v0.5 — cleanup orphan code, add MIDI master volume learn, fix turn-deck crashes

- Remove vestigial lufs_meter_widget.py and debug_audio.py
- Delete unused WaveformWidget/WaveformMonitor classes, dead stubs, duplicate code
- Fix turn-mode deck crashes (deck3/deck4 missing from engine.decks, uninitialized manual_elapsed/duration)
- Replace raw print() with logging in main.py
- Add master_volume MIDI learn signal + settings popup entry
- Bump version to 0.5

audio_engine.py

@@ -89,6 +89,8 @@ class DeckState:
         self.position = 0
         self.playing  = False
         self.lock     = threading.Lock()
+        self.manual_elapsed = 0.0
+        self.manual_duration = 0.0
 
     def load(self, track: Track):
         with self.lock:
@@ -131,15 +133,17 @@ class DeckState:
                 self.position = self.track.num_samples - 1
 
     def get_elapsed(self) -> str:
-        if not self.track:
-            return "00:00"
-        s = self.position / self.track.sr
+        with self.lock:
+            if not self.track:
+                return "00:00"
+            s = self.position / self.track.sr
         return f"{int(s//60):02d}:{int(s%60):02d}"
 
     def get_remaining(self) -> str:
-        if not self.track:
-            return "-00:00"
-        remaining = max(0, self.track.duration - (self.position / self.track.sr))
+        with self.lock:
+            if not self.track:
+                return "-00:00"
+            remaining = max(0, self.track.duration - (self.position / self.track.sr))
         return f"-{int(remaining//60):02d}:{int(remaining%60):02d}"
 
 
@@ -228,6 +232,8 @@ class MasterBus:
         self.limiter = Limiter()
         self.vu_peak = 0.0
         self.lufs_current = -70.0
+        self.volume = 1.0
+        self._lufs_accum = 0
 
 
 class AudioEngine:
@@ -289,6 +295,8 @@ class AudioEngine:
         self.decks = {
             'deck1': DeckState(),
             'deck2': DeckState(),
+            'deck3': DeckState(),
+            'deck4': DeckState(),
             'cart1': DeckState(),
             'cart2': DeckState(),
             'cart3': DeckState(),
@@ -301,10 +309,6 @@ class AudioEngine:
     def get_channel(self, index: int) -> MixerChannel:
         return self.mixer['channels'][index]
 
-    def set_channel_name(self, index: int, name: str):
-        if 0 <= index < NUM_MIXER_CHANNELS:
-            self.mixer['channels'][index].name = name
-
     def set_channel_volume(self, index: int, volume: float):
         if 0 <= index < NUM_MIXER_CHANNELS:
             self.mixer['channels'][index].volume = max(0.0, min(1.0, volume))
@@ -327,25 +331,30 @@ class AudioEngine:
         buf_L.fill(0.0)
         buf_R.fill(0.0)
 
-        if not deck.playing or deck.track is None:
+        with deck.lock:
+            playing = deck.playing
+            track   = deck.track
+            pos     = deck.position
+
+        if not playing or track is None:
             return
 
-        pos   = deck.position
-        track = deck.track
         end   = min(pos + frames, track.num_samples)
         n     = end - pos
 
         if n <= 0:
-            deck.playing = False
+            with deck.lock:
+                deck.playing = False
             return
 
         buf_L[:n] = track.audio[0, pos:end]
         buf_R[:n] = track.audio[1, pos:end]
-        deck.position += n
 
-        if deck.position >= track.num_samples:
-            deck.playing  = False
-            deck.position = track.num_samples - 1
+        with deck.lock:
+            deck.position += n
+            if deck.position >= track.num_samples:
+                deck.playing  = False
+                deck.position = track.num_samples - 1
 
     def _process(self, frames: int):
         # ── Digital decks ───────────────────────────────────────────────
@@ -360,21 +369,25 @@ class AudioEngine:
 
         for cart_key in ('cart1', 'cart2', 'cart3', 'cart4'):
             deck = self.decks[cart_key]
-            if not deck.playing or deck.track is None:
+            with deck.lock:
+                playing = deck.playing
+                track   = deck.track
+                pos     = deck.position
+            if not playing or track is None:
                 continue
-            pos   = deck.position
-            track = deck.track
             end   = min(pos + frames, track.num_samples)
             n     = end - pos
             if n <= 0:
-                deck.playing = False
+                with deck.lock:
+                    deck.playing = False
                 continue
             buf_L[:n] += track.audio[0, pos:end]
             buf_R[:n] += track.audio[1, pos:end]
-            deck.position += n
-            if deck.position >= track.num_samples:
-                deck.playing  = False
-                deck.position = track.num_samples - 1
+            with deck.lock:
+                deck.position += n
+                if deck.position >= track.num_samples:
+                    deck.playing  = False
+                    deck.position = track.num_samples - 1
 
         # ── External input monitors (deck3, deck4) ─────────────────────
         gate_linear = 10 ** (-46.0 / 20.0)
@@ -456,7 +469,10 @@ class AudioEngine:
         master_peak = max(np.max(np.abs(master_audio[0])), np.max(np.abs(master_audio[1])))
         self.mixer['master'].vu_peak = master_peak
 
-        if frames % 512 < frames:
+        master = self.mixer['master']
+        master._lufs_accum += frames
+        if master._lufs_accum >= 512:
+            master._lufs_accum -= 512
             self._calculate_lufs(master_audio)
 
     def _calculate_lufs(self, audio: np.ndarray):