VB Matrix

[Keith_W]

With your answers, it is almost impossible to tell where the signal chain is broken.

However, I suspect that given that you said this:

With VB-Cable instead on VB Matrix, I had sound on channels L & R when I use VB-Audio cable as Roon endpoint.
But Mitch from Accurate Sound, told me that I have to use VB-Audio Matrix to support multichannel (2.2) as VB-Audio Cable only supports stereo

If you get sound with VB Cable but not with VB Matrix, it is likely that you have configured VB Matrix improperly.

You do not need VB Matrix to send 2ch audio from Roon to HLH. Remember that the audio remains 2ch until it goes out of the Dirac VST! I suspect you misunderstood Mitch, or you told him something else. Maybe he thought that you were trying to send 4ch audio from Roon to HLH. I don't know. But for the software pipeline that you wrote, all you need is VB Cable or VAC to send audio from Roon to HLH.

Let's keep this very simple. Let's say you want to use an electric lawnmower. You don't have an extension cord long enough, so you make one up by joining a bunch of shorter cords together. Somewhere in there, you decide that it would be a good idea to include an electrical multiplexer which is capable of routing electricity from one source to another. You try to turn on your lawnmower, and it doesn't work.

The problem is that you are overcomplicating your system. Cut it down to the simplest system that will work. It will look something like this:

Roon --> Dirac standalone --> DAC

If it works, end of story. No need for VB Matrix, software cables, HLH, or anything else. But I can understand that you might want the extra functionality that you get from HLH, so the next step would be something like this:

Roon --> 2ch software cable --> HLH --> Dirac VST --> DAC

 

[sebpoterie]

With your answers, it is almost impossible to tell where the signal chain is broken.

However, I suspect that given that you said this:



If you get sound with VB Cable but not with VB Matrix, it is likely that you have configured VB Matrix improperly.

You do not need VB Matrix to send 2ch audio from Roon to HLH. Remember that the audio remains 2ch until it goes out of the Dirac VST!

Yes, I understand but I thought that maybe the matrix was necessary to built the crossover.
I need to feed my four channels from out of the Dirac vst and this is the second part of my questions.

I suspect you misunderstood Mitch, or you told him something else. Maybe he thought that you were trying to send 4ch audio from Roon to HLH. I don't know.

To Mitch :

"Thank you for your email.
I try to use Dirac vst processor plugin instead of Dirac standalone processor.
I don't know how to set the configuration in 2.2 with your vst host.
I don't have a good grasp of the concepts of virtual cable.
I do not want to bother you, but, maybe, you could point me in the right direction?"


Answered :

Hi Sébastien,
No worries, on Windows you will likely need to use VB-Audio Matrix to support multichannel as VB-Audio Cable only supports stereo.
While this is stereo, you should be able to see how to make it multichannel:


Now you know everything....;-)

But for the software pipeline that you wrote, all you need is VB Cable or VAC to send audio from Roon to HLH.

Let's keep this very simple. Let's say you want to use an electric lawnmower. You don't have an extension cord long enough, so you make one up by joining a bunch of shorter cords together. Somewhere in there, you decide that it would be a good idea to include an electrical multiplexer which is capable of routing electricity from one source to another. You try to turn on your lawnmower, and it doesn't work.

The problem is that you are overcomplicating your system. Cut it down to the simplest system that will work. It will look something like this:

Roon --> Dirac standalone --> DAC

This is the way it works until now... but I would like to try another vst plugin and be able to switch from Dirac to something else.

If it works, end of story. No need for VB Matrix, software cables, HLH, or anything else. But I can understand that you might want the extra functionality that you get from HLH, so the next step would be something like this:

Roon --> 2ch software cable --> HLH --> Dirac VST --> DAC

Yes, that's what I would like to achieve...
Thank U again

 

[sebpoterie]

Thank U Keith.

 

[Keith_W]

I presume it's all good now? I see that your Dirac VST is getting signal. That is a good sign, it means that everything upstream of it is working.

BTW, when I am testing, I do not like using high sample rates. For me, it's 48kHz until I confirm that everything is working. Only when it works, then I start playing around with higher sample rates. Not because it sounds better, but because high sample rates reduce latency.

 

[sebpoterie]

Yes, it is working now.
last question : Do you have any recommendations on the choice of the audio buffer size ?

 

[Keith_W]

Yes, it is working now.
last question : Do you have any recommendations on the choice of the audio buffer size ?

First, a quick primer on why the buffer exists. If you have a sample rate of 48kHz, this means that your CPU needs to grab and process samples 48000 times per second. This is inefficient for CPU's to stop what it's doing and grab audio one sample at a time, it would slow your CPU to a crawl. So we have a buffer, which fills up with data, and every now and then the CPU grabs all the data from the buffer and processes it in a nice big chunk.

How fast the buffer fills up depends on the sample rate. And how small the buffer needs to be depends on how well your CPU can cope having to grab data from the buffer more often. In short, your buffer size depends on your sample rate, how many channels you are processing, and how powerful your CPU is. If your buffer is too large, it will add latency. If it's too small, it will starve the CPU of data (we call this "buffer starvation") or throttle the efficiency of the CPU. The result is audible glitches in your music.

There is no standard recommendation for buffer size. It is determined by simple experimentation: reduce the audio buffer until you start hearing artefacts. Then increase it again.