Subject: Re: [linux-audio-user] recent hydrogen / jack / ardour
From: Mathias Lundgren (mathias_lundgren_AT_bredband.net)
Date: Sat Oct 25 2003 - 16:28:50 EEST
lördagen den 25 oktober 2003 05.42 skrev Jesse Chappell:
> Mathias Lundgren wrote on Sat, 25-Oct-2003:
> > lördagen den 25 oktober 2003 01.10 skrev Paul Winkler:
> > > On Fri, Oct 24, 2003 at 06:44:31PM -0400, Paul Winkler wrote:
> > > > seems to be building now, thanks!
> > >
> > > and it runs.
> > > damn, hydrogen is fun. wish i had this years ago.
> >
> > Yes, it's neat. The things you don't do to run bleeding edge...
> > One thing that I think is a little sad is that it's not realtime safe...
> > (at least it wasn't last time I checked). I'd really love to have the
> > possibility to use it from a sequencer and get the output via Jack.
> > Okay, it works, but in case you need to increase jack's period things
> > get shaky and unsynced. Hydrogen and zynadd running realtime safe
> > together with jack and MusE, that would be something. Oh, and the
> > possibility to have ladspa send effects in hydrogen. Then I'd be happy
> > as a bee.
>
> You can turn on JACK ports for each instrument, then run them
> through jack-rack or similar (or into ardour).
Neat, is this one of the latest features? I haven't found it (honestly, I
haven't looked very hard for it). But doesn't that require one specific
effect for each channel? I guess it's possible to do it in ardour (one
jack-channel for each instruments and then using send-effects on them through
ardour), but I think it's a bit of overkill. I would love to have a couple of
internal send-channels in hydrogen, so that you can share f.ex. one reverb
amongst all your drums. Those send effects could just be sent out to a jack
port, and then connected via f.ex. jack-rack (or even better through ladspa
effects loaded in hydrogen, but maybe ladcca will solve this issue). Yes,
there will probably be some overhead mixing and routing the send-outputs, but
that'll be very little compared to running 5 reverbs.... Zynadd does this in
a very nice way IMHO. Well, I'm just dreaming... :-)
> Can you be more specific about the problems with increased periods?
> I would like to further contribute to hydrogen's realtime safeness
> (although precision and accuracy problems you seem to be describing).
I've run hydrogen feeding it midi via MusE and jack as audio output. When
using -p 512 it sounds OK, even though it's possible to hear that the timing
isn't accurate. When increasing the period, -p 2048, it's really horrible.
I've glanced at the midi input thread sources in hydrogen and noticed there
are a few mutex thingies there. I've tried increasing the real time priority
of the midi thread, with no luck. I guess jack's callback function (audio
processing) and midi input thread are locking each other out, and when the
buffer gets bigger it results in greater inaccuracy. When running hydrogen
with alsa output in the same scenario as above, there's no timing problems
(but then I can't use it together with any other apps). The above scenario
applies to Zynadd as well.
/Mathias
This archive was generated by hypermail 2b28 : Sat Oct 25 2003 - 16:29:34 EEST