Openai gym库用Monitor输出视频报错处理

问题&&解决方案

今天在用openai gym库的时候想用monitor来输出视频，但是最后失败了，先是看到了如下的错误提示

dyld: Library not loaded: @rpath/libopenh264.5.dylib
  Referenced from: /usr/local/Caskroom/miniconda/base/envs/myenv/lib/libavcodec.58.91.100.dylib
  Reason: image not found
zsh: abort      ffmpeg --version

感觉应该是ffmpeg的问题，我就去Terminal对应的conda环境里输了一下ffmpeg --version发现的确报错了，而且错误信息是一样的

1⃣️尝试运行conda update ffmpeg，看更新是否能解决问题

在更新后输出视频的时候没有报错了，但是输出的视频全都是一样的大小「262bytes」，而且还无法播放

2⃣️顺藤摸瓜接着找bug，最后找到了解决方案⬇️

问题出在gym/wrappers/monitoring/video_recorder.py这个文件的303行

本来是⬇️

    def capture_frame(self, frame):
        if not isinstance(frame, (np.ndarray, np.generic)):
            raise error.InvalidFrame('Wrong type {} for {} (must be np.ndarray or np.generic)'.format(type(frame), frame))
        if frame.shape != self.frame_shape:
            raise error.InvalidFrame("Your frame has shape {}, but the VideoRecorder is configured for shape {}.".format(frame.shape, self.frame_shape))
        if frame.dtype != np.uint8:
            raise error.InvalidFrame("Your frame has data type {}, but we require uint8 (i.e. RGB values from 0-255).".format(frame.dtype))
	    self.proc.stdin.write(frame.tobytes())  # 😫

应该更改最后一行的缩进⬇️

    def capture_frame(self, frame):
        if not isinstance(frame, (np.ndarray, np.generic)):
            raise error.InvalidFrame('Wrong type {} for {} (must be np.ndarray or np.generic)'.format(type(frame), frame))
        if frame.shape != self.frame_shape:
            raise error.InvalidFrame("Your frame has shape {}, but the VideoRecorder is configured for shape {}.".format(frame.shape, self.frame_shape))
        if frame.dtype != np.uint8:
            raise error.InvalidFrame("Your frame has data type {}, but we require uint8 (i.e. RGB values from 0-255).".format(frame.dtype))
	self.proc.stdin.write(frame.tobytes())	# 😄

参考

https://github.com/openai/gym/pull/2139/commits/5c94ebabded3af1929033b72cba1c00e87c84dcf