我写了一个实时跟踪器（用于神经生物学研究），我用它与许多网络摄像头，并注意到我的一些相机不坚持帧速率非常精确;它们可能有点快或慢。为了保存“合理正确”的视频，从网络摄像头捕获帧的代码调用我的VideoWriter的write(frame)方法，该方法将帧放入队列中，并且帧由以恒定速率写入帧的单独的“写入器”线程检索。如果写入器线程在要写入下一帧时发现队列为空，则它重复最后一帧。如果写入器线程在队列中发现多于一个帧，它会写入最近的帧并丢弃其他帧。（可以在没有单独线程的情况下实现这一点，但对于实时跟踪器，让write(frame)快速返回是很好的。）
下面是我的代码摘录。它们不会逐字运行，但会显示我刚才描述的内容。（我计划在接下来的几周内将实时跟踪器放在GitHub上。）

class VideoWriter:

  def __init__(self, fn=None, fcc='MJPG', fps=7.5):
    ...
    self.fcc, self.fps, self.dt = fcc, fps, 1./fps
    self.q, self._stop, self.n = Queue.Queue(), False, 0
    self.wrtr = threading.Thread(target=self._writer)
    self.wrtr.start()

  def _writer(self):
    frm = firstTime = vw = None
    while True:
      if self._stop:
        break
      # get most recent frame
      while not self.q.empty():
        frm = self.q.get_nowait()
      if frm is not None:
        if vw is None:
          vw = cv2.VideoWriter(self.fn+self._EXT, cvFourcc(self.fcc),
            self.fps, imgSize(frm), isColor=numChannels(frm)>1)
          firstTime = time.time()
        vw.write(frm)
        self.n += 1
      dt = self.dt if firstTime is None else max(0,
        firstTime + self.n*self.dt - time.time())
      time.sleep(dt)

  # write frame; can be called at rate different from fps
  def write(self, frm):
    self.q.put(frm)

我更新了the code by Ulrich Stern，使它适用于我的OAK D相机，几乎不跳帧。他提到，代码不应该立即工作，但我仍然想指出，我们需要.release()的cv2.VideoWriter得到完整的视频文件。

# https://stackoverflow.com/questions/35370360/recording-video-in-real-time-with-opevcv-videowriter
import threading
import cv2
import queue
import time

class ReasonableVideoWriter:

    def __init__(self, fn=None, fcc='MJPG', fps=30, res=(1280, 720)):
        self.fn = fn
        self.fcc, self.fps, self.dt = fcc, fps, 1./fps
        self.res = res
        self.q, self._stop, self.n = queue.Queue(), False, 0
        self.wrtr = threading.Thread(target=self._writer)
        self.wrtr.setDaemon(True)   # make the thread daemonic
        self.wrtr.start()
    

    def _writer(self):
        frm = firstTime = vw = None
        while True:
            if self._stop:
                self._stop = not self._stop
                break
            # get most recent frame
            while not self.q.empty():
                frm = self.q.get_nowait()

            if frm is not None:
                if vw is None:
                    vw = cv2.VideoWriter(self.fn, cv2.VideoWriter_fourcc(*self.fcc),
                        self.fps, self.res)
                    firstTime = time.time()
                vw.write(frm)
                self.n += 1

            dt = self.dt if firstTime is None else max(0,
                firstTime + self.n*self.dt - time.time())
            time.sleep(dt)

        vw.release()    # release the video file

    # write frame; can be called at rate different from fps
    def write(self, frm):
        self.q.put(frm)
    
    # stop
    def stop(self):
        self._stop = True

创建一个ReasonableVideoWriter对象，并使用.write(frame)和.stop()方法进行记录。