Audio on Windows Loopback to send via Ultragrid

[maybites]

Hi

We are trying to create a virtual loopback on a windows machine to pipe the output of a Multichannel Mix in Reaper and send it via ultragrid.

Does anyone have an idea to realize this reliably?

[MartinPulec]

Hi, maybe a dumb question - some 3rd party audio loopback SW like VB Cable won't do the job? Also, UG wasapi audio capture module should be capable to capture the computer audio output with -s wasapi:loopback. Unfortunately I don't know the Reaper specifics - does the SW use some uncommon output or just the OS-offered API?

[maybites]

we need a solution for 48+ channels.

https://vb-audio.com/Matrix/index.htm is very promising, it has a virtual 64 channel ASIO device that can route its input to its output through a matrix and can thus be used for loopback, but ultragrid doesn't recognize it, while reaper does just fine.

If ultragrid was able to connect to the virtual ASIO Slot, the problem would be solved.

[MartinPulec]

UltraGrid doesn't support ASIO directly, i.a. for licensing reason - we couldn't distribute the binary builds with ASIO.

Nevertheless, PortAudio does support ASIO. So with the help with Portaudio DLL, this can worked around. If you download current UG build (the word current this is important, I've just done one fix for PA/ASIO to work) and if you replace the libportaudio.dll in the directory with this one, it may work.

While I was trying the above, I must have set the sample rate to match the VB mixer setting, which was 44100 Hz (48 kHz is UG default), so something like this:
-s portaudio:dev=VASIO-64A -a sample_rate=44100,channels=32

Note that I didn't tested much (actually nearly not at all - except that it captures some data). So if you decide to try out, feel free to report problems.

[maybites]

Marvelous! I will try it next week and get back to you with my report.

[maybites]

It works like a charm. Very much appreciated!

In the below screenshot I am sending 32 audio channels from maxmsp via VBAudioMatrix to Ultragrid (I am using Telemersive Gateway as a UI wrapper).

It works fine with up to 16 channels (OPUS - 256000 bit/s - 48000Hz).

when sending 32 or even 64 channels the sound quality suffers and I have lots of crackling and dropouts. What would be the suggested settings for such a use case?

[MartinPulec]

This could be perhaps a performance issue.

Can you look if the "slow" part is the sender or the receiver? You can look into for this lines:
[Audio sender] Sent 233472 samples in last 5.06 seconds. or [audio dec.] Received 466944/466944 B, decoded 233472. In this example, obviously the sender is not managing to send all samples (it is 48 kHz), the decoder as well, but this is the consequence in this particular case. If neither case, is there anything suspicious in the UG output (packet drops etc.)?

Also I believe that 256 kbps is perhaps superfluously much for Opus - I don't believe that the quality scales much beyond - let say - 128 kbps per channel with that codec.