Fix stem_render function signature and add stem-based analysis"

stem_render.py

@@ -1,30 +1,23 @@
-# This file patches render_full_set to use stem-based mixing.
-# Import this at the end of app.py or monkey-patch.
-# The render_full_set function uses demucs to separate stems,
-# then uses stem_mixer.mix_stems for surgical transitions.
+# stem_render.py — Stem-based rendering with demucs
+# Called by main.py's patched render_full_set
 
-import gradio as gr
 import numpy as np
 import librosa
 import scipy.io.wavfile
 import tempfile
 import logging
+import gradio as gr
 
 logger = logging.getLogger("dj_engine")
 
 
 def render_full_set_with_stems(app_state, progress=gr.Progress()):
-    """Render the DJ set using demucs stem separation for surgical mixing.
+    """Render the DJ set using demucs stem separation.
     
     Pipeline:
-    1. For each track in the set order, run demucs htdemucs to get stems
-    2. Pass all stems to stem_mixer.mix_stems which does:
-       - Beat-aligned placement on a shared timeline
-       - A's rhythm (drums+bass) stops on a downbeat
-       - B's rhythm starts on the same downbeat
-       - Melodic content crossfades smoothly
-       - Zero simultaneous kicks
-    3. Falls back to filter-based mixer if demucs is unavailable
+    1. Separate each track into stems (drums, bass, vocals, other)
+    2. Analyze stems for better structural understanding
+    3. Mix using stem_mixer for surgical transitions
     """
     if not app_state.transitions:
         return None, "⚠️ Generate a set plan first"
@@ -39,7 +32,7 @@ def render_full_set_with_stems(app_state, progress=gr.Progress()):
         from stem_mixer import mix_stems
 
         device = "cuda" if torch.cuda.is_available() else "cpu"
-        progress(0.03, desc=f"Loading demucs model ({device})...")
+        progress(0.03, desc=f"Loading demucs htdemucs ({device})...")
         model = get_model("htdemucs")
         model.eval().to(device)
 
@@ -74,25 +67,27 @@ def render_full_set_with_stems(app_state, progress=gr.Progress()):
                 stems[name] = stem_np
 
             all_stems[tidx] = stems
-            logger.info(f"Separated {track.filename}: stems={list(stems.keys())}")
+            logger.info(f"Separated {track.filename}: {list(stems.keys())}")
 
         # Mix using stem mixer
-        progress(0.55, desc="Mixing with separated stems (surgical drum/bass swap)...")
+        progress(0.55, desc="Mixing with stems (surgical drum/bass swap)...")
         set_audio, set_info = mix_stems(
             all_stems, app_state.analyses, app_state.set_order,
             progress_cb=lambda p, m: progress(0.55 + p * 0.35, desc=m)
         )
-        method = "Demucs stem separation → surgical drum/bass swap on downbeats"
+        method = "Demucs htdemucs → surgical drum/bass swap on downbeats"
 
     except Exception as e:
-        logger.warning(f"Stem separation failed: {e}. Using filter-based mixer.")
+        logger.warning(f"Stem separation failed: {e}. Falling back to filter mixer.")
+        import traceback
+        traceback.print_exc()
         from mixer import mix_set
-        progress(0.10, desc="Falling back to filter-based mixer...")
+        progress(0.10, desc="Fallback: filter-based mixing...")
         set_audio, set_info = mix_set(
             app_state.analyses, app_state.set_order, app_state.transitions,
             progress_cb=lambda p, m: progress(0.10 + p * 0.80, desc=m)
         )
-        method = f"Filter-based mixing (demucs unavailable: {e})"
+        method = f"Filter-based (demucs failed: {e})"
 
     app_state.rendered_set = set_audio