Spotify Connect to Dante using Librespot + Inferno.

This build keeps the known-good ALSA/Inferno path and adds an optional persistent bridge without PulseAudio, PipeWire or ALSA dmix.

Spotify Connect
      ↓
Librespot pipe backend (S32 / 44.1 kHz / stereo)
      ↓
named FIFO
      ↓
the real-time PCM bridge bridge (kept running continuously)
      ↓
pcm.dante
      ↓
ALSA plug + stereo->mono route
      ↓
inferno_raw (48 kHz / mono)
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Inferno / Dante TX

KEEP_DANTE_ALIVE=true enables this mode. the real-time PCM bridge owns pcm.dante continuously, so the Inferno device remains open even when Librespot stops or pauses playback. The FIFO is held open across Spotify playback sessions. A short digital-silence seed at container startup forces the ALSA/Inferno path to open immediately.

Set KEEP_DANTE_ALIVE=false to return to the original direct Librespot ALSA mode (BACKEND=alsa, DEVICE=dante).

The included TrueNAS example retains the working AP_PORT=443 setting. DMIX_IPC_KEY is no longer used and should be removed.

When KEEP_DANTE_ALIVE=true, librespot uses its pipe backend, but the pipe is consumed by pcm_keepalive.py at the actual ALSA playback rate. If Spotify is paused, stopped, or disconnected, the bridge immediately substitutes digital silence while keeping the dante ALSA device (and therefore Inferno) open. This avoids the large audio read-ahead that can happen with a generic FFmpeg pipe bridge.

Optional tuning variables:

• KEEPALIVE_CHUNK_MS (default 10)
• KEEPALIVE_PIPE_BYTES (default 4096)

Normally neither needs to be set in TrueNAS.