Abstract: A data streaming apparatus broadcasts data, encoded by a layered encoding algorithm, each layer of encoded data frames being conveyed within separate respective streams of data packets of a predetermined packet structure. A packet numbering facility assigns to each data packet a data sequence number indicating the correct order for subsequent decoding of encoded data conveyed by that packet. Corresponding client apparatus receives data packets having such data sequence numbers assigned to them, including a packet ordering facility to place out-of-sequence packets into the correct order for output to a decoder.

Abstract: A method and apparatus to encode a video signal representing a moving picture, the method comprising:receiving successive frames of a video signal;coding each frame of the video signal with reference to a preceding frame of the video signal, so generating a first set of data which, when reconstructed, represents a first playback mode of the moving picture;coding each frame of the video signal, where n is an integer, so generating a second set of data which, when reconstructed, represents a second playback mode of the moving picture;decoding the first set of data to produce a first reconstructed video signal;decoding the second set of data to produce a second reconstructed video signal;calculating the differences between a frame of the second reconstructed video signal and a frame of the first reconstructed video signal corresponding to the frame succeeding the frame of the second video signal and, when the differences exceed a threshold, coding the differences and so generating a further set of data.