Sound encoder and sound decoder

a sound encoder and encoder technology, applied in the field of sound encoders and decoders, can solve the problems of deteriorating erroneous code separation, and increased deterioration of the tone quality of the sound signal, so as to achieve high bit error immunity, and high bit error immunity

Inactive Publication Date: 2008-02-28
TASAKI HIROHISA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This approach enhances bit error immunity by adaptively arranging codes to minimize erroneous decoding, particularly for high-frequency regions, thereby reducing tone quality deterioration and improving signal-to-noise ratio.

Problems solved by technology

Thus, in the prior art sound encoder and the prior art sound decoder, since band-by-band codes provided for high-frequency regions are often multiplexed fixedly into locations closer to the tail of the multiplexed code, there is a possibility that such band-by-band codes are separated erroneously when an bit error occurs before the locations where they are multiplexed.
A problem with such a prior art sound encoder and such a sound decoder constructed as above is that since the order in which a plurality of band-by-band codes which are variable length codes is so fixed as not to vary from frame to frame, erroneous demultiplexing can often occur in band-by-band codes provided for high-frequency regions, which are multiplexed in locations closer to the tail of the multiplexed code.
Another problem is that since the deterioration in the tone quality of the sound signal increases when band-by-band codes with a larger envelope value are erroneously separated, the deterioration in the tone quality of the sound signal increases due to the occurrence of bit errors when band-by-band codes provided for high-frequency regions have a larger envelope value.
In other words, since the multiplexing is not carried out in consideration of the distribution of bit error sensitivities that varies from frame to frame, the deterioration in the tone quality of the sound signal increases due to the occurrence of bit errors.
The other codes other than the code indicating the order are fixed length codes and therefore the problem of the occurrence of erroneous demultiplexing caused by the existence of variable length codes cannot be solved.
A problem with prior art sound encoder and prior art sound decoders as disclosed in Japanese patent application publication No. 2000-183751 is that since the sound encoder does not perform multiplexing that reflects the distribution of bit error sensibilities that varies from frame to frame, but only sorts data to be encoded according to a predetermined reference so that they are arranged in a fixed order that does not vary from frame to frame, the deterioration in the sound signal due to the occurrence of bit errors cannot be sufficiently prevented, as in the case of the prior art sound encoder and the prior art sound decoder as shown in FIGS. 10 and 11.

Method used

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embodiment 1

[0038]FIG. 1 is a block diagram showing the structure of a sound encoder according to embodiment 1 of the present invention, and FIG. 2 is a block diagram showing the structure of a sound decoder according to embodiment 1 of the present invention. In the figure, reference numeral 11 denotes an encoding unit that accepts a sound signal, which is the target to be encoded, for each frame of a predetermined length, and encodes the sound signal so as to produce a plurality of codes, such as an envelope code and a plurality of band-by-band codes, reference numeral 12 denotes a multiplexing order determination unit for determining the order in which the plurality of band-by-band codes are to be multiplexed into a multiplexed code based on the envelope code output from the encoding unit 11, reference numeral 13 denotes a multiplexing unit for multiplexing the envelope code and the plurality of band-by-band codes in the order determined by the multiplexing order determination unit 12, and fo...

embodiment 2

[0056]FIG. 6 is a block diagram showing the structure of a sound encoder according to embodiment 2 of the present invention, and FIG. 7 is a block diagram showing the structure of a sound decoder according to embodiment 2 of the present invention. In the figure, reference numeral 21 denotes an encoding unit for accepting a sound signal which is the target to be coded, for each frame of a predetermined length, and for encoding the sound signal so as to produce a plurality of codes (a plurality of subframe-by-subframe power codes and a plurality of subframe-by-subframe shape codes, which are respectively provided for a plurality of subframes), reference numeral 22 denotes a multiplexing order determination unit for determining the order in which the plurality of shape codes are to be multiplexed into a multiplexed code, based on the plurality of subframe-by-subframe power codes output from the encoding unit 21, reference numeral 23 denotes a multiplexing unit for multiplexing the plur...

embodiment 3

[0070] In a sound encoder according to a variant of either of the first to second embodiments, the multiplexing unit can interchange a plurality of codes multiplexed into a multiplexed code based on the order determined by the multiplexing order determination unit after multiplexing the plurality of codes into the multiplexed code in a fixed order once, instead of multiplexing the plurality of codes into the multiplexed code in the determined order. Even in this case, the same advantages are provided. Similarly, in a sound decoder according to a variant of either of the first to fifth embodiments, the demultiplexing unit can demultiplex an input multiplexed code into a plurality of codes in a fixed order after interchanging the plurality of codes multiplexed into the multiplexed code based on the order determined by the demultiplexing order determination unit once, instead of demultiplexing the multiplexed code into the plurality of codes in the determined order. Even in this case, ...

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Abstract

A sound encoder multiplexes a plurality of codes into a sound code in an order determined by a multiplexing order determination unit (12), and a sound decoder demultiplexes the sound code into a plurality of codes one by one in an order determined by a demultiplexing order determination unit (14).

Description

[0001] This application is a Divisional of co-pending application Ser. No. 11 / 701,461, filed on Feb. 2, 2007, which is a Divisional of co-pending application Ser. No. 10 / 222,902, filed on Aug. 19, 2002, which claims priority to Japanese Application No. 2001-266253, filed Sep. 3, 2001, the entire contents of which are hereby incorporated by reference and for which priority is claimed under 35 U.S.C. §120.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a sound encoder that outputs a sound code acquired by compressing a digital sound signal, such as a musical sound or a voice, into a small volume of information, and a sound decoder that decodes the sound code so as to reproduce a sound signal. [0004] 2. Description of the Prior Art [0005] Most prior art sound encoders acquire a plurality of codes having a small volume of information from a sound signal, and multiplex them into a sound code. Most prior art sound decoders demultiplex t...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): G10L19/00G10L19/02H03M7/30H04B1/66H04J3/00
CPCH04B1/667G10L19/167
InventorTASAKI, HIROHISA
OwnerTASAKI HIROHISA