WO1983003935A1 - Appareil de conversion, transmission et reconversion d'un signal echantillonne - Google Patents

Appareil de conversion, transmission et reconversion d'un signal echantillonne Download PDF

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Publication number
WO1983003935A1
WO1983003935A1 PCT/SE1983/000165 SE8300165W WO8303935A1 WO 1983003935 A1 WO1983003935 A1 WO 1983003935A1 SE 8300165 W SE8300165 W SE 8300165W WO 8303935 A1 WO8303935 A1 WO 8303935A1
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WO
WIPO (PCT)
Prior art keywords
samples
unit
signal
delay chain
frequency
Prior art date
Application number
PCT/SE1983/000165
Other languages
English (en)
Inventor
Tore TORSTENSSON-FJÄLLBRANT
Original Assignee
Torstensson Fjaellbrant Tore
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Torstensson Fjaellbrant Tore filed Critical Torstensson Fjaellbrant Tore
Priority to GB08333702A priority Critical patent/GB2130054B/en
Priority to JP58501528A priority patent/JPS59500791A/ja
Publication of WO1983003935A1 publication Critical patent/WO1983003935A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/66—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission

Definitions

  • This invention relates to an apparatus for converting, transmitting and reconverting a sampled signal and, more precisely, for converting a signal, preferably a speech signal, sampled in the time domain to a non-uniformly sampled signal in the frequency domain while excluding blocks of samples and, respectively, certain samples in blocks of samples in a transmitter, transmitting the signal thus non-uniformly sampled to a receiver, and reconverting the transmitted non-uniformly sampled signal to a uniformly sampled signal in the receiver.
  • a signal preferably a speech signal
  • Apparatuses are known previoulsy, which comprise at the transmitter end a delay chain with a number of outputs, a time-frequency converter for converting short signal blocks of samples (for example eight samples) in the time domain to corresponding signal blocks of samples (eight samples) in the frequency domain, a logic unit for analys ⁇ ing the signals in the frequency domain and generating a control signal depending on the result of said analys ⁇ ing, and a change-over switch for excluding certain sampl ⁇ es (for example four) in blocks of samples in the frequen- cy domain.
  • the change-over switch is connected-in between the time- -frequency converter and the transmitting medium to the receiver end of the apparatus and is controlled by the control signal from a logic unit.
  • the control signal in- eludes information of frequency ranges comprising samples with low signal amplitudes in relation to samples in rem ⁇ aining ranges.
  • a second change- -over switch is located at the input at the transmitter end and excludes blocks of samples in the time domain prior to the conversion to the frequency domain in the time-frequency converter.
  • a frequency-time converter is locat ⁇ ed, which converts signal blocks of samples in the frequ ⁇ ency domain to corresponding signal blocks of samples in the time domain and also reconstructs the blocks of sampl- es previously excluded by said second change-over switch.
  • Samples in these missing blocks of samples are reconstruct ⁇ ed in principle in the same way as samples in the other blocks by inverse conversion from frequency domain to time domain, but hereby they are formed, for example, as the mean value between corresponding samples in the adjacent two blocks or, in a more general and more applicable way, by weighting with suitable interpolation coefficients of corresponding samples in more than the very most i ⁇ edi- ate blocks.
  • the said inverse conversion of a block from frequency domain to time domain takes place by means of a delay chain with a number of outputs, a multiplication unit connected to the outputs of the delay chain and intended for weighted multiplication and subsequent addition of samples with coefficients stored in a memory, by controll ⁇ ing by means of control signals from the logic unit.
  • T ⁇ stored multiplication coefficients are so chosen that a desired reconversion to the time domain is obtained. Apparatuses of the aforesaid kind are known, for example through SE-PS 7905- ⁇ 08-6.
  • Apparatuses of the kind described above per se have proved to operate well, and they utilize much of the redundancy comprised in speech signals, whereby good speech quality is obtained even when, for example, the data speed is reduced by the transmitting medium to 12-16 kbits/second.
  • the present invention has the object, thus, to modify the aforementioned previously known apparatuses so as in a simple and more efficient way, but to a still higher degree be capable of utilizing the redundancy comprised in speech signals. It was found by investigation that, when in- these apparatuses the transmitted frequency samples are; combined in pairs to an amplitude signal and a phase signal, these signals reflect the redundancy of the speech signals much better than frequency signals and, besides, are much more suitable for interpolation for obtaining previously excluded blocks of samples of the speech sign ⁇ als. This renders it possible to obtain a substantial data reduction at the transmission while maintaining a very good speech quality.
  • the mathematic operations in available calculation units preferably can be carried out with so-called "look-up tables", because at short blocks of samples (for example eight samples) the number of quantization levels for transmitted frequency samples is low, for example eight levels at three-bits quantization.
  • the pattern for excluding certain blocks of samples can be varied, for example from every .second block to two subs ⁇ - 3 quent blocks or even several blocks in one sequence corresponding to about the length of a pitch period of a speech signal, in order to obtain a greater data reduction.
  • Fig. 1 shows schematically an embodiment of an app ⁇ aratus according to the invention
  • Fig. 2 shows sample configurations in eight di ferent points in the apparatus according to Fig. 1.
  • the apparatus according to Fig. 1 comprises a transmitter unit and a receiver unit.
  • the transmitter unit comprises a delay chain Fa with a plurality of outputs, which is connected via a change- -over switch 02 (second change-over switch) to the input I of the apparatus, a time-frequency converter TFC conn ⁇ ected at the input end to said outputs, and a logic unit LO connected at its input end to the output of the time- -frequency converter TFC, and at its output end to the control .
  • the change-over switch 01 (first change-over switch) is connected-in between the output of the frequen- cy converter TFC and the transmission ⁇ edium L.
  • the receiver end comprises in series from the transmitt ⁇ ing medium L a delay chain Fb, a calculating unit Bl, which converts frequency samples to samples of an amplit ⁇ ude signal and samples of a phase signal and has two out- puts d and, respectively, e, of which a first output d is connected to a delay chain Fl with subsequent multiplicat ⁇ ion unit Ml for weighted multiplication of samples with coefficients stored in a memory, and an addition unit SI, while a second output e is connected to a delay chain F2 with subsequent multiplication unit M2 of the same type as the unit Ml and an addition unit S2.
  • a second calculation unit B2 with two inputs, of which a first input f is connected to the output of the addition unit SI, and a second input g is connected to the output of the addition unit S2, a third delay chain F3, a third multiplication unit M3 for weighted multiplic ⁇ ation of samples, and an addition unit S3, the output of which is connected to the output U of the apparatus.
  • the calculation unit B2 is capable to reconvert samples of the amplitude signal and phase signal to frequency
  • the delay chains Fb,Pl,F2 and F3 comprise an equal number of delay elements.
  • Frequency samples are transmitted by a first line in the transmitting medium L via the first change-over switch 01 to the delay chain Fb, and by a second line control signals from the logic unit LO are transmitted to the multiplications units M1,M2, and from the unit M2 to the multiplication M3-
  • a uniformly sampled signal in the time domain ingoing to the input i is . ' .converted one block after the other
  • the logic unit LO also emits a control signal to the change-over switch 02, which excludes, for example, every second block or every second group of a number of blocks in series among those samples which lateron are reconstructed one block after the other in the ti ⁇ e- -frequency converter FTC.
  • the logic " unit LO also emits a control signal to the change-over switch 02, which excludes, for example, every second block or every second group of a number of blocks in series among those samples which lateron are reconstructed one block after the other in the ti ⁇ e- -frequency converter FTC.
  • a positions for a number of samples in an input signal, more precisely three blocks of samples designated I,II and III, with eight samples in each block, are shown.
  • a' positions for samples in the blocks I and III and for excluded samples in block II are shown with regard to the point a'immediately after the change-over switch 02.
  • TFC blocks ' are con ⁇ verted one after the other to samples in the frequency domain according to prior art (see for example SE-PS 7905-408-6).
  • Pig. 2, b shows the position pattern for samples in the point b at the output end of the converter TFC.
  • frequency samples are convert ⁇ ed to amplitude samples A.;.»4- + ⁇ an d phase samples ⁇ - ⁇ . . . by combination in pairs of adjacent frequency samples
  • i 1,3,5 in the interval 1-p, where p is the number of samples (for example eight) in one block of samples.
  • the delay chains Fl and F2 together with the multiplications units Ml and M2 are units for interpolation for obtaining signal samples in excluded blocks in a manner known per se, i.e. by weighting with suitable multiplication coefficients of corresponding samples in adjacent blocks of samples.
  • Fig. 2, f and g examples
  • frequency samples are reconverted to uniformly distr ⁇ icited samples in the time domain according to prior art, see SE-PS 7905408-6.
  • the number of blocks in such a group preferably is determined by possible periodicity of the speech signal.
  • the speech signal in the frequency domain has a periodicity with, for ex- ample, close to four blocks, preferably the size of such a group is chosen to be four blocks.
  • the change-over switch 02 preferab1y ;i s pos i ti ' onedi immedi ate-1y before or after the change-over switch 01, so that the signal to the logic unit is not affected by the function of the change-over switch 02.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transceivers (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Radio Relay Systems (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
  • Transmitters (AREA)

Abstract

Un appareil permettant de convertir un signal échantillonné uniformément dans le domaine de temps en un signal échantillonné dans le domaine de fréquences, certains échantillons étant exclus, de transmettre le signal échantillonné non uniformément et de reconvertir le signal transmis en un signal échantillonné uniformément dans le domaine de temps comprend, côté émetteur, une chaîne de temporisation (Fa), un convertisseur temps/fréquence (TFC), une unité logique (LO) et un commutateur de transition (O1) pour exclure certains échantillons par commande depuis l'unité logique (LO), et comprend, côté récepteur, deux unités de calcul (B1 et, respectivement B2) et entre elles deux connexions identiques en série dont chacune comprend un circuit de temporisation (F1 et, respectivement, F2), une unité de multiplication (M1 et, respectivement, M2) et une unité d'addition (F1 et, respectivement, F2), la première unité de calcul (B1) convertit les échantillons de fréquence en un échantillon d'amplitude qui est envoyé à l'une (F1-M1-S1) des connexions en série pour générer des échantillons exclus, et en un échantillon de phase qui est envoyé à l'autre des connexions en série (F2-M2-F2), et la seconde unité de calcul (B2) reconvertit l'échantillon d'amplitude et l'échantillon de phase en un échantillon de fréquence. Dans une connexion en série ultérieure d'une unité de temporisation (F3), d'une unité de multiplication (M3) et d'une unité d'addition (S3), l'échantillon de fréquence est reconverti en des échantillons distribués uniformément dans le domaine de temps.
PCT/SE1983/000165 1982-04-27 1983-04-26 Appareil de conversion, transmission et reconversion d'un signal echantillonne WO1983003935A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB08333702A GB2130054B (en) 1982-04-27 1983-04-26 Apparatus for converting transmitting and reconverting a sampled signal
JP58501528A JPS59500791A (ja) 1982-04-27 1983-04-26 サンプル信号の変換、伝送及び再変換装置

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8202629-5 1982-04-27
SE8202629A SE430739B (sv) 1982-04-27 1982-04-27 Anordning for omvandling, overforing och ateromvandling av en samplad signal

Publications (1)

Publication Number Publication Date
WO1983003935A1 true WO1983003935A1 (fr) 1983-11-10

Family

ID=20346653

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1983/000165 WO1983003935A1 (fr) 1982-04-27 1983-04-26 Appareil de conversion, transmission et reconversion d'un signal echantillonne

Country Status (5)

Country Link
EP (1) EP0106877A1 (fr)
JP (1) JPS59500791A (fr)
GB (1) GB2130054B (fr)
SE (1) SE430739B (fr)
WO (1) WO1983003935A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0193143A2 (fr) * 1985-02-27 1986-09-03 TELEFUNKEN Fernseh und Rundfunk GmbH Procédé de transmission d'un signal audio
EP0309974A1 (fr) * 1987-09-30 1989-04-05 Deutsche Thomson-Brandt GmbH Procédé pour transmettre un signal audible
WO1991005412A1 (fr) * 1989-10-06 1991-04-18 Telefunken Fernseh Und Rundfunk Gmbh Procede pour transmettre un signal

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0193143A2 (fr) * 1985-02-27 1986-09-03 TELEFUNKEN Fernseh und Rundfunk GmbH Procédé de transmission d'un signal audio
EP0193143A3 (en) * 1985-02-27 1988-07-20 Telefunken Fernseh Und Rundfunk Gmbh Audio signal transmission method
EP0309974A1 (fr) * 1987-09-30 1989-04-05 Deutsche Thomson-Brandt GmbH Procédé pour transmettre un signal audible
WO1989003140A1 (fr) * 1987-09-30 1989-04-06 Deutsche Thomson-Brandt Gmbh Procede de transmission de signaux audio
WO1991005412A1 (fr) * 1989-10-06 1991-04-18 Telefunken Fernseh Und Rundfunk Gmbh Procede pour transmettre un signal

Also Published As

Publication number Publication date
EP0106877A1 (fr) 1984-05-02
GB2130054A (en) 1984-05-23
GB8333702D0 (en) 1984-01-25
GB2130054B (en) 1986-01-08
SE430739B (sv) 1983-12-05
JPS59500791A (ja) 1984-05-04
SE8202629L (sv) 1983-10-28

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