2. A video memory according to claim 1, in which each said input video data block comprises pixel data words representing a single video field.
1. A video memory comprising: a video store for storing video data comprising a plurality of input video data blocks, each of said input video data blocks comprising a plurality of pixel data words and at least one ancillary data word associated with the input video data block for identifying at least one video field represented by said plurality of pixel data words; a recirculating output buffer having a storage capacity equal to the number of ancillary data words associated with each said input video data block times the number of said input video data blocks stored in said video store, said recirculating output buffer for storing data words, reading out the stored data words and re-storing the read out data words; means for reading the ancillary data words associated with a predetermined sequence of said input video data blocks from said video store into said recirculating output buffer in response to a read control signal; and serial reading means for reading successive output video data blocks from said video store in response to said read control signal, each output video data block comprising pixel data words from said predetermined sequence of said input video data blocks, said serial reading means and said recirculating output buffer being operable in response to said read control signal to output concurrently each pixel data word in each output video data block with said at least one ancillary data word associated with said input video data block of the pixel data word being output.