Catch-up, as mentioned in the previous section, is a relatively simple workflow to engineer, although there is a wide scope to the interpretation as to what a “catch-up service” is! Essentially the customer proposition is to enable them to review a library of content through some form of electronic program guide (EPG), and allow them to see programs on-demand that have already been broadcast.
Catch-up differs from DVR in as much as the user doesn't need to proactively request the content is made on demand: the content is available to any user with access to the EPG. For example, if you join a TV series at episode 3, you could elect to find episodes 1 and 2 in the catch-up library and watch the entire series from the start.
Some rights may mean that content is only available for a short period. For example, news headlines can be “replaced” every few hours, since the requirement to watch “last week's news” will probably be very infrequent. However, this is not a technical decision, it is a business decision between the broadcaster and the rights holder.
One aspect worth commenting on is the instant availability of live-to-air events. Given the diversity of devices on the market, and the corresponding formats of content encoding that are required to service that array of devices, some good planning can accelerate the availability of the archives to the audience.
I would quickly like to provide a couple of contrasting stories to help clarify how that planning can make a difference.