Delay with busses

[jasonmiller0607]

@Carlone Create a session with one audio track. Route that audio track to a bus. Is there a delay showing in the delay compensation window?

[AdamPT8]

There is literally no advantage in recording through an aux with effects on, if anything it is bad practise.

If you record with compression, and then decide later on you don't want as much compression as you originally put on then you're screwed because you're stuck with it.

As for the delay I don't know, you're not routing your aux out of the box and back into it in anyway are you?

[jasonmiller0607]

Adam... everyone has their own workflow. The point of this thread is not to discuss how to record things. However, it is wrong to say what I do is bad practice. If you know what you're doing you can EQ, compress, and process anything you want to tape. As a mixer, it makes it much easier later. Anyway... that's not the conversation.

No, I am not routing anything out of PT. All internal.

[crizdee]

Originally Posted by jasonmiller0607

For the record... I am using Pro Tools HD, but it's NOT a TDM system.

Here is a screenshot of my mix window. One aux track, bussed to one audio track. 206 samples of delay.

http://dl.dropbox.com/u/6925090/Bussing%20Delay.png

Hi,

Firstly you are not using PT HD you are using PT Native! this would explain the extra latency as its governed by your soundcard/driver and buffer setting.

On PT HD i get 33 samples delay in the same situation as your setup which shows 206!...

http://i229.photobucket.com/albums/e.../33samples.jpg


Chris

[jasonmiller0607]

Chris... sort of. I think HD|Native implies using an HD|Native card, which I am not. Thanks for the screenshot. So, it looks like we all have this problem but I am still wondering WHY it's a problem.

[crizdee]

Originally Posted by jasonmiller0607

Chris... sort of. I think HD|Native implies using an HD|Native card, which I am not. Thanks for the screenshot. So, it looks like we all have this problem but I am still wondering WHY it's a problem.

Hi,

If you're not using a TDM system then you are running a native system with a third party audio driver.

So we don't all have this problem! only certain users with certain soundcards are having this known scenario.

33 samples on an AUX in Pro tools HD is exactly right and expected and has always been that way. 33 samples is less than 1 millisecond


Chris

[AdamPT8]

Originally Posted by jasonmiller0607

Adam... everyone has their own workflow. The point of this thread is not to discuss how to record things. However, it is wrong to say what I do is bad practice. If you know what you're doing you can EQ, compress, and process anything you want to tape. As a mixer, it makes it much easier later. Anyway... that's not the conversation.

No, I am not routing anything out of PT. All internal.

Of course you can, however you can't undo it, and the effects take up hardly any DSP power.

However, back to the problem in hand. I hadn't actually noticed this issue before so I thought I would just test it out...

I have 1193 samples of delay at 1024 buffer...
http://i301.photobucket.com/albums/n...30at003304.png

But, when you put it into record mode the delay goes back down to 0
http://i301.photobucket.com/albums/n...30at003318.png

Maybe it is just a bug that doesn't actually do anything as when you record you are recording with 0 samples delay.

[jasonmiller0607]

@Adam... That is the exact same problem. When you put it in record, it is no longer compensating for the delay, therefore whatever you record to that track IS DELAYED. RE: Not being able to undo it... right. That's why you have to get it right. I recorded and mixed for years before I was comfortable enough with the concept. Now that I'm cozy with it, it works great for my workflow.

@Chris... yup, 33 is less than 1 ms. No prob. But 206 is nearly 5 ms (on top of the already-existing system delays) and starting to push it. For the record, I am yet to have a musician notice or complain about a delay but I still want to know WHY there is a delay.

To everyone reading this thread... I want to know WHY there is a delay in my system and what I can do to resolve it, if anything. That's all.

Any Avid engineers out there? Bueller? Bueller?

[carlone]

Originally Posted by jasonmiller0607

@Carlone Create a session with one audio track. Route that audio track to a bus. Is there a delay showing in the delay compensation window?

When I route as you suggest my delay for the track is 0 (when record enabled). When not record enable it's 135.

I'm on an HD native system with the HD Omni and I'm not using any kind of LLM. My playback buffer is 128 in a 48k session.

To everyone reading this thread... I want to know WHY there is a delay in my system and what I can do to resolve it, if anything. That's all.

Any Avid engineers out there? Bueller? Bueller?

Why all the delay? First of all - everyone here has delay (or latency).
Latency is caused by multiple factors.

1. Convertors (varies but FW or USB devices are around 2ms)
2. HW Settings (this is under your control)
3. Protocol buffering (based on whether you have a pcie, firewire or usb device. HD and HD native are around 10 samples while FW or USB are between 1-3 ms).
4. Safety buffer (help ensure that the data makes it to the cpu - not needed with pcie pro tools systems but FW or USB devices will add another 1-3 ms).

You should also know that Pro Tools WILL NOT compensate for 3rd party interfaces because it has no idea what the latency is and as a few people have mentioned your interface (and it's drivers) are the 1st culprit when it comes to determining why your getting more delay than others.

You should also know that 5-6 ms of latency is average for FW systems while 7-9 ms of latency is average for USB systems.

The biggest factor is your HW buffer setting. The fastest (or least amount of latency) you can get is a PCIe system because it has direct communication with the CPU. The worst is USB because ... well it's USB and there are interrupts so it requires much more buffering.

[daeron80]

Originally Posted by carlone

Why all the delay? First of all - everyone here has delay (or latency).
Latency is caused by multiple factors.

1. Convertors (varies but FW or USB devices are around 2ms)
2. HW Settings (this is under your control)
3. Protocol buffering (based on whether you have a pcie, firewire or usb device. HD and HD native are around 10 samples while FW or USB are between 1-3 ms).
4. Safety buffer (help ensure that the data makes it to the cpu - not needed with pcie pro tools systems but FW or USB devices will add another 1-3 ms).

That's all true but it's not the kind of latency he's talking about, as far as I can tell. This seems to be (almost?) entirely an internal routing latency issue. When you output a track (audio or aux type) to an internal bus, the sending track requires a couple hundred ms or more of compensation, depending on the hardware buffer setting. The exception is, if you route to a bus that is in turn routed to another bus, only the track with the second bus gets compensated. Now I'm really confused.

Take a look at this:
http://dl.dropbox.com/u/22074933/AuxBussing.png

• The blue tracks show that bussing an Aux to an Audio track requires compensation.
• The red tracks show that bussing an Aux to an Aux to an Audio track requires compensation only on the second Aux.
• The green ones show that... wait. What?!!! As long as the first one has been bussed off to another Aux, it can still feed an Audio track with no compensation required? Really? That has got to be a bug in the way compensation is being reported.

BTW, the image was taken on Win7x64, 002R, PT 9.0.1, in a 24/48 session. No tracks but the ones shown, no plug-ins.