Audio-Injector adapters with PiPedal

[rerdavies]

I am the author of PiPedal (https://github.com/rerdavies/pipedal)

I have a user who is struggling to get Pipedal working with his Audio-Injector card.

PiPedal uses ALSA from a systemd service. It's an IoT sort of application, by intention. And given that neither jackd nor pipewire support audio from systemd services, ALSA it is.

PiPedal provides a graphical UI (a web interface) that allows selection and configuration of audio adapters. As currently written, it allows selection of "hw" devices only. Not for any compelling reason, but simply because I didn't really have decent understanding of what other types of devices would show up, so I had no reasonable way to test. It does (fwiw) support channel selection for devices with more than two audio channels. I considered, briefly providing optional support for dmixin and dmixer, but the problems with clock domains seemed daunting. So I didn't go far with that. For the meantime, it uses hw: devices only.

The other peculiarity is that Pipedal running as a systemd service does its best to grab the ALSA device for which it has been configured as early as possible in the boot sequence -- preferably before pulseaudio, which is an absolute curse for pro-audio, gets anywhere near using an ALSA device. If users want to use their ALSA device, they can stop or disable the pipedal service, which will then release the ALSA device it's using.

I've been browsing through various github pages associated with various Audio-Injector devices, and I'm concerned that the approach I have taken may not work with your devices (which look amazing, by the way).

My question to you: should I be supporting devices that are not hw: devices in order to better support your audio adapters? I read through the configuration recommendations for your x8 device, and I think things would not go well. Do you have any advice for anticipating configurations that you are recommending for pulseaudio (particularly). And will your dmixer configurations prevent me from opening the hw: device for exclusive use? (I notice you don't provide matching dmixin configurations).

Any advice appreciated.

Regards,

-R