Wǒ zài wǎngshàng xiàzài le yìxiē miǎnfèi de shìpín sùcái.
I downloaded some free video footage online.
Tips
usage
素材 (sùcái) literally 'plain material' = raw material for creative work - extends naturally to writing (写作素材), photography (照片素材), and video. Distinguish from 成片 (finished cut) and 母带 (master tape).