librespot fails to accept ALSA device names as an output device

[jduncanator]

Description

Since commit ce1ab8f, the Rodio backend no longer exposes or recognizes ALSA device names, and instead only lists and recognizes "friendly names" for ALSA outputs.

After this commit the output of librespot --device ? is the following:

[2025-08-21T06:39:33Z INFO  librespot] librespot 0.6.0-dev c4766ce (Built on 2025-08-21, Build ID: QpLfXiGR, Profile: release)
[2025-08-21T06:39:33Z INFO  librespot_playback::audio_backend::rodio] Using Rodio sink with format S16 and cpal host: ALSA
Default Audio Device:
  default
Other Available Audio Devices:
  HDA Intel PCH
  Merging RAVENNA

Prior to this commit the output is the following:

[2025-08-21T06:32:04Z INFO  librespot] librespot 0.6.0-dev be37402 (Built on 2025-08-21, Build ID: HgoztJtj, Profile: release)
[2025-08-21T06:32:04Z INFO  librespot_playback::audio_backend::rodio] Using Rodio sink with format S16 and cpal host: ALSA
Default Audio Device:
  default
Other Available Audio Devices:
  hw:CARD=PCH,DEV=0
  hw:CARD=PCH,DEV=3
  hw:CARD=PCH,DEV=7
  hw:CARD=PCH,DEV=8
  hw:CARD=PCH,DEV=9
  plughw:CARD=PCH,DEV=0
  plughw:CARD=PCH,DEV=3
  plughw:CARD=PCH,DEV=7
  plughw:CARD=PCH,DEV=8
  plughw:CARD=PCH,DEV=9
  default:CARD=PCH
  sysdefault:CARD=PCH
  front:CARD=PCH,DEV=0
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
  surround40:CARD=PCH,DEV=0
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
  surround51:CARD=PCH,DEV=0
  surround71:CARD=PCH,DEV=0
  hdmi:CARD=PCH,DEV=0
  hdmi:CARD=PCH,DEV=1
  hdmi:CARD=PCH,DEV=2
  hdmi:CARD=PCH,DEV=3
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
  dmix:CARD=PCH,DEV=0
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
  dmix:CARD=PCH,DEV=3
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
  dmix:CARD=PCH,DEV=7
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
  dmix:CARD=PCH,DEV=8
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
  dmix:CARD=PCH,DEV=9
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
  hw:CARD=RAVENNA,DEV=0
  plughw:CARD=RAVENNA,DEV=0
  default:CARD=RAVENNA
  sysdefault:CARD=RAVENNA
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
  dmix:CARD=RAVENNA,DEV=0
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream

When attempting to run librespot with an ALSA device (ie. librespot --device dmix:CARD=RAVENNA,DEV=0), the output is as a following:

[2025-08-21T05:59:52Z INFO  librespot_playback::audio_backend::rodio] Using Rodio sink with format S24_3 and cpal host: ALSA
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM pipewire
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM pipewire
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM pulse
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM pulse
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM jack
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM jack
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM oss
ALSA lib pcm.c:2722:(snd_pcm_open_noupdate) Unknown PCM oss

thread '<unnamed>' panicked at playback/src/audio_backend/rodio.rs:219:61:
called `Result::unwrap()` on an `Err` value: DeviceNotAvailable("hw:CARD=RAVENNA,DEV=0")
stack backtrace:
   0:     0x55e507195d79 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hc27021c40099767c
   1:     0x55e5071aa0a3 - core::fmt::write::h4f0770298adcd782
   2:     0x55e507184cff - std::io::Write::write_fmt::h0b2c201fcd300be4
   3:     0x55e507195bc3 - std::sys::backtrace::BacktraceLock::print::hbd491c8a45546b91
   4:     0x55e507160f45 - std::panicking::default_hook::{{closure}}::h65f4a8f2e434ce09
   5:     0x55e507160d38 - std::panicking::default_hook::h73ef68af6ebbb2d3
   6:     0x55e50716151f - std::panicking::rust_panic_with_hook::h1c95e5ef3e82efd3
   7:     0x55e50719684a - std::panicking::begin_panic_handler::{{closure}}::h4ba25af490254d55
   8:     0x55e507195fa9 - std::sys::backtrace::__rust_end_short_backtrace::hcd9c5798c8bf2e2a
   9:     0x55e50716108d - rust_begin_unwind
  10:     0x55e50693f5f0 - core::panicking::panic_fmt::h96856782d9d1734f
  11:     0x55e50693fb76 - core::result::unwrap_failed::hbbe143ff7eea6e77
  12:     0x55e506bcbcc0 - librespot_playback::audio_backend::rodio::mk_rodio::h0733a9a4505391cb
  13:     0x55e506a3c7b1 - std::sys::backtrace::__rust_begin_short_backtrace::hc5c44d38822e029f
  14:     0x55e506a3da4f - core::ops::function::FnOnce::call_once{{vtable.shim}}::hc3eead36c5fb2b9d
  15:     0x55e507161b6b - std::sys::pal::unix::thread::Thread::new::thread_start::hcbb8fcac760f1b8f
  16:     0x7fb15e1acb7b - start_thread
                               at ./nptl/pthread_create.c:448:8
  17:     0x7fb15e22a7b8 - __GI___clone3
                               at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:78
  18:                0x0 - <unknown>

Version

Versions since commit ce1ab8f

How to reproduce

Steps to reproduce the behavior in librespot e.g.

1. Launch librespot with '--devices ?'
2. Observe the lack of ALSA backend devices in the list

Host (what you are running librespot on):

• OS: Debian Trixie, Linux 6.12.41

Additional context

This significantly impacts our ability to use librespot. We run multiple instances, that output to multiple sub-devices of a parent device, and we can no longer target these ALSA devices.

[jduncanator]

Suspect this was broken in cpal here: RustAudio/cpal@f43d36e.

[jduncanator]

I can confirm, manually reverting RustAudio/cpal@f43d36e from cpal, and referencing a local version of the dependency resolves this issue. Not sure how best to proceed with getting 0.7.0 out, however I feel like this will be a fairly significant breaking change for a lot of people downstream.

The quickest way would be to revert cpal and rodio back to 0.15.1/0.20.1, but I'm aware there are a number of changes in the change-log that depend on the dep bump of Rodio.

[2025-08-22T00:46:12Z INFO  librespot] librespot 0.6.0-dev 78ce118 (Built on 2025-08-22, Build ID: 2GkhTSp9, Profile: release)
[2025-08-22T00:46:12Z INFO  librespot_playback::mixer::softmixer] Mixing with softvol and volume control: Log(60.0)
[2025-08-22T00:46:12Z INFO  librespot_playback::audio_backend::rodio] Using Rodio sink with format S32 and cpal host: ALSA
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:878:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dmix.c:973:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
ALSA lib pcm_dsnoop.c:541:(snd_pcm_dsnoop_open) The dsnoop plugin supports only capture stream
[2025-08-22T00:46:12Z INFO  librespot_playback::audio_backend::rodio] Using audio device: plughw:CARD=RAVENNA,DEV=0

[jduncanator]

Looks like @roderickvd is already on it, didn't look close enough at the cpal repo. Relevant issues and PRs here: RustAudio/cpal#991 RustAudio/cpal#992.

We should look to apply their fix as a patch until this is fixed upstream: roderickvd/pleezer@f16802a

[roderickvd]

Thanks for reporting. Yes, known. Let’s continue the technical discussion over at the cpal PR.

For librespot, rather than rolling back now I prefer that users use the dedicated Alsa backend instead.

For the normal use case, Rodio in librespot is still able to open the default Alsa device. If you must use Rodio instead of Alsa (why? 😄 ) then you can work around this by creating an asoundrc and forward the default device to what you want.

[roderickvd]

Over at the cpal I thought I had seen a comment of yours with a very interesting data point, but I can’t find it anymore. Could you re-add there your experience with dmix:CARD=RAVENNA,DEV=0 and add what’s special about it? What kind of device is it, how was it set up?

[jduncanator]

Over at the cpal I thought I had seen a comment of yours with a very interesting data point, but I can’t find it anymore. Could you re-add there your experience with dmix:CARD=RAVENNA,DEV=0 and add what’s special about it? What kind of device is it, how was it set up?

I did make an initial note that it appeared with the fix in your PR the Ravenna device didn't appear in the device list, however it was due to the device being open (with plughw) in another instance of librespot, and not due to an issue with the PR itself. I removed the comment after I realized the PR worked correctly.

For context, the Ravenna device is an AES67 virtual sound card, source here: https://bitbucket.org/MergingTechnologies/ravenna-alsa-lkm

Thanks for reporting. Yes, known. Let’s continue the technical discussion over at the cpal PR.

For librespot, rather than rolling back now I prefer that users use the dedicated Alsa backend instead.

For the normal use case, Rodio in librespot is still able to open the default Alsa device. If you must use Rodio instead of Alsa (why? 😄 ) then you can work around this by creating an asoundrc and forward the default device to what you want.

I'm happy to use the ALSA backend directly, to be honest I wasn't even aware it existed until I started troubleshooting this issue. I've always used the default Rodio backend by default.

[roderickvd]

Over at the cpal I thought I had seen a comment of yours with a very interesting data point, but I can’t find it anymore. Could you re-add there your experience with dmix:CARD=RAVENNA,DEV=0 and add what’s special about it? What kind of device is it, how was it set up?

I did make an initial note that it appeared with the fix in your PR the Ravenna device didn't appear in the device list, however it was due to the device being open (with plughw) in another instance of librespot, and not due to an issue with the PR itself.

I see. In this exact condition of already being opened, did it enumerate with cpal 0.15?

I'm happy to use the ALSA backend directly, to be honest I wasn't even aware it existed until I started troubleshooting this issue. I've always used the default Rodio backend by default.

Cool. Rodio is there for ease of use, but Alsa is more bare metal.

[jduncanator]

I see. In this exact condition of already being opened, did it enumerate with cpal 0.15?

I've tested this, and the behavior is the same between both versions.