초록 ▼

A high efficiency speech coding apparatus which can eliminate repetitions of high efficiency speech coding and decoding processes of a digital speech signal upon inter-office transit switching without employing a special exchange and a transit switching system which can prevent degradation in qualit

A high efficiency speech coding apparatus which can eliminate repetitions of high efficiency speech coding and decoding processes of a digital speech signal upon inter-office transit switching without employing a special exchange and a transit switching system which can prevent degradation in quality of speech information and increase in encode and decode processing delay upon transit switching are disclosed. The apparatus repetitively inserts a synchronizing signal into an output speech signal to an exchange and supervises an input speech signal from the exchange to detect a synchronizing signal in order to determine whether the destination of connection of the exchange is a subscriber line or another trunk circuit connected by way of another high efficiency coding apparatus. When a subscriber line is connected, code conversion and inverse code conversion between a high efficiency coded speech signal and a speech signal for the subscriber line are performed using a coding section and a decoding section, respectively. When another trunk circuit is connected, an invalid signal to raise the bit rate of the speech signal to allow transparent transmission through the exchange is added and removed bypassing the coding section and the decoding section.

대표청구항 ▼

A speech coding apparatus interposed between (1) a digital exchange capable of performing intra-office and inter-office transit switching of a digital speech signal at a first bit rate, and (2) a digital trunk circuit which transmits a high efficiency coded digital speech signal at a second bit rate

A speech coding apparatus interposed between (1) a digital exchange capable of performing intra-office and inter-office transit switching of a digital speech signal at a first bit rate, and (2) a digital trunk circuit which transmits a high efficiency coded digital speech signal at a second bit rate lower than said first bit rate, said apparatus comprising: coding means for coding said digital speech signal of a first format having said first bit rate into said high efficiency coded digital speech signal of a second format having said second bit rate; decoding means for decoding said high efficiency coded digital speech signal of said second format into said digital speech signal of said first format; first rate conversion means for periodically adding an invalid signal of a predetermined bit length to the digital speech signal of said second format inputted thereto from said digital trunk circuit to produce said digital speech signal of a third format having said first bit rate and outputting said digital speech signal of said third format to said digital exchange; synchronizing signal insertion means for inserting a synchronizing signal into a selected one of output signals of said decoding means and said first rate conversion means by periodic replacement of a bit of said selected one of said output signals so that a predetermined bit pattern array may be obtained and sending out a resulted signal to said digital exchange; synchronizing signal detection means for detecting, when said digital speech signal of said first or said third format is inputted thereto from said digital exchange, a synchronizing signal from within said inputted digital speech signal; second rate conversion means for removing, when said digital speech signal of said third format is inputted thereto from said digital exchange, an invalid signal including said synchronizing signal from within said inputted digital speech signal to restore the digital speech signal of said second format and outputting said digital speech signal of said second format to said digital trunk circuit; and selection means operable in response to said detection by said synchronizing signal detection means, for: (1) sending out said output signal of said coding means to said digital trunk circuit and said output signal of said decoding means to said synchronizing signal insertion means, when said synchronizing signal is not detected, and (2) sending out said output signal of said second rate conversion means to said digital trunk circuit and sending out said output signal of said first rate conversion means to said synchronizing signal insertion means, when said synchronizing signal is detected.