[vlc-devel] Plugin downmix-to-stereo

Martin Zuther code at mzuther.de
Wed Feb 29 22:56:15 CET 2012

Dear Rémi!

> Either your JACK server is misconfigured (I don't know JACK), or there is
> a bug somewhere most probably in the VLC JACK output plugin. Sorry, but I
> don't want to have two plugins doing the same with different code in
> slightly different conditions. Remixing is already a big enough mess[1] in
> VLC as things stand.

I can understand you -- I had thought along those lines before starting 
a new channel mixer.  It's usually easier and more useful to fix 
something than to build around it.

Unfortunately, the problem lies deeper (mind you, it might still be easy 
to fix, but not for *me*).  VLC simply assumes a number of output 
channels, and this is were the problem lies.  I don't quite like 
"automagic" settings like this one, because I happen to always run 
against them.  And users simply cannot fix them without actually 
changing the code.  Also, the JACK output plug-in is not the only one 
with this problem, at least the Windows MME output plug-in displays the 
same symptoms.

It might help to have an option to force VLC's number of output 
channels, possibly a global one -- but I fear it might have to be 
implemented for each and every output plug-in.  Actually, the Direct-X 
output plug-in already features such an option.  Having realised all 
this, I finally started coding a simple channel mixer which has the 
additional benefit that you can freely position the stereo downmix in 
your surround array, given you actually own one...

As a side note, jackd always exposes *all* available input and output 
ports of a sound device.  That makes (automatic or manual) 
reconfiguration of your audio setup (like insertion of a meter or EQ) a 
breeze.  So I do not quite see a *bug* in the JACK output plug-in, 
although I'm not sure on that.

Best regards,


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