I found another way to achieve the same goal.
Use Conversion Settings to set the target media files uncompressed.
Use prepareEvent method to load uncompressed media file.
So we don't have to load a soundBank contains compressed media then try to decode the media files on loadinig. The format is already uncompressed when packaged into the soundBank.
By the way , if we want use the advantage of prepareEvent() to load single media file instead of all media files in a soundBanks , there are three options inside the soundBankEditor window , { Events , Structures , Media } , do not check the Media , leave the box empty.