1. What do
the "lossy" and "lossless"
mean?
There are many ways to compress
a wav file - basically, there are methods:
- lossless compression methods - methods that completely maintain
the original quality of the
wav file.
A drawback of keeping a full sound is the rather small
compression ratio (large
files).
- lossy compression methods
- highly effective methods where high compression distorts the original sound.
Here, the sound is damaged once and forever and there is no
way to restore it back to the original.
2. Related software and file
extensions (links)
a) lossless:
|
software(link) |
extension |
features |
|
MKW |
.shn |
An external
checksum allows identiication of the particular recording before trading or download.
Highly used! |
|
MONKEY AUDIO |
.ape |
A
good compression ratio and a friendly software frontend. An
internal
checksum. |
|
FLAC |
.flac |
An
average compression ratio and an awful frontend, but many people
have
got used to this one. An internal checksum. |
|
TTA |
.tta |
A new one, still under development. It is said to have
an extremely high compression ratio - up the 30%
of the original |
b) lossy:
|
software |
extension |
features |
| a variety |
.mp3 |
The
most common format as you know it. |
| "musepack" |
.mpc |
Sneaky
one! the files are really large, but the
sound is still poor. What the f**k is this one for?
|
| no idea |
.vqf |
Not
much to say |
c)
other recommended software:
|
auCDtect
|
The guys who came up with TTA also wrote this little
utility for recognizing lossy / lossless-based wav files.This is a priceless software for any audio collector
- it can recognize the origins of the wav files on your HDD. It is sometimes necessary to analyse a recording you
have
downloaded or traded and you are not surewhetherf the music is an authentic lossless
audio or just mp3s or stuff.
Also, my friend Sasa Kanocz made a frontend for
it.
Visit the auCDtect authors' web:
True Audio Software
 |
download auCDtect and the frontend from this site (zipped package 109 kB) |
| |
|
 |
preview |
NOTE: You will need
Microsoft
.NET Framework to
run the frontend.
|
3. A brief
description how the lossy
compression damages the sound quality
The lossy methods take advantage of the fact that
the human ear does not have the same sensitivity throughout the whole frequency
spectrum. The point
is that the
frequencies people
can't hear properly are completely
removed. This results mainly in colouration of the sound (based on
the the well known fact that
the colour of a sound is created with help of particular
frequency-components of particular intensity).
4. Examples of the
sound-distortion
Since the frequency spectrum changes
with time, I took a snapshot at one particular moment. The links below show how the frequency
spectrum changes after both lossless
and lossy compression (mp3-320kbps
and mp3-160kbps). Note the
changes in the upper part of the frequency spectrum (frequencies
for which the
human ear has relatively little sensitivity were
removed by the mp3 algorithm).
Click on the following links to
see the results:
5. Conclusion
Of course it always depends on the
quality of a person's ears and the degree of compression used,
but at any rate - the file is damaged and there is no way back.
Consider a scratched postage stamp - it can have just a small scratch
somewhere in the corner and its value is gone - although, it still
looks quite good.
6. Similar articles as i have
found them on web
http://www.pwarcham.cjb.net/
http://www.geocities.com/radioheadbootleg/index.html
thanks to Roy and Kate for help and comments :))
|
