Not long ago there was a discussion about on-demand viewing and how BARB handle the data. Essentially it related to which programme the non-live viewing is attributed to. I've had a reply from BARB about this which confirms the method:
Quote:
“ With regards to on demand viewing, we have been including viewing to on demand in our viewing figures since December 2008 so it is not a relatively new development in BARB terms. In terms of the attribution of on demand viewing to a linear schedule, it is not as definitive as your describe although loosely you are correct. On demand viewing is captured via audio matching, so the audio of the content being watched is scanned against the audio of all content broadcast by all channels in the last 7 (now 28) days (think Shazam). Where channels have repeated content, this creates the option of multiple allocation options if the content being watched back is exactly the same as both broadcasts. Where there are two broadcasts on the same channel, the allocation will go to the most recent broadcast as you have suggested. Where there are multiple options across channels (Sky 1 content repeated on Sky 2), it works differently. In this case, the system looks at the context of the viewer doing the viewing, were they watching Sky 1 or Sky 2 earlier that day, and indeed across the last 28 days are they more likely to be a Sky 1 viewer as opposed to a Sky 2 viewer. The system creates a probability and allocates the viewing according. The idea being, if you are a heavy Sky 2 viewer as opposed to Sky 1, the viewing is more likely to be attributed to Sky 2. Does this make sense?
So in answer to your questions, these are design specifications (choices) due to the method of viewing attribution (audio matching).
For +1, we do not match any VOD viewing to +1 variants, and remove them completely as options for matching. This is an industry wide decision that VOD viewing should go back to a ‘parent’ channel rather than its staggercast.”
So basically, any programmes with a quick to air repeat (X Factor, Eastenders etc.) could all have on-demand viewing attributed to those repeats rather than the original showing. That makes any comparisons across shows a bit tricky, especially as it could be attributed to alternative channels! Of course on-demand isn't a massive proportion of viewing at the minute but eventually this could be more of an issue.