Supported format missing for dmix device

[kokosowy]

Hi all,

I would like to ask you for some help. My hardware is Raspberry Pi Zero 2 W + Pirate Audio with a line-out. This s how it introduces itself:

$ sudo aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_dac], device 0: HifiBerry DAC HiFi pcm5102a-hifi-0 [HifiBerry DAC HiFi pcm5102a-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: vc4hdmi [vc4-hdmi], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

librespot was working fine with default ALSA settings, but it was competing with Mopidy for an audio device, this is why I tried to create mixing device with following ALSA configuration:

pcm.hifiberry { 
  type hw card 0 
}

pcm.!default { 
  type plug 
  slave.pcm "dmixer" 
}

pcm.dmixer { 
  type dmix 
  ipc_key 1024 
  slave { 
    pcm "hifiberry" 
    channels 2 
  } 
}

ctl.dmixer { 
  type hw 
  card 0 
}

I configured librespot to use dmix, but unfortunately each time I try to play anything being connected to librespot I get this error message:

lip 25 13:04:02 pirateaudio librespot[177560]: [2023-07-25T11:04:02Z ERROR librespot_connect::spirc] AutoplayError: MercuryError
lip 25 13:04:05 pirateaudio librespot[177560]: [2023-07-25T11:04:05Z ERROR librespot_playback::player] Audio Sink Error Invalid Parameters: <AlsaSink> Device dmix:CARD=sndrpihifiberry,DEV=0 Unsupported Format S16_LE (S16), ALSA function 'snd_pcm_hw_params_set_format' failed with error 'EINVAL: Invalid argument', Supported Format(s): ["S32"]

This is what devices librespot sees:

$ sudo librespot --device ?
[2023-07-25T10:01:21Z INFO  librespot] librespot 0.4.2 a6e1258 (Built on 2023-06-21, Build ID: g9ifMDjd, Profile: release)

        Compatible alsa device(s):

        --------------------------------------------------------------------

        Device:

                hw:CARD=sndrpihifiberry,DEV=0

        Description:

                snd_rpi_hifiberry_dac, HifiBerry DAC HiFi pcm5102a-hifi-0
                Direct hardware device without any conversions

        Supported Format & Sample Rate Combinations:

                Format: S16   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S24   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S32   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz

        --------------------------------------------------------------------

        Device:

                plughw:CARD=sndrpihifiberry,DEV=0

        Description:

                snd_rpi_hifiberry_dac, HifiBerry DAC HiFi pcm5102a-hifi-0
                Hardware device with all software conversions

        Supported Format & Sample Rate Combinations:

                Format: S16   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S24   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S24_3 Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S32   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: F32   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: F64   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz

        --------------------------------------------------------------------

        Device:

                sysdefault:CARD=sndrpihifiberry

        Description:

                snd_rpi_hifiberry_dac, HifiBerry DAC HiFi pcm5102a-hifi-0
                Default Audio Device

        Supported Format & Sample Rate Combinations:

                Format: S16   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S24   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S24_3 Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: S32   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: F32   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz
                Format: F64   Sample Rate(s): 44.1kHz, 48kHz, 88.2kHz, 96kHz

        --------------------------------------------------------------------

        Device:

                dmix:CARD=sndrpihifiberry,DEV=0

        Description:

                snd_rpi_hifiberry_dac, HifiBerry DAC HiFi pcm5102a-hifi-0
                Direct sample mixing device

        Supported Format & Sample Rate Combinations:

                Format: S32   Sample Rate(s): 48kHz

        --------------------------------------------------------------------

ALSA lib pcm_dmix.c:1075:(snd_pcm_dmix_open) unable to open slave

Oh and dtoverlay=hifiberry-dac is inside /boot/config.txt and librespot version is 0.4.2 a6e1258 (Built on 2023-06-21, Build ID: g9ifMDjd, Profile: release).

I'm quite new to ALSA configuration to be honest.. I think I should change dmix device format, but not sure how to achieve that. I also have suspicion about /etc/asound.conf whether it's being applied, because without it "aplay -L" gives me identical output.. Also "unable to open slave" on dmix is worrying me as it was supposed to be shared.

Can you please guide me a little bit? Thank you.

[roderickvd]

The dmix device is configured to support only 32 bit 48 kHz. Librespot with the Alsa backend can do 32 bit (though you need to tell it to do that) but not 48 kHz without the PR #1180.

Options:

• change your dmix device
• Use the PR
• Use Rodio which resamples

[roderickvd]

As this is not an issue with librespot, I’m converting it to a discussion.