the write address 23 and the timing of the store input 20 video can be written to the store either continuously or intermittently in intermittent writing the write address generator 24 provides a finite sequence of frame addresses associated with particular video input frames in continuous writing a finite sequence of frame addresses is repeated so that newly arriving input frames overwrite the oldest frames the store may be partitioned into a number of areas for different clips or stills each having its own address or range of addresses reading from the store is controlled by the read address 26 if a fixed address is supplied to the store 21 the frame at that location is output repetitively i e a still picture is output a clip can be replayed by supplying the relevant sequence of addresses it is of course possible to play a clip repetitively by repeating the sequence of addresses the playing of a clip can be synchronised with a video transition as follows a read address generator 27 receives a clip play control input 28 from the control panel e g the block 6 of fig1 to identify the clip to be played and it outputs the address of the first frame of the clip this address is passed to an address modification block 29 that also receives fader position information 30 about the position of the fader on the mixer 39 s control panel that will control the progress of a video transition as the fader is moved by the operator the clip read address is incremented in proportion to the product of the clip length and the fader position and the resulting sequence of addresses forms the read addresses 26 to the store 21 this can be expressed as follows where the clip length.