Making videos for the web with Godot 4’s Movie Writer

Normally I use OBS for screen recording, but there are cases where it makes sense to use Godot’s built-in movie writer that was recently announced.

For example, if you have a slow PC or really demanding game, OBS will skip frames. It makes sense since OBS is just recording what’s on the screen in real time, while Godot has to do most of the work running the game. Recording with Godot directly will slow down the action at recording time, and you cannot hear any audio while that happens. But the video playback will end up being buttery smooth at 60 fps and include audio. It will also result in huge files. 321MB for 8 seconds, at 1280x800px (also Steam Deck’s native 16:10 resolution). Still, that’s not a video file I want to embed into any webpage or wherever as-is.

The best tool for converting video from the command line or programmatically is still ffmpeg. I’m running this on Windows in WSL2, on Ubuntu 22.04.

The best option for .webm seems to be the VP9 codec. Their docs provide some examples. I’ve tested a few parameters. For two-pass targeting an average bitrate, the target bitrate is specified with the -b:v switch:

# will take longer but smaller file
ffmpeg -i tilemap.avi -c:v libvpx-vp9 -b:v 2M -pass 1 -an -f null /dev/null && \
ffmpeg -i tilemap.avi -c:v libvpx-vp9 -b:v 2M -pass 2 -c:a libopus tilemap-average.webm

This is what the output looks like:

gray@Battlestation:/mnt/c/Users/gray/godot/arpg$ ffmpeg -i tilemap.avi -c:v libvpx-vp9 -b:v 2M -pass 1 -an -f null /dev/null && \
ffmpeg -i tilemap.avi -c:v libvpx-vp9 -b:v 2M -pass 2 -c:a libopus tilemap-average.webm
ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  WARNING: library configuration mismatch
  avcodec     configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared --enable-version3 --disable-doc --disable-programs --enable-libaribb24 --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc --enable-libsmbclient
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, avi, from 'tilemap.avi':
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: mjpeg (Baseline) (MJPG / 0x47504A4D), yuvj420p(pc, bt470bg/unknown/unknown), 1280x800 [SAR 1:1 DAR 8:5], 60 fps, 60 tbr, 60 tbn, 60 tbc
  Stream #0:1: Audio: pcm_s32le ([1][0][0][0] / 0x0001), 48000 Hz, stereo, s32, 3072 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> vp9 (libvpx-vp9))
Press [q] to stop, [?] for help
[swscaler @ 0x55932cefff40] deprecated pixel format used, make sure you did set range correctly
[libvpx-vp9 @ 0x55932cee54c0] v1.11.0
Output #0, null, to '/dev/null':
  Metadata:
    encoder         : Lavf58.76.100
  Stream #0:0: Video: vp9, yuv420p(tv, bt470bg/unknown/unknown, progressive), 1280x800 [SAR 1:1 DAR 8:5], q=2-31, 2000 kb/s, 60 fps, 60 tbn
    Metadata:
      encoder         : Lavc58.134.100 libvpx-vp9
    Side data:
      cpb: bitrate max/min/avg: 0/0/2000000 buffer size: 0 vbv_delay: N/A
frame=  533 fps= 35 q=0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=   0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded
ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  WARNING: library configuration mismatch
  avcodec     configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared --enable-version3 --disable-doc --disable-programs --enable-libaribb24 --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc --enable-libsmbclient
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, avi, from 'tilemap.avi':
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: mjpeg (Baseline) (MJPG / 0x47504A4D), yuvj420p(pc, bt470bg/unknown/unknown), 1280x800 [SAR 1:1 DAR 8:5], 60 fps, 60 tbr, 60 tbn, 60 tbc
  Stream #0:1: Audio: pcm_s32le ([1][0][0][0] / 0x0001), 48000 Hz, stereo, s32, 3072 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> vp9 (libvpx-vp9))
  Stream #0:1 -> #0:1 (pcm_s32le (native) -> opus (libopus))
Press [q] to stop, [?] for help
[swscaler @ 0x562739e33040] deprecated pixel format used, make sure you did set range correctly
[libvpx-vp9 @ 0x562739e14040] v1.11.0
[libopus @ 0x562739e165c0] No bit rate set. Defaulting to 96000 bps.
Output #0, webm, to 'tilemap-average.webm':
  Metadata:
    encoder         : Lavf58.76.100
  Stream #0:0: Video: vp9, yuv420p(tv, bt470bg/unknown/unknown, progressive), 1280x800 [SAR 1:1 DAR 8:5], q=2-31, 2000 kb/s, 60 fps, 1k tbn
    Metadata:
      encoder         : Lavc58.134.100 libvpx-vp9
    Side data:
      cpb: bitrate max/min/avg: 0/0/2000000 buffer size: 0 vbv_delay: N/A
  Stream #0:1: Audio: opus, 48000 Hz, stereo, flt, 96 kb/s
    Metadata:
      encoder         : Lavc58.134.100 libopus
frame=  533 fps=3.2 q=0.0 Lsize=    2600kB time=00:00:08.86 bitrate=2401.8kbits/s speed=0.054x
video:2479kB audio:114kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.289294%

And on this ancient i7-4790K, it runs dog slow. It processed the 8.86-second-long video at 5% speed, dragging it out to almost three minutes. But the payoff is worth it. Instead of 321MB, the video file is down to 2.6MB:

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