• Registered: 2017-04-25
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Topic: Babyface Pro Half/Full Duplex streaming

If USB 2.0 itself is half-duplex, do any of the RME USB units (particularly either the BF Pro or the UC) have trouble streaming audio FROM the computer, while simultaneously having audio played/monitored into the PC with external gear?

Example: Have audio playing from DAW or internet, while simultaneously playing a synth connected to the RME's analog inputs?

I've only used Firewire in the past, so forgive my ignorance. With Firewire, there was always a constant "loop" I guess, of audio streaming in both directions. So I was always able to have hardware synth audio playing into the PC AND audio from the internet, itunes, etc. playing at the same time, even without a DAW open.

I really would love to own the BF Pro if it's able to work in that same manner, but I just don't know. Even with all the reading I've done & so many opposing answers I've received.

I appreciate any knowledge you can share RME! thanks!

2 Reply by MC

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Re: Babyface Pro Half/Full Duplex streaming

I have no clue what 'opposing answers' you might have received, but there are no half duplex audio interfaces on the market, unless they are true one way devices (DAC, only AD, only DA etc). And it doesn't matter what transmission interface they use (USB, FW, PCI, TB etc).

Your question is like asking if cars really can also drive backwards. There sure was a time they could not...

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2017-04-25
  • Posts: 14

Re: Babyface Pro Half/Full Duplex streaming

gearslutz & kvr members have told me that because of the nature of usb 2.0, that the transfer of data would still be half duplex (one direction at a time), but the drivers of certain interfaces may be able to overcome that.

I just never understood how drivers could have the interface work in full-duplex, but the bus itself (usb 2.0) is half-duplex. (like how could you have two-way traffic on a one-way road?)

i've thought it seemed pretty obvious we should be able to listen & playback at the same time, but I didn't know for sure about dropouts or significant latency, because of the USB data transmitting back & forth in "bursts", rather than FW streams.

all the sites I read about USB 2.0/3.0/FW features, say "the difference with 3.0 is that now it's full-duplex, unlike the older 2.0",etc.

4 Reply by ramses (edited by ramses 2017-10-16 18:17:42)

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Re: Babyface Pro Half/Full Duplex streaming

He is right, the internet is full of information, that USB2.0 uses 4 wires, 2 for power and 2 for data transfers
and these were only half-duplex, that data can only be transferred in either the one or the other direction.
And this shall have changed with USB3.0.

https://en.wikipedia.org/wiki/USB
https://www.embedded.com/design/connect … y-engineer

Matthias, can you pls bring a little more light into this, that would be great.

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13

5 Reply by MC

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Re: Babyface Pro Half/Full Duplex streaming

Isn't that obvious? The switch between one and the other direction happens so fast that it simply doesn't matter. And it is buffered as well. In the end your USB port operates like full duplex in real-world applications (which are much slower. Calculate the data rates needed for your amount of channels!). And this not only with one, but several devices all running on it at the same time. And it is not the 'drivers of certain interfaces' that need to overcome that, it is done by the USB hardware and the OS drivers already.

Point is that whoever comes up with half-duplex now and questions the full duplex capability of USB 2 audio interfaces has missed at least 8 years of audio.

Regards
Matthias Carstens
RME

MC's Website

6 Reply by ramses (edited by ramses 2017-10-17 07:42:21)

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Re: Babyface Pro Half/Full Duplex streaming

There is no doubt at least from my side that it works very well, Matthias wink

I know myself from operating several RME devices with different interfaces (USB2, USB3, PCIe) and putting together the RTT times of the different interfaces, that all is working fine and that RTT between them is on par with only minor differencies.

I was simply surprised, as I never had to investigate into this direction, that USB2/3 differentiates in terms of half/full duplex operation.

To the thread owner, I was only interested into some technical details on this topic.

In regards to your question: I was really surprised about this as well and was curious what RME would answer on this topic wink All I can tell is that this is utter bullshit, what some people tell on public forums.

To put an example, I had many years a RME UFX which is an USB2/FW400 interfaces. USB2 operated very stable up to the lowest ASIO buffersizes and was fully on par with Firewire 400 so that at the end I completely switched over to only one USB connection, as from time to time I needed USB anyway for firmware upgrades.

USB2 has been used at least for a decade by many audio interface manufacturers where RME shines with the best robust and performant drivers.

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13

7 Reply by OmegaStylesBC (edited by OmegaStylesBC 2017-10-17 21:59:30)

  • Registered: 2017-04-25
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Re: Babyface Pro Half/Full Duplex streaming

thank you both. I figured the data switching happened so fast that we couldn't tell, but as I've said, I've never bothered with USB anything until recently & I've got so many mixed answers...

My firewire unit (mackie) is dying on me & USB is just about all there is out there today, besides PCI-E & Thunderbolt is up in the air right now (using multiple adapters, motherboard support, etc.)

I never had dropouts with my FW unit & as I've never used USB for audio applications, I didn't want to deal with any problems as far as audio cutting out or freezing, etc.

So it's not until now, I suppose, that I understand the operating of USB 2.

I read all the time where users have problems with audio dropping with other interfaces, NI K6, Scarletts, MOTUs, etc.

I just never knew whether that was a drawback of the USB 2 bus or the particular drivers of those devices & people just learned to put up with them.

I understand better now, thank you again!