Terrible ringing with SuperEQ

2002-06-28 16:03:20

I don't know if it has been addressed before.

Well, the thing is that I had always found curious how Shibatch's Super Equalizer WinAmp plugin works, in the way that doesn't work like a typical graphic eq., because it amplifies "slices" of frequencies in a very precise manner.

Well, the fact is that this is too a precise manner. The sharp filtering between two adjacent bands translates into ringing on time domain, even when the filtering is slight. I had wondered sometimes if it could be audible.

Well, I just tried, and it is *very* audible.

Just get you favourite audio editor, and create a pure impulse, consisting of just a 1 sec. of silence, and 1 single sample at near top amplitude, at the center of the silence. For the people who doesn't know, this is the most impulsive signal possible, and has the same content at all frequencies.

Now save to it as a wav file, and now play it using SuperEQ, but putting every band in a slight different position. Just _-_-.

Now, if you play it, you will hear a very clear tonal pre and post ringing. With other signals it may not be so audible, but I guess that with some it can.

Do your own tests, it's quite easy.

This signal is also one of the worst cases for MP3 pre-ringing, but LAME --aps doesn't sound as noticeable and as bad as SuperEQ's ringing. On the other side, SuperEQ ringing is not so noticeable on samples such as castanets.

An equalizer such as RTEQ, which filters more smoothly, like a classic analog graphic eq., should not cause this kind of artifacts, but I haven't tested it yet.