refactor: simplify clock drift compensation with hardcoded parameters and improved frame drop logic

src/auracast/auracast_config.py

@@ -42,7 +42,6 @@ class AuracastGlobalConfig(BaseModel):
     assisted_listening_stream: bool = False
     # Clock drift compensation: discard excess samples when buffer exceeds threshold
     enable_drift_compensation: bool = False
-    drift_threshold_ms: float = 2.0  # Discard threshold in milliseconds
 
 # "Audio input. "
 # "'device' -> use the host's default sound input device, "

src/auracast/multicast.py

@@ -651,19 +651,22 @@ class Streamer():
         bigs = self.bigs
         self.is_streaming = True
     
-        # Sample discard stats (clock drift compensation)
+        # frame drop algo parameters
         sample_rate = big['audio_input']._pcm_format.sample_rate
         samples_discarded_total = 0  # Total samples discarded
         discard_events = 0  # Number of times we discarded samples
         frames_since_last_discard = 999  # Guard: frames since last discard (start high to allow first drop)
         enable_drift_compensation = global_config.enable_drift_compensation
-        discard_guard_frames = sample_rate // 100  # Don't allow discard within this many frames of previous discard
-        # Calculate threshold based on config (default 2ms)
-        drift_threshold_ms = global_config.drift_threshold_ms if global_config.enable_drift_compensation else 0
+        # Hardcoded parameters (unit: milliseconds)
+        drift_threshold_ms = 2.0 if enable_drift_compensation else 0.0
+        static_drop_ms = 0.5 if enable_drift_compensation else 0.0
+        # Guard interval measured in LC3 frames (10 ms each); 50 => 500 ms cooldown
+        discard_guard_frames = int(2*sample_rate / 1000) if enable_drift_compensation else 0
+        # Derived sample counts
         drop_threshold_samples = int(sample_rate * drift_threshold_ms / 1000.0)
-        static_drop_samples = int(sample_rate * 0.0005)  # Always drop a static amount of samples
-        
-        if global_config.enable_drift_compensation:
+        static_drop_samples = int(sample_rate * static_drop_ms / 1000.0)
+
+        if enable_drift_compensation:
             logging.info(f"Clock drift compensation ENABLED: threshold={drift_threshold_ms}ms, guard={discard_guard_frames} frames")
         else:
             logging.info("Clock drift compensation DISABLED")
@@ -699,12 +702,6 @@ class Streamer():
                         stream_finished[i] = True
                         continue
                     
-                    # Calculate threshold samples based on sample rate (only once per BIG)
-                    if enable_drift_compensation and drop_threshold_samples == 0:
-                        drop_threshold_samples = int(sample_rate * drift_threshold_ms / 1000.0)
-                        logging.info(f"Drift compensation threshold: {drop_threshold_samples} samples ({drift_threshold_ms}ms @ {sample_rate}Hz)")
-                        logging.info(f"Static drop amount: {static_drop_samples} samples (3.0ms @ {sample_rate}Hz)")
-                    
                     # Discard excess samples in buffer if above threshold (clock drift compensation)
                     if enable_drift_compensation and hasattr(big['audio_input'], '_stream') and big['audio_input']._stream:
                         sd_buffer_samples = big['audio_input']._stream.read_available
@@ -713,7 +710,7 @@ class Streamer():
                         if sd_buffer_samples > drop_threshold_samples and frames_since_last_discard >= discard_guard_frames:
                             # Always drop a static amount (3ms) for predictable behavior
                             # This matches the crossfade duration better for smoother transitions
-                            samples_to_drop = static_drop_samples
+                            samples_to_drop = min(static_drop_samples, max(1, big['lc3_frame_samples'] - 1))
                             try:
                                 discarded_data = await anext(big['audio_input'].frames(samples_to_drop))
                                 samples_discarded_total += samples_to_drop

src/auracast/multicast_script.py

@@ -111,7 +111,6 @@ if __name__ == "__main__":
         octets_per_frame = OCTETS_PER_FRAME,
         transport=TRANSPORT1,
         enable_drift_compensation=True,
-        drift_threshold_ms=2.0
     )
     config.debug = False