StemRoller: desktop stem separator, Android stems player, and server daemons

- stemroller/: PySide6/QML desktop app and player for separating music into stems
- android/: Plex music player that plays per-stem mixes, with Android Auto support,
  a graphic + parametric (Equalizer APO-style) EQ, and offline downloads
- server/: stemserve (serves stems to the app) and stemd (separates the library on
  the server's GPU, with "Stem Now" priority requests)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

stemroller/settings.py

@@ -0,0 +1,78 @@
+"""Persistent settings exposed to QML as plain properties."""
+
+import json
+import os
+
+from PySide6.QtCore import Property, QObject, Signal
+
+CONFIG_PATH = os.path.join(os.path.expanduser("~/.config/stemroller"), "settings.json")
+
+DEFAULTS = {
+    "modelId": "htdemucs",
+    "twoStems": False,
+    "deviceId": "auto",
+    "outputMode": "beside",  # "beside" the source file, or "folder" (stemsDir)
+    "stemsDir": os.path.expanduser("~/Music/Stems"),
+    "exportFormat": "wav",  # wav | flac | mp3
+    "segment": 0.0,  # seconds; 0 = model default
+    "shifts": 0,
+    "overlap": 0.25,
+    "fp16": True,
+    "autoExport": False,
+    "frameOverlay": False,
+    "cacheLimitGb": 8.0,
+    "masterVolume": 1.0,  # slider position 0..1 (cubic taper in the audio engine)
+}
+
+
+class _SettingsBase(QObject):
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self._values = dict(DEFAULTS)
+        try:
+            with open(CONFIG_PATH) as f:
+                stored = json.load(f)
+            for k, v in stored.items():
+                if k not in DEFAULTS:
+                    continue
+                want = type(DEFAULTS[k])
+                if type(v) is want or (want is float and type(v) is int):
+                    self._values[k] = want(v)
+        except (OSError, ValueError):
+            pass
+
+    def save(self):
+        os.makedirs(os.path.dirname(CONFIG_PATH), exist_ok=True)
+        tmp = CONFIG_PATH + ".tmp"
+        with open(tmp, "w") as f:
+            json.dump(self._values, f, indent=2)
+        os.replace(tmp, CONFIG_PATH)
+
+    def get(self, name):
+        return self._values[name]
+
+
+def _build():
+    # Qt only sees properties and signals present when the class is created,
+    # so generate one Property + <name>Changed signal per default up front.
+    ns = {}
+    for name, default in DEFAULTS.items():
+        type_ = type(default)
+        sig = Signal()
+        ns[f"{name}Changed"] = sig
+
+        def getter(self, _n=name):
+            return self._values[_n]
+
+        def setter(self, value, _n=name, _t=type_):
+            value = _t(value)
+            if self._values[_n] != value:
+                self._values[_n] = value
+                getattr(self, f"{_n}Changed").emit()
+                self.save()
+
+        ns[name] = Property(type_, getter, setter, notify=sig)
+    return type("Settings", (_SettingsBase,), ns)
+
+
+Settings = _build()