[pulseaudio-discuss] [PATCH] Warn on attempts to build and load module-equalizer-sink

Tanu Kaskinen tanu.kaskinen at linux.intel.com
Tue Dec 2 03:53:51 PST 2014

On Tue, 2014-12-02 at 10:02 +0100, David Henningsson wrote:
> On 2014-12-01 17:14, Alexander E. Patrakov wrote:
> > +    AS_HELP_STRING([--with-fftw],[Build FFTW-using module (equalizer). Note: the module has known-wrong DSP logic]))
> > +AS_IF([test "x$HAVE_FFTW" = "x1"], ENABLE_FFTW="yes (BAD IDEA)", ENABLE_FFTW=no)
> > +You have fftw support enabled. fftw is used only by
> > +module-equalizer-sink, which has many bugs, including wrong DSP
> > +logic. See details at:
> > +
> > +http://lists.freedesktop.org/archives/pulseaudio-discuss/2014-March/020174.html
> > +https://bugs.freedesktop.org/show_bug.cgi?id=41465
> > +https://bugs.freedesktop.org/show_bug.cgi?id=54881
> > +https://bugs.freedesktop.org/show_bug.cgi?id=69229
> > +
> > +It is suggested that you reconsider, unless you are a DSP
> > +specialist willing to fix or rewrite the code and submit patches.
> Please take it down a notch or two.
> Ok, so module-equalizer-sink has known crashers. So has 
> module-dbus-protocol [1], but we don't go all nuts like the above over 
> module-dbus-protocol.

<jump to the footnote>

> [1] AFAIK - I don't think Tanu has fixed all of them yet, but Tanu
> knows this better than I do.

That's correct - I haven't fixed them all yet. The issue is that
module-dbus-protocol uses the asynchronous subscription system to get
notifications about system state changes, and that has been shown to be
prone to bugs. The module should use hooks instead of the subscription
system. I'll definitely get to that some day, but anyone is welcome to
do the "subscription -> hook" translation - it takes a fair bit of work,
but it should be pretty straightforward (also known as "boring").

> Ok, so module-equalizer-sink has "wrong DSP logic". But yet, people find 
> it useful. Hence, DSP logic seems to be something that concerns DSP 
> people more than casual listeners, who does not even know what "wrong 
> DSP logic" means in practice. And since you seem to be the closest to a 
> DSP specialist we have in this community, I'm sure it would be more 
> appreciated if you spend time fixing the sink, rather than trying to 
> take it down.
> That said, I don't mind a warning message or two when trying to load a 
> module that has known crashers, and that we don't have time/energy to 
> fix. But the extent of the warning messages above makes this look more 
> like "vendetta" and less like "politely inform the user". IMO.
> As for building by default, I don't have a strong opinion on whether we 
> do that or not - distros will disable or re-enable as they see fit anyhow.

I'd lean on building the module by default.


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