Initial commit

backend/services/basic_pitch.py

@@ -0,0 +1,50 @@
+"""
+Basic Pitch service: audio (MP3/WAV/etc.) to MIDI via Spotify's Basic Pitch model.
+
+Requires Python 3.11 or 3.12 due to tensorflow-macos constraints.
+See requirements-transcribe.txt for setup instructions.
+"""
+import asyncio
+import tempfile
+from pathlib import Path
+
+_IMPORT_ERROR: str | None = None
+
+try:
+    from basic_pitch.inference import predict  # type: ignore
+    from basic_pitch import ICASSP_2022_MODEL_PATH  # type: ignore
+except ImportError as e:
+    _IMPORT_ERROR = (
+        "basic-pitch is not installed. MP3 transcription requires Python 3.11 or 3.12. "
+        "See backend/requirements-transcribe.txt for setup instructions. "
+        f"Original error: {e}"
+    )
+
+
+async def transcribe_audio_to_midi(audio_bytes: bytes, filename: str) -> bytes:
+    """Transcribe audio bytes to MIDI bytes using Basic Pitch."""
+    if _IMPORT_ERROR:
+        raise RuntimeError(_IMPORT_ERROR)
+    return await asyncio.get_running_loop().run_in_executor(
+        None, _transcribe, audio_bytes, filename
+    )
+
+
+def _transcribe(audio_bytes: bytes, filename: str) -> bytes:
+    suffix = Path(filename).suffix or ".mp3"
+    with tempfile.NamedTemporaryFile(suffix=suffix, delete=False) as f:
+        f.write(audio_bytes)
+        audio_path = f.name
+
+    _model_output, midi_data, _note_events = predict(  # type: ignore[name-defined]
+        audio_path, ICASSP_2022_MODEL_PATH  # type: ignore[name-defined]
+    )
+
+    midi_tmp = tempfile.NamedTemporaryFile(suffix=".mid", delete=False)
+    midi_tmp.close()
+    midi_data.write(midi_tmp.name)
+
+    midi_bytes = Path(midi_tmp.name).read_bytes()
+    Path(audio_path).unlink(missing_ok=True)
+    Path(midi_tmp.name).unlink(missing_ok=True)
+    return midi_bytes