A quick follow up to my post here. As it turns out, VLC refuses to play back any Ogg file generated by recordMyDesktop at normal speed: playback jumps all over the shop, with the net effect of it appearing to run much faster than the speed it was actually originally captured. So, we are shit out of luck with using it to transcode recordMyDesktop files for editing in OpenShot.
You can read what the VLC core developers thought of this issue in posts 8 and 9 here:
Frustrating that recordMyDesktop is so close to being perfect for my needs, but as it’s a defunct project I am forced to look elsewhere. Turns out that the ffmpeg command line utility can be used to capture a live desktop (loads of guides on the web on this topic), so in a follow up post I will outline my efforts to use this instead.