11 Oct
2011
11 Oct
'11
11:42 p.m.
On 10/11/2011 11:36 PM, Fons Adriaensen wrote:
There are at least two good reasons why such a test
is
not valid.
1. The difference signal doesn't tell you anything about
audible differences between two signals. It's fairly easy
to make a linear filter (no compression involved) with
a perfectly flat response and that nobody would be able
to hear. But when you take the difference between in and
out it is 3 dB higher than both.
2. Lossy compression is based on combined temporal and
spectral masking - some signals you can't hear in the
presence of others. Of course when you take away the
masking signal they become apparent...
Makes a lot of sense, thanks!
BTW: Apparently the guy in the link has lifted the idea from this clip:
http://www.youtube.com/watch?v=wzJbjHc6bRE
where George Massenburg does the same. I don't know George Massenburg,
but he supposedly is some kine of authority in the world of audio
engineering. Not that it makes the test more valid...
--
Atte
http://atte.dk http://modlys.dk