H/W insert delay compensation issues with RME converters

[katerkarlo]

I have an RME Fireface 802 audio interface and an RME Adat converter connected to it that I am using with PT 12.7 on Win10. I am trying to set up my gear so that I can use H/W fx with PT but how this works is a mystery to me.

First of all, a general question: Should Pro Tools, if ADC is enabled, account for the roundtrip delays of my converters?

And here's my problem: Sometimes PT seems to do exactly that, and sometimes not.

I measured the delay I get from sending audio out of the Fireface and back in again using the method described in the user manual. And the measurements yielded some pretty weird results, depending on the buffer size I was using (at 44.1k):

buffer 64: delay 131 samples
buffer 128: delay 259 samples
buffer 256: delay 3 samples
buffer 512: delay 3 samples
buffer 1024: delay 3 samples

Testing the Adat I/Os, I seemed to get a constant delay of 75 samples.

Does this make any sense? And how am I supposed to set up H/W insert delay now? Do I need to use a specific setting for each buffer size??? What a drag.

[john1192]

Originally Posted by katerkarlo

I have an RME Fireface 802 audio interface and an RME Adat converter connected to it that I am using with PT 12.7 on Win10. I am trying to set up my gear so that I can use H/W fx with PT but how this works is a mystery to me.

First of all, a general question: Should Pro Tools, if ADC is enabled, account for the roundtrip delays of my converters?

And here's my problem: Sometimes PT seems to do exactly that, and sometimes not.

I measured the delay I get from sending audio out of the Fireface and back in again using the method described in the user manual. And the measurements yielded some pretty weird results, depending on the buffer size I was using (at 44.1k):

buffer 64: delay 131 samples
buffer 128: delay 259 samples
buffer 256: delay 3 samples
buffer 512: delay 3 samples
buffer 1024: delay 3 samples

Testing the Adat I/Os, I seemed to get a constant delay of 75 samples.

Does this make any sense? And how am I supposed to set up H/W insert delay now? Do I need to use a specific setting for each buffer size??? What a drag.

yes you are correct in your findings .. i have the same thing here .. and as the versions change so do the Dly Amounts .. i have documented Dly amounts for MY System .. for PT 11.3.2, 12.5.2.511, 12.6, 12.6.1 .. i will be calculating for 12.7 next ..

know this - with PT 11.3.2 the H/W Insert Dly amounts were 44 - .02ms, 48 - .02 ms, 88 - .01 ms, 96 - .01, 176 - between .11 & .12 so unusable, 192 - Spot On - NO Delay Needed

PT 12.5.511 were 44 - .02, 48 .02, 88 - .01, 96 - .23. 176 & 192 SPOT ON - No Dleay Needed

PT 12.6 were 44 - 3.65, 48 - 5.35, 88 - .01, 96 - .23, 176 & 192 - Both SPOT ON - this is weird - very different

PT 12.6.1 were 44 - same as above EXCEPT 88 - 1.45, 176 & 192 - between 1.33 and 1.34 - Both NO Good as they are IN between

so, you are not alone ..

cheers john

[katerkarlo]

John, looking at your measurements it seems you found that the delay amounts in your system are changing depending on sample frequency (and PT version) but not depending on audio buffer size. Is that correct?

That would be more or less what I would expect. It would mean I have to enter specific H/W insert delay amounts for each sample frequency I use.

What I found, though, is that the delay amount changes depending on buffer size as well. And that doesn't make any sense to me, because Pro Tools should take into account buffer size as it calculates H/W insert delays.

Also, I would like to have an explanation why the delay first increases as I go from buffer 64 to 128 and then becomes a constant 3 samples as I go to higher buffer sizes.

[john1192]

Originally Posted by katerkarlo

John, looking at your measurements it seems you found that the delay amounts in your system are changing depending on sample frequency (and PT version) but not depending on audio buffer size. Is that correct?

That would be more or less what I would expect. It would mean I have to enter specific H/W insert delay amounts for each sample frequency I use.

What I found, though, is that the delay amount changes depending on buffer size as well. And that doesn't make any sense to me, because Pro Tools should take into account buffer size as it calculates H/W insert delays.

Also, I would like to have an explanation why the delay first increases as I go from buffer 64 to 128 and then becomes a constant 3 samples as I go to higher buffer sizes.

i can recheck that .. with different buffer sizes .. i think it was the same no matter which but cannot hurt to double check that ..

and i have asked the question of why they keep changing and have not been given an answer yet ...

[katerkarlo]

Yes, I'd be interested in knowing if in your system H/W insert delay changes with buffer size.

In the meantime, I did some testing with Cubase. It should basically work the same way, except in Cubase there is a ping tool to measure H/W insert latency.

What I found is that using the I/Os of the Fireface converter I get a latency of 3 samples across all buffer sizes. This is the value I need to enter in the respective field (very much the same as in PT). Using the I/Os of the Adat converter I get a constant 74 samples of delay.

So what PT should do but apparently does not is take into account the full software latency including audio buffer size. The values entered in H/W insert delay setup should stay the same across all buffer sizes.

[john1192]

Originally Posted by katerkarlo

Yes, I'd be interested in knowing if in your system H/W insert delay changes with buffer size.

In the meantime, I did some testing with Cubase. It should basically work the same way, except in Cubase there is a ping tool to measure H/W insert latency.

What I found is that using the I/Os of the Fireface converter I get a latency of 3 samples across all buffer sizes. This is the value I need to enter in the respective field (very much the same as in PT). Using the I/Os of the Adat converter I get a constant 74 samples of delay.

So what PT should do but apparently does not is take into account the full software latency including audio buffer size. The values entered in H/W insert delay setup should stay the same across all buffer sizes.

the Ping Function .. i have asked for this many times .. we need this .. Cubase / Logic have it !! they want you to buy HD and their hardware .. Cubase / Logic do not sell hardware .. makes sense i guess but that day it over !!

i can see the ADAT being more than the analog I/O .. and yes it should be exactly the same over all Buffer sizes ...

cheers john

[katerkarlo]

So you took some measurements? And latency was the same over all buffer sizes? Then something in my system is wrong... or maybe generally on the Windows side with this PT version.

I haven't been working with PT for long, but I also do get the impression that it works best with Avid hardware. Some of the programming is just really sloppy.

If you work with Avid converters you don't need to worry about the latency they introduce because the values are programmed into PT.

[john1192]

Originally Posted by katerkarlo

So you took some measurements? And latency was the same over all buffer sizes? Then something in my system is wrong... or maybe generally on the Windows side with this PT version.

I haven't been working with PT for long, but I also do get the impression that it works best with Avid hardware. Some of the programming is just really sloppy.

If you work with Avid converters you don't need to worry about the latency they introduce because the values are programmed into PT.

once again, this is very frustrating .. new version of PT and the numbers are different again ... and YES, it is changing when i change the Buffer ..

i am going to write something up on this and submit it to the powers above ..

you are not alone !!! i am on a MAC .. and am tired of this crap

just give us a Ping PLease

[surstromming]

Hi,

Avid knows about this issue.
I have the exact same issue with buffer sizes 128 and lower.
256 and higher everything is fine.
And it is not just on H/W inserts, it is on recording audio as well.

It started in PT12.6 and i reported it in october and Avid have confirmed this is a bug.

But they have it on low priority because not enough people have reported it.
I was on the phone with someone at Avid a couple of days ago and then it was just me who still had reported this issue.

I have RME as well, but I´m not sure if it is just RME users that are affected or maybe a lot of others using 3:rd party hardware?

If you start a support case maybe they will put this on higher priority.

Originally Posted by katerkarlo

buffer 64: delay 131 samples
buffer 128: delay 259 samples
buffer 256: delay 3 samples
buffer 512: delay 3 samples
buffer 1024: delay 3 samples

Best regards,
Markus

[LDS]

I started a thread along similar lines a few weeks ago - there are a bunch of ideascale links inside it. Avid may well listen!

http://duc.avid.com/showthread.php?t=387958