Abstract: A system for mixing five channel sound which surrounds an audio plane. The position of a sound source is displayed on a VDU (16) relative to the position of a notional listener (31). The sound source is moved within the audio plane by operation of a stylus (23) upon a touch tablet (24). Thus, an operator is only required to specify positions of a sound source over time, whereafter a processing unit (17) calculates actual gain values for the five channels at sample rate. Gain values are calculated for the sound track for each of the loudspeaker channels and for each of these specified points. Gain values are then produced at sample rate by interpolating calculated gain values for each channel at sample rate.

Abstract: Scene changes in a video sequence are detected by generating data representing the amount of information present in each video frame. This information is processed in such a way that significant changes in the information content are identified as positions where scene changes are likely to occur. The amount of information present in each video frame is determined by compressing the video in accordance with a spatial algorithm, such as JPEG. Under such compression techniques, the amount of data present after compression will vary, depending upon the amount of information present in the original scenes. Thus, for each frame, information is available identifying the amount of data present in the compressed video. This information is analysed on a frame-by-frame basis, providing information identifying the presence of scene changes. In a facility for editing the video, or editing audio for synchronisation against a video track, the scene change information may be displayed to an operator.

Abstract: A system is disclosed for controlling the output level of an audio signal, in which a voltage controlled amplifier (18) is provided in addition to a high fidelity motorized fader (17). During normal (first mode) operation, the level of the audio signal is controlled directly by said fader, which may be adjusted in response to data from a storage device (23). On selecting a second mode of operation, the level of the audio signal is controlled by means of the voltage controlled amplifier, arranged to receive said stored data. In addition, said amplifier also receives trimming signals from said manually adjustable fader and movements of said fader in this mode are also stored, so that said modified data may be combined with the original data, to produce new data for use in said first mode of operation. The invention provides "trim mode" while providing a high fidelity resistive fader for normal operation.