webm & ffmpeg

webm from the web, Screencasts and elsewhere

https://smcnally.github.io/kb/webm-ffmpeg-Screencasts

webm is a default animation and video format on multiple sites. Ubuntu 22.04’s default screencast utility creates compact webm files in ~/Videos/Screencasts by default.

ffmpeg handles webm and can convert it to other formats like .gif, .mp4, and .mkv for working in tools with little or no webm capabilities.

This works to output webm to mp4 that plays as expected in VLC and other players and editors:

ffmpeg -i screencast.webm -filter:v "fps=30" screencast.mp4

This works in more cases and avoids ffmpeg throwing ‘not divisible by 2’ errors:

ffmpeg -i screencast.webm -filter:v "scale=trunc(iw/2)*2:trunc(ih/2)*2,fps=30" screencast.mp4

The above sets a constant frame rate of 30 frames per second (fps). It resizes source video by one pixel @ most and makes sure your input width and height (iw and ih) are even numbers.

ffmpeg’s Video Options are plentiful, powerful, and best approached by particulars.

Deeper dives into other ffmpeg recipes

Related Q&A helpful during this research include:

• https://askubuntu.com/questions/1419122/ubuntu-22-04-screencast-to-mp4
• https://askubuntu.com/questions/1460038/how-can-i-convert-my-webm-screencast-to-mp4
• https://askubuntu.com/questions/1153557/edit-webm-video-with-gui/