[linux-audio-dev] TAP EQ problems

Tom Szilagyi tszilagyi at users.sourceforge.net
Fri Aug 5 18:39:00 UTC 2005

Hi all,

just noticed the thread, I hope it's not too late to chime in.

The problem is most likely due to a denormal bug. However, I have not
been able to see it, in fact the machines (two not-so-new Pentium-4
and one fairly old Pentium-3) I can access for testing don't exhibit
any such issue. TAP EQ has been rock solid on all of them (I use it
extensively). I suspect that many others have the same experience,
since I haven't been flooded with bug reports.

This certainly does *not* mean the problem is not real. However, I
have come to suspect that

(1) denormal behavior is very very processor dependant and thus
    fairly unpredictable across different processor types (maybe
    processors newer than mine are getting even worse?),

(2) there is more to excessive CPU usage than a denormal problem.

Regardless of which is true, it seems I'm unable to provide a fix
since I cannot test whether a particular "denormal fix" macro does the
trick. I just can't make a reliable difference.

So, I would be very happy if someone who does have these problems
would try out the various methods discussed so far, and report which
of them works (if any). It should be possible to provide a replacement
for the FLUSH_TO_ZERO macro defined in tap_utils.h. Replacing that
macro should (positively) affect not just the EQ, but all other
plugins as well.

If you get this far, please please please make a patch of it and send
it to me (or this list). I will merge it and release a new version of
TAP-plugins. I can't think of anything else I could do.


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