Abstract: An educational system that includes a content item selector configured to select at least one content item from a database so that the reaction of the user required by the at least one content item matches according to a predetermined criteria a prediction of how the user will react to the type of user reaction required by the at least one content item; and a content item output which presents the selected at least one content item to the user.

Abstract: A method of enchancing a video bit stream using temporal scalability, wherein the number of bits or a temporal position of a bidirectionally predicted picture in an enhancement layer is determined with reference to a corresponding characteristic of pictures in another layer of layers, such as a base layer, of the video bit stream and the peak signal to noise ration of the B picture is matched to that of the pictures in the layer below. By endeavouring to align the characteristics of the bidirectionally predicted picture or pictures with the existing picture or pictures in the lower layer or layers, and improved video sequence can be encoded and decoded for viewing by a user.

Abstract: A method of optimising the quality of a B picture by temporal scalability for an enhancement layer of a video bit stream, wherein the B picture B0.5 is predicted based on an SNR enhancement picture EI0 appearing in the highest enhancement layer of the bit stream. A prediction is achieved using foward prediction based on an enhanced picture already appearing in the same enhancement layer. As a result, information contained in the enhanced picture is not wasted.

Abstract: A method of enchancing a video bit stream using temporal scalability, wherein the number of bits or a temporal position of a bidirectionally predicted picture in an enhncement layer is determined with reference to a corresponding characteristic of pictures in another layer of layers, such as a base layer, of the video hit stream and the peak signal to noise ration of the B picture is mathched to that of the pictures in the layer below. By endeavouring to align the characteristics of the bidirectially predicted picture or pictures with the existing picture or pictur4es in the lower layer or layers, and improved video sequence can be encoded and decoded for viewing by a user.