RoonBridge on Linux connection to Linux PCM device of a type other than hw

Roon Core Machine

Synology DS418play

Networking Gear & Setup Details

Unifi network, wired connection

Connected Audio Devices

Raspberry Pi4 running RoonBridge > [see below] > UltraLite-mk5 via USB

Description of Issue

I’d like to be able to direct RoonBridge to output to a PCM device on Linux which is not a hw device.
I understand from Roon help : Audio on Linux that RoonBridge as standard is configured to “[use] ‘hw:X,X’ device identifiers”. Is it possible to amend a configuration file or otherwise tailor my instance of RoonBridge to address a PCM device defined in asound.conf which is of a type other than “hw”?

By way of background, if this is helpful, I’m currently routing my audio to the UltraLite-mk5 through CamillaDSP using an ALSA loopback device. Since the ALSA loopback device is a (virtual) hw type it shows up fine in the Roon Audio Settings as an Audio Device. This chain all works well, but it’s limited to running at a fixed sample rate. This is because once launched, CamillaDSP runs at a fixed rate that can only be changed by stopping and restarting with a different configuration file. This is impractical to do manually.

To overcome this fixed sample rate limitation I’d like to be able to use an ALSA plugin for CamillaDSP that facilitates dynamic changing of the sample rate automatically once a change in sample rate is detected. This plugin relies on defining in asound.conf a PCM device of a bespoke type (“cdsp”) and sending audio to this device. Since it is not a hw device, RoonBridge does not currently identify and report it to Roon as an Audio Device. Hence the question. Can I add this cdsp type PCM device to the list of devices that my RoonBridge recognises, reports back to Roon as an Audio Device, and can output to?


Hey @John_Warden, no, there’s no way to do this – Roon Bridge can’t be modified or configured to accept non-hw connections.

My best recommendation is to open an issue in the CamillaDSP repo, they might have some ideas for modifying the plugin to work with Roon Bridge.

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Thanks @kevin. I already asked on the forum for CamilaDSP … and the suggestion made there was to talk to you guys. Ha. I can see why you might want to only interact with hw type devices, and why the alsa_cdsp pluggin relies on a bespoke cdsp type device. And neither of you has any appetite to change to achieve compatibility. I thought it much more likely that you might have a config file that could be amended, but there we are.

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