VST AmbiDecoder channel panner double processing / bypass?

Hello,

New to Nuendo, having an issue with routing third-order ambisonics (“3oa”) to stereo.

Specifically, I use a third-party plugin to downmix HOA ambisonics to stereo. Nuendo ships with the VST AmbiDecoder, which has similar uses and can be used as a plugin or as a channel panner, but I want to use my plugin instead for its variety of advanced options.

I have to run this plugin on a 3oa track, 3oa group or 3oa FX bus. (If I place it on a stereo stream, it obviously does not receive multichannel ambisonics input.) When I route the “stereo” output of my plugin to any form of stereo group or output, Nuendo adds VST AmbiDecoder as a channel panner, double-processing and mangling the output, and I cannot bypass this channel panner.

When the plugin is on a 3oa track, group or FX bus, it receives its 16-channel ambisonics input, and outputs 16 channels, with channels 0–1 containing my preferred L/R stereo downmix as expected, and with channels 2–15 silent. But as far as Nuendo is concerned, this is still a 3oa datastream.

If I then route the output of this track, group or FX bus to a stereo group or output, Nuendo adds a VST AmbiDecoder channel panner, which treats my two stereo channels as AmbiX 1-2 (W-Z) and double-processes them, breaking my downmix.

Naturally I tried to bypass the AmbiDecoder channel panner. When I turn on “bypass”, the panner displays as yellow on the channel strip, but it remains active and continues to double-process my sound. So the bypass has no effect.

I tried using Direct Routing slot #2 to send to my stereo output instead (main output routing using either “No Bus” or a throwaway 3oa bus), but in that case nothing goes to the stereo output at all. I tried using a Send to a stereo group, but the result still appears to be a double-processed signal.

I tried different channel panners (only other choices for 3oa-to-stereo routing were Anymix Pro and MixConvert V6) but none would work.

Ideally, my third-party plugin would be usable directly as a channel panner in Nuendo, as in this case it is serving that very function. Unfortunately, this is not an option.

It should be fundamentally simple for a DAW to take a 16-channel stream and route channels 0–1 to channels 0–1 of a 2-channel stream (would be easy in Reaper), but I can’t figure out how to do it in Nuendo. So I have to assume I’m missing something easy and obvious.

Is there a best practice here? Or a workaround? Is there a third-party channel panner that can treat 3oa as generic 16-channel audio and do custom channel mapping/mixing (0=0, 1=1) or just a 1-1 mapping with truncation?

I raised this matter with Steinberg, and they said they do not provide technical support for Ambisonics routing, suggesting I ask here. I saw a similar topic about third-party ambisonic plugins, but it seemed to be a different issue.

Is this really the official wording? Do you have a link where this was published?

The exact wording to my support ticket was:

Unfortunately we are not able to provide support for Ambisonics routing as we do not have the ability to run tests with the software or the necessary equipment. Please post your query to the Nuendo user forums: Nuendo - Steinberg Forums
The developers moderate the forums and the users are quite knowledgeable.

Thanks

Steinberg US Support

1 Like

8-0 …
That’s ---- uhm ---- astonishing. :face_with_spiral_eyes:
Kinda building a car and selling it without checking if it can go up-hill, too (because the company is located on the flat countryside).

So, any guidance here, anyone? All I want is channels 0 and 1 of 3rd Order Ambisonics track to route to channels 0 and 1 of stereo track without passing through the AmbiDecoder channel panner. This would be a no-brainer in Reaper, and seems like such a simple use case. Haven’t been able to progress past this, and frustrated that my very first and only issue has been punted by Support.

We actually do Atmos. But one of our colleagues has also worked with Ambisonics. I will confer with him. I can’t imagine that you can’t route your signal as desired in Nuendo.
(I really want to have the coffee mug with Nuendo logo. So I will leave no stone unturned to find a solution to this problem. :rofl:)

What third-party Ambisonis plug-in are you using?

Unfortunately this is (in my opinion) one more showcase of Nuendos (channel and plugin-) routing being inferior to Reaper or ProTools. And inconsistent as well…

To your problem, I found a way:

Route your 3rd Order Ambisonics Track to a Quadro group, and then this Quadro group to the desired stereo output.
This way you are able to select the “standard Panner” as panner of the 3rd Order Ambisonics track (which is not availabe when routing directly to a stereo bus…why? no Idea…)
Then you can disable this standard Panner, which will lead to channel 0,1,2,3 to be present in the Quadro bus.
Then insert “Mix 6 to 2” in the Quadro bus, and mix only the first two channels.

Ridiculusly inconvenient…

I hope this helps in your case…

Cheers,
Dirx

2 Likes

This is really extremely inconvenient. (Sounds like occupational therapy.)
Just read with amazement that using Ambisonics disables the cue sends. Does anyone know the background as to why this is? (I’ve been awake for 26 hours and can’t find the solution myself. :person_shrugging:)

@Thyme-Traveler Even if the problem is now also (halfway) solved, I would still be interested in which Ambisonics plug-in you use?

@Dirx, I look forward to trying this as soon as I’m back home. Keeping my fingers crossed that this will do it. You’re right that it’s “ridiculous”, but brilliant as well: thank you for thinking outside the box and providing such a detailed response!

I picked up Nuendo specifically for doing Ambisonics and spatial audio work (Logic does Atmos but wasn’t cutting it for Ambisonics), and so I haven’t encountered Nuendo’s Standard Panner or the Mix 6-to-2 yet. Hoping the panner can be bypassed or disabled successfully, and that the Ambisonics track’s channels 0/1 will indeed pass straight through the Quad 0/1 and onto the Stereo 0/1. I will let you know how it works out!

Strange that some panners like AmbiDecoder “appear” to be bypassed but don’t actually get bypassed. It would seem like a simple thing for Steinberg to include a “Channel Map” panner that would accept routings between any track types and act like a simple patchbay (or even a patchbay with lever faders). Or just bypass the AmbiDecoder panner as indicated in the first place.

I used Cubase years ago before standardizing on Logic 7, so some of Nuendo seems familiar. (Earlier DAWs included MOTU and, way back in the day, Opcode Vision.)

Thank you again for this workaround suggestion! Cheers!

@MAS, I have a whole bag of various Ambisonics plugins, including Sennheiser (for A-format tetrahedral to 1st order), Harpex-X (which appears to input only first-order ambisonics but maybe accepts more, and definitely outputs third-order), IEM, a few others, and Flux SPAT Revolution Essential.

Harpex-X worked flawlessly with Logic and Reaper, but doesn’t play so well with Nuendo. When inserted on a track, it will not receive input until I reset the channel type as ambisonic, which has no effect until I move the plugin pre- to post- fader or back. Every time I restart Nuendo or reload the session, I have to do this again just to get it to work. Harpex knows about the issue (it is in their documentation), but either they couldn’t find a fix with Steinberg, or else they determined that Nuendo is not worth the development effort. Too bad, because Harpex-X is a solid plugin. In fact, ideally, Harpex-X would be available as an ambi channel panner in Nuendo.

SPAT Revolution has some powerful spatial features and some weird quirks. It seems to plug into Nuendo pretty well (Logic, not so much). SPAT Revolution supports multiple “rooms”, to mix HOA, stereo, binaural, WFS/speaker arrays, etc, but the Essential version only allows one “room”. If I had the expensive Full version I could technically have a second stereo or binaural room and return both to Nuendo tracks or groups. With only one “room” available, for my current workflow I arrange for SPAT Revolution’s HOA “room”, return the full HOA to a Nuendo 3rd order Group and then use a few of my other plugins (well, try to!) to mix HOA down to an alternate binaural or stereo bus. Nuendo’s AmbiDecoder does a decent stereo/binaural downmix, but my other plugins have some nice options not available in AmbiDecoder and I want to continue to use them.

Curious if your colleague that works with Ambisonics has any opinions on this whole topic.

Cheers!

@Dirx , just wanted to report back that this does indeed work. Routing 3rd Order Ambisonics to a Quadro group using the Standard Panner was the key! The Quadro group routes to the Stereo bus. In fact, it all seems to work even without disabling the standard panner or inserting “Mix 6 to 2” on the Quadro bus.

Thank you!

Hi Thyme-Traveler,

cool, that it works.

Even more simple, nice!
The “Mix 6 to 2” would be necessarry if you need to get rid of the signal from channel 2 and 3 of the 3rd Order Ambisonics stream, otherwise it will be folded down to stereo in the output of the quad group?

Cheers,
Dirx

Makes sense. In my case, channels 2–15 are silent after the plugin mixes down the HOA to stereo.

Now if only we could just bypass/disable AmbiDecoder on HOA-to-stereo routes (well, bypass it and actually have the bypass take effect), or use the Standard Panner, life would be that much easier. Steinberg, are you reading this?