No audio from Chromecast Audio via Alsa line-in

[PHLAK]

I have a physical server with a Creative sound card connected via PCIe. I've plugged a Chromecast Audio into the Line-in on this sound card. My OS can see the card and I can see it listed via lspci and have devices listed via arecord.

$ lspci
05:00.0 Audio device: Creative Labs CA0132 Sound Core3D [Sound Blaster Recon3D / Z-Series / Sound BlasterX AE-5 Plus] (rev 01)

$ sudo arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: Creative [HDA Creative], device 0: ALC898 Analog [ALC898 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: Creative [HDA Creative], device 2: ALC898 Alt Analog [ALC898 Alt Analog]
  Subdevices: 2/2
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #100 

I have my snapserver running in a Docker container. I've exposed the sound devices to this container.

services:
  snapcast:
    image: phlak/snapcast-server
    network_mode: host
    devices:
      - /dev/snd:/dev/snd
    volumes:
      - ./volumes/snapcast/snapserver.conf:/etc/snapserver.conf:ro
      - snapcast-cache:/var/cache/snapcast
      - /etc/localtime:/etc/localtime:ro

$ docker compose run snapcast snapserver --version
snapserver v0.27.0
Copyright (C) 2014-2022 BadAix (snapcast@badaix.de).
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Johannes M. Pohl and contributors <https://github.com/badaix/snapcast/graphs/contributors>.

$ docker compose run snapcast ls /dev/snd/
controlC0  hwC0D1     pcmC0D0c   pcmC0D0p   pcmC0D2c   seq        timer

The container has alsa-utils installed and can see the capture devices the same as the host.

$ docker compose exec snapcast arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: Creative [HDA Creative], device 0: ALC898 Analog [ALC898 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: Creative [HDA Creative], device 2: ALC898 Alt Analog [ALC898 Alt Analog]
  Subdevices: 2/2
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1

I have the following streams configured in my snapserver.conf file.

[stream]

source = spotify:///usr/bin/librespot?name=Spotify&username=[REDACTED]&password=[REDACTED]

source = alsa:///?name=Chromecast&device=default

Note

I've tried other device names, (e.g. hw:0,0, hw:Creative [HDA Creative] and some others) but none have worked.

The capture device volume is turned up.

$ docker compose exec snapcast alsamixer

I have a snapclient running on a Libre Computer Le Potato connected to my TVs sound bar AUX in. I'm also running a snapweb instance on my PC.

If I play music via Spotify and select the "Snapcast" device (i.e. the spotify source) everything works.

However, if I cast anything to the Chromecast Audio and select the "Chromecast" device (i.e. the alsa source) this is not working (i.e. no audio) and the source on the snapweb client is perpetually stuck showing "Chromecast: idle".

What am I missing? How can I get this to work?

[PHLAK]

Solved it myself. I didn't realize I had to . I was able to solve this myself by activating the capture source from alsamixer. This is possible by pressing Spacebar while having the capture source source selected. Once activated it shows CAPTURE listed under the capture source to indicate it's activated.