Inverse quantization using table with reduced size

Details Inverse quantization using table with reduced size Inverse quantization using table with reduced size

2000-03-09

2001-11-13

JeanPierre, Peguy (Department: 2819)

Coded data generation or conversion

Digital code to digital code converters

Coding by table look-up techniques

C341S067000

Reexamination Certificate

active

06317063

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of inverse quantization for transmission of data with large change of a physical quantity and an inverse quantization apparatus for the same.
2. Description of the Related Art
Recently, it is requested that audio signal communication is carried out in high precision. For the purpose of the high precision, the digitization of an audio signal is carried out. In this case, it is necessary in a small volume region that the audio signal is quantized using a small volume difference. On the other hand, it is sufficient in a large volume region that the audio signal is quantized using a large volume difference. As shown in
FIG. 1
, the volume of the audio signal is quantized in a small volume region S
1
based on the smallest unit of “1”, and the quantization indexes X are illustrated as “1”, “2” and “3”. In a large volume region S
2
, the volume of the audio signal is quantized based on the larger unit of “100”, and the quantization indexes X are illustrated as “1100”, “1200” and “1300”.
When the volume of the audio signal as continuous data is properly quantized, a quantization index X as a discrete value is obtained. The quantization index X is subject to a binary conversion for the digital communication. At this time, if the quantization index X is large, the number of bits of the binary value also becomes huge.
A method using a table is known as the technique for preventing the production of the binary value with a large number of bits.
FIG. 2
shows such a method. In this method, a quantization index X is obtained through quantization of continuous data. An inverse quantization value Y corresponding to the quantization index X is retrieved from the table and is decoded. To improve precision of the reproduced sound, the scale of the table becomes enormous even in the method using such a table. As a result, a huge memory region is used for the table in one chip.
The technique for preventing the use of such a huge table is known in Japanese Laid Open Patent Application (JP-A-Heisei 5-48905). When a large value is handled, it is generally known to use a non-linear function in a logarithm scale calculator. Such conversion is also carried out in case of the audio communication. As one candidate for standardization of the non-linearizaion in the future, the following equation is proposed in the Japanese Laid Open Patent ApplicatiOn (JP-A-Heisei 5-48905).
Y=X
c
where X is a quantization index and Y is an inverse quantization value. A variable X is transmitted using the above function, and the value Y is determined from the received variable X. Even in this case, the size of a table necessary in the receiving side is equal to the width of the definition region of the quantization index X. Therefore, the table size has become very large. For example, the definition region of the quantization index X is from 0 to 8191 in MPEG1-layer3 decoder and MPEG2-AAC decoder. At this time, the size of table is 8192. In this way, there is a problem that the size of the inverse quantization table becomes very large in the above conventional examples.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a method of inverse quantization, in which a table size can be made small in the inverse quantization, and an inverse quantization apparatus for the same.
Another object of the present invention is to provide a method of inverse quantization, in which two tables with small sizes are used in the inverse quantization, and an inverse quantization apparatus for the same.
Still another object of the present invention is to provide a method of inverse quantization, in which a basic table for a quantization index in a predetermined region and a scaling table for a quantization index in a region larger than the predetermined region are used in the inverse quantization, and an inverse quantization apparatus for the same.
In order to achieve an aspect of the present invention, an inversely quantizing method of determining an inverse quantization value Y from an original quantization index value X, is attained by performing scale conversion to a quantization index value X
1
as at least a part of the original quantization index value X to produce first and second values which indicate the quantization index value X
1
, by referring to first and second tables based on the first and second values, to determine third and fourth values corresponding to the first and second values, respectively, and determining an inverse quantization value Y from the third and fourth values.
Here, the method may further include determining whether the quantization index value X
1
falls within a predetermined basic region. In this case, the performing includes performing the scale conversion to the quantization index value X
1
using a parameter larger than 1, when it is determined that the quantization index value X
1
does not fall within the predetermined basic region.
In this case, the scale conversion may be conversion of the quantization index value X
1
to an exponential function value having the first value as a mantissa and the second value as an exponential part. Also, the performing may include dividing the quantization index value X
1
with the parameter, to determine a rounded quotient, wherein the parameter is a first parameter value power of a second parameter value, the rounded quotient is the first value and the first parameter value is the second value and determined based on the quantization index value. In this case, it is desirable that the second parameter value is “2”. Also, it is desirable that the first parameter value is variable based on the quantization index value X
1
.
Also, the method may further include determining whether the quantization index value X
1
falls within a predetermined basic region, and setting the second value to “0”without performing the scale conversion, when the quantization index value X
1
falls within the predetermined basic region.
Also, the referring is carried out without referring to the second table, to set the fourth value to “0” when the quantization index value X
1
falls within the predetermined basic region.
Also, the referring may include referring to the first table based on the first value to retrieve fifth and sixth values, and carrying out interpolation using the fifth and sixth values and the first value to determine the third value.
Also, the method may further include determining whether the quantization index value X
1
falls within a predetermined basic region. In this case, the performing may include performing the scale conversion to the quantization index X such that a value after the scale conversion falls within the basic region, when it is determined that the quantization index value X
1
does not fall within the predetermined basic region, and producing the value after the scale conversion as the first value ana a value indicative of relation between the quantization index value X
1
and the value after the scale conversion as the second value.
Also, the determining may include calculating a value of an exponential function using the third and fourth values. In this case, it is desirable that the exponential function value is c power of a production of the third value and the fourth value, and that c is a predetermined value. It is further desired that c ={fraction (4/3)}.
Also, the method may further include dividing the original quantization index value X into an addition quantization index value X
2
and the quantization index value X
1
. In this case, the determining may include calculating a value of an exponential function using the third and fourth values, and calculating a production of the addition quantization index value and the calculated exponential function value.
In order to achieve another aspect of the present invention, an inversely quantizing apparatus includes a first table outputting first value in response to a second value which is in a predetermined range, and a second table outputting a th

Affiliated with

Also associated with

Rating

Inverse quantization using table with reduced size does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Inverse quantization using table with reduced size, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Inverse quantization using table with reduced size will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2602520