app.py

import random
import numpy as np
import torch
from chatterbox.src.chatterbox.tts import ChatterboxTTS
import gradio as gr
import spaces

DEVICE = "cuda" if torch.cuda.is_available() else "cpu"
print(f"🚀 Running on device: {DEVICE}")

# --- Global Model Initialization ---
MODEL = None

def get_or_load_model():
    """Loads the ChatterboxTTS model if it hasn't been loaded already,
    and ensures it's on the correct device."""
    global MODEL
    if MODEL is None:
        print("Model not loaded, initializing...")
        try:
            MODEL = ChatterboxTTS.from_pretrained(DEVICE)
            if hasattr(MODEL, 'to') and str(MODEL.device) != DEVICE:
                MODEL.to(DEVICE)
            print(f"Model loaded successfully. Internal device: {getattr(MODEL, 'device', 'N/A')}")
        except Exception as e:
            print(f"Error loading model: {e}")
            raise
    return MODEL

# Attempt to load the model at startup.
try:
    get_or_load_model()
except Exception as e:
    print(f"CRITICAL: Failed to load model on startup. Application may not function. Error: {e}")

def set_seed(seed: int):
    """Sets the random seed for reproducibility across torch, numpy, and random."""
    torch.manual_seed(seed)
    if DEVICE == "cuda":
        torch.cuda.manual_seed(seed)
        torch.cuda.manual_seed_all(seed)
    random.seed(seed)
    np.random.seed(seed)

@spaces.GPU
def generate_tts_audio(
    text_input: str,
    audio_prompt_path_input: str,
    exaggeration_input: float,
    temperature_input: float,
    seed_num_input: int,
    cfgw_input: float
) -> tuple[int, np.ndarray]:
    """
    Generate high-quality speech audio from text using ChatterboxTTS model with reference audio styling.
    
    This tool synthesizes natural-sounding speech from input text, using a reference audio file 
    to capture the speaker's voice characteristics and speaking style. The generated audio 
    maintains the prosody, tone, and vocal qualities of the reference speaker.

    Args:
        text_input (str): The text to synthesize into speech (maximum 300 characters)
        audio_prompt_path_input (str): File path or URL to the reference audio file that defines the target voice style
        exaggeration_input (float): Controls speech expressiveness (0.25-2.0, neutral=0.5, extreme values may be unstable)
        temperature_input (float): Controls randomness in generation (0.05-5.0, higher=more varied, default=0.8)
        seed_num_input (int): Random seed for reproducible results (0 for random generation)
        cfgw_input (float): CFG/Pace weight controlling generation guidance (0.2-1.0, default=0.5)

    Returns:
        tuple[int, np.ndarray]: A tuple containing the sample rate (int) and the generated audio waveform (numpy.ndarray)
    """
    current_model = get_or_load_model()

    if current_model is None:
        raise RuntimeError("TTS model is not loaded.")

    if seed_num_input != 0:
        set_seed(int(seed_num_input))

    print(f"Generating audio for text: '{text_input[:50]}...'")
    wav = current_model.generate(
        text_input[:300],  # Truncate text to max chars
        audio_prompt_path=audio_prompt_path_input,
        exaggeration=exaggeration_input,
        temperature=temperature_input,
        cfg_weight=cfgw_input,
    )
    print("Audio generation complete.")
    return (current_model.sr, wav.squeeze(0).numpy())

with gr.Blocks() as demo:
    gr.Markdown(
        """
        # Chatterbox TTS Demo
        Generate high-quality speech from text with reference audio styling.
        """
    )
    with gr.Row():
        with gr.Column():
            text = gr.Textbox(
                value="Now let's make my mum's favourite. So three mars bars into the pan. Then we add the tuna and just stir for a bit, just let the chocolate and fish infuse. A sprinkle of olive oil and some tomato ketchup. Now smell that. Oh boy this is going to be incredible.",
                label="Text to synthesize (max chars 300)",
                max_lines=5
            )
            ref_wav = gr.Audio(
                sources=["upload", "microphone"],
                type="filepath",
                label="Reference Audio File (Optional)",
                value="https://storage.googleapis.com/chatterbox-demo-samples/prompts/female_shadowheart4.flac"
            )
            exaggeration = gr.Slider(
                0.25, 2, step=.05, label="Exaggeration (Neutral = 0.5, extreme values can be unstable)", value=.5
            )
            cfg_weight = gr.Slider(
                0.2, 1, step=.05, label="CFG/Pace", value=0.5
            )

            with gr.Accordion("More options", open=False):
                seed_num = gr.Number(value=0, label="Random seed (0 for random)")
                temp = gr.Slider(0.05, 5, step=.05, label="Temperature", value=.8)

            run_btn = gr.Button("Generate", variant="primary")

        with gr.Column():
            audio_output = gr.Audio(label="Output Audio")

    run_btn.click(
        fn=generate_tts_audio,
        inputs=[
            text,
            ref_wav,
            exaggeration,
            temp,
            seed_num,
            cfg_weight,
        ],
        outputs=[audio_output],
    )

demo.launch(mcp_server=True)