Sometimes I have to create recordings of a presentation beforehand for recruiting people (PhD program) or conferences.
I’ve used Zoom previously for this, but it was not very good.
Here’s my little guide for creating high-quality screencast recordings on an Ubuntu Linux laptop.
It uses utilities like guvcview, xprop, xdpyinfo, and (of course) ffmpeg to customize and optimize the recording process.
The process is roughly like this:
- Have a little window on your screen showing your camera always on top of any window (
guvcview) - Record whole screen with
ffmpeg(raw mkv full resolution) - Edit (trim) and convert to mp4 for sharing
recordmydesktop at first seemed like a good option but it has a bug which ruined my recording :/.
My setup (guvcview, ffmpeg)
Display own video on screen
guvcview provides a very minimal camera window that is ideal for screencasts.
Run guvcview to get your own camera on the screen, select “Always on top” on its window, drag to corner.
Hide gnome top bar of guvcview window
guvcview uses the native window manager (gnome in Ubuntu) and this still has decorations (top bar window). Use xprop to temporarily remove the gnome top bar window:
Click on window to hide:
xprop -format _MOTIF_WM_HINTS 32c -set _MOTIF_WM_HINTS 2
Specify window name beforehand:
xprop -name 'Your window name' -format _MOTIF_WM_HINTS 32c -set _MOTIF_WM_HINTS 2
Query display dimensions (for ffmpeg)
xdpyinfo | grep dimensions
Note: xrandr | grep '*' does not work correctly in high dpi screens.
Record desktop with ffmpeg, edit and convert with ffmpeg
RESOLUTION=5120x3200 # laptop screen
RESOLUTION=6144x3456 # external display
ffmpeg -f x11grab -framerate 30 -video_size $RESOLUTION -i $DISPLAY -f pulse -ac 2 -i default -c:v libx264 -preset ultrafast -crf 0 -c:a aac -strict experimental -b:a 128k output.mkv
This will output a massive video file in full quality (~4Gb per 10 min).
Downsample to 1080p and convert to mp4:
ffmpeg -i output.mkv -vf "scale=1920:-1" -c:v libx264 -preset slow -crf 22 -c:a aac output.mp4
Trim first 5 seconds re-encoding (better to re-encode otherwise it may not match a keyframe) - should’ve been done already from the mkv but forgot!
ffmpeg -ss 5 -i output.mp4 -c:v libx264 -preset fast -crf 22 -c:a aac -strict experimental output.trimmed.mp4
Alternative: recordmydesktop (not recommended!)
recordmydesktop --no-frame --fps 30 --v_quality 22 --s_quality 10
Beware of this issue: https://github.com/Enselic/recordmydesktop/issues/23 Last time it meant my recording was unusable - none of the solutions online worked!
Trim the top and bottom 160 pixels
recordmydesktop --no-frame --fps 30 --v_quality 22 --s_quality 10 --width 5120 --height 3040 -y 160