In a blog, a BBC engineer explained how the system would work:
“The classification system automatically analyses programmes for a range of different video and audio features, such as luminosity, laughter and motion. The results of this are then used to assign each programme a rating on a set of mood scales. For example, a programme with a high level of motion but not much laughter might score 5/5 on the ‘slow-moving to fast-paced scale’, but 1/5 on the ‘serious to humorous’ scale, meaning it is quick but not very funny (a thrilling drama for instance). The advantage here is that it is then possible to compare different programmes based on their mood scores, allowing you to, for example, search for something ‘more exciting than Spooks’. Moreover, the combination of scores on each scale gives the programme a kind of mood fingerprint, so the system could recommend programmes with similar mood fingerprints to ones it knows you like.”
The blog states that the BBC are currently in the process of researching how users might interact with this mood data.