIRO.AU> awoolf@rp.CSIRO.AU writes:

   You're obviously asking to get flamed rather severely, Mr Gunthroat, so I'll
   oblige you. 

Well, I don't think he was. However, you have completely misunderstood
what the original poster intended.

   > Analog recording and storage methods are inherently lossy, but the loss
   > depends on the quality of the recording and playback mechanisms.  As
   > mechanisms improve, the quality of the recorded, stored, and played information
   > improves.

   Lossy in what sense?? You mean compared with the 'perfect' signal. What defines
   the perfect signal? A better recording/storage device? Then use that device to
   do your recording/storage. Voila, no loss now!! Loss in data compression refers
   to the act of coding, ie AFTER the measurements.

	   USE THE CORRECT TERMINOLOGY IF YOU WANT TO PARTICIPATE.

Totally unnecessary flame. I took this statement to be a preamble to
speaking about why or why not you should use lossy compression.
And looking at the process, we see:

	1) source
	2) sensor
	3) transfer
	4) coding
	5) recording
	6) media
	7) playback
	8) de-coding
	9) output

You describe only parts 1-3, whereas the original poster was
concerned about the effects and artifacts in the signal introduced
in stages 4 and 8. And, indeed, his terminology was correct.

   > waveform.  While the conventional wisdom is that we cannot hear sound above
   > 22 KHz, this is not completely true; we are sensitive to phase changes at
   > higher frequencies.  Now proposals like PASC and audio MPEG are coming along
   > that are lossy; they filter out sounds "we can't hear anyway".  We are moving

   If you can REALLY hear phase at > 22kHz, your'e a better man than the vast
   majority of normal human beings, gungadin. That, however is not the point, and in

That's not at all true.

Try listening to a studio-quality master deck, and compare to a CD,
and you'll hear a difference in brilliance, or you're too damaged
by noise. I've lost some of my sensitivity, but I can perceive
differences. In fact, most people < 40 still can, especially if they
have lived and worked in non-noisy environments.

   fact defeats your own argument, assuming you have stuck to the topic of
   compression. If you get better compression techniques, you can go higher than
   22kHz for the same data rate, so you can put your bloody phase changes in if you
   so desire. Yes, Virginia, there IS a use for compression, that some idiots
   can't see.

No, the sampling is still made at 44,1 kHz, so you never can go
above those 22 kHz with that signal, once quantisized.
However, using LOSSY compression will most probably NOT retain
phase consistency; if it did it perfectly, it would not be lossy,
and we're talking lossy compression, not lossless.

So, lossy compression can't help preserving overall sound
quality BY DEFINITION. It just tries to remove data while
introducing as SMALL artifacts as possible. However, in a
few years time, we might come to regretting having those
artifacts.

I don't think it's a big deal, as long as the master tape
and original data is stored non-lossy. If the only representation
of data available was lossy-coded, I'd be more sceptic.

   > It's just the same in the video world; complex formats based on removing
   > visual data "we can't perceive anyway" are multiplying.  Only it isn't
   > always true.  There are problem images, like sports and other fast motion
   > subjects.  

   Again, BULLSHIT. There is even more redundancy in moving images. You mentioned

Now you don't know what you're talking about. The redundancy between
two moving frames is much LOWER than the redundancy between two still
frames. You need a much higher data rate to transmit thedata between
two moving frames than between two alike frames - lossy compression
limits the bandwidth available for recording frame differences, and
when you hit that limit, you get artifacts.

   You're obviously superhuman. Not only can you easily hear phase changes above
   22kHz, but you can see interframe pixel changes EVEN IF THEY DON'T EXIST!!

Get real dude.

Lossy compression is BY DEFINITION lossy. As soon as it's lossy,
YOU GET PIXEL DIFFERENCES OR IT WOULDN'T BE LOSSY. SHould be clear
even to a moron like yourself.

   > appeared (as they always have before), aren't we going to be really pissed
   > off that we accepted so much lossy encoding that we can in fact detect?
   > I hope everybody implementing this technology will think about this.  You
   > are going to have to live with your decisions.  

   What a wank of a statement!!!! GROW A BRAIN, CLOWN!! Do you really think that
   people will use JPEG to compress images down to 22k when they have 300GB of
   storage???? If the technology gets better, people will use compression less, or

But the data that HAS ALREADY BEEN ENCODED WITH THE CURRENT METHODS
will still have lost some qualities, right ? That's what the original
poster wasconcerned about. However, as long as the original data is
retained somewhere, the use of lossy compression for distribution
media is no big deal to me, as long as it's adequate for its purpose.

   Usenet treats such people very harshly.........

You ought to meet yourself someday; I'm sure you'd hate it.
-- 
h+@nada.kth.se; Jon W{tte, the Diplomat - NOT!