Just wanted to chime in...this worked perfectly for me.
tracker-processes -r wiped everything out
and then starting up media player seemed to kick off trackerd process of rescanning my SD card. I closed media player, and then reopened...and THEN it gave me the message "Retrieving information on the new media files. Estimated time remaining: 04:44" and started counting down.

Thanks for the tips on this!! Much appreciated.