[linux-audio-user] midi timing problems

[James Stone]

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).

James