import os
import subprocess
def audio_speed(in_file: str, speed: float):
    """ change audio file speed
    :param in_file: input file path
    :param speed: speed
    :return: None
    sample command line:
    >>ffmpeg -i 0.mp3 -filter:a "atempo=0.9, atempo=0.9" -vn 0.speed.0.9.mp3
    """
    if not os.path.exists(in_file):
        raise Exception('input file not exist')
    name, ext = os.path.splitext(in_file)
    out_file = f'{name}.speed.{speed}.{ext}'
    if os.path.exists(out_file):
        os.remove(out_file)
    cmd = f'ffmpeg -i {in_file} -filter:a "atempo={speed}, atempo={speed}" -vn {out_file}'
    print(cmd)
    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    for line in p.stdout.readlines():
        # print(line.decode())
        continue
    if not os.path.exists(out_file):
        raise Exception(f'音频变速失败:{in_file}')
    return p.wait()
if __name__ == '__main__':
    for i in range(90, 100):
        speed = i / 100
        audio_speed('0.mp3', speed)