class_docstr: extract keyframes from a video and save it as jpg.
  TODO: consider to merge with `CodecProcessor`.
class_docstr_tok: ["extract","keyframes","from","a","video","and","save","it","as","jpg",".","TODO",":","consider","to","merge","with","`","CodecProcessor","`","."]
code: def __init__(
      self,
      csv=None,
      video_dict=None,
      framerate=1,
      size=112,
      centercrop=False,
      max_num_frames=5,
      **kwargs,
  ):
      super().__init__(csv, video_dict, framerate, size, centercrop)
      self.max_num_frames = max_num_frames
  
imports: import torch
  import pandas
  import os
  import numpy
  import ffmpeg
  import random
  from torch.utils.data import Dataset
label_desc: Use image node_id 1 to create a new AvKeyframeVideoCompressor object from inherited base classes: VideoLoader with example: obj = AvKeyframeVideoCompressor(csv, video_dict, framerate, size, centercrop, max_num_frames)