I/o plugin problems/suggestions

[georgerarnold]

Hello,

I have a quandary, it's quite lengthy to explain but I'd be very grateful for any suggestions.

I have a furman hds6 personalised headphone system in my studio.

The way I have found to use it which best suits my needs is like this:

On the stereo out in logic I use the i/o plugin, set the output to out 3-4, the input I don't worry about, I then put the mix to 0.
This sends the same output of the stereo out to output 3-4 (which I then send to the HDs6) but with the benefit of me being able to turn the stereo out fader up or down without affecting the level of the out 3-4. 
Are you with me?

Normally this works quite well, there is maybe a slight delay on the stereo out (the one I listen to) but this is not a problem because I'm not performing, and the out 3-4 (the one sent to the headphones) is in time and the performances of the musicians are in time correctly.

Today after doing it that way for some years it behaved differently.
The output on out 3-4 must have been ahead because the tracks that we were overdubbing ended up being playing early, before the track they were playing along to.
I'm certain that he played in time.
In the control room it sounded like he was playing early but if you monitored through their headphones, he was playing perfectly in time.

The only setting that I have changed from the usual way I work is the sample rate. I usually work in 96khz and today it was 48khz.

I hope I've explained the problem clearly.

If anyone has any suggestions why this has happened today and what I can do about it, or suggestions of other ways to work, I'd be very grateful.

Thanks.

[Atlas007]

Did you check the I/O plugin latency offset setting?

BTW, besides a little mixer configuration complexification, why not use the Send approach?

Edited January 24, 2023 by Atlas007

[georgerarnold]

15 minutes ago, Atlas007 said:

Did you check the I/O plugin latency offset setting?

I'll try some stuff tomorrow, that included but I've never had to use it in all the years I've done this so I'm confused why I need to start now.

[Atlas007]

Please, keep us posted!

[georgerarnold]

37 minutes ago, Atlas007 said:

Did you check the I/O plugin latency offset setting?

BTW, besides a little mixer configuration complexification, why not use the Send approach?

you can't put a send on the stereo out so it'd have to be some pretty complex routing to get it work.

[georgerarnold]

10 hours ago, Atlas007 said:

Please, keep us posted!

I've tried the latency offset now.
I set the input to a channel in order for it to work. Pressed the ping but the latency offset doesn't change.

If I put the control room headphones to one ear and the live room headphones to the other I can definitely hear a small time difference. If I manually move the latency offset it makes no difference whatsoever.

There are no other plugins in the project. What's happening?

[ulit]

22 hours ago, Atlas007 said:

Did you check the I/O plugin latency offset setting?

Is it known where the latency offset is applied, at the output path or the input path of the I/O plugin?
If the OP uses just the output path, then a potentially compensation in the input path does not have an effect.

[georgerarnold]

44 minutes ago, ulit said:

Is it known where the latency offset is applied, at the output path or the input path of the I/O plugin?
If the OP uses just the output path, then a potentially compensation in the input path does not have an effect.

I imagine it's slightly more complicated than that.
If there's latency on a track caused by an I/o plugin, then it's all the tracks that have to be delayed in order for them all to line up.

[georgerarnold]

 

Upon further exploration I'm starting to understand the problem but I'm still no closer to finding a solution.
The problem is with the i/o plugin. When used in the way I've been using it, it adds latency to out 1-2 and not to out 3-4.
The existing audio within logic is compensated for the latency on out 1-2 so the result is that the new audio track is ahead of the beat.
Using 48khz instead of 96 makes the latency larger and therefor more noticeable.
If I reduce the buffer size the latency is reduced.

If I use "low latency" mode then the i/o plugin doesn't work until I set the limit to 26ms.

What I've yet to ascertain is if I turn off plugin compensation, whether the audio will line up. I will test that as it'd be interesting to know.

What I really don't understand is why the i/o plugin would introduce latency when all it is doing is routing. Surely it takes no more processing than an ordinary send?

I'm finding more and more strange quirks with logic.

[georgerarnold]

I've just done another little test and the results are very interesting.

Somebody suggested why don't I set it up with sends to do the same thing:

If I use an aux send to out 3-4 on an audio track, there is also  the same latency between out 1-2 (stereo out) and out 3-4. why?? there's no plugin involved at all, out 3-4 should out put the same audio at the same time, why is there a delay on out 1-2?

[ulit]

I've tried to reproduce your setup, at least partly: in the HW mixer of my interface, Output 1-2 and 3-4 from Logic are mixed together to the headphones, 1-2 is panned to left, 3-4 to the right.

A software instrument track (short hi hat) uses 1-2 as output.

Setup a send to an aux routed to output 3-4. I cannot hear any latency on the right channel of my headphones (expect when adding e.g. the Adaptive  Limiter to the aux and switching Latency Compensation not to 'All').

Also no latency when using instead the I/O plugin ("Output": 3-4) on the software instrument track.
The Latency Offset behaves as expected.

[georgerarnold]

9 minutes ago, ulit said:

I've tried to reproduce your setup, at least partly: in the HW mixer of my interface, Output 1-2 and 3-4 from Logic are mixed together to the headphones, 1-2 is panned to left, 3-4 to the right.

A software instrument track (short hi hat) uses 1-2 as output.

Setup a send to an aux routed to output 3-4. I cannot hear any latency on the right channel of my headphones (expect when adding e.g. the Adaptive  Limiter to the aux and switching Latency Compensation not to 'All').

Also no latency when using instead the I/O plugin ("Output": 3-4) on the software instrument track.
The Latency Offset behaves as expected.

Thanks for trying, interesting results. 
No latency at all? Which sample rate are you using and buffer size?
The latency is not noticeable if I use 96khz and a small buffer like 128 but if I use 48khz and a longer buffer its very noticeable.

[ulit]

2 hours ago, georgerarnold said:

Which sample rate are you using and buffer size?

44.1kHz and 128 samples buffer size; perhaps I should try again with larger buffers.

[georgerarnold]

9 hours ago, ulit said:

44.1kHz and 128 samples buffer size; perhaps I should try again with larger buffers.

It would be interesting to know.

[triplets]

18 hours ago, georgerarnold said:

small buffer like 128

That's not small for headphone mixes. Gotta go to 64 or even 32 to not notice latency.

[georgerarnold]

32 minutes ago, triplets said:

That's not small for headphone mixes. Gotta go to 64 or even 32 to not notice latency.

Point taken but I think the real question here is why is the any difference at all between stereo out (out 1-2) and out 3-4, without plugins, using a send?

[triplets]

45 minutes ago, georgerarnold said:

why is the any difference at all between stereo out (out 1-2) and out 3-4, without plugins, using a send?

Sends are digital, no conversion. I/O plugin uses hardware, so there's is conversion getting out and getting back in creating latency, thus Logic has to compensate the playback to line everything up on the stereo out.

[georgerarnold]

2 hours ago, triplets said:

Sends are digital, no conversion. I/O plugin uses hardware, so there's is conversion getting out and getting back in creating latency, thus Logic has to compensate the playback to line everything up on the stereo out.

Thanks for the lesson.

Read the thread and you'll see what I'm trying to achieve and what I mean by "using a send".

[ulit]

12 hours ago, georgerarnold said:

It would be interesting to know.

With my setup using a Send to Output 3-4, there is no latency at all between Output 1-2 and Output 3-4 (at 44.1kHz, all buffer sizes between 32 and 1024).

When using the I/O plugin, the signal to Output 3-4 is shifted 'earlier' (ok, in reality, Output 1-2 is delayed). The latency that I measure between Output 1-2 and Output 3-4 is  - drum roll - exactly the round trip latency that is reported in the Audio Settings (for all buffer sizes).
(so I must revoke my previous statement "Also no latency when using instead the I/O plugin ("Output": 3-4) on the software instrument track.", sorry, the measurement reveals a latency).

I would interprete that as: the I/O plugin is meant to be used with both an Output and an Input. Using just one half of it (using it just for routing to an Output) leads to over-compensanted latency.

 

 

Edited January 28, 2023 by ulit

[triplets]

On 1/28/2023 at 12:00 PM, georgerarnold said:

Thanks for the lesson.

Read the thread and you'll see what I'm trying to achieve and what I mean by "using a send".

Thanks for the passive aggressive comment. I did read the thread and I think you're trying to do thing with the I/o plugin that it's not designed for.

[georgerarnold]

On 1/28/2023 at 9:29 PM, ulit said:

With my setup using a Send to Output 3-4, there is no latency at all between Output 1-2 and Output 3-4 (at 44.1kHz, all buffer sizes between 32 and 1024).

When using the I/O plugin, the signal to Output 3-4 is shifted 'earlier' (ok, in reality, Output 1-2 is delayed). The latency that I measure between Output 1-2 and Output 3-4 is  - drum roll - exactly the round trip latency that is reported in the Audio Settings (for all buffer sizes).
(so I must revoke my previous statement "Also no latency when using instead the I/O plugin ("Output": 3-4) on the software instrument track.", sorry, the measurement reveals a latency).

I would interprete that as: the I/O plugin is meant to be used with both an Output and an Input. Using just one half of it (using it just for routing to an Output) leads to over-compensanted latency.

Very interesting. Thank you for your help!
Can I ask how you measured the latency?

I think I might be getting closer to a work around with your help.

Although I'm still none the wiser why I get the same latency while routing a send to out 3-4 than I do while using the i/o plugin.

[ulit]

25 minutes ago, georgerarnold said:

Can I ask how you measured the latency?

Sure, I've recorded the headphone output of my interface with an external audio recorder (the Output 1-2 is panned hard to the left, Output 3-4 is panned hard to the right). Then import these recordings again in Logic and use the sample editor for measuring the delay between the peaks on left and right channel.

[georgerarnold]

10 hours ago, ulit said:

Sure, I've recorded the headphone output of my interface with an external audio recorder (the Output 1-2 is panned hard to the left, Output 3-4 is panned hard to the right). Then import these recordings again in Logic and use the sample editor for measuring the delay between the peaks on left and right channel.

Thank you. very kind.

I'm thinking about how I can use sample delay combined with recording delay to make this work.
Thanks for your help very much appreciated.