app.py

"""
AutoLyrics — Gradio Demo
Fine-tuned Whisper-small + LoRA for lyrics transcription.

Usage:
    pip install gradio transformers peft torch torchaudio librosa pyloudnorm jiwer
    python app.py
"""

import re
import torch
import torchaudio
import torchaudio.transforms as T
import librosa
import pyloudnorm as pyln
import numpy as np
import gradio as gr
from transformers import WhisperForConditionalGeneration, WhisperProcessor
from peft import PeftModel

# ──────────────────────────────────────────────────────────────────
# CONFIGURATION — adjust paths if needed
# ──────────────────────────────────────────────────────────────────
MODEL_NAME   = "openai/whisper-small"
LORA_DIR     = "./checkpoints/lora_best"   # path where you saved the LoRA adapter
DEVICE       = "cuda" if torch.cuda.is_available() else "cpu"
MODEL_DTYPE  = torch.float16 if DEVICE == "cuda" else torch.float32
TARGET_SR    = 16000
MAX_DURATION = 30.0
LANGUAGE     = "en"
TASK         = "transcribe"
BEAM_SIZE    = 3
MAX_NEW_TOKENS = 200

# ──────────────────────────────────────────────────────────────────
# AUDIO PREPROCESSING (mirrors your notebook pipeline)
# ──────────────────────────────────────────────────────────────────
LUFS_TARGET   = -23.0
LUFS_HEADROOM =  1.0
SILENCE_TOP_DB = 30


def _remove_dc_offset(waveform: torch.Tensor) -> torch.Tensor:
    return waveform - waveform.mean()


def _trim_silence(waveform: torch.Tensor) -> torch.Tensor:
    arr = waveform.numpy()
    trimmed, _ = librosa.effects.trim(arr, top_db=SILENCE_TOP_DB)
    return torch.from_numpy(trimmed)


def _loudness_normalize(waveform: torch.Tensor, sr: int) -> torch.Tensor:
    arr = waveform.numpy().astype("float64")
    meter = pyln.Meter(sr)
    loudness = meter.integrated_loudness(arr)
    if not (loudness > -70.0):
        peak = arr.max() if arr.max() != 0 else 1.0
        arr = arr / peak
    else:
        arr = pyln.normalize.loudness(arr, loudness, LUFS_TARGET)
        limit = 10 ** (-LUFS_HEADROOM / 20.0)
        arr = arr.clip(-limit, limit)
    return torch.from_numpy(arr.astype("float32"))


def preprocess_audio(waveform: torch.Tensor, sr: int) -> torch.Tensor:
    """Full preprocessing chain: resample → mono → DC → trim → loudness."""
    # Convert to mono
    if waveform.dim() == 1:
        waveform = waveform.unsqueeze(0)
    if waveform.shape[0] > 1:
        waveform = waveform.mean(dim=0, keepdim=True)
    # Resample
    if sr != TARGET_SR:
        waveform = T.Resample(sr, TARGET_SR)(waveform)
    waveform = waveform.squeeze(0)
    # Preprocessing chain
    waveform = _remove_dc_offset(waveform)
    waveform = _trim_silence(waveform)
    if len(waveform) == 0:
        return waveform
    waveform = _loudness_normalize(waveform, TARGET_SR)
    return waveform


# ──────────────────────────────────────────────────────────────────
# MODEL LOADING
# ──────────────────────────────────────────────────────────────────
print(f"Loading model on {DEVICE}…")
processor = WhisperProcessor.from_pretrained(LORA_DIR, language=LANGUAGE, task=TASK)
base_model = WhisperForConditionalGeneration.from_pretrained(
    MODEL_NAME, torch_dtype=MODEL_DTYPE
).to(DEVICE)
base_model.config.forced_decoder_ids = None
base_model.generation_config.forced_decoder_ids = None
base_model.generation_config.suppress_tokens = []

model = PeftModel.from_pretrained(base_model, LORA_DIR).to(DEVICE)
inner_model = model.base_model.model
inner_model.eval()
print("Model loaded ✓")


# ──────────────────────────────────────────────────────────────────
# TRANSCRIPTION FUNCTION
# ──────────────────────────────────────────────────────────────────
def transcribe(audio_path: str, beam_size: int, max_new_tokens: int) -> str:
    """Load audio, preprocess, run Whisper LoRA, return transcript."""
    if audio_path is None:
        return "⚠️ Please upload or record an audio file."

    try:
        waveform, sr = torchaudio.load(audio_path)
    except Exception as e:
        return f"❌ Error loading audio: {e}"

    waveform = preprocess_audio(waveform, sr)

    if len(waveform) == 0:
        return "⚠️ Audio appears to be silent after preprocessing."

    duration = len(waveform) / TARGET_SR
    if duration > MAX_DURATION:
        waveform = waveform[: int(MAX_DURATION * TARGET_SR)]
        duration = MAX_DURATION

    # Pad to 30 s for the feature extractor
    max_samples = int(MAX_DURATION * TARGET_SR)
    if len(waveform) < max_samples:
        waveform = torch.nn.functional.pad(waveform, (0, max_samples - len(waveform)))

    features = processor.feature_extractor(
        waveform.numpy(), sampling_rate=TARGET_SR, return_tensors="pt"
    ).input_features.to(DEVICE, dtype=MODEL_DTYPE)

    with torch.no_grad():
        generated_ids = inner_model.generate(
            input_features=features,
            num_beams=int(beam_size),
            max_new_tokens=int(max_new_tokens),
            language=LANGUAGE,
            task=TASK,
            suppress_tokens=[],
            forced_decoder_ids=None,
        )

    transcript = processor.tokenizer.batch_decode(generated_ids, skip_special_tokens=True)[0].strip()
    info = f"_(duration: {duration:.1f}s, device: {DEVICE})_"
    return f"{transcript}\n\n{info}"


# ──────────────────────────────────────────────────────────────────
# GRADIO INTERFACE
# ──────────────────────────────────────────────────────────────────
with gr.Blocks(title="AutoLyrics — Whisper LoRA", theme=gr.themes.Soft()) as demo:

    gr.Markdown(
        """
        # 🎵 AutoLyrics — Whisper-small + LoRA
        **Fine-tuned on `gmenon/slt-lyrics-audio` for music lyrics transcription.**

        Upload a song clip (≤ 30 s) or record directly from your microphone, then hit **Transcribe**.
        """
    )

    with gr.Row():
        with gr.Column(scale=1):
            audio_input = gr.Audio(
                label="🎤 Audio Input",
                sources=["upload", "microphone"],
                type="filepath",
            )
            with gr.Accordion("⚙️ Advanced settings", open=False):
                beam_slider = gr.Slider(
                    minimum=1, maximum=5, value=BEAM_SIZE, step=1,
                    label="Beam size (1 = greedy, higher = better but slower)"
                )
                tokens_slider = gr.Slider(
                    minimum=50, maximum=448, value=MAX_NEW_TOKENS, step=10,
                    label="Max new tokens"
                )
            transcribe_btn = gr.Button("🎶 Transcribe", variant="primary")

        with gr.Column(scale=1):
            output_text = gr.Textbox(
                label="📝 Transcription",
                lines=8,
                placeholder="Lyrics will appear here…",
                show_copy_button=True,
            )

    transcribe_btn.click(
        fn=transcribe,
        inputs=[audio_input, beam_slider, tokens_slider],
        outputs=output_text,
    )

    gr.Examples(
        examples=[],          # add example audio paths here if you have them
        inputs=audio_input,
    )

    gr.Markdown(
        """
        ---
        **Model:** `openai/whisper-small` + LoRA (r=8, α=16) &nbsp;|&nbsp;
        **Dataset:** `gmenon/slt-lyrics-audio` &nbsp;|&nbsp;
        **Preprocessing:** EBU R128 loudness normalisation, silence trimming
        """
    )

if __name__ == "__main__":
    demo.launch(share=True)   # share=True gives a public URL; remove for local only