Method and system for transmitting variable rate speech signal

• US 4,903,301 A
• Filed: 02/12/1988
• Issued: 02/20/1990
• Est. Priority Date: 02/27/1987
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kondo, Kazuhiro, Suzuki, Toshiro
• Primary Examiner(s): KEMENY, EMANUEL
• Application Number:
  US07/155,392
• Time in Patent Office: 739 Days
• Field of Search: 381/30, 381/31, 370/81, 375/122
• US Class Current: 704/501
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients

Abstract

A speech signal transmission system for transmitting coded speech signals with variable bit rate is disclosed, which comprises a coder for analyzing digital speech signals inputted in a one-frame period and transforming them into coded data comprising a plurality of parameters indicating characteristics of the inputted speech signals, a data arranging circuit for arranging the coded data outputted by the coder in the order of the priority in the decoding of the speech signals and outputting them, and a bit stealer allowing a series of coded data outputted successively by the data arranging circuit to pass through only in a period of time determined by the transmission bit rate. The bit arranging circuit outputs the parameters in the order of the priority of decomposes each of them in unit of a bit and outputs them with decreasing priority. Parameters or bits of low priority are omitted by the bit stealer, depending on the transmission bit rate. One the receiver side the parameters are extracted and the speech signals are decoded on the basis of arrangement type identification codes transmitted together with the coded data.

Claims

1. A method for transmitting coded signals with variable bit rate comprising:

the step of transforming original signals each inputted during a predetermined period of time into a first group of coded data representing characteristics of said original inputted signals;

the step of obtaining error signals corresponding to the difference between signals reproduced on the basis of said first group of coded data and said inputted original signals;

the step of transforming said error signals into a second group of coded data, said first group of coded data being assigned a high priority and said second group of coded data being assigned a low priority; and

the further step of transmitting said coded data by an amount corresponding to a determined transmission rate.

2. A method for transmitting coded signals with variable bit rate comprising:

the step of analyzing signals inputted during a predetermined period of time and transforming the inputted signals into a plurality of coded data representing characteristics of said original inputted signals;

the step of arranging said plurality of coded data in an order of decreasing priority in the decoding of the signals wherein said plurality of coded data are decomposed in units of a bit and rearranged in said order of bits of decreasing priority, or on the basis of one order selected from a plurality of previously prepared sort patterns, depending on inputted signals, and

the step of transmitting said arranged coded data in the order of decreasing priority by an amount of data corresponding to a determined transmission rate.

3. A method for transmitting coded signals according to claim 2, wherein a series of data comprising said rearranged bits are transmitted, following identification of the sort pattern applied to said rearrangement.

4. A method for transmitting coded signals according to claim 2 wherein said step of arranging comprises:

the step of applying successively a plurality of previously prepared sort patterns so as to transform the bits of said coded data into a plurality of series of data having different bit arrangement; and

the step of evaluating the deterioration of coded signals for each of sad series of data, when they are data-compressed, depending on said transmission bit rate, and finding the optimum sort pattern, said transmitting step being effected to the series of data obtained by using said optimum sort pattern.

5. A method for transmitting coded signals according to claim 4, wherein said series of data are transmitted, following the determination of said optimal sort pattern.

6. A method for transmitting coded signals according to claim 4, wherein said step of arranging includes a step of first deciding the type of said inputted signals and then the formation of said plurality of series of data having different bit arrangement according to a plurality of sort patterns selected on the basis of the result of said decision.

7. A speech transmission system for transmitting coded signals with variable bit rate comprising:

coding means for transforming original signals each inputted in a predetermined period of time into a plurality of coded data representing characteristics thereof, wherein said coding means comprises

first coding means for transforming said inputted signals into a first group of coded data with a predetermined coding algorithm,

means for obtaining error signals corresponding to the difference between signals reproduced on the basis of said first group of coded data and said inputted original signals, and

second coding means for transforming said error signals into a second group of coded data, said first group of coded data at first and then said second group of coded data being outputted by said data arranging means;

data arranging means connected with said coding means for outputting said plurality of coded data in an order of decreasing priority in the reproducing of the original signals; and

means for allowing a series of coded data outputted by said data arranging means to pass an amount of data corresponding to a determined transmission rate.

8. A signal transmission system for transmitting coded signals with variable bit rate comprising:

coding means for analyzing speech signals inputted in a predetermined period of time and transforming the inputted signals into a plurality of coded data representing characteristics thereof;

data arranging means connected with said coding means for outputting said plurality of coded data in an order of decreasing priority in the decoding of the speech signals, wherein said data arranging means includes means for decomposing said plurality of coded data in unit of a bit and memory means for storing a plurality of sort patterns, the rearranging means rearranging the bits on the basis of a sort pattern read-out from said memory means depending on the inputted speech signals, said coded data being outputted in an order of bits of decreasing priority; and

means for allowing a series of coded data outputted by said data arranging means to pass an amount of data corresponding to a determined transmission rate.

9. A signal transmission system according to claim 8, wherein said data arranging means comprises:

rearranging means for applying successively a plurality of sort patterns previously prepared so as to transform the bits of said coded data into a plurality of series of data having different bit arrangements; and

means for selecting the series of data for which the deterioration of the speech quality is smallest among said plurality of series of data when the amount of data is reduced, depending on said determined bit rate.

10. A speech signal transmission system according to claim 9, wherein said data arranging means includes means for outputting identification information of the sort pattern corresponding to the selected series of data together with said series of data.

11. A speech signal transmission system according to claim 9, wherein said data arranging means includes:

classifying means for assigning said inputted speech signals to one of a plurality of classifications previously determined;

said memory means storing a plurality of sort patterns for every classification;

said rearranging means reading-out said plurality of sort patterns for rearranging data bits on the basis of the decision of said classifying means.