May 17, 2007

It's all in the time----ing...

by Chris Randall

I'm having an odd problem with my system, and I was wondering if perhaps one of my dear readers has had a similar problem, and what the solution might be. Here is the general layout of things:

1. When I have an empty project with no recordings playing back (and thus no disk access) my MIDI timing is rock-solid sampleframe accurate. This is MIDI either being played back from the sequencer or being passed through to an external device. (I'll grant that the latter is hard to test, and I'm more or less just going on feel.)

2. The more tracks I add to the project, the worse the timing gets, and by the time I'm up to my normal track count for an instrumental (which is 30 to 50 stereo tracks) the MIDI timing is so bad as to be essentially useless. Here is an example. What you're hearing is 32nd notes fired every 16th from the DAW to an MKS80, and recording the result. The only way I can get it that good is to open my buffer all the way; I normally run it at 64, but with it set that low, maybe 5 of those notes will trigger, and in the wrong spot, natch. That's at the AES16's highest buffer setting, 1024.

So that's what's happening. The rig is Cubase 4 on Vista Business, on an Athlon64 machine. The audio is streaming off a half-TB RAID 0 array, and the MIDI interface is a MOTU MIDI Express 128. I have tried all the usual methods of getting Cubase to comply; you can rest assured on that account. I've been using PCs for music for over a decade, and Cubase almost that long. I know how to run and tune this rig; this is why this particular issue is giving me some trouble, as it falls outside my experience.

In any event, it is obviously related to the disk streaming. The more audio that is getting played back from the DAW, the worse the timing. Anyone run in to this before? If so, what's the fix?



Page 1 of 4

May.17.2007 @ 3:08 PM
I have heard that using a second hard drive and streaming off of that for all your larger files can make a big difference.

May.17.2007 @ 3:16 PM
Chris Randall
"The audio is streaming off a half-TB RAID 0 array" I think I said. You've heard that because it's correct. To save everyone a lot of typing, if there's an obvious solution (like the above) or a helpful tip, you can rest assured that I've done it. My system is a top-of-the-line computer, tuned by someone that makes a living making music and software.

This is an esoteric issue, and there's an esoteric answer; I just haven't run across it yet.



May.17.2007 @ 3:27 PM
How large block sizes you use on the raid? Maybe the cpu is chuffing on streaming too many small clusters? How does the raid connect to your system?

May.17.2007 @ 3:29 PM
i think i read that the RIAA and Microsoft decided that you couldn't use Vista to play 16th notes.

May.17.2007 @ 3:49 PM
Chris Randall
The RAID is the SATA RAID controller (a Silicon Image 3512) on the motherboard. I'll fool with the block size; that's not a terrible idea.



May.17.2007 @ 3:56 PM
Strange... I have had extensive problems with MIDI timing but on the other side of the coin, when I am laying down the first few MIDI tracks. This was on SX1, and come to think of it, I haven't noticed it since upgrading to version 3.whateva. I assume you have checked all of your sync settings, I seem to remember some timecode options there... perhaps like sending timecode info out to the MOTU via software. You have probably done this already if it's even possible, but I do not know. I am thinking while I am typing, instead of beforehand... HD, audio... hmm. If your compy is badass in the memory dept., perhaps you could change your disk cache settings to shift the activity from the disks to the memory. Doesn't the RAID array duplicate all of your data and pull it alternatively from two drives in order to double read/write times? If so, you would really need 3-4 drives to truly get audio poppin' on it's own drive. You know this too, thus the "audio is streaming off" part of the post. 2 strikes, one ball.

Only other thing I can think of is the USB nature of the MOTU. I notice significant performance gains by switching off a single usb device (Radeon controller) in projects with a lot of audio. This sucks when I am trying to add MIDI-based tracks to a project of my own. The last suggestion would be to decrease the priority of audio from "very high" to "high" ot the step below that. OK, three strikes... I'm outta here.

Peace Fish,


May.17.2007 @ 3:58 PM
Is the Motu MIDI on USB? Perhaps another USB device is stealing bandwidth/CPU cycles via some background service? Or the USB IRQ is shared with the RAID?


May.17.2007 @ 4:19 PM
Chris Randall
It is USB. (I find that USB MIDI interfaces are almost always annoying in some form, fwiw.) However, it's one of those fancy new-fangled drivers; AFAICT there is no IRQ assigned.

The RAID has one, of course.

To answer thesimulacre's last point, I've been fooling with the priority and buffer size and how they relate. In a high track-count song, if I put audio priority to "low" then I can run at a lower buffer size (call it 512) and get reasonably accurate timing. I'm currently trying out the DirectMedia emulated ports, since I've read a couple places that MOTU interfaces are happier with them.

Christ, this is annoying.



May.17.2007 @ 4:33 PM
It might be the RAID setup actually. "Onboard" RAID controllers are actually implemented largely in the software drivers, and often make very poor use of interrupts - which spells increased access latency, especially as the number of simultaneous accesses increase.

Also, these limitations will be "hard", as in running software won't be able to recognize it because it doesn't operate on a driver/kernel level.

Do you get the same effect when streaming off a single, non-striped, hard drive?

As a sidenote; performance-wise, using modern drives, it's unlikely you'd need striping unless you need several hundred MB/s throughput.


May.17.2007 @ 5:18 PM
You wouldn't by any chance still be running some of your VSTs in Novation Automap-wrapped-mode would you? I had some major MIDI timing issues with my Automapped Battery VST last week and had to disable it. Obviously this shouldn't affect MIDI going to your external gear, but it couldn't hurt to disable Automap if you're still using that Remote SL.

Page 1 of 4



Sorry, commenting is closed for this blog entry.