The delay can be caused either at the encoding stage or the playback stage.
If you play that recording back on a different PC / OS / Browser is the delay still evident?
In any case its a bit of a tricky one to solve. If you use the tokyo.poodll.com server to convert your recordings to MP4 you will be restricted to trying it with smaller video capture sizes, and lower audio rates. But do try that.
If you are using FFMPEG on your Moodle server to do the encoding then you can get very detailed with how your instruct FFMPEG to do that. Thats a whole new world though.