Efficient excitation quantization in noise feedback coding with general noise shaping

• US 7,206,740 B2
• Filed: 08/12/2002
• Issued: 04/17/2007
• Est. Priority Date: 01/04/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Chen, Juin-Hwey, Thyssen, Jes
• Primary Examiner(s): {hacek over (S)}mits; Talivaldis Ivars
• Assistant Examiner(s): YEN, ERIC L
• Application Number:
  US10/216,276
• Publication Number:
  US 20030135367A1
• Time in Patent Office: 1,709 Days
• Field of Search: 704/219, 704/223, 704/228, 704/220, 704/222, 704/230
• US Class Current: 704/222
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering

Abstract

In a Noise Feedback Coding (NFC) system operable in a ZERO-STATE condition and a ZERO-INPUT condition, the NFC system including at least one filter having a filter memory, a method of updating the filter memory. The method comprises: (a) producing a ZERO-STATE contribution to the filter memory when the NFC system is in the ZERO-STATE condition; (b) producing a ZERO-INPUT contribution to the filter memory when the NFC system is in the ZERO-INPUT condition; and (c) updating the filter memory as a function of both the ZERO-STATE contribution and the ZERO-INPUT contribution.

Claims

1. In a Noise Feedback Coding (NFC) system operable in a ZERO-STATE condition and a ZERO-INPUT condition, the NFC system including a long-term noise feedback filter having a first filter memory and a short-term noise feedback filter having a second filter memory, a method of updating the first and second filter memories, comprising:

(a) producing a first ZERO-STATE contribution to the first filter memory and a second ZERO-STATE contribution to the second filter memory when the NFC system is in the ZERO-STATE condition;

(b) producing a first ZERO-INPUT contribution to the first filter memory and a second ZERO-INPUT contribution to the second filter memory when the NFC system is in the ZERO-INPUT condition;

(c) updating the first filter memory as a function of both the first ZERO-STATE contribution and the first ZERO-INPUT contribution; and

(d) updating the second filter memory as a function of both the second ZERO-STATE contribution and the second ZERO-INPUT contribution.

2. The method of claim 1, wherein step (c) comprises

adding together the first ZERO-STATE and the first ZERO-INPUT contributions to produce a first filter memory update;

and

updating the first filter memory with the first filter memory update.

3. The method of claim 1, further comprising:

prior to step (a), searching N VQ codevectors associated with the NFC system for a best VQ codevector,

wherein step (a) comprises producing the first ZERO-STATE contribution and the second ZERO-STATE contribution corresponding to the best VQ codevector.

4. The method of claim 1, wherein the short-term noise feedback filter includes

an all-zero filter section, and

an all-pole filter section.

5. The method of claim 4, wherein the all-zero filter section is of the form

$F_{\mathrm{sz}}$

( z ) = ∑

i = 1 N N1 - 1 ⁢

a 1 ·

( γ

p i - γ

z i ) ·

z - 1

where N_NFF is the order of the all-zero filter section,

a_i, is i^th prediction coefficient,

γ

_z is a bandwidth expansion factor for the all-zero filter section, and

γ

_p is a bandwidth expansion factor for the all-pole filter section.

6. The method of claim 4, wherein the all-pole filter section is of the form:

$\frac{1}{F_{\mathrm{sp}}<br><br>\left(z\right)}=\frac{1}{1-\underset{i=1}{\overset{N_{\mathrm{N1}-1}}{\sum <br><br>}}<br><br>a_i·<br><br>{\mathrm{\gamma <br><br>}}_p^i·<br><br>z^{-1}}.$

7. A computer readable medium carrying one or more sequences of one or more instructions for execution by one or more processors to perform, in a Noise Feedback Coding (NFC) system operable in a ZERO-STATE condition and a ZERO-INPUT condition, the NFC system including a long-term noise feedback filter having a first filter memory and a short-term noise feedback filter having a second filter memory, a method of updating the first and second filter memories, the instructions when executed by the one or more processors, causing the one or more processors to perform the steps of:

(a) producing a first ZERO-STATE contribution to the first filter memory and a second ZERO-STATE contribution to the second filter memory when the NFC system is in the ZERO-STATE condition;

(b) producing a first ZERO-INPUT contribution to the first filter memory and a second ZERO-INPUT contribution to the second filter memory when the NFC system is in the ZERO-INPUT condition;

(c) updating the first filter memory as a function of both the first ZERO-STATE contribution and the first ZERO-INPUT contribution; and

(d) updating the second filter memory as a function of both the second ZERO-STATE contribution and the second ZERO-INPUT contribution.

8. The computer readable medium of claim 7, wherein step (c) comprises:

adding together the first ZERO-STATE and the first ZERO-INPUT contributions to produce a first filter memory update; and

updating the first filter memory with the first filter memory update.

9. The computer readable medium of claim 7, carrying the one or more instructions, causing the one or more processors to perform, prior to step (a), the further step of:

searching N VQ codevectors associated with the NFC system for a best VQ codevector,

wherein step (a) comprises producing the first ZERO-STATE contribution and the second ZERO-STATE contribution corresponding to the best VQ codevector.

10. The computer readable medium of claim 7, wherein the short-term noise feedback filter includes

an all-zero filter section, and

an all-pole filter section.

11. A Noise Feedback Coding (NFC) system operable in a ZERO-STATE condition and a ZERO-INPUT condition, the NFC system including a long-term noise feedback filter having a first filter memory and a short-term noise feedback filter having a second filter memory, the system comprising:

first means for producing a first ZERO-STATE contribution to the first filter memory and a second ZERO-STATE contribution to the second filter memory when the NFC system is in the ZERO-STATE condition;

second means for producing a first ZERO-INPUT contribution to the first filter memory and a second ZERO-STATE contribution to the second filter memory when the NFC system is in the ZERO-INPUT condition;

third means for updating the first filter memory as a function of both the first ZERO-STATE contribution and the first ZERO-INPUT contribution; and

fourth means for updating the second filter memory as a function of both the second ZERO-STATE contribution and the second ZERO-INPUT contribution.

12. The system of claim 11, wherein the third means includes:

means for adding together the first ZERO-STATE and the first ZERO-INPUT contributions to produce a first filter memory update; and

means for updating the first filter memory with the first filter memory update.

13. The system of claim 11, further comprising:

fourth means for searching N VQ codevectors associated with the NFC system for a best VQ codevector,

wherein the first means includes means for producing the first ZERO-STATE contribution and the second ZERO-STATE contribution corresponding to the best VQ codevector.

14. The system of claim 11, wherein the short-term noise feedback filter includes

an all-zero filter section, and

an all-pole filter section.