in one of the magazines where program listings were published, there is a 'film projector' program. allowing you to create short videos on the ZX Spectrum. the magazine is in Polish, but with a translator the content of the article should not be a problem, and the program is a listing in BASIC
https://www.t2e.pl/pl/readyrun/moreinfo/144/ZX-Spectrum/Bajtek-031987/144/Projek...