[LAD] No audible MIDI jitter anymore for hw MIDI out

Ralf Mardorf ralf.mardorf at alice-dsl.net
Tue May 3 08:37:51 UTC 2011

Thank you coders :)

now I can use Linux to make music :).

Regarding to 'nobody does report success, just bugs are reported' I guess NO MIDI JITTER is worth a crossposting.

$ uname -a
Linux edubuntu #1 SMP PREEMPT RT Tue Apr 26 15:05:31 CEST 2011 i686 GNU/Linux

jackd 1.9.8 I guess svn 4290 or earlier

Qtractor svn 1978

Ardour2 1:2.8.11-1ubuntu1

a2jmidi_bridge 6-0ubuntu3

jackd --sync -Xalsarawmidi -dalsa -r48000 -p256

snd-hrtimer loaded and used as ALSA seq timer source, unfortunately there aren't enough timers to be used with JACK clients, when using the "-c" switch.

With Ardour (synced to Qtractor by JACK transport) I recorded

- Yoshimi, JACK MIDI
- Hydrogen (as sample player only, not using it's pattern sequencer)and
  DSSI plugins hosted by Qtractor, ALSA MIDI
- via PCI Envy24 MPU an Oberheim Matrix-1000, Yamaha DX7, Yamaha TG33
  connected by a MIDI thru chain

I didn't record all instruments at the same time, but one after the other and sync is perfect, no audible jitter.

Unfortunately I couldn't use -Xalsarawmidi for recording MIDI events on MIDI tracks, because there's no bridge.

FWIW, Ardours latency compensation is ok too. Ardour just isn't restoring the SMPTE offset, which isn't a big deal, because I don't use it now and manually setting it does work.

My machine is a

$ hwinfo --cpu
  Model: 15.107.2 "AMD Athlon(tm) X2 Dual Core Processor BE-2350"
  Clock: 2100 MHz
$ hwinfo --memory
  Memory Size: 4 GB
  When building the kernel I set
  'echo "CONFIG_HIGHMEM4G is not set" >> .config' and
  'echo "CONFIG_HIGHMEM64G=y" >> .config' and btw.
  'echo "CONFIG_MK8=y" >> .config' too.

The distro is Edubuntu 10.10 Maverick 32-bit + Ubuntu Studio meta packages. Using the FLOSS nv driver for a NVIDIA GeForce 7200 GS on an ASUS M2A-VM HDMI motherboard. The two PCI sound cards are not used as one virtual sound card. Both are active, but I only did use one of the cards. I didn't use any USB device, but e.g. a PS/2 mouse and keyboard. PPPoE and screen saver were enabled, CPU frequency scaling was set to performance.

Still one issue left. Any recommendations for a sound card with good audio qualitiy ;)? I guess I could spend around 700,- EUR and I need minimal 2 or better 4 analog IOs, mic pre amps etc. aren't needed, I'm using a mixing console.
At the moment I 've got two TerraTec EWX 24/96 PCI cards, which cause a muddy bass sound.

Thank you very much for the good work again,


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