ReNamed - Stompas Latency and Jitter happy hour

[emphazer]

Agreed. I was under the impression though that his friend had created this 'test' to show that there was some 'issue' afoot (there isn't if I finally understood everything).

here is an issue
the problems seems to be the motherboard.
tried the same cards on another pc and there wasnt the problem
so i will just buy a new motherboard.

[Stompa81]

did you try my suggestion?

Yes I did Piddi sorry I should have put that in the post.. My Brain cant think of too many things at the same time so i must have forgotten I havent been able to get on my PC very often this week, Hence me not posting very much.

So it looks like my issue is just midi latency and all the other confision was caused by using 2 different midi notes to trigger. And my friend (Emphazer ) just needs a new motherboard

Thankyou everyone for helping me understand what was happening!! Now its time to go play. woo hoo

[valis]

lol, go have fun!

[Stompa81]

Just one last quick Question..

(BTW everytning is sweeet as now )

Is there an acceptable Jitter level ??

The reason I ask this, Now I have my Midi Track delay setup the Beats Land exactly on the mark every time ( its actually better for me in Ableton live 6.0.5 as opposed to cubase)

However when I Zoom right into the recording audio (like a microscope , looking at a field covering a couple of ms) sometimes the audio will land approximately 1/4 a ms early or late from the Beat it was meant to land on, Not very often, most of the time its dead on the mark.

Is this what jitter is?? IF yes, Is what I described a "normal" level of jitter or are there some things I may be able to tweak to improve it ?

Sometimes it is noticeable as there is some slight Phazing when this occurs, but as I said, its not a very frequent event, but again this random phazing is probably due to the error of my ways )

I am asking this to learn, not to imply that there is an issue here, well there is an issue which is my lack of knowledge

Please feed my hungry brain
( I hope this topic isnt boring any of you because this is all very interesting to me)

[astroman]

no problem - 'jitter' isn't quantified in any way (and not restricted to digital audio either)
if something is supposed to happen repeatingly at a constant time interval, but doesn't always hit that point precisely, then the deviation is called jitter.

as your example shows, you already know the 'more subtle' sideeffects.
the 'range' mentioned is of course not tolerable when stacking sounds - with drums it may be quite obvious, but anything 'stacked' will change it's tonal color heavily.
That's why it's important to monitor at the proper 'position' of the signal chain.

what you describe can be rather nasty, if you monitor the audio (let's assume perfectly aligned), but record the midi data - and then on the next playback the 'spread' midi notes will have 'magically' changed the sound of the mix .

cheers, Tom

[Stompa81]

The Jitter appears to be identical for multiple tracks as well , all hits happen at the same time but they all "Jitter around" in time together. You cant see it unless u zoom in a great deal, but definatly at times U can hear something is just not cool.

I have to apply -11.0 ms of track delay on my midi tracks to make the audio land where its supposed to .. Im thinking such a big delay may have something to do with the problem. Does this sound like I have an Incorrect Scope setup , driver issues or XP configuration, Im thinking my Motherboard could be causing this, Empahzer was having same issues until he swapped to new Mother board

Hmm I dont really know where to start, where would you start looking if this were you ?

Edit:- The jitter does not seems to be happenening anymore this is good , now I have to try and figure out what the possible causes of this could have been

[valis]

You have to apply -11ms in what application? It could be that the application isn't properly dealing with compensating for your ASIO latency? Also again the signal chain would have to be looked at. If motherboard seems to be affecting things there may be some reason why?

As for jitter, there are multiple considerations still. In my posted example on the previous page there is only ONE midi event sent at a time, on one channel & one output port. The simplest possible test that yields an understanding of the level of jitter in the route. I also knew beforehand to what degree my sequencer (Logic) accounted for ASIO latency. Some signal routing/application/soundcard combinations will get the software buffer size for your ASIO latency correct but won't account for the small additional overhead imposed by any converters in the path. Whether they are AD/DA or ADAT, spdif etc. they all have at least SOME amount of internal overhead (a data buffer). Most are on the order or one or a few samples so it's negligable in most cases, a few cards will impose close to an additional millisecond, especially when firewire is in the picture.

The place where I got the most clear info on these subjects was SoundOnSound over my years of reading it. Almost everything I refer to here is available by searching through their site here: http://www.soundonsound.com/articles/Technique.php Artciles under 6 months old need a magazine subscription but the rest is fair game. I also have gleaned some additional info from various other forums, newsgroups & mailling lists I have lurked on over the years (LUG used to be excellent for instance, the same with our own Z!)

Now when you take a 'real world case' such as a full blown project where you're dealing with quite a few audio & midi tracks, it's much harder to track down exactly what issues are present. This is why I stress isolating things with specific tests, be it using a single line of notes to trigger kickme in isolation, or using a single cycle click (impulse) or very clicky 'kick' with enough midrange content to test my audio chains in scope for phase coherence. There are actually ways to do this in a current project so you can make corrections 'in real time' but I wasn't any good at this until I had a thorough understanding of what issues were occuring.

There are a few rules of thumb here really:

Isolate one thing at a time to determine what the source of a problem may be. Trying 14 things at once then completely changing 11 of them before testing again will yield wildly different results each time. If you're pressed for time use some workaround that you know you can rely on until you have the time to test. Blindly fudging around to try to make something 'better' is akin to just randomly twisting knobs on a piece of rackmount studio gear. You might accidentally make things 'better' but more often than not you're just making random changes.

In the SCOPE environment a high cpu load on your main computer can cause timing issues to worsen when dealing with midi within Scope. Midi in scope is known as Async (asyncronous) data and is handled in software by the cpu. It's a no-brainer to understand that driving your main sequencer up to 90% might steal some performance from Scope.

I generally try to use from 3-5 'software' midi ports with Scope when doing complex control routings. Ie, if you have 2 'live' synths and then a bunch of midi cc's coming in to automate mixers & effects, its probably best to give each synth its own Sequencer i/o and then at least 1 additional one for your cc automation (or even more if you have some timing critical mutes or filter sweeps).

Above all consider resampling, be it a single note or a full musical phrase. It can be your friend when it comes to composing music in a digital environment.for more reasons than just correcting phase relationships when layering drums or thick basses (the main reasons I worry about timing). There are certain things that will always be easier when you are dealing with a prerecorded section than 'live' data. One of my favorite examples applies to drums:

If you take a decent section of drums, say a break or two layered with some hihats and a lowpassed kick & snare combo underneath to thicken things up, all eq'd properly to 'fit' together, apply reverb to that and then a bit of buss compression across the whole 'drum bus' and record that, and THEN edit it by chopping it you'll get a gated effect that wouldn't be at all possible when keeping all of that data live. THere are so many other ways to add onto this idea. For instance consider a bass sequence where you have complex note-driven filtering going on. If you take that and toss it into a sampler and retrigger it again you open up new possibiilities for again layering & driving filters and envelopes from the note on events, possibly triggering complicated step sequenced envelopes or etc. While you might be able to come to some sort of close approximation of this in a complicated signal chain, the committing to the audio simplifies things so that your musical choices are easy to make at each stage, and there are ways to retain the things that 'got you there' (saving multiple versions of projects, presets, and even just muting/disabling signal chains and moving them out of view).

[Stompa81]

Thats going to keep me going for a while ,Thanx

I will take all of that into account and have a look around @ sound on sound and Im sure with all this info I'll have a better understanding of the many factors that affect latency / Jitter ,and should be able to sort it out.

Thanks for taking the time for that biblical post , answered all my questions