rvsttd: hold-back last drain chunk for fade, same faded audio to Moonshine + WAV

rvsttd/src/main.rs

@@ -113,14 +113,6 @@ impl DebugRecorder {
         self.audio.extend_from_slice(samples);
     }
 
-    fn audio_len(&self) -> usize {
-        self.audio.len()
-    }
-
-    fn truncate_audio(&mut self, len: usize) {
-        self.audio.truncate(len);
-    }
-
     fn save(self) {
         // Write log
         let log_path = self.dir.join("session.log");
@@ -332,45 +324,50 @@ fn transcriber_loop(
     // Drain trailing audio from ALSA buffer (cpal stream still alive).
     // Fixed 100ms window — cpal delivers every ~50ms (800 samples @ 16kHz),
     // so this captures 1-2 more callbacks worth of trailing audio.
+    // Hold one chunk back so we can apply a fade-out to the very last one.
     let drain_deadline = std::time::Instant::now() + Duration::from_millis(100);
-    let mut drained: Vec<f32> = Vec::new();
+    let mut held_chunk: Option<Vec<f32>> = None;
     while std::time::Instant::now() < drain_deadline {
         match rx.recv_timeout(drain_deadline - std::time::Instant::now()) {
             Ok(chunk) => {
-                if let Some(ref mut r) = recorder {
-                    r.add_audio(&chunk);
+                // Feed previously held chunk to Moonshine + recorder (no fade)
+                if let Some(prev) = held_chunk.take() {
+                    if let Some(ref mut r) = recorder {
+                        r.add_audio(&prev);
+                    }
+                    unsafe {
+                        moonshine_transcribe_add_audio_to_stream(
+                            handle, stream_handle,
+                            prev.as_ptr(), prev.len() as u64,
+                            SAMPLE_RATE, 0,
+                        );
+                    }
                 }
-                drained.extend_from_slice(&chunk);
+                held_chunk = Some(chunk);
             }
             Err(mpsc::RecvTimeoutError::Timeout) => break,
             Err(mpsc::RecvTimeoutError::Disconnected) => break,
         }
     }
 
-    // Apply 5ms fade-out to the trailing edge of the drained audio.
-    // Both the debug WAV and Moonshine receive the same faded audio.
-    let fade_samples = (SAMPLE_RATE as usize * 5) / 1000;
-    if drained.len() > fade_samples {
-        let start = drained.len() - fade_samples;
-        for i in 0..fade_samples {
-            let t = 1.0 - (i as f32 / fade_samples as f32);
-            drained[start + i] *= t;
+    // Apply 5ms fade-out to the last chunk, then feed to both Moonshine and recorder
+    if let Some(mut chunk) = held_chunk.take() {
+        let fade_samples = (SAMPLE_RATE as usize * 5) / 1000;
+        if chunk.len() > fade_samples {
+            let start = chunk.len() - fade_samples;
+            for i in 0..fade_samples {
+                let t = 1.0 - (i as f32 / fade_samples as f32);
+                chunk[start + i] *= t;
+            }
         }
-    }
 
-    // Update recorder with the faded audio (replaces the raw versions added above)
-    if let Some(ref mut r) = recorder {
-        // Remove the raw drained samples and re-add the faded ones
-        let raw_drained_len = r.audio_len();
-        r.truncate_audio(raw_drained_len.saturating_sub(drained.len()));
-        r.add_audio(&drained);
-    }
-
-    if !drained.is_empty() {
+        if let Some(ref mut r) = recorder {
+            r.add_audio(&chunk);
+        }
         unsafe {
             moonshine_transcribe_add_audio_to_stream(
                 handle, stream_handle,
-                drained.as_ptr(), drained.len() as u64,
+                chunk.as_ptr(), chunk.len() as u64,
                 SAMPLE_RATE, 0,
             );
         }