Dante PTP Clocking

[B-Grade]

We have had the MTRX in the studio for less than a month, and it has been pretty great. But of course, we are looking at ways to tighten it up.

-we want to use an external IEEE 1588 PTP source (specialized RbXO, GPS-steered, ultra-low-phase noise, and globally coordinated to GPS/GNSS timescales)
-we want to understand if there are any issues with using externalized PTP sources with x-dante, as well as the Avid MTRX Studio
-we'd like to know if enabling AES67 alongside Dante poses any special issues or challenges to plan ahead for; we are aware of, for example, the fact that AES67 utilizes PTP v2, whereas Dante utilizes PTP v1

Of course, any dante/aes67/ptp related pros/cons/experience anyone can share would be super helpful. Or perhaps a web forum that might be more appropritate for this type of discussion.

[Hugh-H]

Hello B-Grade,

Dante uses PTP-2002 (v1) however it must be from an Audinate device which can include an Audinate card for a master signal generator system. A few years ago a particular large broadcast equipment company (might begin with "T" might not) put out an MSG and one of the option cards was a PTPv1 generator marketed as an accurate clock for Dante. Of course it didn't work, they had to license from Audinate and replace the early orders. Oops.

Audinate's clock designation hierarchy, while annoying for broadcast users used to a numerical tiered clock hierarchy, will give preference to a GPS locked unit. So if you purchase an Audinate option card for your MSG, Dante will prefer it.

Hugh

[LukeHoward]

It's a rabbit hole :)

But if you're running in AES67 mode, you can use a PTPv2 clock and a Dante device will act as a boundary clock to PTPv1. But, AES67 comes with a bunch of other limitations such as being limited to 48k and 1ms latency.

[B-Grade]

The whole 48K only thing is quite disappointing with AES67, same thing in Via! I can't believe that programs and standards created in recent years would be locked that way. Its a real shame, because clocking through GPS would be so tight compared to plain old word clock.

[ntp-jl]

As Luke points out, enabling AES67 in a Dante device imposes some limitations on what you can do. There is however an alternative or work-around.

You can use an AES67-enabled Dante device to bridge between PTPv2 and PTPv1. This device will receive the PTPv2 clock form your clockmaster and generate a PTPv1 clock for all Dante devices. Just make sure that none of your Dante devices (except the one acting as clock bridge) have AES67 enabled. The device acting as clock bridge does not need to have any Dante audio routed to/from it and as far as I know it can be something as simple as an AVIO adapter.

This document has some useful information on that topic:

https://go.audinate.com/resources/as...dcast-ddm-wp-f

[Hugh-H]

Hello,

As Jan said a Dante device can be used as a boundary clock between v2 and v1. Except for small setups I would not recommend an AVIO adaptor. The Audinate Ultimo chip used in the AVIO systems is too underpowered to adequately service a large PTP setup. I don't know what the limit is and I haven't found an online spec listing max number of devices. But if your setup is large enough, whatever that means, then going with the larger BroadwayII chip will enable a PTP server to a larger number of devices. There's probably a magic number of recommended devices an AVIO can serve PTP to but I can't find that information.

Hugh