Over the last few years I've done quite a bit of wedding photography and videography, and have quite a lot of footage. As a rule of thumb, I keep footage for 5 years, in case people need some additonal stuff, photos or videos later (happened only like 3 times ever, but still).
For quite some time i've been using OM-D E-M5 Mark III, which as far as I know can only record with h.264. (at least thats what we've always recorded in), and only switched to h.265/hevc camera quite recently. Problem is, I've got terabytes of old h.264 files left over, and space is becoming an issue., there's only so many drives I can store safely and/or connect to computer.
What I'd like is to convert h.264 files to h.265, which would save me terabytes of space, but all the solutions I've found by researching so far include very small amount of files being converted, and even then it takes quite some time.
What I've got is ~3520 video files in h.264, around 9 terabytes total space.
What would be the best way to convert all of that into h.265?