[linux-audio-user] midi timing problems

[Aaron Trumm]

I've followed this thread lightly, I should've followed it closer

I've a question for you - what version of hydrogen are you using, and how do
you get it to sync to ardour?  this is something I haven't had any luck
with, and haven't even had a chance to spend enough time on, given how
important it is to my setup...


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----- Original Message -----
From: "James Stone" <stone1 at btinternet.com>
To: "A list for linux audio users" <linux-audio-user at music.columbia.edu>
Sent: Tuesday, November 18, 2003 4:32 PM
Subject: Re: [linux-audio-user] midi timing problems


> On Sat, Nov 15, 2003 at 05:12:45PM +0000, James Stone wrote:
> > On Tue, Nov 11, 2003 at 09:13:58PM +0000, James Stone wrote:
> > > Hello everyone.
> > >
> > > I have a problem with midi timing.. I think I have set up enhanced rtc
> > > correctly and low latency patch on kernel 2.4.20.
> > >
> > > When I drive hydrogen (or even the inbuilt soundfont player on my
> > > SBLive) with seq24 or ardour, there is a noticable variation in midi
> > > timing. This was tested by using a run of closed hihats. When I play
the
> > > sequence back, the hihats are grouped in batches rather than being
> > > evenly spaced. This was noticable when running as root and when using
> > > alsa and (to a lesser extent) jack. The midi connection is via alsa.
> > >
> > > Any hints on what I should do?
> > >
> > > James
> >
> > Just to reply to myself,
> >
> > I solved the problem:
> >
> > I needed to install the snd-rtctimer for alsa. This required a patch to
> > the kernel RTC (patch included with ALSA but also needed a tweak. see:
> >
> > http://www.geocrawler.com/archives/3/12349/2001/7/0/6299315/
> >
> > )
> >
> > After that, snd-rtctimer built okay. Then I added the following to
> > modules.conf:
> >
> > options snd-timer snd_timer_limit=2
> > options snd-seq snd_seq_default_timer_resolution=2000
snd_seq_default_timer=1
> > options snd-rtctimer rtctimer_freq=2048
> > alias snd-timer-1 snd-rtctimer
> >
> > Now, midi timing is sorted (at least for muse when running as root so it
> > can access the RTC.. seq24 doesn't seem to be quite there yet in my
> > experience).
>
> Just a further note.. Needed to apply the variable frequency kernel
> scheduling patch and set the frequency to 1000Hz and now the timing
> problem with seq24 is solved.
>
> James