Prioritization method and device for speech frames coded by a linear predictive coder

• US 5,253,326 A
• Filed: 11/26/1991
• Issued: 10/12/1993
• Est. Priority Date: 11/26/1991
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Codex Corporation (Motorola Solutions, Inc.)
• Inventors: Yong, Mei
• Primary Examiner(s): Fleming, Michael R.
• Assistant Examiner(s): Doerrler, Michelle
• Application Number:
  US07/797,881
• Time in Patent Office: 686 Days
• Field of Search: 381/29-45, 395/2, 370/84, 370/94.3, 370/60, 370/94.1, 370/80, 370/81
• US Class Current: 704/200
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients

Abstract

A priority assignment method and device are set forth for assigning a priority to a selected speech frame coded by a linear predictive coder based on at least two of: an energy of the speech frame, a log spectral distance between a frame and a frame immediately previous, and a pitch predictor coefficient for the selected speech frame. The invention protects against loss of perceptually important and hard-to-reconstruct speech frames.

Claims

1. A method for assigning a priority to each of selected speech frames generated by a linear predictive speech coder in a packet-switched communication network, comprising the steps of:

A) initializing a memory unit to desired settings for at least an onset condition for an immediately preceding speech frame (IPSF) and linear predictive coding (LPC) coefficients and prediction error energy for the IPSF;

B) receiving at least a first selected current speech frame (CSF) having digitized speech samples;

C) determining for the CSF;

LPC coefficients, a prediction error energy, and at least two of;

an energy (E_c);

a log spectral distance (LSD) between the CSF and the CSF'"'"'s IPSF; and

a pitch predictor coefficient (β

_c);

D) utilizing at least two of;

E_c, LSD, and β

_c, together with the onset condition of the IPSF for assigning a priority for the CSF and for determining an onset condition of the CSF, where an onset condition of the CSF is used for determining the priority of a next frame;

and updating the IPSF onset condition of the memory unit and the IPSF LPC coefficients and prediction error energy of the memory unit by the CSF onset condition and CSF LPC coefficients and prediction error energy; and

E) reiterating steps 1(B) through 1(D) until desired selected speech frames have been prioritized.

2. The method of claim 1, wherein:

assigning a priority to the CSF further includes at least one of;

utilizing a set of predetermined energy thresholds E₁, E₂, and E₃ ;

utilizing a set of LSD thresholds LSD₁, LSD₂, and LSD₃ ;

utilizing a pitch predictor coefficient threshold β

₁ ;

and further includes at least one of the sets of steps of;

A) where the IPSF onset condition is ONSET and LSD>

LSD₃,

setting the onset condition for the CSF to NON-ONSET and assigning a high priority (HP) to the CSF;

B) where at least one of;

the IPSF onset condition is NON-ONSET and LSD≦

LSD₃,

setting the onset condition for the CSF to NON-ONSET, and determining whether E_c ≧

E₁ ;

C) where E_c <

E₁, assigning a low priority (LP) to the CSF;

D) where E_c ≧

E₁, determining whether β

_c >

β

₁ and whether E_c >

E₂, and

1) where both β

_c >

β

₁ and E_c >

E₂,

setting the onset condition for the CSF to ONSET and assigning a HP to the CSF;

2) where at least one of;

space="preserve" listing-type="equation">β

.sub.c ≦

β

.sub.1 and E.sub.c ≦

E.sub.2,

determining whether LSD>

LSD₂ and whether E_c >

E₃, and one of;

a) where both LSD>

LSD₂ and E_c >

E₃, assigning a HP to the CSF;

b) where at least one of;

space="preserve" listing-type="equation">LSD≦

LSD.sub.2 and E.sub.c ≦

E.sub.3,

determining whether LSD<

LSD₁ and whether at least one of two frames immediately preceding the current frame was assigned a HP, and

aa) where both LSD<

LSD₁ and at least one of two frames immediately preceding the CSF was assigned a HP,

assigning a LP to the CSF, and

bb) where at least one of;

LSD≧

LSD₁ and two frames immediately preceding the current frame were both assigned a LP,

aaa) assigning a HP to the CSF where the immediately previous frame is assigned a LP, and

bbb) assigning a LP to the CSF where the immediately previous speech frame is assigned a HP; and

further including, in step 1(D), one of;

where the onset condition of the CSF indicates an onset speech frame, setting the IPSF onset condition in the memory unit to ONSET; and

where the onset condition of the CSF indicates a non-onset speech frame, setting the IPSF onset condition in the memory unit to NON-ONSET.

3. The method of claim 2 wherein the onset condition of the CSF is determined by both comparing the pitch prediction coefficient β

_c of the CSF with the pitch predictor coefficient threshold β

₁ and by comparing the energy E_c with a predetermined threshold E₂ such that, typically, where β

_c >

β

₁ and E_c >

E₂, the CSF is determined to be an onset speech frame and the CSF onset condition is set to ONSET.

4. The method of claim 2 wherein the log spectral distance is determined by determining a mean squared error of cepstral coefficients between the selected current frame (CSF) and the CFS'"'"'s immediately preceding frame, the cepstral coefficients for a speech frame being determined iteratively from the LPC coefficients and prediction error energy for the CSF.

5. The method of claim 2 wherein the pitch predictor coefficient is determined by a desired method of linear predictive analysis.

6. The method of claim 2 wherein the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are predetermined utilizing training data obtained for a selected application.

7. The method of claim 6 wherein the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are selected such that;

space="preserve" listing-type="equation">E.sub.1 <

E.sub.2 <

E.sub.3,

space="preserve" listing-type="equation">LSD.sub.1 <

LSD.sub.3 <

LSD.sub.2, and

space="preserve" listing-type="equation">β

.sub.1 <

1.

8. A method for assigning a priority to a current speech frame (CSF) having digitized speech samples generated by a linear predictive speech coder in a packet-switched communication network, comprising the steps of:

A) initializing to desired settings a memory unit having at least a first memory location (M1) for onset condition storage of an immediately preceding speech frame (IPSF) and a second memory location (M2) for storage of linear predictive coding (LPC) coefficients and linear prediction error energy of the IPSF;

B) receiving the current speech frame (CSF) having digitized speech samples and determining the LPC coefficients and a prediction error energy for the CSF;

C) determining, for the selected CSF, at least two of;

1) an energy (E_c) of the selected CSF;

2) a log spectral distance (LSD) between the CSF and the CSF'"'"'s IPSF utilizing at least the LPC coefficients of the CSF and of the IPSF; and

3) a pitch predictor coefficient (β

_c) for the selected CSF;

D) utilizing at least two of;

E_c, LSD, and β

_c, and the onset condition of the IPSF for assigning a priority for the selected CSF and for determining an onset condition of the CSF, where an onset condition of the CSF is used for determining the priority of a next frame;

E) utilizing the at least first and second memory locations for storing the onset condition of the CSF, the LPC coefficients and prediction error energy for the CSF, respectively, to provide at least for utilizing same as a next IPSF onset condition, LPC coefficients for the next IPSF, and prediction error energy for the next IPSF, i.e., by utilizing the CSF onset condition and CSF LPC coefficients and prediction error energy, respectively, for processing a next CSF; and

F) reiterating steps 8(B) through 8(E) until desired selected speech frames have been prioritized.

9. The method of claim 8, wherein:

assigning a priority to the selected current speech frame further includes at least one of;

utilizing a set of predetermined energy thresholds E₁, E₂, E₃ where an energy (E_c) of the selected CSF is determined;

utilizing a set of LSD thresholds LSD₁, LSD₂, LSD₃ where a log spectral distance (LSD) between the selected current frame and the CSF'"'"'s immediately preceding speech frame utilizing at least the LPC coefficients and prediction error energy of the CSF and of the IPSF is determined;

utilizing a pitch predictor coefficient threshold β

₁, respectively, where the pitch predictor coefficient (β

_c) for the selected CSF is determined; and

also further includes at least one of the sets of steps of;

A) where the IPSF onset condition is ONSET and LSD>

LSD₃, setting the onset condition for the CSF to NON-ONSET and assigning a high priority (HP) to the CSF;

B) where at least one of;

the IPSF onset condition is NON-ONSET and LSD≦

LSD₃, setting the onset condition for the CSF to NON-ONSET, and determining whether E_c >

E₁ ;

C) where E_c <

E₁, assigning a low priority (LP) to the CSF;

D) where E_c >

E₁, determining whether β

_c >

β

₁ and whether E_c >

E₂, and

1) where both β

_c >

β

₁ and E_c >

E₂, setting the onset condition for the CSF to ONSET and assigning a HP to the CSF;

2) where at least one of;

space="preserve" listing-type="equation">β

.sub.c ≦

β

.sub.1 and E.sub.c ≦

E.sub.2,

determining whether LSD>

LSD₂ and whether E_c >

E₃, and one of;

a) where both LSD>

LSD₂ and E_c >

E₃, assigning a HP to the CSF;

b) where at least one of;

space="preserve" listing-type="equation">LSD≦

LSD.sub.2 and E.sub.c ≦

E.sub.3,

determining whether LSD<

LSD₁ and whether at least one of two frames immediately preceding the current frame was assigned a HP, and

aa) where both LSD<

LSD₁ and at least one of two frames immediately preceding the CSF was assigned a HP, assigning a LP to the CSF, and

bb) where at least one of;

LSD>

LSD₁ and two frames immediately preceding the current frame were both assigned a LP,

aaa) assigning a HP to the CSF where the immediately previous frame is assigned a LP, and

bbb) assigning a LP to the CSF where the immediately previous speech frame is assigned a HP; and

further including, in step 8(E), one of;

where the onset condition of the CSF indicates an onset speech frame, setting the IPSF onset condition in the first memory location to ONSET; and

where the onset condition of the CSF indicates a non-onset speech frame, setting the IPSF onset condition in the first memory location to NON-ONSET.

10. The method of claim 9 wherein at least one of:

(A) the onset condition of the CSF is determined by both comparing the pitch prediction coefficient β

_c of the CSF with the pitch predictor coefficient threshold β

₁ and by comparing the energy E_c with a predetermined threshold E₂ such that, typically, where β

_c >

β

₁ and E_c >

E₂, the CSF is determined to be an onset speech frame and the CSF onset condition is set to ONSET;

(B) the log spectral distance is determined by determining a mean squared error of cepstral coefficients between the selected current frame and the CSF'"'"'s immediately preceding frame, the cepstral coefficients for a speech frame being determined iteratively from the LPC coefficients and prediction error energy for the CSF;

(C) the pitch predictor coefficient is determined by a desired method of linear predictive analysis;

(D) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are predetermined utilizing training data obtained for a selected application; and

(E) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are selected such that;

space="preserve" listing-type="equation">E.sub.1 <

E.sub.2 <

E.sub.3,

space="preserve" listing-type="equation">LSD.sub.1 <

LSD.sub.3 <

LSD.sub.2,

and

space="preserve" listing-type="equation">β

.sub.1 >

1.

11. A method for assigning a priority to a current speech frame (CSF) generated by a linear predictive speech coder in a packet-switched communication network, comprising the steps of:

A) initializing to desired settings a memory unit for storing an onset condition of, and for storing linear predictive coding (LPC) coefficients and linear prediction error energy for, an immediate preceding speech frame (IPSF);

B) receiving the CSF having digitized speech samples and determining the LPC coefficients and a prediction error energy for the CSF;

C) determining for the CSF;

an energy (E_c), a log spectral distance (LSD) between the CSF and the IPSF, and a pitch predictor coefficient (β

_c);

D) utilizing the E_c, LSD, and β

_c together with the onset condition for assigning a priority for the CSF, determining an onset condition for the CSF where an onset condition of the CSF is used for determining the priority of a next frame, updating the IPSF onset condition, updating the IPSF LPC coefficients, and updating the IPSF prediction error energy by utilizing the CSF onset condition and CSF LPC coefficients and prediction error energy; and

E) reiterating steps 11(B) through 11(D) until desired CSFs have been prioritized.

12. The method of claim 11, wherein:

assigning a priority to the selected current speech frame further includes;

utilizing a set of predetermined energy thresholds E₁, E₂, E₃ where an energy (E_c) of the selected CSF is determined;

utilizing a set of LSD thresholds LSD₁, LSD₂, LSD₃ where a log spectral distance (LSD) between the selected current frame and its immediately preceding speech frame utilizing at least the LPC coefficients and prediction error energy of the CSF and of the IPSF is determined;

utilizing a pitch predictor coefficient threshold β

₁, respectively, where the pitch predictor coefficient (β

_c) for the selected CSF is determined; and

includes at least one of the sets of steps of;

A) where the IPSF onset condition is ONSET and LSD>

LSD₃,

setting the onset condition for the CSF to NON-ONSET and assigning a high priority (HP) to the CSF;

B) where at least one of;

the IPSF onset condition is NON-ONSET and LSD≦

LSD₃,

setting the onset condition for the CSF to NON-ONSET, and determining whether E_c ≧

E₁ ;

C) where E_c <

E₁, assigning a low priority (LP) to the CSF;

D) where E_c ≧

E₁, determining whether β

_c >

β

₁ and whether E_c >

E₂, and

1) where both β

_c >

β

₁ and E_c >

E₂,

setting the onset condition for the CSF to ONSET and assigning a HP to the CSF;

2) where at least one of;

space="preserve" listing-type="equation">β

.sub.c ≦

β

.sub.1 and E.sub.c ≦

E.sub.2,

determining whether LSD>

LSD₂ and whether E_c ≦

E₃, and one of;

a) where both LSD>

LSD₂ and E_c >

E₃, assigning a HP to the CSF;

b) where at least one of;

space="preserve" listing-type="equation">LSD≦

LSD.sub.2 and E.sub.c ≦

E.sub.3,

determining whether LSD<

LSD₁ and whether at least one of two frames immediately preceding the current frame was assigned a HP, and

aa) where both LSD<

LSD₁ and at least one of two frames immediately preceding the CSF was assigned a HP,

assigning a LP to the CSF, and

bb) where at least one of;

LSD≧

LSD₁ and two frames immediately preceding the current frame were both assigned a LP,

aaa) assigning a HP to the CSF where the immediately previous frame is assigned a LP, and

bbb) assigning a LP to the CSF where the immediately previous speech frame is assigned a HP; and

further including, in step 11(D), one of;

where the onset condition of the CSF indicates an onset speech frame, setting the IPSF onset condition in the first memory location to ONSET; and

where the onset condition of the CSF indicates a non-onset speech frame, setting the IPSF onset condition in the first memory location to NON-ONSET.

13. The method of claim 12 wherein at least one of:

(A) the onset condition of the CSF is determined by both comparing the pitch prediction coefficient β

_c of the CSF with the pitch predictor coefficient threshold β

₁ and by comparing the energy E_c with a predetermined threshold E₂ such that, typically, where β

_c >

β

₁ and E_c >

E₂, the CSF is determined to be an onset speech frame and the CSF onset condition is set to ONSET;

(B) the log spectral distance is determined by determining a mean squared error of cepstral coefficients between the selected current frame and the CSF'"'"'s immediately preceding frame, the cepstral coefficients for a speech frame being determined iteratively from the LPC coefficients and prediction error energy for the CSF;

(C) the pitch predictor coefficient is determined by a desired method of linear predictive analysis;

(D) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are predetermined utilizing training data obtained for a selected application; and

(E) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are selected such that;

space="preserve" listing-type="equation">E.sub.1 <

E.sub.2 <

E.sub.3,

space="preserve" listing-type="equation">LSD.sub.1 <

LSD.sub.3 <

LSD.sub.2,

and

space="preserve" listing-type="equation">β

.sub.1 >

1.

14. A device for assigning a priority to each of selected speech frames having digitized speech samples generated by a linear predictive speech coder in a packet-switched communication network, having an initializing means comprising at least memory means for storing an onset condition, linear predictive coding (LPC) coefficients, and LPC prediction error energy, respectively, of an immediately preceding speech frame (IPSF), initialized to desired settings upon beginning prioritization, comprising at least:

A) receiving means, operably coupled to receive at least a first selected current speech frame (CSF) having digitized speech samples;

B) determining means, operably coupled to the receiving means, for determining LPC coefficients and a LPC prediction error energy, and for determining, for the CSF, at least two of;

an energy (E_c);

a log spectral distance (LSD) between the CSF and its immediately preceding speech frame (IPSF); and

a pitch predictor coefficient (β

_c);

C) prioritizing means, operably coupled to the memory unit and to the determining means, for utilizing at least two of;

E_c, LSD, and β

_c, together with the onset condition of the IPSF for assigning a priority for the CSF and for determining an onset condition of the CSF and for updating the IPSF onset condition of the memory unit, the IPSF LPC coefficients, and the prediction error energy of the memory unit; and

D) iteration means, operably coupled to the prioritizing means, for, where further desired speech frames are desired to be prioritized, recycling to the receiving means.

15. The device of claim 14, wherein:

the prioritizing means for assigning a priority to the selected current speech frame further includes a threshold utilization unit for;

utilizing a set of predetermined energy thresholds E₁, E₂, E₃ where an energy (E_c) of the selected CSF is determined;

utilizing a set of LSD thresholds LSD₁, LSD₂, LSD₃ where a log spectral distance (LSD) between the selected current frame and its immediately preceding speech frame utilizing at least the LPC coefficients and prediction error energy of the CSF and of the IPSF is determined;

utilizing a pitch predictor coefficient threshold β

₁, respectively, where the pitch predictor coefficient (β

_c) for the selected CSF is determined;

and further, wherein the prioritizing means is utilized for at least one of;

A) where the IPSF onset condition is ONSET and LSD>

LSD₃,

setting the onset condition for the CSF to NON-ONSET and assigning a high priority (HP) to the CSF;

B) where at least one of;

the IPSF onset condition is NON-ONSET and LSD≦

LSD₃,

setting the onset condition for the CSF to NON-ONSET, and determining whether E_c ≧

E₁ ;

C) where E_c <

E₁, assigning a low priority (LP) to the CSF;

D) where E_c ≧

E₁, determining whether β

_c >

β

₁ and whether E_c >

E₂, and

1) where both β

_c >

β

₁ and E_c >

E₂,

setting the onset condition for the CSF to ONSET and assigning a HP to the CSF;

2) where at least one of;

space="preserve" listing-type="equation">β

.sub.c ≦

β

.sub.1 and E.sub.c ≦

E.sub.2,

determining whether LSD>

LSD₂ and whether E_c >

E₃, and one of;

a) where both LSD>

LSD₂ and E_c >

E₃, assigning a HP to the CSF;

b) where at least one of;

space="preserve" listing-type="equation">LSD≦

LSD.sub.2 and E.sub.c ≦

E.sub.3,

determining whether LSD<

LSD₁ and whether at least one of two frames immediately preceding the current frame was assigned a HP, and

aa) where both LSD<

LSD₁ and at least one of two frames immediately preceding the CSF was assigned a HP,

assigning a LP to the CSF, and

bb) where at least one of;

LSD≧

LSD₁ and two frames immediately preceding the current frame were both assigned a LP,

aaa) assigning a HP to the CSF where the immediately previous frame is assigned a LP, and

bbb) assigning a LP to the CSF where the immediately previous speech frame is assigned a HP;

and further including utilizing the prioritizing means to;

update the IPSF LPC coefficients of the memory unit using the LPC coefficients of the CSF, update the IPSF prediction error energy of the memory unit using the prediction error energy of the CSF, and one of;

where the onset condition of the CSF indicates an onset speech frame, update the IPSF onset condition of the memory unit to ONSET; and

where the onset condition of the CSF indicates a non-onset speech frame, update the IPSF onset condition of the memory unit to NON-ONSET.

16. The device of claim 15 wherein the prioritizing means includes at least one of:

(A) an onset condition determining unit, operably coupled to receive E_c, E₂, β

_c, and β

₁, for determining the onset condition of the CSF by both comparing the pitch prediction coefficient β

_c of the CSF with the pitch predictor coefficient threshold β

₁ and by comparing the energy E_c with a predetermined threshold E₂ such that, typically, where β

_c >

β

₁ and E_c >

E₂, the CSF is determined to be an onset speech frame and the CSF onset condition is set to ONSET;

(B) a log spectral distance determining unit, operably coupled to receive the LPC coefficients and prediction error energy for the CSF, for substantially determining a mean squared error of cepstral coefficients between the selected current speech frame and its immediately preceding speech frame, the cepstral coefficients for a speech frame being determined iteratively from the LPC coefficients and prediction error energy for the CSF;

(C) the pitch predictor coefficient is determined by a desired method of linear predictive analysis;

(D) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are predetermined utilizing training data obtained for a selected application; and

(E) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are selected such that;

space="preserve" listing-type="equation">E.sub.1 <

E.sub.2 <

E.sub.3,

space="preserve" listing-type="equation">LSD.sub.1 <

LSD.sub.3 <

LSD.sub.2,

and

space="preserve" listing-type="equation">β

.sub.1 ≧

1.

17. A device for assigning a priority to at least a first current speech frame (CSF) of digitized speech samples generated by a linear predictive speech coder in a packet-switched communication network, comprising at least:

A) initializing means, operably coupled to receive an onset condition, linear predictive coding (LPC) coefficients and linear predictive coding (LPC) prediction error energy for an immediately preceding speech frame (IPSF), for initializing at least a first memory unit to desired settings for the IPSF onset condition, IPSF LPC coefficients and prediction error energy upon beginning prioritization;

B) receiving means, operably coupled to receive the at least first CSF having digitized speech samples;

C) determining means, operably coupled to the receiving means, for determining, for the CSF, LPC coefficients and a prediction error energy and at least two of;

1) an energy (E_c) of the selected CSF;

2) a log spectral distance (LSD) between the selected current frame and its immediately preceding speech frame utilizing at least the LPC coefficients of the CSF and of the IPSF; and

3) a pitch predictor coefficient (β

_c);

D) prioritization means, operably coupled to the determining means and to the initializing means, for;

utilizing the at least two of;

E_c, LSD, and β

_c, and the onset condition of the IPSF for assigning a priority for the CSF and for determining an onset condition of the CSF; and

utilizing the at least first memory unit for storing the onset condition of the CSF, the LPC coefficients for the CSF, and the prediction error energy for the CSF, respectively, to provide at least for utilizing same as a next IPSF onset condition, LPC coefficients for the next IPSF, and prediction error energy for the next IPSF, respectively, for processing a next CSF; and

E) iteration means, operably coupled to the prioritizing means, for, where further desired speech frames are desired to be prioritized, recycling to the receiving means.

18. The device of claim 17, wherein:

the prioritizing means for assigning a priority to the selected current speech frame further includes a threshold utilization unit for;

utilizing a set of predetermined energy thresholds E₁, E₂, E₃ where an energy (E_c) of the selected CSF is determined;

utilizing a set of LSD thresholds LSD₁, LSD₂, LSD₃ where a log spectral distance (LSD) between the selected current frame and its immediately preceding speech frame utilizing at least the LPC coefficients and prediction error energy of the CSF and of the IPSF is determined; and

utilizing a pitch predictor coefficient threshold β

₁, respectively, where the pitch predictor coefficient (β

_c) for the selected CSF is determined;

and further, wherein the prioritizing means is utilized for at least one of;

A) where the IPSF onset condition is ONSET and LSD>

LSD₃,

setting the onset condition for the CSF to NON-ONSET and assigning a high priority (HP) to the CSF;

B) where at least one of;

the IPSF onset condition is NON-ONSET and LSD≦

LSD₃,

setting the onset condition for the CSF to NON-ONSET, and determining whether E_c ≧

E₁ ;

C) where E_c <

E₁, assigning a low priority (LP) to the CSF;

D) where E_c ≧

E₁, determining whether β

_c >

β

₁ and whether E_c >

E₂, and

1) where both β

_c >

β

₁ and E_c >

E₂,

setting the onset condition for the CSF to ONSET and assigning a HP to the CSF;

2) where at least one of;

space="preserve" listing-type="equation">β

.sub.c ≦

β

.sub.1 and E.sub.c ≦

E.sub.2,

determining whether LSD>

LSD₂ and

whether E_c >

E₃, and one of;

a) where both LSD>

LSD₂ and E_c >

E₃, assigning a HP to the CSF;

b) where at least one of;

space="preserve" listing-type="equation">LSD≦

LSD.sub.2 and E.sub.c ≦

E.sub.3,

determining whether LSD<

LSD₁ and whether at least one of two frames immediately preceding the current frame was assigned a HP, and

aa) where both LSD<

LSD₁ and at least one of two frames immediately preceding the CSF was assigned a HP,

assigning a LP to the CSF, and

bb) where at least one of;

LSD≧

LSD₁ and two frames immediately preceding the current frame were both a LP,

aaa) assigning a HP to the CSF where the immediately previous frame is assigned a LP, and

bbb) assigning a LP to the CSF where the immediately previous speech frame is assigned a HP;

and further wherein the prioritizing means is utilized to;

update the memory unit for the IPSF LPC coefficients using the linear predictive (LPC) coefficients of the CSF, update the memory unit for the IPSF prediction error energy, and one of;

where the onset condition of the CSF indicates an onset speech frame, update the memory unit for the IPSF onset condition to ONSET; and

where the onset condition of the CSF indicates a non-onset speech frame, update the memory unit for the IPSF onset condition to NON-ONSET.

19. The device of claim 18 wherein the prioritization unit includes at least one of:

(A) an onset condition determining unit, operably coupled to receive E_c, E₂, β

_c, and β

₁, for determining the onset condition of the CSF by both comparing the pitch prediction coefficient β

_c of the CSF with the pitch predictor coefficient threshold β

₁ and by comparing the energy E_c with a predetermined threshold E₂ such that, typically, where β

_c >

β

₁ and E_c >

E₂, the CSF is determined to be an onset speech frame and the CSF onset condition is set to ONSET;

(B) a log spectral distance determining unit, operably coupled to received the LPC coefficients and prediction error energy for the CSF, for determining a mean squared error of cepstral coefficients between the selected current frame and its immediately preceding frame, the cepstral coefficients for a speech frame being determined iteratively from the LPC coefficients and prediction error energy for the CSF; and

(C) a pitch predictor coefficient determining unit, operably coupled to receive the digitized speech sample, for determining the pitch predictor coefficient by a desired method of linear predictive analysis;

wherein;

the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are predetermined utilizing training data obtained for a selected application; and

the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are selected such that;

space="preserve" listing-type="equation">E.sub.1 <

E.sub.2 <

E.sub.3,

space="preserve" listing-type="equation">LSD.sub.1 <

LSD.sub.3 <

LSD.sub.2,

and

space="preserve" listing-type="equation">β

.sub.1 ≧

1.

20. A device for assigning a priority to at least a first current speech frame (CSF) of digitized speech samples generated by a linear predictive speech coder in a packet-switched communication network, having an initializing means comprising at least memory means for storing an onset condition, linear predictive coding (LPC) coefficients and prediction error energy, respectively, of an immediately preceding speech frame (IPSF) that are initialized to desired settings upon beginning prioritization, and further comprising at least:

A) receiving means, operably coupled to receive the at least first CSF having the digitized speech samples;

B) determining means, operably coupled to the receiving means, for determining LPC coefficients and a prediction error energy for the CSF, and for determining, for the CSF;

an energy (E_c), a log spectral distance (LSD) between the CSF and the IPSF, and a pitch predictor coefficient (β

_c);

C) prioritizing means, operably coupled to the memory unit and to the determining means, for utilizing the E_c, LSD, and β

_c together with the IPSF onset condition for assigning a priority for the CSF, determining an onset condition for the CSF, and for updating the IPSF onset condition of the memory unit, the IPSF LPC coefficients and the IPSF prediction error energy of the memory unit; and

D) iterating means, operably coupled to the prioritizing means, for, where further desired speech frames are desired to be prioritized, recycling to the receiving means.

21. The device of claim 20, wherein:

the prioritizing means for assigning a priority to the selected current speech frame further includes a threshold utilization unit for;

utilizing a set of predetermined energy thresholds E₁, E₂, E₃ where an energy (E_c) of the selected CSF is determined;

utilizing a set of LSD thresholds LSD₁, LSD₂, LSD₃ where a log spectral distance (LSD) between the selected current frame and its immediately preceding speech frame utilizing at least the LPC coefficients and prediction error energy of the CSF and of the IPSF is determined;

utilizing a pitch predictor coefficient threshold β

₁, respectively, where the pitch predictor coefficient (β

_c) for the selected CSF is determined;

and further, wherein the prioritizing means is utilized for at least one of;

A) where the IPSF onset condition is ONSET and LSD>

LSD₃,

setting the onset condition for the CSF to NON-ONSET and assigning a high priority (HP) to the CSF;

B) where at least one of;

the IPSF onset condition is NON-ONSET and LSD≦

LSD₃,

setting the onset condition for the CSF to NON-ONSET, and determining whether E_c ≧

E₁ ;

C) where E_c <

E₁, assigning a low priority (LP) to the CSF;

D) where E_c ≧

E₁, determining whether β

_c >

β

₁ and whether E_c >

E₂, and

1) where both β

_c >

β

₁ and E_c >

E₂,

setting the onset condition for the CSF to ONSET and assigning a HP to the CSF;

2) where at least one of;

space="preserve" listing-type="equation">β

.sub.c ≦

β

.sub.1 and E.sub.c ≦

E.sub.2,

determining whether LSD>

LSD₂ and

whether E_c >

E₃, and one of;

a) where both LSD>

LSD₂ and E_c >

E₃, assigning a HP to the CSF;

b) where at least one of;

space="preserve" listing-type="equation">LSD≦

LSD.sub.2 and E.sub.c ≦

E.sub.3,

determining whether LSD<

LSD₁ and whether at least one of two frames immediately preceding the current frame was assigned a HP, and

aa) where both LSD<

LSD₁ and at least one of two frames immediately preceding the CSF was assigned a HP,

assigning a LP to the CSF, and

bb) where at least one of;

LSD≧

LSD₁ and two frames immediately preceding the current frame were both assigned a LP,

aaa) assigning a HP to the CSF where the immediately previous frame is assigned a LP, and

bbb) assigning a LP to the CSF where the immediately previous speech frame is assigned a HP;

and further wherein the prioritizing means is utilized to;

update the IPSF linear predictive (LPC) coefficients of the memory unit using the linear predictive (LPC) coefficients of the CSF, update the IPSF prediction error energy of the memory unit using the prediction error energy of the CSF, and one of;

where the onset condition of the CSF indicates an onset speech frame, update the IPSF onset condition of the memory unit to ONSET; and

where the onset condition of the CSF indicates a non-onset speech frame, update the IPSF onset condition of the memory unit to NON-ONSET.

22. The device of claim 21 wherein at least one of:

(A) the onset condition of the CSF is determined by both comparing the pitch prediction coefficient β

_c of the CSF with the pitch predictor coefficient threshold β

₁ and by comparing the energy E_c with a predetermined threshold E₂ such that, typically, where β

_c >

β

₁ and E_c >

E₂, the CSF is determined to be an onset speech frame and the CSF onset condition is set to ONSET;

(B) the log spectral distance is determined by determining a mean squared error of cepstral coefficients between the selected current frame and its immediately preceding frame, the cepstral coefficients for a speech frame being determined iteratively from the LPC coefficients and prediction error energy for the CSF;

(C) the pitch predictor coefficient is determined by a desired method of linear predictive analysis;

(D) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are predetermined utilizing training data obtained for a selected application; and

(E) the set of energy thresholds E₁, E₂, E₃, the set of log spectral distance thresholds LSD₁, LSD₂, LSD₃ and pitch predictor coefficient threshold β

₁ are selected such that;

space="preserve" listing-type="equation">E.sub.1 <

E.sub.2 <

E.sub.3,

space="preserve" listing-type="equation">LSD.sub.1 <

LSD.sub.3 <

LSD.sub.2,

and

space="preserve" listing-type="equation">β

.sub.1 ≧

1.