Patent
1994-10-04
1998-02-03
MacDonald, Allen R.
395 27, G10L 302, G10L 900, G10L 502
Patent
active
057153620
DESCRIPTION:
BRIEF SUMMARY
A method of transmitting and receiving coded speech
FIELD OF THE INVENTION
The invention relates to a method of transmitting coded speech, in which method samples are taken of a speech signal and reflection coefficients are calculated from these samples.
The invention relates also to a method of receiving coded speech.
BACKGROUND OF THE INVENTION
In telecommunication systems, especially on the radio path of radio telephone systems, such as GSM system, it is known that a speech signal entering the system and to be transmitted is preprocessed, i.e. filtered and converted into digital form. In known systems the signal is then coded by a suitable coding method, e.g. by the LTP (Long Term Prediction) or RPE (Regular Pulse Excitation) method. The GSM system typically uses a combination of these, i.e. the RPE-LTP method, which is described in detail e.g. in "M. Mouly and M. B. Paute, The GSM System for Mobile Communications, 1992, 49, rue PALAISEAU F-91120, pages 155 to 162". These methods are described in more detail in the GSM Specification "GSM 06.10, January 1990, GSM Full Rate Speech Transcoding, ETSI, 93 pages".
A drawback of the known techniques is the fact that the coding methods used require plenty of transmission capacity. When using these methods according to the prior art, the speech signal to be transmitted to the receiver has to be transmitted entirely, whereby transmission capacity is unnecessarily wasted.
SUMMARY OF THE INVENTION
The object of this invention is to offer such a speech coding method for transmitting data in telecommunication systems by which the transmission speed required for speech transmission may be lowered and/or the required transmission capacity may be reduced.
This novel method of transmitting coded speech is provided by means of the method of the invention, which is characterized in that characteristics of the reflection coefficients are compared with respective sound-specific characteristics of the reflection coefficients of at least one previous speaker for the identification of the sounds and identifiers of the identified sounds are transmitted, speaker-specific characteristics are calculated for the reflection coefficients representing the same sound and stored in a memory, the calculated characteristics of the reflection coefficients representing the same sound and stored in the memory are compared with the following characteristics of the reflection coefficients representing the same sound, and if the following characteristics of the reflection coefficients representing the same sound differ essentially from the characteristics of the reflection coefficients stored in the memory, the new characteristics representing the same sound are stored in the memory and transmitted, and before transmitting them, information is sent of the transmission of these characteristics and if the following characteristics of the reflection coefficients representing the same sound do not essentially differ from the characteristics of the reflection coefficients stored in the memory, differences between the characteristics of the reflection coefficients representing the same sound of the speaker and the characteristics of the reflection coefficients calculated from the previous sample are calculated and transmitted.
The invention relates further to a method of receiving coded speech, which method is characterized in that an identifier of an identified sound is received, differences between characteristics of the stored sound-specific reflection coefficients of one previous speaker and characteristics of the reflection coefficients calculated from samples are received, the speaker-specific characteristics of the reflection coefficients corresponding to the received sound identifier are searched for in a memory and added to the differences, and from this sum are calculated new reflection coefficients used for sound production, and if information of a transmission of new characteristics sent by a communications transmitter as well as new characteristics of the reflection coefficients
REFERENCES:
patent: 5121434 (1992-06-01), Mrayati et al.
patent: 5165008 (1992-11-01), Hermansky et al.
Edouard Patrick N.
MacDonald Allen R.
Nokia Telecommunications Oy
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