Mac HDD still losing space after deleting files I'm working on videos. I'm capturing them with a software and I save them as MP4. Then I compress them as MOV. After that I upload them to YouTube. However I lose about 1.5 GB from my hard disk while I'm doing this. (I delete these videos after I upload.)

How can I fix this situation?
it could be just used a swap space that should be cleared up by a reboot (probably some terminal command too).

Could also be you are on a laptop with time machine and have mobile backups enabled (aka local snapshots).