AUDIO ENCODING DEVICE AND AUDIO ENCODING METHOD

• US 20100179807A1
• Filed: 08/07/2007
• Published: 07/15/2010
• 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
• Granted Patent: US 8,112,271 B2
• Time in Patent Office: Days
• 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 (113) cuts out one specified by a comparison unit (117) from adaptive code vectors stored in an internal buffer and outputs it to a filtering unit (101) and a switching unit (121). The filtering unit (101) performs a predetermined filtering process on the adaptive sound source signal and outputs the obtained adaptive code vector to the switching unit (121). According to an instruction from the comparison unit (117), the switching unit (121) outputs the adaptive code vector directly outputted from the adaptive codebook (113) to a gain adjusting unit (115) when the adaptive codebook (113) is searched and outputs the adaptive code vector outputted from the filtering unit (101) after being subjected to the filtering process to the gain adjusting unit (115) when a fixed sound source is searched after the adaptive sound source search.

Claims

1. A speech coding apparatus comprising:

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

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

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

a fixed codebook that stores a plurality of fixed excitations and extracts a fixed excitation indicated from the excitation search section,

wherein the excitation search section performs a search using the adaptive excitation clipped from the adaptive codebook upon the adaptive excitation search, and performs a search using the adaptive excitation after the filtering processing upon 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 search section.

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 search section performs a gain adjustment for and adds the adaptive excitation after the filtering processing and the fixed excitation clipped from the fixed codebook, and performs the fixed excitation search using the addition result.

5. A speech coding method comprising the steps of:

performing an adaptive excitation search of an adaptive excitation stored in an adaptive codebook;

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

performing predetermined filtering processing on the adaptive excitation clipped from the adaptive codebook; and

performing a fixed excitation search of a plurality of fixed excitations stored in a fixed codebook using the adaptive excitation after the filtering processing.