A decoder configured to decode a plurality of encoded streams into a reconstructed output video, the decoder configured to: receive an encoded base stream, wherein the encoded base stream is configured to be decoded by a base decoder to produce a first output video; receive one or more encoded streams (416, 428); decode respective frames of the one or more encoded streams to derive respective sets of residuals, each frame of the respective frames being divided into a plurality of tiles and each tile of the plurality of tiles being divided into a plurality of blocks; and combine the sets of residuals with the first output video to generate the reconstructed output video, wherein, to decode respective frames, the decoder is configured to: obtain, for each block of the plurality of blocks, a preliminary set of residuals from the one or more encoded streams; derive a set of temporal predictions using a temporal buffer; and combine the set of temporal predictions with the preliminary set of residuals to output data for combination with the first output video; characterised such that the decoder is configured to provide for zeroing of values of the set of temporal predictions by being specifically configured to: receive a second parameter at the block level from data from the one or more encoded streams for each respective block of the plurality of blocks, wherein the second parameter has a second value that provides temporal signalling for the respective block and indicates that the decoder is to refresh the values of the temporal predictions for the block; receive a third parameter at the tile level having a third value which indicates that receiving the second parameter for the specified block with the second value indicates that values in the temporal buffer associated with the tile are to be refreshed; refresh the values of the temporal buffer associated with the tile by setting the values of the temporal predictions for the respective tile of the plurality of tiles to zero. receive an encoded base stream, wherein the encoded base stream is configured to be decoded by a base decoder to produce a first output video; receive one or more encoded streams (416, 428); decode respective frames of the one or more encoded streams to derive respective sets of residuals, each frame of the respective frames being divided into a plurality of tiles and each tile of the plurality of tiles being divided into a plurality of blocks; and combine the sets of residuals with the first output video to generate the reconstructed output video, wherein, to decode respective frames, the decoder is configured to: obtain, for each block of the plurality of blocks, a preliminary set of residuals from the one or more encoded streams; derive a set of temporal predictions using a temporal buffer; and combine the set of temporal predictions with the preliminary set of residuals to output data for combination with the first output video; characterised such that the decoder is configured to provide for zeroing of values of the set of temporal predictions by being specifically configured to: receive a second parameter at the block level from data from the one or more encoded streams for each respective block of the plurality of blocks, wherein the second parameter has a second value that provides temporal signalling for the respective block and indicates that the decoder is to refresh the values of the temporal predictions for the block; receive a third parameter at the tile level having a third value which indicates that receiving the second parameter for the specified block with the second value indicates that values in the temporal buffer associated with the tile are to be refreshed; obtain, for each block of the plurality of blocks, a preliminary set of residuals from the one or more encoded streams; derive a set of temporal predictions using a temporal buffer; and combine the set of temporal predictions with the preliminary set of residuals to output data for combination with the first output video; characterised such that the decoder is configured to provide for zeroing of values of the set of temporal predictions by being specifically configured to: receive a second parameter at the block level from data from the one or more encoded streams for each respective block of the plurality of blocks, wherein the second parameter has a second value that provides temporal signalling for the respective block and indicates that the decoder is to refresh the values of the temporal predictions for the block; receive a third parameter at the tile level having a third value which indicates that receiving the second parameter for the specified block with the second value indicates that values in the temporal buffer associated with the tile are to be refreshed; receive a second parameter at the block level from data from the one or more encoded streams for each respective block of the plurality of blocks, wherein the second parameter has a second value that provides temporal signalling for the respective block and indicates that the decoder is to refresh the values of the temporal predictions for the block; receive a third parameter at the tile level having a third value which indicates that receiving the second parameter for the specified block with the second value indicates that values in the temporal buffer associated with the tile are to be refreshed; refresh the values of the temporal buffer associated with the tile by setting the values of the temporal predictions for the respective tile of the plurality of tiles to zero.