Method and apparatus for performing speech frame encoding mode selection in a variable rate encoding system

An apparatus for selecting an encoding rate from a predetermined set of encoding rates and for encoding a frame of speech including a plurality of speech samples, comprising:

• a mode measurement calculator that generates a set of parameters indicative of characteristics of said frame of speech in accordance with said speech samples and a signal derived from said speech samples;
• and
• a rate determination logic for receiving said set of parameters, for determining the psychoacoustic significance of said speech samples in accordance with said set of parameters, and for selecting an encoding rate from said predetermined set of encoding rates.

In a communication system wherein a remote station communicates with a central communication center, a subsystem for dynamically changing the transmission rate of a frame of speech transmitting from said remote station, comprising:

• means, responsive to said speech frame and to a signal derived from said speech frame, for generating a set of parameters indicative of characteristics of said speech frame;
• and
• means for receiving said set of parameters, for determining the pyschoacoustic significance of said speech samples in accordance with said set of parameters, for receiving a rate command signal for generating at least one threshold value in accordance with said rate command signal, for comparing at least one parameter of said set of parameters with said at least one threshold value, and for selecting an encoding rate in accordance with said comparison.

In a communication system wherein a remote station communicates with a central communication center, a subsystem for dynamically changing the transmission rate of a frame of speech transmitting from said remote station, comprising:

• a mode measurement calculator that generates a set of parameters indicative of characteristics of said frame of speech in accordance with said speech samples and a signal derived from said speech samples;
• and
• a rate determination logic that receives said set of parameters for determining the psychoacoustic significance of said speech samples in accordance with said set of parameters, receives a rate command signal for generating at least one threshold value in accordance with said rate command signal, compares at least one parameter of said set of parameters with said at least one threshold value, and selects an encoding rate in accordance with said comparison.

A method for selecting an encoding rate of a predetermined set of encoding rates for encoding a frame of speech including a plurality of speech samples, comprising:

• generating a set of parameters indicative of characteristics of said frame of speech in accordance with said speech samples and with a signal derived from said speech samples;
• and
• selecting an encoding rate from said predetermined set of encoding rates in accordance with said set of parameters, said set of parameters for determining the psychoacoustic significance of said speech samples.

A method for adjusting the average data rate of a variable rate encoder that encodes speech frames based on mode measurements of the speech frames, comprising:

• increasing a threshold value for an output of a target matching signal to noise ratio (TMSNR) element within the variable rate encoder if the average data rate of the speech frames is to be increased;
• and
• decreasing the threshold value for the output of the TMSNR element within the variable rate encoder if the average data rate of the speech frames is to be decreased.