A method of providing a preview and or replay function for a content on demand service provided by a service provider to a plurality of users. A method in accordance with an embodiment of the invention includes: generating a first stream of content for transmission to a user; generating one or more other streams of content, each of which are derived from the first stream of content and differ therefrom in that the other streams are each in advance of or after the first stream by a time difference; transmitting the first stream of content to the user; receiving a request from the user to view a preview or replay of a part of the content; and switching the user to one of the other streams of content, which other stream is at the time difference that matches the requested preview or replay part of the content.