snd-aloop working no more on 1.2.7.1

13 Jul 2022


      alsa-project/alsa-lib issue #251 was edited from tramchamploo:
```
pcm.er4s {
    # Direct hardware access
    type        hw
# Loopback card name
    #
    # Has to match "id" in the options of the snd-aloop module
    card        "Loopback"
# Loopback device ID
    device      0
# Number of audio channels
    #
    # Has to match the number of channels in music player app
    # and in the CamillaDSP input configuration
    channels    2
# Format of audio stream
    #
    # Has to match the format defined in the
    # of the CamillaDSP input configuration
    format      "FLOAT_LE"
# Sampling-rate of audio stream
    #
    # Has to match the sampling-rate defined in the
    # CamillaDSP configuration
    rate        48000
}
ctl.er4s {
    type hw
    card "Loopback"
}
```
This is the .asoundrc I'm using, it worked before this update.
Now aplay -L doesn't show this device.
Using mpd to play to the Loopback gets `snd_pcm_hw_params() failed: Invalid argument`.
Here's my mpd config:
```
audio_output {
    type "alsa"
    name "Etymotic ER4S"
    device "er4s"
    format "48000:f:2"
    mixer_type "none"
    replay_gain_handler "none"
    auto_resample "no"
    auto_format "no"
}
resampler {
  plugin "soxr"
  quality "custom"
  precision "28"
  phase_response "50"
  passband_end "91"
  stopband_begin "100"
  attenu
```
Btw, alsa should really have a detailed specification on asoundrc file. The value of the format option I specify is from a dsp project, otherwise I have no idea what to write here. And according to [https://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m.html#gaa14b7f26...) it's in a totally different format.
Issue URL     : https://github.com/alsa-project/alsa-lib/issues/251
Repository URL: https://github.com/alsa-project/alsa-lib

snd-aloop working no more on 1.2.7.1

GitHub issues - edited