Keep a lossless container

Returns a FLAC or AIFF input in its own container. It also imports spaces plainly, since it is always installed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app.py

@@ -1,21 +1,10 @@
 from __future__ import annotations
 
+import spaces  # imported first, as ZeroGPU requires
+
 import gradio as gr
 import soundfile as sf
 
-try:
-    import spaces
-except ImportError:
-    class spaces:
-        class GPU:
-            def __init__(self, func=None, duration=180):
-                self.func = func
-
-            def __call__(self, *args, **kwargs):
-                if self.func is not None:
-                    return self.func(*args, **kwargs)
-                return args[0]
-
 from pyharp import ModelCard, build_endpoint
 from pyharp.tags import Subcategory
 

stable_audio_runtime.py

@@ -95,7 +95,12 @@ def _load_audio(path: str):
     return int(sample_rate), audio.to(torch.float32)
 
 
-def _save_audio(output, sample_rate: int) -> str:
+# A lossless input keeps its container. A lossy one comes back as WAV, since encoding the result
+# lossily again would expose the artifacts of the first encode and add a second set.
+LOSSLESS = {".wav", ".flac", ".aiff", ".aif"}
+
+
+def _save_audio(output, sample_rate: int, ext: str = ".wav") -> str:
     import soundfile as sf
     import torch
 
@@ -106,7 +111,7 @@ def _save_audio(output, sample_rate: int) -> str:
 
     OUTPUT_ROOT.mkdir(parents=True, exist_ok=True)
     output_dir = Path(tempfile.mkdtemp(dir=OUTPUT_ROOT))
-    output_path = output_dir / "stable_audio_3_edit.wav"
+    output_path = output_dir / f"stable_audio_3_edit{ext}"
     sf.write(output_path, output, sample_rate, subtype="PCM_16")
     return str(output_path)
 
@@ -178,4 +183,5 @@ def edit_audio(
     # Returned at the input's rate rather than the one the model runs at
     if source_rate != sample_rate:
         output = torchaudio.functional.resample(output.float(), sample_rate, source_rate)
-    return _save_audio(output, source_rate)
+    input_ext = Path(audio_path).suffix.lower()
+    return _save_audio(output, source_rate, input_ext if input_ext in LOSSLESS else ".wav")