Digi001 LATENCY explained (with diagrams n' stuff!)

[lwilliam]

Good job, CCash!

I don't think too many of us can hear 51 samples, but where this is important with drum overheads or other phase-coherent mic'ing setups.

[naireko]

I cant hear 51 samples BUT I can feel 51 samples. it sure sounds jacked up when there is latency of any sort. this was just what we needed to visualize this problem. thanks.

[Gingley]

Last year, while working on a friend's 001 system, we ran my bass tracks through some outboard gear and inserted back into the 001, and the latency was quite audible. Easily fixed by bumping the tracks a bit, but it certainly had us baffled.

Thanks for the explanation!

G.

[CCash]

Thanks for the backup folks... nicely put Dave, thanks.

Jayman... whoah. Don't be so smug man. First of all, these aren't my theories. I'm just passing on the facts.

There's a good reason for this. For way too long a lot of us have been guessing about exactly how LE deals with latency. And we wondered how it affected our music. I'm not sure anyone thought that the monitoring latency was actually twice as high as the Buffer. Did you? This is a real good case for buying an analog mixing board to monitor through... or for using Low-Latency Monitoring. We had thought that using the 128 buffer had only 3 milliseconds of latency. It's really almost 7. That could start to affect performances. To me, using the 248 buffer is totally out of the question for monitoring sources.

As far as the converter latency at 51 samples, I never made a big deal about it. If you read the page you'd notice that I even said, "If you really feel it's necessary to nudge...".

And if you're going to critique my facts then I have to do the same if you're wrong about it. [img]images/icons/smile.gif[/img]

You said 51 samples is 1.7ms. It's really 51/44.1 = 1.15 ms. And you also said

That's after the mixer stage, so when you record a track it's maybe only 0.8ms out of sync at the most. Sorry, that is hardly noticable.

<font size="2" face="Verdana, Arial">Wrong, so here it is one more time: You listen to a track which plays back with a delay of about 25 samples plus the buffer size. You listen to the track and record an overdub... adds 25 samples delay going in (A/D), plus the buffer size. Pro Tools shifts it back 2 times the buffer size. Compared to the reference track, the new track is 51 samples, or 1.15ms late. I agree... NOT a big deal... but as LW said... it could be with phase-coherent stuff.

So it seems the Digidesign engineers did a fine job of accounting for everything, but getting that "useless information" to us never really happened. No hard feelings J.

[bassmac]

Hat's off to anyone attempting to figure out what all these 1's and 0's really mean.

I've gotten around most latency issues with external mixers and stuff, but the one that really KILLS me is the outboard effects latency - arrgh! [img]images/icons/mad.gif[/img]

Good job C.C. [img]images/icons/cool.gif[/img]

[dkrausz]

Bassmac wrote:

I've gotten around most latency issues with external mixers and stuff, but the one that really KILLS me is the outboard effects latency - arrgh!

<font size="2" face="Verdana, Arial">Hey Bassmac, I recently reconfigured my set up so that I no longer monitor outboard gear using AUX returns in PTLE because of the latency issue. I now monitor EVERYTHING via my Mackie 1604. No part of my mixes have any latency now.

The verbs sound MUCH less muddy and clearer. So now, if I need to print a mix where I'm using outboard. I don't bounce to disk anymore. Instead, I make sure I leave a couple of open tracks (easier to do now with 32 [img]images/icons/wink.gif[/img] ) and bring the whole mix back into LE from the console's main outputs. I do a level check with a test tone to make sure I'm ok though before I hit record. (I also make sure the tracks I'm recording to are set to "no output" or a dummy buss or you get, well you know… FEED BACK [img]images/icons/shocked.gif[/img] ).

Since doing this, not only are my mixes warmer, they also seem a bit more open and defined. I guess it's just an analog thing… Anyway, I have been really pleased with the sound I'm getting lately doing it this way. It is really a VERY noticable difference and was worth the time it took for me to set it up.

dk

[Bunting Ho]

Well done CCash!
I hope this info gets included in the PTle32T manual. [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img] [img]images/icons/grin.gif[/img]

[naireko]

I agree about mixing and tracking externally. I have always done this and I dont know if it's the extra a/d/a/d/a conversions but whatever it is it sure sounds better and is less of a headache than trying to mix in PT's. Also it makes me feel like TDM guy with all the i/o's going to a board. as a matter of a fact.. most TDMers do mix externally with an analog console cause it sounds better, is more flexible, and offers more hands on control.

I have seen the math before but can spomeone explain how 51 samples = x.x ms

[Pro Toolio]

Hey, nice job CCash! FYI, there's a very informative post on the subject of latency in the Windows LE forum, courtesy of Ken LeGault..

http://duc.digidesign.com/cgi-bin/ub...;f=32;t=008566

-Pro Toolio

[bassmac]

dk,

I’m using the verb box via s/pdif I/O as an insert on a aux track. Verb is 100% wet, then I buss what I want to the aux.

Now, to avoid the latency, should I run the analog outs of the box to my mixer and mute the aux...or something like that?

Am I even close? [img]images/icons/confused.gif[/img]