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    DIGITAL TRANSMISSION SYSTEM FOR A PACKETIZED VOICE
    1.
    发明专利
    DIGITAL TRANSMISSION SYSTEM FOR A PACKETIZED VOICE 未知

    公开(公告)号：DE3479468D1

    公开(公告)日：1989-09-21

    申请号：DE3479468

    申请日：1984-05-23

    Applicant: IBM ,  IBM FRANCE

    Inventor： CALLENS PAUL ,  NOAILLY PHILIPPE ,  GALAND CLAUDE ,  SECONDO PIERRE ,  GERGAUD CLAUDE

    IPC: H04M3/00 ,  H04J3/17 ,  H04L12/64 ,  H04L11/20

    Abstract: A method of transmitting digitized voice signals as packets of bits in a digital transmission network to which a plurality of terminals acting as sources of voice signals are attached. The method includes, at the transmitting end and for each source, the steps of: a dividing the signal into successive, digitally-coded segments; performing a so-called source activity detection; and assembling the bits resulting from the coding operation into packets, each packet being provided with a header containing, in particular, a parity bit whose logic value is modified whenever an inactivity or long pause is detected. At the receiving end, detection of a change in the value of said parity bit causes the delivery of a packet of bits to the decoder/synthesizer to be delayed by a given time interval called retention delay.

    SPEECH CODING METHODS AND APPARATUS FOR CARRYING OUT THE METHOD
    3.
    发明专利
    SPEECH CODING METHODS AND APPARATUS FOR CARRYING OUT THE METHOD 未知

    公开(公告)号：DE3171990D1

    公开(公告)日：1985-10-03

    申请号：DE3171990

    申请日：1981-04-30

    Applicant: IBM ,  IBM FRANCE

    Inventor： BERAUD JEAN-PAUL ,  ESTEBAN DANIEL ,  GALAND CLAUDE

    IPC: H03M3/02 ,  H03M7/30 ,  H04B1/66 ,  H04B14/04

    Abstract: This improved speech signal Block Coded PCM (BCPCM) system reduces the number of bits allocated to transmitting the scale factor, thereby releasing bits for allocation to coding samples in the associated block of samples. The scale factor (c) is calculated for every 16 millisecond block of samples. However, the scale factor will be transmitted only once per 32 millisecond block if there is no significant difference between the two sequential values. The original speech signal is split into 16 frequency subbands, each subband initials sampled and 12-bit coded, then requantized in BCPCM at dynamically variable bit rates depending on the scale factor transmission rate.

    STARTING-UP METHOD FOR AN ECHO CANCELLER FILTER, AND COMMUNICATION SYSTEM USING THIS METHOD
    5.
    发明专利
    STARTING-UP METHOD FOR AN ECHO CANCELLER FILTER, AND COMMUNICATION SYSTEM USING THIS METHOD 未知

    公开(公告)号：DE3376943D1

    公开(公告)日：1988-07-07

    申请号：DE3376943

    申请日：1983-06-30

    Applicant: IBM ,  IBM FRANCE

    Inventor： DESBLACHE ANDRE ,  GALAND CLAUDE ,  VERMOT-GAUCHY ROBERT

    IPC: H04B3/23

    Abstract: In an echo filter with a 128-tap delay line, successive sequences of real and imaginary components of samples of flat-spectrum signal are sent along the echo path. From the echo a sequence of samples (z(n)) is received and stored, and the terms of its fast Fourier transform (FFT) are calculated. Each term is rotated through a predetermined angle in accordance with its rank, and an inverse FFT is performed on the rotated terms. The results (h(n)) are sorted for location and measurement of the max. term in the inverse transform, on each side of which a given number of terms are selected and measured for the initial coeffts.

    7.
    发明专利
    未知

    公开(公告)号：FR2389277A1

    公开(公告)日：1978-11-24

    申请号：FR7713995

    申请日：1977-04-29

    Applicant: IBM FRANCE

    Inventor： CROISIER ALAIN ,  ESTEBAN DANIEL ,  GALAND CLAUDE

    IPC: H03M1/00 ,  G10L19/02 ,  H03M7/30 ,  H04B1/66 ,  H04B14/04 ,  H03K13/01

    Abstract: A coding process, given a total number of available bits per unit time, allocates to each of a plurality of signal channels a number of bits proportional to information in the channel. The process is useful for transcoding BCPCM (Block Coded PCM) voice signals for lower bit rate and conserving transmission channel bandwidth.

    DIGITAL CODING METHOD AND DEVICE FOR CARRYING OUT THE METHOD
    9.
    发明专利
    DIGITAL CODING METHOD AND DEVICE FOR CARRYING OUT THE METHOD 未知

    公开(公告)号：DE3270212D1

    公开(公告)日：1986-05-07

    申请号：DE3270212

    申请日：1982-04-30

    Applicant: IBM ,  IBM FRANCE

    Inventor： CALLENS PAUL ,  GALAND CLAUDE

    IPC: H03M7/30 ,  H04B1/66 ,  H04B14/04 ,  H04J3/00

    Abstract: This coder dispatches the bits resulting from the coding operation of a speech signal into a format for transmission at a rate chosen from a plurality of predetermined transmission rates. More specifically, the contents of at least part of the speech signal frequency bandwidth is split into several sub-bands. Said sub-bands are regrouped into sub-groups, each of said sub-groups corresponding to at least one of said possible transmission rates, i.e. to at least one sub-group coding bit rate. The signal samples belonging to each sub-group are recoded through a dynamical allocation of requantizing steps between the sub-bands. The obtained bits resulting from the recoding are dispatched into a multirate frame according to the sub-group which they belong to.

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