Audio encoding device and audio encoding method

• US 8,112,271 B2
• Filed: 08/07/2007
• Issued: 02/07/2012
• Est. Priority Date: 08/08/2006
• Status: Active Grant

• Current Assignee: III Holdings 12, LLC (Intellectual Ventures LLC)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Morii, Toshiyuki
• Primary Examiner(s): Vo, Huyen X.
• Application Number:
  US12/376,640
• Publication Number:
  US 20100179807A1
• Time in Patent Office: 1,645 Days
• Field of Search: 704/223, 704/221, 704/222, 704/219, 704/220, 704/230, 704/500
• US Class Current: 704/223
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering

Abstract

Provided is an audio encoding device capable of improving performance of an adaptive codebook and improving quality of a decoded audio. In this audio encoding device, an adaptive codebook cuts out a vector specified by a comparator from adaptive code vectors stored in an internal buffer and outputs it to a filter and a switch. The filter performs a predetermined filtering process on the adaptive sound source signal and outputs the obtained adaptive code vector to the switch. According to an instruction from the comparator, the switch outputs the adaptive code vector directly output from the adaptive codebook to a adjuster when the adaptive codebook is searched and outputs the adaptive code vector output from the filter after being subjected to the filtering process to the gain adjuster when a fixed sound source is searched after the adaptive sound source search.

Claims

1. A speech coding apparatus comprising:

an excitation searcher that performs an adaptive excitation search and fixed excitation search;

an adaptive codebook that stores an adaptive excitation and clips a part of the adaptive excitation;

a filter that performs predetermined filtering processing on the adaptive excitation clipped from the adaptive codebook;

a fixed codebook that stores a plurality of fixed excitations and extracts a fixed excitation indicated by the excitation searcher; and

a switch that switches between the adaptive excitation clipped by the adaptive codebook and the adaptive excitation after the filter processing by the filter,

wherein the excitation searcher performs a search using the adaptive excitation clipped from the adaptive codebook, by controlling the switch to output the adaptive excitation clipped by the adaptive codebook during the adaptive excitation search, and performs a search using the adaptive excitation after the predetermined filtering processing, by controlling the switch to output the adaptive excitation after the filter processing by the filter during the fixed excitation search.

2. The speech coding apparatus according to claim 1, wherein the adaptive codebook clips the part of the adaptive excitation according to an indication from the excitation searcher.

3. The speech coding apparatus according to claim 1, wherein the adaptive codebook clips the part of the adaptive excitation according to an indication from an outside.

4. The speech coding apparatus according to claim 1, wherein the excitation searcher performs a gain adjustment for the adaptive excitation after the filtering processing and the fixed excitation extracted from the fixed codebook, adds the adaptive excitation and the fixed excitation for which the gain adjustment is performed, and performs the fixed excitation search using the addition result.

6. The speech coding apparatus according to claim 1, further comprising an LPC synthesizer that acquires a synthesis signal by performing filtering processing on the adaptive excitation clipped from the adaptive codebook, using an LPC coefficient obtained by performing an LPC analysis on an input signal,

wherein the predetermined filtering processing performed by the filter is different from the filtering processing performed by the LPC synthesizer.

7. The speech coding apparatus according to claim 1, wherein the filter performs MA (Moving Average) type multi-tap filtering processing.

5. A speech coding method, performed by a processor, comprising:

performing, by the processor, an adaptive excitation search of an adaptive excitation stored in an adaptive codebook;

clipping, by the processor, a part of the adaptive excitation from the adaptive codebook using a result of the adaptive excitation search;

performing, by the processor, predetermined filtering processing on the adaptive excitation clipped from the adaptive codebook;

selecting one of the clipped adaptive excitation search and the adaptive excitation search after the predetermined filtering processing; and

performing, by the processor, a fixed excitation search of a plurality of fixed excitations stored in a fixed codebook using the adaptive excitation after the predetermined filtering processing, which is selected during the fixed excitation search,

wherein the selecting selects the clipped adaptive excitation search during the adaptive excitation search.

8. The speech coding method according to claim 5, further comprising acquiring a synthesis signal by performing filtering processing on the adaptive excitation clipped from the adaptive codebook, using an LPC coefficient obtained by performing an LPC analysis on an input signal,

wherein the predetermined filtering processing is different from the filtering processing using the LPC coefficient obtained by performing the LPC analysis on the input signal.

9. The speech coding method according to claim 5, wherein the predetermined filtering processing performs MA (Moving Average) type multi-tap filtering processing.