text: import ffmpeg
  import sys
  
  
  #rtsp://admin:abcd1234@192.168.31.167:554/h264/ch2/sub/av_stream
  
  if __name__ == '__main__':
      if len(sys.argv) !=3:
          sys.exit("need 2 extra parameters")
      # url filePath
      process=(
          ffmpeg
              .input(sys.argv[1],allowed_media_types='audio', rtsp_transport='tcp')['a']  # allowed_media_types='audio' 只读取音频流
              .filter('volume', 5)  # 音量大小控制
              .output(sys.argv[2], ac=1, ar='16k')  # ac是声道，ar是采样率
              .overwrite_output()
      )
      process.run(capture_stdout=True)