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BigBlueButton Presentation Renderer

The BigBlueButton web conferencing system provides the ability to record meetings. Rather than producing a single video file though, it produces multiple assets (webcam footage, screenshare footage, slides, scribbles, chat, etc) and relies on a web player to assemble them.

This project provides some scripts to download the assets for a recorded presentation, and assemble them into a single video suitable for archive or upload to other video hosting sites.

Prerequisites

The scripts are written in Python, and rely on the GStreamer Editing Services libraries. On an Ubuntu 20.04 system, you will need to install at least the following:

sudo apt install python3-gi gir1.2-ges-1.0 ges1.0-tools python3-intervaltree

You may also want to install the Pitivi video editor to tweak the result before rendering:

sudo apt install pitivi

Downloading a presentation

The first script will download the presentation assets locally:

./download.py presentation_url outdir

The presentation_url should be a full URL containing the string /playback/presentation/2.0/playback.html?meetingId=. This will download the presentation metadata, video footage and slides.

Create a GES project

The second script combines the downloaded assets into a GStreamer Editing Services project.

./make-xges.py outdir presentation.xges

It takes the following optional parameters to influence the project:

  • --start=TIME and --end=TIME can be used to trim footage from the start or end of the recording. This can be helpful if the recording was started early, or you want to split the recoridng into multiple projects.
  • --width=WIDTH and --height=HEIGHT control the dimensions of the video. The default resolution is 1920x1080.
  • --webcam-size=PERCENT controls how much of the frame width will be devoted to the webcam footage. This defaults to 20%.
  • --stretch-webcam stretches the webcam footage by 33%. This was added to correct the camera aspect ratio in some of our recordings.
  • --backdrop=FILE sets a still image to place behind other elements. This can be used to fill in the empty space in the frame.
  • --opening-credits=FILE[:DURATION] and --closing-credits=FILE[:DURATION] will add credits to project. These can either be videos or still images (which will default to 3 seconds duration). These options can be repeated to add multiple credits.
  • --annotations will include whiteboard annotations and red dot cursor to slides.

Some accepted TIME formats:

  • ss seconds (example: 1500 or 1500.3)
  • mm:ss minutes and seconds
  • hh:mm:ss hours minutes and seconds
  • dd:hh:mm:ss days, hours, minutes and seconds

Currently the project includes the following aspects of the BBB recording:

  • Slides
  • Screensharing video
  • Webcam video+audio
  • Mouse cursor
  • Whiteboard scribbles (excluding text)

It does not cover:

  • Text chat

The project can be previewed using the ges-launch-1.0 command line tool:

ges-launch-1.0 --load presentation.xges

It can also be loaded in Pitivi if you want to tweak the project before rendering.

Render Video

If everything looks good, the project can be rendered to a video. The following should produce an MP4 file suitable for upload to YouTube:

ges-launch-1.0 --load presentation.xges -o presentation.mp4

Or alternatively, it can be rendered as WebM:

ges-launch-1.0 --load presentation.xges -o presentation.webm \
  --format 'video/webm:video/x-vp8:audio/x-vorbis'

License

Copyright (c) 2020-2021 James Henstridge and contributors

The project is Free as in freedom software, released under the terms of the MIT License.

See the LICENSE file.