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Author Topic: multichannel audio DAC channel mapping question  (Read 2817 times)

TheShoe

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multichannel audio DAC channel mapping question
« on: December 26, 2020, 02:12:18 pm »

I have a multichannel DSD DAC (8 channel).

In JRiver, I have DSD set to bitstreaming, so no conversion.

If I play a multichannel 5.1 DSD file, the surrounds are mapped to the surround back channels vs the surround side channels.  All other channels are fine.

If I enable conversion and disable bitstreaming, then JRiver will convert to PCM and map the surrounds to the surround side channels instead of the back channels.

Curious - what is considered "correct"?  the DAC provides no channel mapping - should multi-channel audio (DSD, PCM (flac)) map surrounds to surround side, or surround back?

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mwillems

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Re: multichannel audio DAC channel mapping question
« Reply #1 on: December 26, 2020, 02:29:51 pm »

So there's an issue in that the default channel maps for 5.1 and 7.1 are different and incompatible.  In a standard 5.1 channel map SL and SR are channels 5 and 6, but in a standard 7.1 channel map SL and SR are channels 7 and 8, while RL and RR are 5 and 6.  So depending on which channel count your source material has (i.e. 5.1 or 7.1) you will get different content out of channels five and six when bitstreaming or using the "source number of channels" option in output format, which is not ideal as 5.1 mixes are not intended to play out of rear surrounds.

I'm not sure that there is a good way to resolve this while bitstreaming other than physically changing the speaker connections. If you're willing to disable bitstreaming, you can set output format to your actual channel setup (sounds like 7.1?) and then disable up and downmixing, and you should get the correct outputs in the correct speakers all the time.
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TheShoe

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Re: multichannel audio DAC channel mapping question
« Reply #2 on: December 26, 2020, 08:25:25 pm »

I have a lot of multichannel DSD, and don't want to convert it to PCM as the DAC can handle native DSD.

It seems silly that the DAC would not at least have the capability to map this correctly with bit streamed DSD since it's a multichannel DAC geared towards people who likely have a lot of multichannel audio - which is typically 5.1, not 7.1 (movie soundtracks not withstanding).

I emailed George over at exasound (my DAC is an e38 Mark II) to see what he has to say.

For PCM, I suppose I could set up a separate zone and change the channels to 7.1 in DSP & Output format settings.  That does map to the side L/R surrounds vs the back surrounds.  But for native DSD, that's not an option.

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mwillems

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Re: multichannel audio DAC channel mapping question
« Reply #3 on: December 26, 2020, 11:16:30 pm »

Yeah, if there's a way to handle routing changes in the DAC driver (or in the DAC's firmware) that would be the easiest solution for sure.

If the DAC doesn't support that kind of remapping, though, another potential solution (if all of your DSD content is 5.1) is to reverse the physical wiring for your Rear and Side speakers (i.e. wire the surrounds to channels five and six and the rears to channels seven and eight).  Then make two zones, a bitstreaming zone and a PCM zone.  In the bitstreaming zone everything will work as expected for 5.1, but in the PCM zone you can set the output format to 7.1 and use DSP Studio to swap the channels so they'll be correct using the parametric equalizer block.  I'm sure that's not an ideal solution, but bitstreaming really limits what you can do on the JRiver side to resolve the problem, unfortunately.
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TheShoe

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Re: multichannel audio DAC channel mapping question
« Reply #4 on: December 27, 2020, 06:24:28 am »

Your idea sounds brilliant to me!  Will try it this morning.

I typically use my exasound for audio playback only.  Video is played through my Marantz which handles the audio in that use case.

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TheShoe

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Re: multichannel audio DAC channel mapping question
« Reply #5 on: December 27, 2020, 02:19:27 pm »

Here's what I ended up with:

I swapped the inputs on the DAC for side L/R and rear L/R.  Then I set up two zones:

zone 1: DAC (5.1) - source # of channels.  DSD and PCM 5.1 audio play through the expected side L/R channels, no conversion in MC.

zone 2: DAC (7.1) - configure for 7.1 speakers.  Set up Parametric Equalizer - added Order Channels, and swapped the side L/R and rear L/R to effectively map them back correctly.  Playing 7.1 audio is as expected

Now need to set up some rules for zone switching depending on source.

Thanks for the tips!  This is an acceptable work around.  If George@exaSound replies with anything interesting, will be happy to share it.



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mwillems

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Re: multichannel audio DAC channel mapping question
« Reply #6 on: December 27, 2020, 04:33:48 pm »

Glad it worked out!  I'll be interested to hear if there's a hardware solution from Exasound
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TheShoe

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Re: multichannel audio DAC channel mapping question
« Reply #7 on: December 28, 2020, 02:25:18 pm »

George responded and said not possible to do channel mapping in the ASIO driver.

he liked the solution with JRiver however that i implemented
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