RME User Forum — Babyface Pro FS misreports RTL in Class Compliant mode

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (MC) — Fri, 06 Sep 2024 02:35:33 +0000

Tnanks for the info. The best way would be to have a table of the latencies in hardware that is communicated the usual way from CC hardware directly to the CC driver of the OS. That seems not to exist, though. And yes, as we have drivers coding an extra 'CC driver' does not make sense.

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (DanRand) — Thu, 05 Sep 2024 17:33:09 +0000

It's possible to override the latency figures published by Apple's CC USB driver for a device using a codeless KEXT, which is what Focusrite allows with some of its CC interfaces. See this link:

https://support.focusrite.com/hc/en-gb/ … ace-on-Mac

Apple talk about customising some properties of their CC driver at the bottom of the following page under "Ways to Extend the Class Driver":

https://developer.apple.com/library/arc … index.html

And the sample code for the "SampleUSBAudioOverrideDriver" codeless KEXT is in the following link:

https://developer.apple.com/library/arc … Intro.html

EDIT: Of course this is of limited use with RME devices and their custom drivers, and having to install a codeless kext driver kind of defeats the point of CC mode for devices with their own drivers, but I thought I'd point out that Apple does indeed provide a mechanism for customising its CC USB driver, including a CC device's reported latencies ...

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (Benzinger) — Thu, 05 Sep 2024 13:59:43 +0000

Thanks MC for chiming in.
I’ ve now learnt that it’s the audio driver that reports latency to RTL Utility (or to your DAW). And since it’s Apple that is responsible for the Class compliant audio driver I guess it’s up to them to fix this.

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (MC) — Thu, 05 Sep 2024 00:46:17 +0000

Waedi, download RTL Utility and play with it - this saves us all some time and obsolete posts.

Benzinger, we are not aware of a mechanism to send the latency numbers to macOS in CC mode, so the reported numbers are fake, we don't send any.

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (waedi) — Wed, 04 Sep 2024 20:21:59 +0000

Uh thats weird ! Then the Class-compliant mode was better (faster) than USB driver mode...?!
Did you use cable-Loopback ? Both situations same way ?

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (Benzinger) — Wed, 04 Sep 2024 20:14:29 +0000

waedi wrote:

I guess the measured latency was bigger ?

No the reported RTL was greater than the measured.
For example at 44.1 khz with a buffer size at 64 samples the reported RTL was 411 samples and the measured RTL was 336 samples.

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (waedi) — Wed, 04 Sep 2024 17:33:01 +0000

Thank you for the lesson !
It's interesting, wondering if there is an explanation.

You say the latency differs but you din't reveald in wich direction.
I guess the measured latency was bigger ?

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (Benzinger) — Wed, 04 Sep 2024 15:42:45 +0000

waedi wrote:

The reported latency was reported by who ?
Logic Pro ?

AFAIK it's the native apple driver that's reporting the latency to the RTL Utility.
The RTL utility then measures the actual latency and compare them.
In an optimal system reported latency should equal the measured latency.

RTL Utility is a tool for measuring Round Trip Latency in audio interfaces.
You can find it at https://oblique-audio.com/
You hook up your audio interface and connects your input to your output and let the utility measure the round trip latency. You can do the same in your DAW but I find this easier to work with.

Re: Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (waedi) — Wed, 04 Sep 2024 15:08:51 +0000

The reported latency was reported by who ?
Logic Pro ?

Babyface Pro FS misreports RTL in Class Compliant mode

null@example.com (Benzinger) — Wed, 04 Sep 2024 14:32:46 +0000

I ran the RTL Utility (v1.0.8) on my system trying out my Babyface Pro FS.
Running Babyface with the RME driver was spot on.
When running my Babyface in Class compliant mode the measured latency vs the reported latency differed 75 samples at 44,1 kHz and 180 samples at 96 kHz. (Buffer size 64 samples)

Is this intended behavior?

System: MacBook Air M1, MacOs 14.6.1. Firmware: v206. Driver: v4.12