gym.wrappers.Monitor() produces empty video in 0.18.0

[ish913]

I can't play video produced by gym.wrappers.Monitor(). I solved this problem by downgrading gym to 0.17.3.

[daanklijn]

Same issue when using only the VideoRecorder class.

Some code to reproduce the problem:

env = gym.make('Pong-v4')
env.reset()
recorder = VideoRecorder(env, path='/tmp/pong_video.mp4')

for i in range(1000):
    obs, _, _, _ = env.step(0)
    recorder.capture_frame()

recorder.close()

Output file is only 262 bytes, which seems quite a bit too small. I've also included the contents of the meta.json below.

{
  "content_type": "video/mp4",
  "encoder_version": {
    "backend": "ffmpeg",
    "version": "b'ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers\\nbuilt with Apple clang version 11.0.3 (clang-1103.0.32.62)\\nconfiguration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1_1 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack\\nlibavutil      56. 51.100 / 56. 51.100\\nlibavcodec     58. 91.100 / 58. 91.100\\nlibavformat    58. 45.100 / 58. 45.100\\nlibavdevice    58. 10.100 / 58. 10.100\\nlibavfilter     7. 85.100 /  7. 85.100\\nlibavresample   4.  0.  0 /  4.  0.  0\\nlibswscale      5.  7.100 /  5.  7.100\\nlibswresample   3.  7.100 /  3.  7.100\\nlibpostproc    55.  7.100 / 55.  7.100\\n'",
    "cmdline": [
      "ffmpeg",
      "-nostats",
      "-loglevel",
      "error",
      "-y",
      "-f",
      "rawvideo",
      "-s:v",
      "160x210",
      "-pix_fmt",
      "rgb24",
      "-framerate",
      "30",
      "-i",
      "-",
      "-vf",
      "scale=trunc(iw/2)*2:trunc(ih/2)*2",
      "-vcodec",
      "libx264",
      "-pix_fmt",
      "yuv420p",
      "-r",
      "30",
      "/tmp/pong_video.mp4"
    ]
  }
}

[daanklijn]

I believe this is getting fixed in: #2139

[ish913]

Oh, thank you!

[antoniopioricciardi]

In the meantime you can manually solve it by going to gym/wrappers/monitoring/video_recorder.py
and de-indent by une step the function call self.proc.stdin.write(frame.tobytes())
meaning that it does not have to be nested under any if statement.

[ish913]

Thank you for noticing!