Nec Corporation

Juniper Networks, Inc.

Yoshiaki Nozawa

Jun Furukawa

Masahiro Serizawa

Toshio Koga

Yasuhiro Arasawa

The present invention is directed to obtain a statistic multiplexing effect in an image transmission system using terminals stipulated by H.310 of an ITU-T recommendation. In a network including a first local area ATM network, a second local area ATM network and a public ATM network connected to the first and second ATM local area networks, multiplex gateway devices are interposed between the local area ATM networks and the public ATM network, respectively. The multiplex gateway apparatus includes ATM transmission line unitstofor calculating statistic information represented by a mean rate and a peak cell rate of ATM cells in the transmission ATM signal. A statistic multiplexing control unitconducts rate addition after statistic multiplexing according to the statistic information and determines the rate addition result. A piece-wise constant bit rate control unitcalculates a required piece-wise constant bit rate on the basis of the rate addition result and performs cell multiplex control on the basis of this piece-wise constant bit rate. An ATM cell multiplexing/demultiplexing unittransmits a transmission statistic multiplex signal according to cell multiplexing control.

Statistic multiplex transmission system

A speech decoding device is provided is capable of reducing degradation of speech quality caused by concealment processing performed when a loss of a packet has occurred, e.g., in speech packet communications using a VoIP (Voice over Internet Protocol) or the like. A decoding circuit decodes speech from a packet received through an input terminal and stores an internal signal in an updating buffer circuit, the internal signal produced in the decoding process and to be used in a decoding process for a subsequent packet to be subsequently received. The decoding circuit produces, based on the internal signal stored in the updating buffer circuit, concealed speech corresponding to a packet having not been received, and outputs the produced concealed speech. The internal signal is updated using the concealed speech.

Reduction of speech quality degradation caused by packet loss

In a network including a first local area ATM network, a second local area ATM network and a public ATM network connected to the first and second ATM local area networks, multiplex gateway devices are interposed between the local area ATM networks and the public ATM network, respectively. The multiplex gateway apparatus includes ATM transmission line units for calculating statistical information represented by a mean rate and a peak cell rate of ATM cells in the transmission ATM signal. A statistical multiplexing control unit conducts rate addition after statistical multiplexing according to the statistical information and determines the rate addition result. A piece-wise constant bit rate control unit calculates a required piece-wise constant bit rate on the basis of the rate addition result and performs cell multiplex control on the basis of this piece-wise constant bit rate. An ATM cell multiplexing/demultiplexing unit transmits a transmission statistical multiplex signal according to cell multiplexing control.

In a receiving clock reproducing method, an estimated value of delay time fluctuation of a received signal is estimated at intervals defined by transmitting clock included in the received signal. To estimate the estimated value, an oscillator counter counts pulses of a reference clock supplied from an independent oscillator while a reading counter counts pulses of the receiving clock. The estimated value is used to control a voltage controlled oscillator for producing the receiving clock.

Clock reproducing method and receiving clock producing apparatus allowing for absorption of transmission channel jitter

An image signal encoding system which is capable of correctly encoding an editing image signal before and after switching points of a first input dynamic image signal and a second input dynamic image signal. The image signal encoding system selects, as an editing image signal, one of the first and the second input dynamic image signals, each of which has serial image plane frames to encode the editing image signal. A switching signal is produced which is used to select as the editing image signal one of the first and second input dynamic image signals. An image encoder encodes the editing image signal, using spatial correlation, an initial image plane frame of the editing image signal after a switching time point of selection of the first and second input dynamic image signals. The image encoder encodes, using previous forecast in correlation between two successive image plane frames of the serial image plane frames, a final image plane frame before the switching time point of selection of the first and second input dynamic image signals.

Growing community of inventors

Tokyo, Japan

Yoshiaki Nozawa