Who is reflected in the mirror in jan van eyck's double portrait giovanni arnolfini and his wife giovanna cenami?

The Arnolfini portrait holds a myriad of details and complex symbolisms. One of which is the convex mirror that can be found in the center of the rear wall. Four figures are reflected in the mirror, the Italian merchant Giovanni Arnolfini and his wife Costanza. The two other figures are seen standing in the open doorway. Scholars and Art historians assumed that the person in red was that of the artist himself. This assumption was based on the appearances of figures wearing red in some of Van Eyck's other artworks. Another evidence that supports this was a Latin inscription found above the mirror that says "Johannes de eyck fuit hic 1434" (Jan Van Eyck was here 1434). Another theory was that the two figures served as witnesses to the marriage between the main subjects of the portrait.