Involved in the biosynthesis of the yellow-orange carotenoid staphyloxanthin, which plays a role in the virulence via its protective function against oxidative stress (PubMed:15933032, PubMed:22535955). Catalyzes the oxidation of the terminal methyl side group of 4,4'-diaponeurosporene to form 4,4'-diaponeurosporen-4-al (PubMed:15933032, PubMed:22535955). 2 AH2 + all-trans-4,4'-diaponeurosporene + 2 O2 = 4,4'-diaponeurosporenal + 2 A + 3 H2O Carotenoid biosynthesis; staphyloxanthin biosynthesis; staphyloxanthin from farnesyl diphosphate: step 3/5. Upon coexpression with Methylomonas 4,4'-diapophytoene desaturase (CrtN), CrtP produces 4,4'-diapolycopene dialdehyde, thus accepting 4,4'-diapolycopene as substrate. Belongs to the carotenoid/retinoid oxidoreductase family. CrtP subfamily.