Part of my job involves receiving webinars from in-company instructors and uploading them to vimeo. Recently I've been required to start adding a logo sting to the beginning of each webinar.
I've tried merging the two files together with Wondershare video converter, and I've tried editing them together in Final Cut. Both methods increase the file size dramatically - Using wondershare to merge and process (at 600 kbps) can increase a 21 Mb file to 80 Mb!
I'm too ignorant about file conversion to understand where the extra "mass" is coming from. Wondering if there's a way to add two files and not have them end up humongous.