Three Channel (or N Channel) support

[Skip Pack]

Back in discussions about the upcoming 7.1 release there were mentions of the possibility of supporting multiple channel output for active crossover implementations. I'm more interested in hooking up a multichannel dac to play three channel files (created externally from stereo files). I understand that there were missing capabilities in either Alsa or MPD (or both) that precluded this. I'm hoping that newer releases of those packages now built into moOde 8.2 might allow this to happen. I see no need for major interface changes (or any really), just simple buffering and transmission of the number of channels contained in an input PCM file.  Thanks

[bitlab]

Multichanneld output with 2 channels is indeed no issue anymore, see for exmplae this post.
Playing multichannel files is not out of the box. Although Alsa, MPD and CamillaDSP support multichannels files, the configuration of the audiochain in moode is oriented to stereo signals.

But I think, theoretical, you can come a long way with a custom mpd (directly send audio to asla_cdsp) and camilladsp (setup multichannel output) config.

[Skip Pack]

Your multichannel blog post is very informative! Do you know if anyone has implemented 2 to 3 channel upmixing in CamillaDSP (or if it's even possible)? I have used a plugin in F2K that does a Trifield conversion, but I just end up with output files that look good in Audacity. If this were possible, there would likely be no need to modify moOde 8.02 to do what I'm hoping to do.

[Tim Curtis]

I think the Trifield plugin is analyzing the left and right channels and extracting what it thinks should be in a center channel to create a 3.0 channel config (L, C, R)

I don't think Camilla supports this but I'm curious about your usage scenario. Are you feeding into something like a 5.1 AVR?

[Skip Pack]

I think the Trifield plugin is analyzing the left and right channels and extracting what it thinks should be in a center channel to create a 3.0 channel config (L, C, R)


I don't think Camilla supports this but I'm curious about your usage scenario. Are you feeding into something like a 5.1 AVR?

Yes, that's what the plugin is doing, I can look at the output in Audacity and listen to any one or two of the output channels to verify that it works, at least superficially.

The AVR would work, but my preferred path would be a multichannel USB dac, the Motu 4 is the one I would buy today if my player path seems to be practical.

Thanks.

[Tim Curtis]

Are you trying to do 3 channel with 3 speakers, Left Center and Right?

The Motu M4 only supports stereo L/R output.

[Skip Pack]

Yes, L, C, and R.

The M4 is a 4 channel in and 4 out device. The question then is does it handle a 3 or 4 channel PCM input from usb. Time for more research.
In any case (or DAC), I want to try stereo signal upmixed for three speakers to expeience the effects related to improving the experience of listeners not sitting in the sweet spot.

[bitlab]

Trifield in CamillaDSP could be possible, could look something like:

   

The input gains of the mixer DIV are the equivalent of the original potentiometers and the image width control. 
Also prob need an all pass filter between mixer MS and mixer DIV on the S signal as mentioned in the original article about the Trifield conversion.

You can try it out with CamillaDsp on the command line. Use raw 2 channel audio input file and generate a raw 3 channel output file.

[Tim Curtis]

That's cool. So with an M4 and Trifield DSP you would need 3 mono amps or 3 powered speakers, correct?

[Skip Pack]

For a 75 year old diyer, pursuing the hobby off and on for 50 years, finding the hardware to thrash out the process (CamillaDSP learning curve aside) is no problem. Using an AVR straight-through as a 3CH amp is the first thought. Lots of speakers too. Time to start studying.