[LAU] How bad is mp3/ogg

[Fons Adriaensen]

On Tue, Oct 11, 2011 at 11:17:15PM +0200, Atte André Jensen wrote:
> On 10/11/2011 11:07 PM, Fons Adriaensen wrote:
>> On Tue, Oct 11, 2011 at 10:57:38PM +0200, Atte André Jensen wrote:
>>
>>> My question is: is this really a fair way to judge the artifacts
>>> introduced by encoding?
>>
>> No, it's completely invalid.
>
> That's what my gut-feeling told me!

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...

Ciao,

-- 
FA