1 Topic by unodos (edited by unodos 2022-02-20 15:45:33)

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Topic: UFX+ reported latency in Ableton differs

I am using a UFX+ over USB 3.0 (Fresco Logic), Windows x64, with latest driver 0.9747, latest Firmware TB 109, DSP 46, USB 54 (AKM), TB 163, USB 67 (ESS)

There appears to be a tiny discrepancy between what Ableton thinks is the Overall Latency (input + output latency) and the latency itself. I use direct TotalMix monitoring for my externally triggered synths.

Driver Error Compensation in Ableton is as follows:

Your audio interface reports a specific latency value to Live. This value is used to offset recorded audio and MIDI when the recording track's monitor is set to "Off". However certain interfaces may report an incorrect latency. Driver Error Compensation allows Live to compensate for this

To test this they require you connect a physical output to a physical input. On one track (red) they play the sound of a tom drum with no monitoring in Ableton, and route the signal through software channel 8. They then have a separate recording track (blue) that records input 8


I ran the test on 44.1k, 64 samples and connected analog output 8 to analog input 8 on the UFX. I then used Output 8's submix to route the software playback channel 8 of the tom drum, so that it arrived at input 8.

I found a very slight offset in the signal with the recorded blue track https://lensdump.com/i/rSugDv. This is about 0.17ms off the latency of the red tom track - you can see the manual adjustment here https://lensdump.com/i/rSutWC

After then setting Driver Error Compensation in Ableton to -0.17ms (rough approximation of the overreported latency) and re-recording the blue track it ends up with a near-perfect iterpretation as shown https://lensdump.com/i/rSu1V5



Just over a tenth of a millsecond is a tiny difference that is definitely not going to be audible, but I just thought I'd ask about it anyway. Ideally there shouldn't be any difference as it uses native drivers - is this something that can easily go unaccounted for? I'd be curious to see what results other users have.

2 Reply by MC

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Re: UFX+ reported latency in Ableton differs

The easier and more detailed way to check this is RTL:

https://oblique-audio.com/rtl-utility.php

0.17 ms at 44.1 kHz equals 7.5 samples.

Regards
Matthias Carstens
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Re: UFX+ reported latency in Ableton differs

Thank you for your reply. I have tested the RTL of the unit and it comes up with a 'Suspect result', meaning the measured figure is different to what the driver is reporting.

https://lensdump.com/i/rSaV4D

For reference, Ableton interprets the Overall Latency as 4.74ms @ 44.1kHz, 64 samples. If I take the difference between RTL's 4.545ms result and Ableton, it is ~0.20ms. Setting the driver compensation value to -0.20ms and running Ableton's test again gives me an exact match between source and recording.

At 128 samples 44.1kHz, RTL reports 7.438 to Ableton's 7.64
At 256 RTL is 13.243 to Ableton's 13.4.

Running at 96kHz with the above buffers the discrepancy is there but smaller at around 0.1ms


There is still a mismatch here, are drivers needing to be updated to reflect it, or is something else at play?

4 Reply by MC

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Re: UFX+ reported latency in Ableton differs

The 'suspect' is not from the small latency offset, but the bad SNR of only 80 dB (I see 110) and an overloaded input signal (+2 dBFS). I guess you did not properly route only 8 to 8 in TM FX, and the I/O ref level might also have been not identical.

I measure 205 samples with 204 reported. Please go back to the firmware updater and check that you really have USB version 54.

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Matthias Carstens
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5 Reply by unodos (edited by unodos 2022-02-21 19:27:52)

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Re: UFX+ reported latency in Ableton differs

I have ran the test again, this time correcting the reference levels to +4 dBu. If I click 'Sub' while highlighting analog output 8, it only shows the analog 8 playback channel, so no other signals can be going through it.

Routing: https://lensdump.com/i/rejbs9

The noise floor is a lot nicer, but the values remain the same: https://lensdump.com/i/rejwD2 The value is consistent even if I set a different input level.

I meant to say the most recent firmware I have is based on ESS (USB 67) so it is up to date: https://lensdump.com/i/rejyAv


Thanks again, and please let me know if there's something else I can try

6 Reply by MC

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Re: UFX+ reported latency in Ableton differs

So you have the latest UFX+ with ESS chips. We will adjust the latency values in the next driver update to match better for this version.

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Matthias Carstens
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Re: UFX+ reported latency in Ableton differs

Interesting, I didn’t think about how that might differ between chips! Thank you for the awesome support smile