How are you compressing the movie?
What software are you using?
What source format are you using?
What output format are you choosing?
What frame size?
What frame rate?
What datarate are you setting?
If you’re in the business of transcoding video you really, really need plenty of spare disk space. 9GB files are nothing these days and external hard drives are very cheap (250GB for $100).
BTW 624×352 is an aspect ratio of 16:9, resizing it to 720×480 would distort it (into 4:3)
If you don;t have access to the Pro vesion of Quicktime as Rich suggests, try MPEG-Streamclip (it’s free) https://www.squared5.com/