Comment 7 for bug 1294303

That log file indicates that you might be missing some codecs, because some of your mp3 files fail on indexing. You might want to install gstreamer1.0 plugin packages "bad" and/or "ugly".

The fact that Mediascanner keeps using CPU even though a volume is unmounted should be fixed by this branch: https://code.launchpad.net/~jpakkane/mediascanner2/generator/+merge/217426

For general CPU usage there is not much we can do. Mediascanner must scan the files or they can't be queried by the music scope or the music player app. Inspecting tens of thousands of files takes its time, unfortunately. It should be noted, though, that it is only slow the first time. Mediascanner remembers what files you had on the volume and the next time you plug it in it only scans what has changed.

I guess we could add a way for users to tell Mediascanner not to scan certain directories, such as by writing an empty file called .donotscan in directories that should be omitted.