US RE38593 E1 Abstract In an adaptive transform coding system and/or and adaptive transform decoding system, coding efficiency in the case where a small number of quantized values having large absolute value are present, is improved. The adaptive transform coding system codes the small number of quantized values having large absolute values and other quantized values are coded separately. More particularly, the adaptive transform coding system includes a selector (
6) discriminating the small number of quantized value having large absolute value from other quantized value, a pulse coding means for coding the small number of quantized values having large absolute values (8) and the pulse decoding means (16) for decoding the same, a coding means (7) for coding the quantized value other than those having large absolute values and a decoding means (15) decoding the same, and a synthesis means (18) for synthesizing the small number of quantized values having large absolute value and other quantized values.Claims(66) 1. An adaptive transform coding system comprising:
a transform means for transforming an input signal into a frequency domain signal;
an analysis means for analyzing said input signal and said frequency domain signal to derive an allowable quantization error;
a quantizing means for quantizing the amplitude value of said frequency domain signal on the basis of a quantization step size to derive a quantized value and a quantization error,
a quantization parameter determining means for determining said quantization step size with reference to said allowable quantization error and said quantization error and a total code amount;
a selector for analyzing the quantized value of said frequency domain signal to derive a first signal and a second signal;
a first coding means for coding said quantized value of said first signal with reference to said second signal to derive a first code and a first code amount;
a second coding means for coding said quantized value of said second signal to derive a second code and a second code amount;
a parameter coding means for coding said quantization step size to derive a third code and a third code amount;
an adder for deriving said total code amount of said first code amount, said second code amount and said third code amount; and
a multiplexer for multiplexing said first code, said second code and said third code to generate a bit stream.
2. An adaptive transform coding system as set forth in
3. An adaptive transform coding system as set forth in
4. An adaptive transform coding system as set forth in
5. An adaptive transform coding system as set forth in
6. An adaptive transform coding system as set forth in
7. An adaptive transform coding system as set forth in
8. An adaptive transform coding system as set forth in
9. An adaptive transform coding system as set forth in
10. An adaptive transform decoding system comprising:
a demultiplexer for separating an input signal into a first code, a second code and a third code;
a first decoding means for decoding said first code with reference to said second code to derive a first signal;
a second decoding means for decoding said second code to derive a second signal;
a parameter decoding means for decoding said third signal code to derive a quantization step size;
a synthesis means for synthesizing said first signal and said second signal for deriving to derive a synthesized signal;
an inverse quantizing means for inverse quantizing said quantized value of said synthesized signal to derive an inverse quantized signal; and
an inverse transform means for transforming said inverse quantized signal into a time domain to derive a time domain signal.
11. An adaptive transform decoding system as set forth in
12. An adaptive transform decoding system as set forth in
13. An adaptive transform decoding system as set forth in
14. An adaptive transform decoding system as set forth in
15. An adaptive transform decoding system as set forth in
16. An adaptive transform decoding system as set forth in claim
15, 11, wherein said frequency belongs to one of the predetermined frequency regions, and wherein the said frequency signal is divided into a plurality of region, in said first decoding means, the number of region boundaries and the difference between said frequencies are derived by decoding, and a value derived derived by adding a difference of said frequencies predetermined frequency which is included in said first signal to a frequency of region boundary which is indicated by said the number of region boundary is taken as the frequency of the sample having the lowest frequency said frequency regions, and wherein said number is included in said first signal.17. An adaptive transform decoding system as set forth in
18. An adaptive transform coding and decoding system comprising:
a transform means for transforming an input signal into a frequency domain signal;
an analysis means for analyzing said input signal and said frequency domain signal to derive an allowable quantization error;
a quantizing means for quantizing amplitude value of said frequency domain signal on the basis of a quantization step size to derive a quantized value and a quantization error,
a quantization parameter determining means for determining said quantization step size with reference to said allowable quantization error and said quantization error and a total code amount;
a selector for analyzing the quantized value of said frequency domain signal to derive a first signal and a second signal;
a first coding means for coding said quantized value of said first signal with reference to said second signal to derive a first code and a first code amount;
a second coding means for coding said quantized value of said second signal to derive a second code and a second code amount;
a parameter coding means for coding said quantization step size to derive a third code and a third code amount;
an adder for deriving said total code amount of said first code amount, said second code amount and said third code amount;
a multiplexer for multiplexing said first code, said second code and said third code to generate a bit stream
a demultiplexer for separating an input signal into a first code, a second code and a third code;
a first decoding means for decoding said first code with reference to said second code to derive a first signal;
a second decoding means for decoding said second code to derive a second signal;
a parameter decoding means for decoding said third signal to derive a quantization step size;
a synthesis means for synthesizing said first signal and said second signal for deriving a synthesized signal;
an inverse quantizing means for inverse quantizing said quantized value of said synthesized signal to derive an inverse quantized signal; and
an inverse transform means for transforming said inverse quantized signal into a time domain to derive a time domain signal.
19. A decoding system comprising:
first decoding means for decoding a first code which relates to the number of a replaced element;
second decoding means for decoding a second code relating to an amplitude of said replaced element and a third code relating to a frequency of said replaced element if said number of said replaced element satisfies a predetermined condition; and
reconstructing means for reconstructing a pulse on the basis of the decoded second and third codes.
20. A decoding system as set forth in
synthesis means for synthesizing said pulse and a Huffman decoded signal to derive a synthesized signal.
21. A decoding system as set forth in
22. A decoding system comprising:
first decoding means for decoding a first code which relates to the number of replaced elements;
second decoding means for decoding a second code relating to amplitudes of said replaced elements and a third code relating to frequencies of said replaced elements if said number of said replaced elements satisfies a predetermined condition; and
reconstructing means for reconstructing pulses on the basis of the decoded second and third codes.
23. A decoding system as set forth in
synthesis means for synthesizing said pulses and a Huffman decoded signal to derive a synthesized signal.
24. A decoding system as set forth in
25. A decoding system as set forth in
26. A decoding system as set forth in
27. An adaptive transform decoding system comprising:
a demultiplexer for separating an input signal into a first code, a second code and a third code;
a first decoder for decoding said first code to derive a first signal;
a second decoder for decoding said second code to derive a second signal;
a parameter decoder for decoding said third code to derive a quantization step size;
a synthesizer for synthesizing said first signal and said second signal to derive a synthesized signal;
an inverse quantizing circuit for inverse quantizing said synthesized signal based on said quantization step size to derive an inverse quantized signal; and
an inverse transforming circuit for transforming said inverse quantized signal into a time domain signal.
28. An adaptive transform decoding system as set forth in
29. An adaptive transform decoding system as set forth in
30. An adaptive transform decoding system as set forth in
31. An adaptive transform decoding system as set forth in
32. An adaptive transform decoding system as set forth in
33. An adaptive transform decoding system as set forth in
34. An adaptive transform decoding system as set forth in
35. A decoding system comprising:
a first decoder for decoding a first code which relates to the number of a replaced element;
a second decoder for decoding a second code relating to an amplitude of said replaced element and a third code relating to a frequency of said replaced element if said number of the replaced element satisfies a predetermined condition; and
a reconstructing circuit for reconstructing a pulse on the basis of the decoded second and third codes.
36. A decoding system as set forth in
a synthesizer for synthesizing said pulse and a Huffman decoded signal to derive a synthesized signal.
37. A decoding system as set forth in
38. A decoding system comprising:
a first decoder for decoding a first code which relates to the number of replaced elements;
a second decoder for decoding a second code relating to amplitudes of said replaced elements and a third code relating to frequencies of said replaced elements if said number of the replaced elements satisfies a predetermined condition; and
a reconstructing circuit for reconstructing pulses on the basis of the decoded second and third codes.
39. A decoding system as set forth in
a synthesizer for synthesizing said pulses and a Huffman decoded signal to derive a synthesized signal.
40. A decoding system as set forth in
41. A decoding system as set forth in
42. A decoding system as set forth in
43. A decoding method comprising:
separating an input signal into a first code, a second code and a third code;
decoding said first code to derive a first signal;
decoding said second code to derive a second signal;
decoding said third code to derive a quantization step size;
synthesizing said first signal and second signal to derive a synthesized signal;
inverse quantizing said synthesized signal based on said quantization step size to derive an inverse quantized signal; and
transforming said inverse quantized signal into a time domain signal.
44. A decoding method as set forth in
45. A decoding method as set forth in
46. A decoding method as set forth in
47. A decoding method as set forth in
48. A decoding method as set forth in
49. A decoding method as set forth in
50. A decoding method as set forth in
51. A decoding method comprising:
decoding a first code which relates to the number of a replaced element;
decoding a second code relating to an amplitude of said replaced element and a third code relating to a frequency of said replaced element if said number of the replaced element satisfies a specific condition; and
reconstructing a pulse on the basis of the decoded second and third codes.
52. A decoding method as set forth in
synthesizing said pulse and a Huffman decoded signal to derive a synthesized signal.
53. A decoding method as set forth in
54. A decoding method comprising:
decoding a first code which relates to the number of replaced elements;
decoding a second code relating to amplitudes of said replaced elements and a third code relating to frequencies of said replaced elements if said number of the replaced elements satisfies specific condition; and
reconstructing pulses on the basis of the decoded second and third codes.
55. A decoding method as set forth in
synthesizing said pulses and a Huffman decoded signal to derive a synthesized signal.
56. A decoding method as set forth in
57. A decoding method as set forth in
58. A decoding method as set forth in
59. An adaptive transform decoding system, comprising:
a demultiplexer for separating an input signal into a first code, a second code and a third code;
a second decoding means for decoding said second code to derive a second signal;
a parameter decoding means for decoding said third signal to derive a quantization step size;
a synthesis means for synthesizing said first signal and said second signal for deriving a synthesized signal;
60. An adaptive transform decoding system as set forth in
61. An adaptive transform decoding system as set forth in
62. An adaptive transform decoding system as set forth in
63. An adaptive transform decoding system as set forth in
64. An adaptive transform decoding system as set forth in
65. An adaptive transform decoding system as set forth in
66. An adaptive transform decoding system as set forth in
Description 1. Field of the Invention The present invention relates generally to an adaptive transform coding and/or decoding system. More specifically, the invention relates to a system for efficiently coding and decoding speech and audio signals with maintaining high quality. 2. Description of the Related Art Conventionally, as an adaptive transform coding system and an adaptive transform decoding system for efficiently coding and decoding a speech signal and an audio signal with maintaining high quality, there are MPEG (Moving Pictures Expert Group)/Audio Layers 3 or so forth. The technology of MPEG/Audio Layer 3 has been discussed in 1993 ISO/IEC 11172-3, “Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 Mb/s” (hereinafter simply referred to as reference No. FIG. 3 is a block diagram showing one example of the conventional adaptive transform coding system. The conventional adaptive transform coding system is constructed with an input terminal In the input terminal In the transform means In the analysis means In the quantizing means
Wherein nint ( ) represents rounding process for rounding the fraction off after the decimal point, and pow (a, b) represents a to the (b)th power. The quantized values in each frame are grouped in ascending order in the frequency to be fed to the coding means
Therefore, the quantization error YZ is expressed as:
In the coding means In the parameter coding means In the adder The total code amount outputted from the adder In the multiplexer The bit stream is outputted from the output terminal In the coding means At first, a method for dividing the quantized values in the frame into three regions will be discussed. The N quantized-values are grouped in ascending order of the frequency and compose the vector X as follows:
Each element x(1), x(2), . . . , x(N) of the vector X represents respective quantized value. The type
The value rzero is calculated by
where t is the maximum value satisfying
(x1 mod x2) represents the remainder in division of x1 by x2. The value count1 is calculated by
where t2 is the maximum value satisfying |x(t2)|>1. The value bigvalues is derived from
Each element included in the type Huffman tables prepared for coding respective elements in the type The bigvalues, rzero and information relating to the Huffman tables to be used in the type FIG. 4 is a block diagram showing one example of the adaptive transform decoding system. The conventional adaptive transform decoding system includes an input terminal To the input terminal In the demultiplexer In the decoding means In the inverse quantizing means
The inverse quantized values thus derived are outputted to the inverse transform means The inverse transform means Then, the time domain signal is outputted from the output terminal A first problem encountered in the foregoing adaptive transform coding and decoding systems is low coding efficiency upon coding the element in the vicinity of the boundary to the type Most elements of the type The second problem to be encountered is that when the type The size of the Huffman table to be selected upon coding the elements in the type It is therefore an object of the present invention to provide an adaptive transform coding system, an adaptive transform decoding system and an adaptive transform coding and decoding system, which can improve the coding efficiency by performing a special process for the elements having a large absolute value. According to the first aspect of the invention, an adaptive transform coding system comprises: a transform means for transforming a set of input signal samples into a frequency domain; an analysis means for analyzing the input signal and the frequency domain signal to derive an allowable quantization error; a quantizing means for quantizing the amplitude value of the frequency domain signal on the basis of a quantization step size to derive a quantized value and a quantization error, a quantization parameter determining means for determining the quantization step size with reference to the allowable quantization error and the quantization error and a total code amount; a selector for analyzing the quantized value of the frequency domain signal to derive a first signal and a second signal; a first coding means for coding the quantized value of the first signal with reference to the second signal to derive a first code and a first code amount; a second coding means for coding the quantized value of the second signal to derive a second code and a second code amount; a parameter coding means for coding the quantization step size to derive a third code and a third code amount; an adder for deriving the total code amount of the first code amount, the second code amount and the third code amount; and a multiplexer for multiplexing the first code, the second code and the third code to generate a bit stream. In the construction set forth above, the small number of quantized values having large absolute value and the other quantized values are coded by different means. Therefore, in the coding means for coding the quantized values other than those having the large absolute values, a Huffman code table can be smaller than that in the prior art to reduce the average code amount for one quantized value and thus the improvement of the coding efficiency can be achieved. The second coding means may divide the quantized values of the frequency domain signal into a first signal and a third signal to generate a fourth signal, in which the absolute value of the quantized value of the first signal is replaced with smaller quantized value, and the second signal may be generated by combining the third signal and the fourth signal. Also, the selector may derive the first signal and the second signal so that the total code amount becomes minimum. The first coding means may generate the first code by coding the absolute value of the quantized value of the first signal, the polarity of the quantized value of the first signal and the frequency of the first signal. In this case, the first coding means may derive a threshold for the quantized value of the first signal to code a value derived by subtracting the threshold from the quantized value of the first signal in place of the absolute value of the quantized value of the first signal. In each sample of the first signal, the threshold value may be a value derived by adding one for the absolute value of the quantized value of a sample of the second signal at the same frequency to the sample of the first signal. Also, a region of quantized values to be coded in the second coding means may be limited, and for each sample of the first signal, the threshold may be a value derived by adding one to a maximum absolute value of an input region of the second coding means upon coding the signal having the same frequency as that of the sample by the second coding means. In the alternative, the first coding means may code the frequency of each sample of the first signal in the ascending order of the frequency, and for the sample other than the sample having the lowest frequency, the difference of the frequency between a sample and its adjacent predecessor is coded. The frequency signal may be divided into a plurality of regions, and in the first coding means, in place of the frequency of the sample having the lowest frequency, the number of boundaries lower than the frequency of the sample having the lowest frequency, and the difference between the maximum region boundary frequency lower than the frequency of the sample having the lowest frequency and the said lowest frequency, are coded. According to the second aspect of the invention, an adaptive transform decoding system comprising: a demultiplexer for separating an input signal into a first code, a second code and a third code; a first decoding means for decoding the first code with reference to the second code to derive a first signal; a second decoding means for decoding the second code to derive a second signal; a parameter decoding means for decoding the third signal to derive a quantization step size; a synthesis means for synthesizing the first signal and the second signal for deriving a synthesized signal; an inverse quantizing means for inverse quantizing the quantized value of the synthesized signal to derive an inverse quantized signal; and an inverse transform means for transforming the inverse quantized signal into a time domain signal. The first decoding means may derive a frequency of the quantized value, an absolute value of the quantized value and the polarity of the quantized value by decoding the first code to set a frequency of the quantized value, an absolute value of the quantized value and the polarity of the quantized value of the first signal, respectively. The first decoding means may derive a threshold and take a value derived by adding the threshold to the absolute value of the quantized value derived by decoding the first code as an absolute value of the quantized value of the first signal, in place of the absolute value of the quantized value derived by decoding the first code. In each sample of the first signal, the threshold may be obtained by quantizing the second signal at the same frequency and taking its absolute value. The second decoding means may have a restriction in an inverse quantized value, and in each sample of the first signal, the threshold may be a value derived by adding one to the maximum absolute value of the restriction when the second decoding means decodes the signal having the same frequency as the sample. The first decoding means may derive a difference of the frequency and the frequency of the sample of the lowest frequency, and derives the frequency of the sample other than the sample having the lowest frequency by adding the difference of the frequency to the frequency of its adjacent predecessor. In this case, the frequency domain signal is divided into a plurality of region. In the first decoding means, the number of region boundaries and the difference of the frequencies may be derived by decoding, and a value derived by adding a difference of the frequencies to a frequency of the region boundary indicated by the number of the region boundary is taken as the frequency of the sample having the lowest frequency. The synthesis means may generate a signal replacing the quantized value of the sample having the same frequency as the frequency of each sample of the first signal with the quantized value of the first signal to take the replaced signal as the synthesized signal. According to the third aspect of the invention, an adaptive transform coding and decoding system comprises: a transform means for transforming an input signal into a frequency domain signal; an analysis means for analyzing the input signal and the frequency domain signal to derive an allowable quantization error; a quantization means for quantizing the amplitude value of the frequency domain signal on the basis of a quantization step size to derive a quantized value and a quantization error, a quantization parameter determining means for determining the quantization step size with reference to the allowable quantization error and the quantization error and a total code amount; a selector for analyzing the quantized value of the frequency domain signal to derive a first signal and a second signal; a first coding means for coding the quantized value of the first signal with reference to the second signal to derive a first code and a first code amount; a second coding means for coding the quantized value of the second signal to derive a second code and a second code amount; a parameter coding means for coding the quantization step size to derive a third code and a third code amount; an adder portion for deriving the total code amount of the first code amount, the second code amount and the third code amount; a multiplexer for multiplexing the first code, the second code and the third code to generate a bit stream a demultiplexer for separating an input signal into a first code, a second code and a third code; a first decoding means for decoding the first code with reference to the second code to derive a first signal; a second decoding means for decoding the second code to derive a second signal; a parameter decoding means for decoding the third signal to derive a quantization step size; a synthesis means for synthesizing the first signal and the second signal for deriving a synthesized signal; an inverse quantizing means for inverse quantizing the quantized value of the synthesized signal to derive an inverse quantized signal; and an inverse transform means for transforming the inverse quantized signal into a time domain signal. The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the preferred embodiments of the present invention, which, however, should not be taken to be limitative to the present invention, but are for explanation and understanding only. In the drawings: FIG. 1 is a block diagram showing the preferred embodiment of a coding system according to the present invention; FIG. 2 is a block diagram showing the preferred embodiment of a decoding system according to the present invention; FIG. 3 is a block diagram showing the conventional coding system; FIG. 4 is a block diagram showing the conventional decoding system; FIG. 5 is a flowchart for deriving the number of elements to be replaced with zero in the present invention; FIG. 6 is a flowchart for deriving the number of elements for replacing with a value having a smaller absolute value, such as zero; FIG. 7 is an illustration showing a waveform of a sound source employed in a coding experiments; FIG. 8 is an illustration showing a reduced code amount by the present invention; and FIG. 9 is an illustration showing a reduced code amount by the present invention. The present invention will be discussed hereinafter in detail in terms of the preferred embodiment of the present invention with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instance, well-known structures are not shown in detail in order to avoid unnecessary obscure of the present invention. FIG. 1 is a block diagram showing one embodiment of an adaptive transform coding system according to the present invention. The adaptive transform coding system according to the invention is constructed with an input terminal In comparison with the prior art, the shown embodiment of the adaptive transform coding system includes the selector In the selector At the first step, similarly to the coding means
Then, in the similar manner to that in the coding means Next, as the second step, a that represents the number of elements of the vector X which are located in the type Then, m at which minimizes the total code amount L(m) is set as the number a of elements whose values are replaced with zero. FIG. 5 is a flowchart showing a process for deriving the number a of the elements. Each step in the process will be discussed hereinafter. At step At step At step
At step At step At step At step At the step Finally, at the third step, the value of the elements in the vector X are replaced with zero to generate:
By subtracting the vector Y from the vector X,
is generated. The vector Y is outputted to the coding means The vector Y is initially set as
Then, if the number of the replaced element a is greater than or equal to one, the vector Y is derived by establishing
with respect to m=1, 2, . . . , a using the frequency index P(m) of replaced elements and the value Q(m) of replaced elements obtained in the foregoing second step. The vector Z is obtained as (Vector X−Vector Y). As information relating to non-zero elements of the vector Z, the number of the replaced element a, the frequency indexes P(1), P(2), . . . , P(a) of replaced elements and the values Q(1), Q(2), . . . , Q(a) of replaced elements are outputted to the pulse coding means Here, discussion has been given for the method that x(P(m)) is replaced with zero in the third step. However, it is also possible to replace the absolute value with 1 or −1 instead of 0. In this case, replacement may be performed with any one of 0, 1 and −1 at which the code amount of the code outputted by the coding means The pulse coding means
is established. Then, using the number of replaced elements a and the frequency index P(m) of replaced elements, if a is greater than or equal to one, for m=1, 2, . . . a, a frequency index offset PP(m) of replaced elements:
and, the polarity of QQ(m):
and the amplitude QQQ(m) of replaced elements:
are encoded as the pulse code. It should be noted that it is possible to encode |QQ(m)| for the amplitude QQQ(m) of the replaced element. However, since |QQ(m)| is greater than or equal to two, it may be more efficient to encode (|QQ(m)|−2). Also, as the frequency index offset of replaced elements, P(m) can be coded. However, in general, higher coding efficiency can be achieved by PP(m). The pulse code and the number a of replaced elements are multiplexed to be outputted to the multiplexer The adder The multiplexer FIG. 2 is a block diagram showing one embodiment of an adaptive transform decoding system according to the present invention. The adaptive transform decoding system includes an input terminal The shown embodiment of the adaptive transform decoding system is differentiated from the prior art shown in FIG. 4 in that the pulse decoding means In the demultiplexer In the pulse decoding means
For each m which is incremented by 1 from 1 to a, it is established:
It is also established:
It should be noted when |QQ(m)| is coded for QQQ(m), it is established:
On the other hand, when P(m) is used in place of PP(m) upon coding, the operation of
becomes unnecessary. When the polarity of QQ(m) is negative, z(PP(m)) is multiplied by −1. The vector Z thus obtained is outputted to the synthesis means In the synthesis means
is established. Otherwise,
is established. The synthesized quantized values are fed to the inverse quantizing means Discussion will be given for the reduction of the code amount in the case where the quantized value inputted to the coding means It should be noted that, in the first embodiment, concerning the frequency index offset PP(m) of the replaced element with respect to m=1, instead of coding PP(m) by
The following coding method can be taken. At first, the frequency domain signal is divided into AR regions. Then, in the pulse coding means
and the value expressed as
are coded. When this coding method is taken, upon decoding in the pulse decoding means
Next, in the present invention, concerning a combination of the adaptive transform coding system and the adaptive transform decoding system, a discussion will be given for another embodiment. The second embodiment of the adaptive transform coding system of the present invention is illustrated in the block diagram of FIG. 1 similarly to the first embodiment. In the second embodiment of the present invention is differentiated from the first embodiment of the present invention in the operation of the selector The selector In the first step, similarly to the coding means Next, as the second step, a that represents the number of the elements in the type FIG. 6 shows a flowchart showing the process to derive the number a. Respective steps will be discussed hereinafter. At step At step At step At step
is established to derive n which minimizes the code amount of the code outputted upon Huffman coding of respective elements in the type
At step
as a sum of the code amount B1 of the code outputted from the coding means At step At step At step Finally, at the third step, a elements of the vector X obtained at the second step are replaced with a value having a smaller absolute value, such as zero. Then,
is generated, and by the procedure set out later,
is generated. The vector Y is outputted to the coding means To derive the vector Y and the vector Z, at first, the vector Z is set as the zero vector with the same dimension as the vector X and the vector Y is initialized by:
Next, if the number a of the replaced element derived in the second step is greater than or equal to one, the frequency index P(m) of the replaced element and the value Q(m) of the replaced element derived in the second step are employed with respect to m=1, 2, . . . , a to derive:
The number a of the replaced element, the frequency indexes P(1), P(2), . . . , P(a) of replaced elements and the values Q(1), Q(2), . . . , Q(a) of replaced elements that represent information relating to the non-zero elements of the vector Z are outputted to the pulse coding means Pulse coding means
is established. When a is greater than or equal to one, the frequency index offset SPP(m) of the replaced element, SPP(m)=(SP(m)−SP(m−1)), the polarity of SQ(m), and the amplitude SQQ(m) of the replaced element, SQQ(m)=(|SQ(m)|−|y(SP(m))|) are coded to obtain the pulse code. It should be noted that the coding may be performed by coding the amplitude |SQ(m)| of replaced elements. However, since |SQ(m)| is greater than |y(SP(m))|, it is more efficient to code SQQ(m). The pulse code and the number a of the replaced element are multiplexed as C3 to be outputted to the multiplexer The block diagram of the second embodiment of the adaptive transform decoding system according to the present invention is the same as the first embodiment of the adaptive transform decoding system of the present invention, as shown in FIG. In the pulse decoding means
Then, while m is incremented from one to a by one, with respect to each m, SPP(m−1) is added to SPP(m), and |y(SPP(m))| is added to the amplitude SQQ(m) of the replaced element to establish z(SPP(m)). If SQ(m) has a negative value, z(SPP(m)) is multiplied by −1. The derived vector Z is outputted to the synthesis means In the synthesis means
is established. Otherwise,
is established. The synthesized quantized values are outputted to the inverse quantizing means Discussion will be given hereinafter with respect to the reduction of the code amount when the quantized value supplied to the coding means It should be noted that the second embodiment of the present invention is to improve the coding efficiency of the type It should be noted that, in the second embodiment of the present invention, concerning the frequency index offset SPP(m) of the replaced element with respect to m=1, instead of coding SPP(m) by
The following coding method can be taken. At first, the frequency signal is divided into AR regions. Then, in the pulse coding means
and the value of
may be encoded. When this method is taken, the decoder derives SPP(1) in the pulse coding means
According to the present invention set forth above, coding efficiency can be remarkably improved. The reason is that since a small number of quantized values having large absolute values and the remaining quantized values are coded by different means, the Huffman code table to be used for coding in the means (coding means Although the invention has been illustrated and described with respect to exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without departing from the spirit and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalents thereof with respect to the feature set out in the appended claims. Patent Citations
Non-Patent Citations
Referenced by
Classifications
Legal Events
Rotate |