Source: http://www.google.com/patents/US5978761?dq=Frischling
Timestamp: 2014-12-22 08:57:25
Document Index: 291185493

Matched Legal Cases: ['art 5', 'art. 4', 'art. 5', 'art 5', 'art. 4', 'art. 5']

Patent US5978761 - Method and arrangement for producing comfort noise in a linear predictive ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsComfort noise is produced in a linear predictive speech decoder which operates discontinuously, i.e., treats data frames which alternately represent speech information and background noise. During decoding of received data frames which contain background noise-describing parameters, a first number of...http://www.google.com/patents/US5978761?utm_source=gb-gplus-sharePatent US5978761 - Method and arrangement for producing comfort noise in a linear predictive speech decoderAdvanced Patent SearchPublication numberUS5978761 APublication typeGrantApplication numberUS 08/928,523Publication dateNov 2, 1999Filing dateSep 12, 1997Priority dateSep 13, 1996Fee statusLapsedAlso published asWO1998011536A1Publication number08928523, 928523, US 5978761 A, US 5978761A, US-A-5978761, US5978761 A, US5978761AInventorsIngemar JohanssonOriginal AssigneeTelefonaktiebolaget Lm EricssonExport CitationBiBTeX, EndNote, RefManPatent Citations (15), Non-Patent Citations (10), Referenced by (12), Classifications (6), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetMethod and arrangement for producing comfort noise in a linear predictive speech decoderUS 5978761 AAbstract Comfort noise is produced in a linear predictive speech decoder which operates discontinuously, i.e., treats data frames which alternately represent speech information and background noise. During decoding of received data frames which contain background noise-describing parameters, a first number of these data frames which have been received directly before a speech frame are excluded and replaced with one or more background noise describing frames which have been received earlier. Another number of the background noise-describing frames which have been received immediately after a sequence of speech frames are also left out during the decoding and replaced by one or more background noise-describing frames which have been received before the sequence of speech frames. This results in a minimized degradation of the background noise information and gives an optimal comfort noise on the receiver side.
What is claimed is: 1. Method in a telecommunication system in which speech information is transmitted from a transmitter side to a receiver side, whereby speech information for a given speech connection is transmitted discontinuously in the form of data frames, which can be speech frames and background noise describing frames, in order to form a background noise on the receiver side from the received background noise describing frames, the method comprising:calculating parameters which describe the background noise on the transmitter side through interpolation between the information content in two or more of the received background noise describing frames, excluding K of the background noise describing frames, which directly precede a speech frame, during said calculation of the parameters which describe the background noise for a given data frame, and using one or more earlier received background noise describing frames in order to calculate the background noise for said data frame. 2. Method of claim 1, wherein K=1.
3. Method of claim 1, further comprising:excluding M of the background noise describing frames, which follow directly after a received sequence of speech frames, during said calculation of parameters which describe the background noise, and using M background noise describing frames of the background noise describing frames which have been received before said sequence of speech frames in order to calculate the background noise. 4. Method according to claim 3, wherein M=1.
6. Apparatus for generating a reconstructed speech signal out of received data frames which can be formed from speech frames and background noise describing frames, comprising:a control unit, a first memory unit for storage of speech frames, a second memory unit for storage of background noise describing frames, a data frame directing unit which guides a received data frame to the first memory unit if the actual data frame is a speech frame and to the second memory unit if the actual data frame is a background noise describing frame, and a decoding unit in which data frames are decoded and form the reconstructed speech signal, wherein the control unit comprises a memory shift unit in order to control the memory positions in the second memory unit from which the reading of the background noise describing frames to the decoding unit takes place. Description
TECHNICAL FIELD The present invention relates to a method for generating comfort noise in a linear predictive speech decoder which operates discontinuously, i.e. processes data which alternately represent speech information and background noise.
BACKGROUND In discontinuous speech coding according to the VOX-principle (VOX=Voice Operated Transmission) a unit which detects voice activity, a so-called VAD-unit (VAD=Voice Activity Detector) decides for each sound sequence received whether the received sound information represents human speech or not. The VAD-unit can have two different conditions. A first condition means that a current sound is classified as human speech and a second condition means that a certain sound is classified as non-speech.
SUMMARY An object for the present invention is to minimize the degeneration of the parameters of the SID-frames during both changing from the first to the second, and from the second to the first of the condition signals of the VAD-unit.
BRIEF DESCRIPTION OF THE FIGURES FIG. 1 shows a prior art arrangement of a VAD-unit and a speech coder unit;
DETAILED DESCRIPTION FIG. 1 shows a prior art arrangement of a VAD-unit 110 and a speech coder unit 120), where the VAD-unit 110 for each received sequence of sound information S decides whether the sound represents human speech or not. If the VAD-unit 110 detects that a given sound sequence S represents speech then a first condition signal 1 is sent to a speech frame generator 121 in the speech coder unit 120), which in this way is controlled to deliver a speech frame FS containing coded speech information based on the sound sequence S. If on the other hand the sound sequence S is determined by the VAD-unit 110 to be non-speech then a second condition signal 2 is sent to an SID-generator 122 in the speech coder unit 120), which in this way is controlled to, based on the sound sequence S), every N'th frame deliver an SID-frame FSID), which contains parameters which describe the frequency spectrum and the energy level of the sound S. During the intermediate N-1 possible opportunities to transmit data the SID-frame generator, however, does not generate any information. Each generated speech frame FS and SID-frame FSID passes a combining unit 123), which delivers the frames FS, FSID on a common output in the shape of data frames F.
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