app.py

import os
import glob
import gradio as gr
import numpy as np
import soundfile as sf
import noisereduce as nr
from audio_separator.separator import Separator

# -----------------------------
# Locate the local ONNX model already committed to this repo
# (avoids any network download and avoids hardcoding a filename
# that may have changed in past rename commits)
# -----------------------------
MODELS_DIR = "models"
onnx_candidates = sorted(glob.glob(os.path.join(MODELS_DIR, "*.onnx")))

if not onnx_candidates:
    raise FileNotFoundError(
        f"No .onnx model found in '{MODELS_DIR}/'. "
        f"Make sure your UVR-MDX-Net model file is committed to that folder."
    )

MODEL_PATH = onnx_candidates[0]
MODEL_DIR = os.path.dirname(MODEL_PATH) or "."
MODEL_FILENAME = os.path.basename(MODEL_PATH)

print(f"Using local model: {MODEL_PATH}")

# -----------------------------
# Load the separator once at startup
# (model_file_dir points at the folder that ALREADY has the file,
# so audio-separator uses it directly instead of trying to download it)
# -----------------------------
separator = Separator(
    output_dir="/tmp/audio_separator_outputs",
    model_file_dir=MODEL_DIR,
)
separator.load_model(model_filename=MODEL_FILENAME)


def denoise_vocals(vocals_path: str) -> str:
    """
    Run spectral-gating noise reduction on the isolated vocals track.

    Uses `noisereduce` instead of a neural denoiser (e.g. DeepFilterNet2)
    because that pulled in a conflicting, unmaintained torch/torchaudio/onnx
    dependency chain that could no longer be resolved alongside
    audio-separator. noisereduce has no heavy ML dependencies, so it can't
    collide with audio-separator's stack the same way.
    """
    audio, sr = sf.read(vocals_path)

    # soundfile returns shape (frames, channels) for stereo; noisereduce
    # expects channels-first for multi-channel input.
    is_stereo = audio.ndim == 2
    y = audio.T if is_stereo else audio

    reduced = nr.reduce_noise(y=y, sr=sr)

    if is_stereo:
        reduced = reduced.T

    denoised_path = os.path.join(
        os.path.dirname(vocals_path),
        f"denoised_{os.path.basename(vocals_path)}",
    )
    sf.write(denoised_path, reduced, sr)
    return denoised_path


def separate_audio(audio_file):
    if audio_file is None:
        return None, None

    raw_outputs = separator.separate(audio_file)

    # separator.separate() returns bare filenames, not full paths — they
    # actually get written under separator.output_dir. Without joining them
    # back to that directory, Gradio resolves the relative filename against
    # the app's cwd instead of where the files really are, which is what
    # caused the empty players / 403 on download.
    output_paths = [
        p if os.path.isabs(p) else os.path.join(separator.output_dir, p)
        for p in raw_outputs
    ]
    output_paths = [os.path.abspath(p) for p in output_paths]

    vocals_path = next((p for p in output_paths if "vocal" in p.lower()), None)
    instrumental_path = next(
        (p for p in output_paths if p != vocals_path), None
    )

    if vocals_path is not None:
        try:
            vocals_path = denoise_vocals(vocals_path)
        except Exception as e:
            # If denoising fails for any reason, fall back to the raw
            # separated vocals rather than losing the whole result.
            print(f"Denoising failed, returning raw vocals: {e}")

    return vocals_path, instrumental_path


# -----------------------------
# Gradio Interface
# -----------------------------
ui = gr.Interface(
    fn=separate_audio,
    inputs=gr.Audio(type="filepath", label="Upload Audio"),
    outputs=[
        gr.Audio(type="filepath", label="Vocals"),
        gr.Audio(type="filepath", label="Instrumental"),
    ],
    title="Vocal / Instrumental Separator",
    description=(
        f"CPU-friendly vocal & instrumental separation using the local "
        f"UVR-MDX-Net ONNX model ({MODEL_FILENAME}), with vocals cleaned "
        f"up via spectral-gating noise reduction."
    ),
)

if __name__ == "__main__":
    # Explicitly whitelist the output directory for Gradio's file server —
    # avoids 403s when serving files from a directory outside the app's cwd.
    ui.launch(allowed_paths=[separator.output_dir])