feat(output): Add parameter metadata to final audio files

Saves the complete set of `AppParameters` used for each render into the metadata of the output FLAC file.

This makes each render self-documenting and allows users to easily track the settings used for any given result. The parameters are stored as a JSON string in the file's `comment` tag.

app.py

@@ -49,6 +49,7 @@ import shutil
 import librosa
 import pyloudnorm as pyln
 import soundfile as sf
+from mutagen.flac import FLAC
 
 import torch
 import ffmpeg
@@ -198,6 +199,19 @@ class AppParameters:
 # === Helper Functions ===
 # =================================================================================================
 
+def format_params_for_metadata(params: AppParameters) -> str:
+    """
+    Formats the AppParameters object into a human-readable string
+    suitable for embedding as metadata in an audio file.
+    """
+    import json
+    # Convert the dataclass to a dictionary
+    params_dict = params.__dict__
+    # Use json.dumps for clean, well-formatted, multi-line string representation
+    # indent=2 makes it look nice when read back
+    return json.dumps(params_dict, indent=2)
+
+
 def preprocess_midi_for_harshness(midi_data: pretty_midi.PrettyMIDI, params: AppParameters):
     """
     Analyzes and modifies a PrettyMIDI object in-place to reduce characteristics
@@ -2173,8 +2187,24 @@ def run_single_file_pipeline(input_file_path: str, timestamp: str, params: AppPa
     # Also, copy the final processed MIDI to a consistent output directory with a timestamped name
     final_midi_path = os.path.join(output_midi_dir, f"{timestamped_base_name}_processed.mid")
 
-    
-    sf.write(final_audio_path, final_audio_data, final_srate)
+    # --- Save audio with embedded parameter metadata ---
+    try:
+        # Generate the metadata string from the final parameters used for the render.
+        metadata_string = format_params_for_metadata(params)
+        
+        sf.write(final_audio_path, final_audio_data, final_srate)
+        audio = FLAC(final_audio_path)
+        audio["comment"] = metadata_string
+        audio.save()
+        
+        print(f"  - Successfully saved audio with embedded parameters to {os.path.basename(final_audio_path)}")
+
+    except Exception as e:
+        print(f"  - Warning: Could not save audio with metadata. Error: {e}")
+        print("  - Falling back to standard save method.")
+        # Fallback to the original simple write method if the advanced one fails.
+        sf.write(final_audio_path, final_audio_data, final_srate)
+
     # Use shutil to copy the final midi file to its new home
     shutil.copy(final_midi_path_from_render, final_midi_path)
     

requirements.txt

@@ -17,6 +17,7 @@ networkx
 scikit-learn
 psutil
 pretty_midi
+mutagen
 soundfile
 pyloudnorm
 ffmpeg-python