Comment 1 for bug 119725

This has nothing to do with either libburn, nor brasero. You are free to burn at lower speed if it suits you.
There are no different mimetypes for iso, only one. Thus you could have only one speed for all iso files.
And if that's your intention, it's pretty trivial to set speed in Brasero. Right now I don't see what other
type of images except .iso would you like to burn, so there is no point in this bug.