It seems that I just got a thought that might be a contribution to the problem of qualia.
Qualia might be, simple and amazing, the sense impression of a sense impression.
What does that mean? Sense impressions per se, that is, data as such, cannot generate qualia, as data is only sufficient for identifying external entities, but does not say what inner experience should be caused by these entities. So, the latter must be a property of the inner “screen” where all sense impressions and received and then interpreted. However, what sense data causes on this screen would go unnoticed if there would not be another “inner sense” or “meta sense” that would capture that and feed it back as sensual data, perhaps even on the same screen. So qualia is proposed here to mean the self-perception of the brain in the state of perceiving, or, as above, the sense impression of sense impressions.