Abstract: A combined picture data generating apparatus allowing the dramatically reduced amount of hardware of a multipoint control unit for a videoconference system is disclosed. An intra-frame coding picture is extracted from each of terminal picture data signals received from videoconference terminals. Intra-frame coding pictures extracted from the terminal picture data signals are combined to produce a combined picture data signal providing each of the videoconference terminals with a partitioned display screen having separate portions corresponding to respective ones of the videoconference terminals.

Abstract: A video conference control apparatus includes a decoding circuit, a thinning circuit, an image synthesizing circuit, an encoding circuit, and an encoding area setting circuit. The decoding circuit decodes terminal images received from a plurality of video conference terminals. The thinning circuit thins the terminal images decoded by the decoding circuit. The image synthesizing circuit multiplexes the terminal images thinned by the thinning circuit on a predetermined image frame, thereby generating a synthesized image. The encoding circuit encodes the synthesized image generated by the image synthesizing circuit. The encoding area setting circuit sets encoding areas while making the boundary between the encoding areas coincide with the boundary between corresponding divided window areas. A video conference control method and video conference control system are also disclosed.

Abstract: In a multi-point control unit for use in a multi-point videoconference system, an encoding controller is connected to first through N-th decoders and an encoder to produce a controlling signal in response to first through N-th decoding information signals supplied from the first through the N-th decoders and to supply the controlling signal to the encoder. The encoder is connected to a picture combining section to encode a combined signal supplied from the picture combining section into a combined picture data signal so that each of divisional picture signals included in the combined signal is encoded by the use of individual quantizing characteristic controlled by the controlling signal. A data exchanger is connected to the encoder to transmit the combined picture data signal to the first through the N-th videoconference terminals through a network.

Abstract: A predictive decoder includes a decoding section, an adder, an inverse quantizer, a processor, and a superposing section. The decoding section decodes a coded signal to obtain a predictive error signal. The adder adds the predictive error signal to a local decoded signal and outputs a sum signal. The inverse quantizer has a plurality of quantization characteristics. The inverse quantizer receives a control signal for designating one of the plurality of quantization characteristics and the sum signal, selects one of the plurality of quantization characteristics in accordance with the control signal, and performs inverse quantization of the sum signal by using the selected characteristic to obtain an inversely quantized signal. The processor converts the inversely quantized signal into the local decoded signal.

Abstract: At the transmit end of a video communications system, a first motion vector is derived from successive frames during a frame transmit mode and a second motion vector is derived during or immediately following a frame discard mode. An interframe predicted error signal is generated which is representative of the difference between each input frame and a motion-compensated, previous frame during the frame transmit mode, the difference being zero during the frame discard mode. The predicted error signal and the vectors are transmitted to the receive end of the system. In a first embodiment, the second motion vector is derived at the transmit end from frames spaced apart by a discarded frame, and at the receive end, original frames are recovered from the predicted error signal as well as from the first and second motion vectors, and the second motion vector is down-scaled and evaluated whether it is valid or not.

Abstract: In an encoding device for transforming a sequence of digital image signals into a sequence of transformed signals which is subjected to interframe predictive coding by the use of a subtracter and a local decoding loop, the subtracter supplies a block judgement circuit with a sequence of error signals divided into a sequence of blocks. The block judgement circuit judges whether each block is a significant block or a less significant block to produce significant and less significant block signals, respectively. The local decoding loop is selectively put into normal and specific modes in response to the significant and the less significant block signals, respectively. In the normal mode, an inverse transform circuit and a local transform circuit are normally operated through a frame memory in the local decoding loop by producing a sequence of inverse transformed signals and a sequence of local decoded signal, respectively.