app.py

import binascii
import os

import gradio as gr
import librosa
import numpy as np
import pretty_midi
import torch
import yt_dlp
from transformers import Pop2PianoForConditionalGeneration, Pop2PianoProcessor

from utils import cli_to_api, mp3_write, normalize

yt_video_dir = "./yt_dir"
outputs_dir = "./midi_wav_outputs"
os.makedirs(outputs_dir, exist_ok=True)
os.makedirs(yt_video_dir, exist_ok=True)

device = "cuda" if torch.cuda.is_available() else "cpu"
model = Pop2PianoForConditionalGeneration.from_pretrained("sweetcocoa/pop2piano").to(device)
processor = Pop2PianoProcessor.from_pretrained("sweetcocoa/pop2piano")
composers = model.generation_config.composer_to_feature_token.keys()


def get_audio_from_yt_video(yt_link: str):
    filename = binascii.hexlify(os.urandom(8)).decode() + ".mp3"
    filename = os.path.join(yt_video_dir, filename)
    yt_opt = cli_to_api(
        [
            "--extract-audio",
            "--audio-format",
            "mp3",
            "--restrict-filenames",
            "-o",
            filename,
        ]
    )
    with yt_dlp.YoutubeDL(yt_opt) as ydl:
        ydl.download([yt_link])

    return filename, filename


def inference(file_uploaded, composer):
    # to save the native sampling rate of the file, sr=None is used, but this can cause some silent errors where the
    # generated output will not be upto the desired quality. If that happens please consider switching sr to 44100 Hz.
    pop_y, sr = librosa.load(file_uploaded, sr=None)

    inputs = processor(audio=pop_y, sampling_rate=sr, return_tensors="pt").to(device)
    model_output = model.generate(input_features=inputs["input_features"], composer=composer)
    tokenizer_output = processor.batch_decode(
        token_ids=model_output.to("cpu"), feature_extractor_output=inputs.to("cpu")
    )["pretty_midi_objects"]

    return prepare_output_file(tokenizer_output, sr, pop_y)


def prepare_output_file(tokenizer_output: pretty_midi.PrettyMIDI, sr: int, pop_y: np.ndarray):
    # Add some random values so that no two file names are same
    output_file_name = "p2p_" + binascii.hexlify(os.urandom(8)).decode()
    midi_output = os.path.join(outputs_dir, output_file_name + ".mid")

    # write the .mid and its wav files
    tokenizer_output[0].write(midi_output)
    midi_y: np.ndarray = tokenizer_output[0].fluidsynth(sr)
    midi_y_path: str = midi_output.replace(".mid", ".mp3")
    mp3_write(midi_y_path, sr, normalize(midi_y), normalized=True)

    # stack stereo audio
    if len(pop_y) > len(midi_y):
        midi_y = np.pad(midi_y, (0, len(pop_y) - len(midi_y)))
    elif len(pop_y) < len(midi_y):
        pop_y = np.pad(pop_y, (0, -len(pop_y) + len(midi_y)))
    stereo = np.stack((midi_y, pop_y * 0.5))

    # write stereo audio
    stereo_path = midi_output.replace(".mid", ".mix.mp3")
    mp3_write(stereo_path, sr, normalize(stereo.T), normalized=True)

    return midi_y_path, midi_y_path, midi_output, stereo_path, stereo_path


block = gr.Blocks()

with block:
    gr.HTML(
        """
            <div style="text-align: center; max-width: 400px; margin: 0 auto;">
              <div
                style="
                  display: inline-flex;
                  align-items: center;
                  gap: 0.8rem;
                  font-size: 1.75rem;
                "
              >
                <h1 style="font-weight: 900; margin-bottom: 7px;">
                  Pop2piano
                </h1>
              </div>
              <p style="margin-bottom: 10px; font-size: 94%">
                A demo for Pop2Piano:Pop Audio-based Piano Cover Generation.<br>
                Please select the composer(Arranger) and upload the pop audio or enter the YouTube link and then click Generate.
              </p>
            </div>
        """
    )
    with gr.Group():
        with gr.Column():
            with gr.Blocks() as audio_select:
                with gr.Tab("Upload Audio"):
                    file_uploaded = gr.Audio(label="Upload an audio", type="filepath")
                with gr.Tab("YouTube url"):
                    with gr.Row():
                        yt_link = gr.Textbox(
                            label="Enter YouTube Link of the Video", autofocus=True, lines=3
                        )
                        yt_btn = gr.Button("Download Audio from YouTube Link", size="lg")
                    yt_audio_path = gr.Audio(
                        label="Audio Extracted from the YouTube Video", interactive=False
                    )
                    yt_btn.click(
                        get_audio_from_yt_video,
                        inputs=[yt_link],
                        outputs=[yt_audio_path, file_uploaded],
                    )
            with gr.Column():
                composer = gr.Dropdown(label="Arranger", choices=composers, value="composer1")
                generate_btn = gr.Button("Generate")

    with gr.Group():
        gr.HTML(
            """
            <div> <h3> <center> Listen to the generated MIDI. </h3> </div>
            """
        )
        with gr.Row(equal_height=True):
            stereo_mix1 = gr.Audio(label="Listen to the Stereo Mix")
            wav_output1 = gr.Audio(label="Listen to the Generated MIDI")

        with gr.Row():
            stereo_mix2 = gr.File(label="Download the Stereo Mix (.mp3")
            wav_output2 = gr.File(label="Download the Generated MIDI (.mp3)")
            midi_output = gr.File(label="Download the Generated MIDI (.mid)")
            generate_btn.click(
                inference,
                inputs=[file_uploaded, composer],
                outputs=[wav_output1, wav_output2, midi_output, stereo_mix1, stereo_mix2],
            )

    with gr.Group():
        gr.Examples(
            [
                ["./examples/custom_song.mp3", "composer1"],
            ],
            fn=inference,
            inputs=[file_uploaded, composer],
            outputs=[wav_output1, wav_output2, midi_output, stereo_mix1, stereo_mix2],
            cache_examples=True,
        )

        gr.HTML(
            """
        <div class="footer">
                    <center><p><a href="http://sweetcocoa.github.io/pop2piano_samples" style="text-decoration: underline;" target="_blank">Project Page</a> 
                    <center><a href="https://huggingface.co/docs/transformers/main/model_doc/pop2piano" style="text-decoration: underline;" target="_blank">HuggingFace Model Docs</a>
                    <center><a href="https://github.com/sweetcocoa/pop2piano" style="text-decoration: underline;" target="_blank">Github</a>
                    </p>
        </div>
        """
        )

block.launch(debug=False)