Preserve music source nature (two-channel and multichannel) using HDMI [Solved in Build 242]

I like to listen to both two-channel music and multichannel music using the HDMI inputs of my audio processor and audio receivers. All of my other sources (DVD player, Blu-ray player, Windows PC running JRiver Media Center, various other sources) preserve the nature of the music source – two-channel or multichannel – via their HDMI outputs. That it, the audio processors and receivers recognize the music source as 2.0 or 5.1. For 2.0 sources this makes available various upmixing modes that are only available for 2.0 sources, such as Anthem Music, Dolby ProLogic IIx, etc. I often like to use these upmixers.

But Roon does things differently, apparently. If you choose 2.0 channel output you can’t listen to multichannel music, and if you choose 5.1 output or 7.1 it outputs 2.0 sources as 5.1 or 7.1 channels with silence on unused channels. The problem with this method is that the processor or receiver sees this as a multichannel signal and therefore won’t make the various upmixer modes available.

I’d very much prefer that Roon act like all my other HDMI sources, including JRiver Media Center, and put out two-channel sources as 2.0, regardless of the maximum number of channels I set for HDMI. I don’t like to have to change the channel-layout setting to 2.0 every time I want to use an upmixing mode on stereo music, and then change the layout back to 5.1 if I want to listen to multichannel music.

By the way, I’m running ROCK on a NUC that I put in a fanless case, and otherwise love it.

I’ll try this again. The Roon knowledge base explains Roon’s approach to channel mapping:

‘Channel mapping for 2.0, 5.0, 5.1, and 7.1 is straightforward, since each larger layout simply adds channels to the previous one. In these cases, Roon matches up the channels from the source material with the channels on the output device and fills any unused channels with silence.’

This is not how it should be done.

All of my other HDMI sources (Including JRiver Media Centeron a windows PC) present 2-channel audio to my processor or receivers as 2-channel audio, not as 5.1 or 7.1 channel audio with unused channels silenced. With Roon if I select the 5.1 layout and play some 2-channel music my Anthem processor identifies it as a multichannel signal. Therefore, none of the upmixing modes for 2-channel audio are available. I have to switch to a 2.0 layout to use these upmixing modes, but then I can’t listen to multichannel music without switching back. HDMI is capable of carrying both stereo and multichannel signals. Please implement that capability.

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Hmm, it sounds to me as though the upmixing of a stereo channel is being done by your Anthem AVR. That is, if your JRiver and PC just presents a stereo signal, then the Anthem AVR automatically upmixes it to play back the stereo through all channels.

This is not the case for all AVRs. On my Denon, for example, I have push a button to invoke the “7 channel stereo” mode, when a stereo signal is received from any source; otherwise only the L, R, and LFE speakers are used. The upmixing is there, but it is manually invoked.

So your feature request, if implemented, would save you and other Anthem owners from having to push a button, but it wouldn’t help all of us, I think.

No, that isn’t the problem.

I can have my Anthem processor upmix two-channel audio with various upmixing algorithms, including Anthem Music. I select the mode, which defaults to stereo. I don’t listen to All or 7 Channel Stereo. I usually listen to stereo in straight stereo, but sometimes I like Anthem Music. But I can’t select Anthem Music because Roon send out a multichannel signal with several channels having silent signals. I can’t just push a button on my processor or remote to invoke Anthem Music or Dolby ProLogic IIx! I have to go into Roon setup, select the HDMI output, and reconfigure it to the 2.0 layout. But then I can’t play multichannel until I reconfigure it to 5.1 or 7.1. Switching between the two in setup is cumbersome, time consuming, and unessesary.

This works the same for my Denon receiver and my Integra processor when I want to invoke Dolby ProLogic IIx. They see a multichannel input because Roon sends out a multichannel signal with several channels silent, as they explain in the passage I quoted. I just don’t understand why they don’t send stereo as stereo, rather than stereo as multichannel with silent channels. All my other HDMI sources work that way.

These upmixing modes attempt to analyze two-channel music and steer ambient clues to the surrounds. Some also steer common signals to the center channel, but Anthem Music does not. They are far more convincing in creating an ambient surround sound than all channel stereo. They don’t do this to multichannel music because the signals are already there. They are logically incapable of doing so with multichannel where some channels are silent. So these modes are simply unavailable for multichannel music. Since Roon presents stereo as multichannel when the 5.1 and 7.1 layouts are selected, stereo can’t be upmixer with these modes. Some other modes may be available, but the ones that extract ambience to surround channels are not.

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We are planning to make an option to let stereo content play as stereo instead of using the selected channel layout. Still debating whether this will be the default behavior or not. It is probably safe either way since no-one screws up stereo.

Anything that is more than mono or stereo will keep the current behavior with Roon performing channel mapping onto the selected layout.

There is some compromise there, but delivering correct and predictable channel mapping behavior is by far the highest priority. Doing it our way allows us to take responsibility for channel mapping instead of having to point fingers at 3rd parties who are unlikely to make changes when things go wrong.


Thanks, Brian. It would be great to have stereo or mono come through HDMI as stereo or mono, while still preserving the ability to also play multichannel without changing the channel layout. The channel layout could still tell Roon how many channels can be used, while not precluding the use of fewer channels. Please implement this!

I agree completely with this. I usually listen to two channel music in Trifield in my Meridian set up and this simply isn’t available if outputting 2.0 music with Roon’s 5.1 layout.

Brian and Mike, thanks so much for changing this in the new build! I can’t wait to try it out.

This is exactly what I hoped for!


Me too, thanks for listening!