Constraining pulse positions in CELP vocoding

• US 6,539,349 B1
• Filed: 02/15/2000
• Issued: 03/25/2003
• Est. Priority Date: 02/15/2000
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Benno, Steven A.
• Primary Examiner(s): Dorvil, Richemond
• Application Number:
  US09/504,626
• Time in Patent Office: 1,134 Days
• Field of Search: 704/230, 704/229, 704/220, 704/221, 704/225, 704/223, 704/219, 704/222
• US Class Current: 704/219
• CPC Class Codes: G10L 19/10 the excitation function being a multipulse excitation

Abstract

An apparatus and method for vocoding an input signal comprising a linear predictive filter for generating a filtered signal with a first signal pulse and a second signal pulse in response to receiving the input signal and a processor having a lookup table with a plurality of track positions and a set of rules for constraining the first signal pulse to a first track position in the first plurality of track positions and constraining the second signal pulse to a second track position in the second plurality of pulse positions in accordance with the set of rules. Additionally, the apparatus has a transmitter which transmits the plurality of excitation parameters in a transmission signal in response to receiving the plurality of excitation parameters from the processor.

Claims

1. A method of vocoding an input signal comprising the steps of:

filtering the input signal resulting in a filtered signal having a first signal pulse and a second signal pulse;

encoding the first signal pulse by association of the first signal pulse with a first pulse position within a first track of a data structure;

assigning the second signal pulse to a second pulse position within a second track of the data structure; and

verifying that the first pulse position and the second pulse position are not a constrain combination.

2. The method of claim 1 in which the step of filtering further comprises the step of processing the signal with a linear predictive filter.

3. The method of claim 1 further comprising the step of dividing the signal into a plurality of signal frames.

4. The method of claim 3 in which the step of dividing further comprises the step of receiving an analog signal.

5. The method of claim 3 in which the step of dividing further comprises the step of receiving a digital signal.

6. The method of claim 1 in which the step of verifying further comprises the step of identifying the second signal pulse as being a predetermined distance from the first signal pulse.

7. The method of claim 6 in which the step of identifying further comprises the step of checking that the predetermined distance is at least two pulse positions.

8. An apparatus for vocoding an input signal comprising:

a linear predictive filter for generating a filtered signal with a first signal pulse and a second signal pulse in response to receiving the input signal;

a processor having a lookup table with a plurality of track positions and a set of rules for constraining the first signal pulse to a first track position in the first plurality of track positions and constraining the second signal pulse to a second track position in the second plurality of pulse positions in accordance with the set of rules; and

a transmitter which transmits the plurality of excitation parameters in a transmission signal in response to receiving the plurality of excitation parameters from the processor.

9. The apparatus of claim 8 further comprising an input port having a memory buffer to divide the input signal into input signal frames in response to the input port reception of the input port.

10. The apparatus of claim 8 in which the set of rules comprises at least on restriction on the placement of the second signal pulse in the second track in relationship to the first signal pulse in the first track.

11. The apparatus of claim 10 in which the relationship of the second signal pulse and the first signal pulse comprises the second signal to be placed in the second track such that the first signal is in a non-adjacent second track position.

12. The apparatus of claim 8 in which the input signal is an input analog signal.

13. The apparatus of claim 8 in which the input signal is a digital signal.

14. An article of manufacture comprising:

a computer usable medium having computer readable program code means embodied therein for vocoding of a signal, the computer readable program code means in said article of manufacture having;

means having a first computer readable program code for filtering of the signal resulting in an residual signal,

means having a second computer readable program code for long term predictive filtering of the residual signal resulting in at least a first signal pulse and a second signal pulse,

means having a third computer readable program code for identifying a first codebook index associated with the first signal pulse from a codebook, and

means having a fourth computer readable program code for identifying a second codebook index associated with the second signal pulse from a codebook such that the second codebook index is constrained by the first codebook index.

15. The article of manufacture of claim 14 in which the fourth computer readable program code means in said article of manufacture further comprises a computer readable program code means for determining the distance of the first codebook index from the second code book index, and

assigning the second code book index if the distance is greater than a predetermined distance.