• Registered: 2023-02-27
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Topic: Fireface UCX II Latencies

Dear RME team,

We are planning to use the RME Fireface UCX II in a neuroscience experiment involving brain signal acquisition (EEG) and six audio channel outputs. The experiment would run on the "Presentation Neurobehavioral software". We were wondering whether the "zero-latency" property would be effective in such a setting ? We would need either no latency (<5 ms) or a fixed one between the stimulus onset and the associated trigger on the EEG signal.
Would you think the 6 channels will easily displayed on the "Presentation" software ? (https://www.neurobs.com/menu_presentati … figuration)

For reference, we likewise asked the "Presentation" support team on this subject matter (https://www.neurobs.com/menu_support/me … d?id=11936).

Thanks in advance for your help,
Alexandra & Robin

2 Reply by ramses (edited by ramses 2023-02-27 12:59:16)

  • ramses
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Re: Fireface UCX II Latencies

Hi Alexandra, Robin,

welcome to the RME user forum.

Just curious, does the software run on Windows or macOS? There are few differences. Windows might be ideal because when using ASIO drivers, then you have direct access to the HW of the recording interface and do not have to go through the audio subsystem of the OS (neither Windows nor macOS).

If Windows:
- best would be if your software supported ASIO drivers,
  then you have then direct access from the application to the recording interface.
- 2nd option is to enable WDM drivers in the RME driver settings and to access the WDM devices
  Not known by me, what additional latency this brings. It uses the ASIO driver but might have to go through
  WDM related layers of Windows Sound system as well.

In the end, I assume the application will be capable of doing the one (ASIO) or other (WDM),
sending/receiving audio to/from the Windows default sound device would usually only be 2ch.
IMHO, ASIO support in the application would be ideal (recommended)

As a side note … "Zero-latency" is not possible as you surely know, but everybody likes/uses this term wink

The lowest latencies "near zero" you only get when routing audio on the physical interface from an input to an output. Then you have only the latencies for AD and DA conversion, the higher the sample rate, the lower the latencies (but only small differences, see below.

These values you can get from the manual, see ch 40.2 Latency and Monitoring
https://www.rme-audio.de/downloads/fface_ucx2_d.pdf
https://www.rme-audio.de/downloads/fface_ucx2_e.pdf

To put an example for 44.1 kHz: AD 5 samples, 0.11ms, DA 5.8 samples, 0.13ms = 0.24ms

I am not sure how the audio flow is in your use case
a) A/D --- USB --- PC/application or
b) A/D --- USB --- PC/application --- USB --- D/A (this is the full RTL, round trip latency)

Here a few examples of full RTL @44.1 kHz for some RME products / product combination that I own(ed).
https://www.tonstudio-forum.de/attachment/2343-ufx-ufx-raydat-latencies-v2-jpg/

To stay under 5ms RTL you would require ASIO buffer sizes of max 64 samples at 44.1 kHz.
If it is only A/D and one time over USB, then maybe also 128 samples might work.

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14

3 Reply by Muffin (edited by Muffin 2023-02-27 13:07:14)

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Re: Fireface UCX II Latencies

Here is one post of a round trip latencies for UCX II on Windows, and for several choices of sample rate and buffer size the RTL is less than 5 ms.

https://www.audiosciencereview.com/forum/index.php?attachments/1674306624330-png.258743/

4 Reply by ramses (edited by ramses 2023-02-27 13:07:47)

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Re: Fireface UCX II Latencies

Here the latencies as reported by the RME ASIO driver (MADIface USB3) to the application (here Cubase)

Sample rate: 44.1 kHz, ASIO buffersize=128 samples

https://www.dropbox.com/s/edum5l1rmq6i14v/2023-02-27%20%20UFX%2B%20Latencies%20Cubase%20ASIO%2044.1%20128%20samples.jpg?dl=1

Sample rate: 44.1 kHz, ASIO buffersize=64 samples

https://www.dropbox.com/s/3n9an6033o7ri7d/2023-02-27%20%20UFX%2B%20Latencies%20Cubase%20ASIO%2044.1%2064%20samples.jpg?dl=1

Sample rate: 44.1 kHz, ASIO buffersize=32 samples

https://www.dropbox.com/s/t88qhzv78hraema/2023-02-27%20%20UFX%2B%20Latencies%20Cubase%20ASIO%2044.1%2032%20samples.jpg?dl=1

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14
  • ramses
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Re: Fireface UCX II Latencies

The UCX II with USB2 driver allows for a minimum ASIO buffersize of 48 samples at single speed (44.1/48 kHz).
It depends on several factors whether you can use the smallest ASIO buffersize without getting audio loss:
a) PC load
b) PC performance
c) other "bad" drivers which block CPU cores for too long (high DPC latencies)

Other things to consider: a higher sample rate lowers AD/DA conversion a little (not much), but puts more stress to the CPU (double/quad speed up to 192 kHz)

I would try to stay at single speed (either 44.1/48) so that the PC/application has to process a lower audio bandwidth.
With that setting, I would try to reach the sweet spot between low latency and highest stability.
Most likely by using 64 or 128 samples buffersize.

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14

6 Reply by ramses (edited by ramses 2023-02-27 13:17:39)

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Re: Fireface UCX II Latencies

Muffin wrote:

Here is one post of a round trip latencies for UCX II on Windows, and for several choices of sample rate and buffer size the RTL is less than 5 ms.

https://www.audiosciencereview.com/forum/index.php?attachments/1674306624330-png.258743/

Thanks Muffin :-) BTW .. is there perhaps another table showing only the input latency, not the complete RTL, just in case they need only A/D and time for transport of audio over USB to PC/application?

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14

7 Reply by Muffin (edited by Muffin 2023-02-27 13:30:28)

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Re: Fireface UCX II Latencies

ramses wrote:
Muffin wrote:

Here is one post of a round trip latencies for UCX II on Windows, and for several choices of sample rate and buffer size the RTL is less than 5 ms.

https://www.audiosciencereview.com/forum/index.php?attachments/1674306624330-png.258743/


Is there another table showing only the input latency, just in case they need only A/D?

This is just the output from the Windows utility https://oblique-audio.com/rtl-utility.php and I can't see any options for what to output apart from this.

In the applications About box Matthias Carstens is credited with testing. :-)

Edit: The utility runs on MacOS as well but I've not tested that.

8 Reply by MC

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Re: Fireface UCX II Latencies

The input part alone is a useless information as such, and can not be measured. The RTL is what you need to align tracks on overdubbing.

The Mac version is absolutely phantastic, as before RTL no such tool existed at all (on Windows there was at least one alternative). And it was an honour for me to test this phantastic tool and help to make it even better.

Regards
Matthias Carstens
RME

MC's Website