JP2765268B2 - High efficiency coding method and high efficiency code decoding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-efficiency encoding method and a high-efficiency code decoding method for reducing the amount of information such as data obtained by sampling and quantizing analog signals such as video and audio. .

[0002]

2. Description of the Related Art There are various schemes for high-efficiency coding, and there is also a scheme combining these. At present, standardization of a high-efficiency coding method for image and audio is being performed, and standardization of a coding method for still images is being advanced by JPEG, a subordinate organization of the International Standards Organization (ISO).

A conventional high-efficiency encoding method will be described using an example of a DCT method, which is a high-efficiency encoding method of JPEG (Reference: Journal of the Institute of Television Engineers of Japan, Vol. 44, No. 2 (1990), pp. 15).
8-159).

The input signal is a sampled and quantized image signal, that is, digital image data. Image data, which is a raster scan pixel array, is placed in a rectangular area of 8 pixels each in the horizontal and vertical directions of the screen (this is called a block).
And convert the data in block units. This is called blocking. An 8th-order two-dimensional discrete cosine transform (hereinafter, referred to as DCT) is performed for each block, and the obtained DCT coefficients are quantized at a predetermined quantization step Q determined for each coefficient (that is, divided by Q and rounded). ). The AC coefficient of the quantized DCT coefficient is subjected to two-dimensional Huffman coding, and the DC coefficient of the quantized DCT coefficient is subjected to predictive coding.

[0005] The predictive encoding method of the DC coefficient will be described. The input data is a DC coefficient of the quantized DCT coefficient, which is referred to as data Di (i = 0, 1, 2,.
3, ..., i are data numbers and are equal to the block numbers). The prediction coding is to calculate a prediction value Pi using coded input data, obtain a prediction error Si that is a difference between the input data Di and the prediction value Pi, and encode the prediction error Si. The prediction method uses the previous input data as the predicted value in the previous value prediction.

An encoding method of the prediction error Si will be described. The prediction error Si is classified into a predetermined category according to its magnitude, a corresponding category number is obtained, and this is subjected to Huffman coding. The category number corresponds to upper bit information of the prediction error. For the prediction error, lower bits are cut out by the number of bits L determined by the category number, and output following the Huffman-encoded category number. That is, the prediction error is encoded separately for the upper bit information and the lower bit information. Note that if the lower L bits of the prediction error are cut out as they are, a duplicate sign occurs between a positive value and a negative value.
Bits are cut out.

Huffman coding is a reversible coding method in which a code having a short word length is assigned to data having a high probability of occurrence and a code having a long word length is allocated to data having a low probability of occurrence. It is. Since the correlation between adjacent input data is high and the prediction error has a high probability of becoming a value close to 0, highly efficient encoding is performed by assigning a short code to a category number representing a range in which the absolute value of the prediction error is small. realizable.

[0008]

However, in predictive coding, a decoded value is obtained by accumulating the prediction error. Therefore, if an error occurs in the coded output, the effect of the error is accumulated and error propagation occurs. Had.

[0009]

A first high-efficiency encoding method according to the present invention uses a sampled and quantized signal as input data, obtains a predicted value of the input data, and obtains the input data and the predicted value. Obtaining a prediction error, which is a difference between the above, a step of classifying the prediction error according to its magnitude and outputting a category number representing a corresponding category, and a predetermined upper limit value defining a range of the corresponding category. And a step of dividing the input data to obtain a remainder with a predetermined value larger than a difference between the predetermined lower limit and a divisor, and a step of encoding and outputting the category number and the remainder. It is a feature.

[0010] A second high-efficiency encoding method according to the present invention comprises:
Data that is a sampled and quantized signal is used as an encoding input,
A step of forming a block by combining a predetermined number of the input data,
Obtaining a C coefficient and an AC coefficient and quantizing them; encoding the quantized DC coefficient data D to output DC encoded data; encoding the quantized AC coefficient Outputting the AC coded data, wherein the step of outputting the DC coded data obtains a prediction error which is a difference between the data D and its predicted value, and classifies the prediction error into a category according to its magnitude. To obtain a category number, divide the data D by a divisor determined by the corresponding category to obtain a remainder, and encode the category number and the remainder to obtain DC encoded data. is there.

Further, according to the first high-efficiency code decoding method of the present invention, a prediction error which is a difference between data D to be encoded and a predicted value thereof is obtained, and the prediction errors are classified into categories according to their magnitudes. Obtain a category number, divide the data to be coded by a divisor determined by the corresponding category to obtain a remainder, and obtain the coded data by coding the category number and the remainder to obtain coded data. A method for decoding a high-efficiency code using coded data as input data, the method comprising: decoding the coded data to obtain the category number and the remainder; and obtaining a prediction value from already decoded output data. A step, at least one of an upper limit value and a lower limit value of a range of a prediction error of the category indicated by the category number, a divisor obtained from the category number, and the prediction Generating an offset that is an integral multiple of the divisor using: and obtaining the new output data by adding the offset and the remainder, when the control signal is input from the outside, the prediction The step of obtaining a value obtains a predicted value by performing a prediction method different from that at the time of encoding using the control signal, and the step of generating an offset includes a step of correlating output data obtained by decoding with the control signal with the predicted value. The offset is generated so that is higher.

In a second method for decoding a high-efficiency code according to the present invention, data which is a sampled and quantized signal is used as an encoded input, and a predetermined number of the input data are combined to form a block; Performing a predetermined conversion on the data to obtain a DC component and an AC component and quantizing each of them; encoding the data D of the quantized DC component and outputting DC encoded data; Encoding the converted AC component and outputting AC encoded data, wherein the step of outputting the DC encoded data obtains a prediction error that is a difference between the data D and a prediction value thereof, The prediction error is classified into categories according to its magnitude to obtain a category number, the data D is divided by a divisor determined by the corresponding category to obtain a remainder,
A method of decoding a high-efficiency code using encoded data of the high-efficiency encoding method as input data, wherein the category number and the remainder are encoded to obtain DC encoded data, wherein the AC encoded data is And quantized AC
Obtaining the DC component, obtaining the quantized DC component by decoding the DC encoded data, dequantizing the quantized AC component to obtain the AC component, A step of performing inverse transformation on the DC component to obtain decoded data in the block, and a step of deblocking the block to obtain and output decoded data in the same order as the encoded input data,
Obtaining the quantized DC component comprises:
Decoding encoded data to obtain the category number and the remainder; obtaining a predicted value from the already decoded quantized data; and an upper limit or lower limit of a range of a prediction error of the category indicated by the category number. Generating an offset that is an integral multiple of the divisor using at least one of the values, the divisor obtained from the category number, and the predicted value; and adding the offset and the remainder to generate new quantized data D. Obtaining a predicted value, when the control signal is input from the outside, the step of obtaining the predicted value performs a different prediction method than at the time of encoding by the control signal, the step of generating the offset, the step of generating the offset, the control signal The decoded data of the block being decoded is adjacent to the block being decoded, and the correlation with the decoded data of the block in which no error has occurred is Is characterized in that to generate the offset to be higher.

[0013]

According to the first high-efficiency encoding method of the present invention, since the lower bit information of the input data is transmitted by the above-described configuration, error propagation does not always occur, and transmission error tolerance is reduced by the conventional predictive encoding method. It can be further improved.

According to the second high-efficiency encoding method of the present invention, when a transmission error occurs, the DC component is decoded by using the correlation of the AC component even when a transmission error occurs. In some cases, decoding can be performed accurately, and error resilience can be greatly improved.

According to the first high efficiency code decoding method of the present invention, a prediction value is obtained using decoded data having no transmission error even if a transmission error having a large error occurs, and a prediction value having a small error is obtained. Is obtained, accurate decoding is enabled.

Further, according to the second high efficiency code decoding method of the present invention, even if a transmission error having a large error occurs in the DC component of the block, the correlation between the decoded data including the AC component of the adjacent block can be obtained. Is used to obtain a highly accurate predicted value of the DC component, thereby enabling decoding with a small error.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an encoding method according to the present invention will be described below.

1. A predicted value Pi of the input data Di is obtained, and this is subtracted from the input data Di to obtain a prediction error Si.
Note that Di represents the i-th input data, and in the following, a symbol with a subscript i indicates that it is data corresponding to Di.

2. Using a predetermined classification table, the prediction error S
Classify i according to its size. A category number Ji representing the range to which the prediction error Si belongs is determined. Therefore, if the upper limit value and the lower limit value of the prediction error range indicated by the category number Ji are SXi and SNi, respectively,

[0020]

(Equation 1)

The following holds. Further, it corresponds one-to-one with the category number Ji,

[0022]

(Equation 2)

The predetermined divisor data OUi that satisfies is obtained. 3. The remainder Ei is obtained by dividing the input data Di by the divisor data OUi. That is,

[0024]

(Equation 3)

The following holds. However, Ni is a quotient. 4. The category number Ji and the remainder data Ei are encoded.

A specific example of the prediction error classification table is shown in Table 1.

[0027]

[Table 1]

Table 1 shows not only the category number Ji and the range of the prediction error corresponding to the category number Ji (SNi to SXi), but also
The word length Mi of the divisor data OUi and the remainder data Ei are shown in correspondence.

As apparent from the above description, the encoding method of the present invention encodes and transmits the category number which is the upper bit information of the prediction error and the residual data which is the lower bit information of the input data. It is.

Next, this decoding method will be described. In the encoding method of the present invention, the category number Ji and the remainder data Ei
Is encoded and transmitted. In order to obtain the data Di, the divisor data OUi, the remainder data Ei, and the quotient data Ni are necessary as shown by the equation (Equation 3). Category number J
Since i and the divisor data OUi correspond one-to-one,
A category number-divisor data conversion table is prepared, and by using this table, divisor data Ei can be obtained from the transmitted category number Ji. Since the remainder data Ei is transmitted, if the quotient data Ni is obtained, the data Di is obtained.

A method for obtaining the necessary quotient data Ni will now be described. By substituting equation (3) into equation (1) and eliminating the prediction error Si, the following equation is obtained.

[0032]

(Equation 4)

Is obtained. Further, by substituting equation (3) into equation (4) and eliminating Di, the following equation is obtained.

[0034]

(Equation 5)

Is obtained. The predicted value Pi is obtained from the decoded data Di, and SXi and SNi are the category numbers Ji.
Since a one-to-one correspondence is established, a conversion table is created in advance, and by using this, a conversion table is obtained from the category number Ji. Further, the quotient data Ni is an integer, and the difference (SXi−SNi) / OUi between the leftmost term and the rightmost term of the equation (Equation 5) is less than 1 than the equation (Equation 2). Can be uniquely determined. Therefore, equation (5)
The following expression extracted the expression on the left side of

[0036]

(Equation 6)

A minimum integer Ni that satisfies the following expression is obtained, or the following expression obtained by extracting the expression on the right side of Expression (5)

[0038]

(Equation 7)

The maximum integer Ni that satisfies the above condition may be obtained. That is, the quotient data Ni can be obtained by using any of the equations (Equation 5), (Equation 6), and (Equation 7). The method using the equation (Equation 7) is the simplest in processing because it is only necessary to cut off the decimal part of the division result on the right side.

By substituting the quotient data Ni obtained as described above into the equation (Equation 3), the data Di can be obtained, that is, decoded. The decoding method is summarized as follows. 1. Decoding the encoded data to obtain the category number Ji
And the remainder data Ei. 2. A predicted value Pi is obtained from data Dk (where k is an integer smaller than i) already obtained by decoding. 3. From the category number Ji, the divisor data OUi, the upper limit value SXi of the prediction error range or the lower limit value S of the prediction error range
Find Ni. 4. The quotient data Ni is obtained by using the equation (7), the equation (6), or the equation (5). 5. Data Di is obtained using the equation (Equation 3).

Since the remainder data Ei is less than the divisor data OUi, its code length Mi is (log ₂ OUi) bits. In order to minimize this, that is, to improve the coding efficiency, the minimum value that satisfies the equation (Equation 2) may be used as the divisor data OUi. Further, by setting the divisor data OUi to a power of 2, a remainder operation and division can be realized by a very simple circuit, and since the code length Mi is an integer value, the remainder data Ei can be efficiently encoded in binary. That is,

[0042]

(Equation 8)

The divisor data and the upper and lower limits of the prediction error may be set so as to satisfy the above. The prediction error classification table (Table 1) is prepared so as to satisfy Expression (Equation 8) when the word length of the input data Di is 8 bits.

FIG. 1 shows an encoding device (FIG. 1A) and a decoding device (FIG. 1B) in the first embodiment using the first high-efficiency encoding method and the decoding method of the present invention. 2) is a block diagram of FIG. The input data is obtained by sampling and quantizing an analog video signal obtained by raster-scanning an image.

In FIG. 1A, 101 is an input terminal of data Di to be encoded, 102 is a prediction circuit for obtaining a predicted value Pi, and 103 is a predictive value P based on the input data Di.
a subtraction circuit for subtracting i to obtain a prediction error Si; a classification circuit 104 for receiving the prediction error Si as input and outputting a category number Ji; a conversion circuit 105 for obtaining divisor data OUi from the category number Ji; Is a remainder operation circuit that divides the data by the divisor data OUi to obtain remainder data Ei, 107 is a first encoding circuit that encodes the category number Ji and the remainder data Ei to obtain coded data Ci, and 108 is a coding circuit that obtains coded data Ci. Output terminal for data Ci, 10
9 encodes the category number Ji and encodes the encoded data C
A second encoding circuit that obtains Ji, 110 is a third encoding circuit that encodes the residual data Ei to obtain encoded data CEi, and 111 connects the encoded data CJi and the encoded data CEi. Is a multiplexing circuit for obtaining encoded data Ci.

In FIG. 1B, reference numeral 112 denotes an input terminal of the encoded data Ci, and 113 denotes the encoded data Ci.
Is a first decoding circuit that obtains a category number Ji and remainder data Ei by decoding data, 114 is a conversion circuit that obtains the upper limit value SXi of the prediction error range of the category of the number Ji, and divisor data OUi, and 115 outputs quotient data Ni. The quotient data calculation circuit 116 includes the divisor data OUi and the quotient data Ni
And a combining circuit for reproducing data Di from the remainder data Ei, 117 is an output terminal of the data Di, and 118 is the already decoded data Dk (k is an integer smaller than i)
A prediction circuit that outputs a prediction value Pi of the data Di using
Reference numeral 119 denotes a buffer memory for temporarily storing the encoded data Ci from the terminal 112. Reference numeral 120 denotes encoded data CJi multiplexed at the head of the encoded data Ci from the buffer memory 119 and decodes the decoded data to obtain a category number Ji. A second decoding circuit 121 for obtaining the coded data CEi multiplexed with the remaining portion of the coded data Ci from the buffer memory 119 and decoding it to obtain the residual data Ei; , 123 are subtraction circuits for subtracting the remainder data Ei from the output from the addition circuit 122,
Reference numeral 124 denotes the output from the subtraction circuit 123 as the divisor data O
Ui, and divides only the integer part of the obtained result into quotient data N
a divider circuit for outputting as i, 125 is the divisor data O
A multiplication circuit 126 multiplies Ui by the quotient data Ni to obtain an offset Fi. An addition circuit 126 adds the remainder data Ei and the offset Fi to obtain new decoded data Di.

The operation of the encoding apparatus and the decoding apparatus of the present embodiment configured as described above will be described below.

In the coding apparatus, input data Di from a terminal 101 is input to a prediction circuit 102, a subtraction circuit 103, and a remainder operation circuit 106. The prediction circuit 102 performs the previous value prediction, and holds ₁ to hold the _immediately preceding data _Di- 1.
It is composed of only one register and outputs a predicted value Pi = _Di-1 .

The subtraction circuit 103 subtracts the prediction value Pi from the data Di to output a prediction error Si. The classification circuit 104 receives the prediction error Si as an input, performs classification according to the size according to (Table 1), and outputs a category number Ji indicating a corresponding classification item. The conversion circuit 105 can be constituted by a ROM (Read Only Memory), and in accordance with (Table 1), the divisor data OUi or the data M from the category number Ji.
Output i. The remainder operation circuit 106 divides the data Di by the divisor data OUi and outputs the remainder Ei. In Table 1, since the divisor data OUi is 2 to the power of Mi, the remainder operation circuit 106 can be realized by a simple gate circuit that extracts only the lower Mi bits of the data Di. In this case, the conversion circuit 105 may output the data Mi instead of the divisor data OUi.

The encoding circuit 109 determines the category number Ji
Is subjected to Huffman coding (a type of entropy coding) and is output in a bit serial format. This output is the encoded data CJi. Since the probability of occurrence of a prediction error having a category number of Ji is substantially the same as the probability of occurrence of a prediction error having a category number of -Ji, in this embodiment, the same Huffman code is assigned to these two categories. The coded data CJi is obtained by adding a 1-bit flag G indicating this to the Huffman code.
When the category number is 0, the flag G is unnecessary. When the flag G = 0, the category number is positive, and G = 1.
In this case, the category number is negative.

The encoding circuit 110 has the category number Ji
Thus, the number Mi of bits of the remainder data Ei shown in (Table 1) is obtained, and the lower Mi bits of the remainder data Ei are output in a bit serial format. This output is the encoded data CEi
It is. Only the lower Mi bits of the remainder data Ei are output because the remainder data Ei can be represented by Mi bits. The multiplexing circuit 111 outputs coded data Ci obtained by connecting the coded data CEi after the coded data CJi from a terminal 118 in a bit serial format. The above operation realizes the encoding of the data Di.

In the decoding device, the encoded data Ci from the terminal 112 is temporarily stored in the buffer memory 119.

First, the decoding circuit 120
19 while determining the code length from the coded data CJi.
Is read and decoded, and the code word length L1 of the read code and the category number Ji are output. Buffer memory 119
Receives the code word length L1 and outputs the encoded data CJ
The head position of the coded data CEi following i is obtained and set to a read pointer contained therein.

Subsequently, the decoding circuit 121
, The word length Mi of the remainder data Ei shown in (Table 1) is obtained from the category number Ji, and the Mi-bit coded data CEi is read from the buffer memory 119, and data 0 is added to the higher order to add bit 0 to the bit parallel format. The remainder data Ei, which is data, is reproduced.

The buffer memory 119 receives the word length Mi from the decoding circuit 121 and receives the encoded data CEi.
Then, the start position of the next encoded data CJi following the above is obtained, and the read pointer is updated to prepare for the next data decoding.

The conversion circuit 114 can be constituted by a ROM, for example, and outputs the upper limit value SXi of the prediction error range and the divisor data OUi shown in (Table 1) from the category number Ji.

The quotient data calculation circuit 115 calculates the residual data Ei, the SXi, and the prediction value P from the prediction circuit 118.
The calculation shown on the right side of the equation (Equation 7) is performed using i and the quotient data Ni which is the integer part is output.

The synthesizing circuit 116 receives the quotient data Ni, the divisor data OUi, and the remainder data Ei as inputs, performs a calculation represented by equation (3), reproduces data Di, and outputs the data Di from a terminal 117.

The prediction circuit 118 has the same configuration as the prediction circuit 102 in the encoding device, and receives the data Di and outputs the predicted value Pi. With the above operation, the decoding of the data Di is realized.

Next, the operation and effect of the present invention will be described with specific data examples. Input data Di to be coded from which the encoding device 46, already entered data D _i-1 of the previous one has completed the coding is assumed to be 35. The prediction circuit 102 outputs a predicted value Pi = D _i-1 = 35.
The prediction error Si = 46−35 in the subtraction circuit 103
= 11 is obtained. In the classification circuit 104, the category number J according to (Table 1) from the prediction error Si = 11
i = 4 is obtained.

In the conversion circuit 105, the category number Ji is converted into a divisor data O which is a power of 2 according to (Table 1).
Ui or its exponent part data Mi = 3 is output. The remainder operation circuit 106 converts the data Di into divisor data OUi = 2 ^Mi
The remainder data Ei = 6 divided by = 8 is output. Since the divisor data OUi is a power of 2, ordinary division does not need to be performed, and the remainder data Ei can be obtained only by extracting only the lower three bits Mi = 3 of the data Di.

In the encoding circuit 109, the category number Ji is Huffman encoded. Ji = 4 or Ji =
The Huffman code representing -4 is "10" having a 3-bit binary number.
1 "(in the following, a binary code is enclosed by""), an encoded code CJi of category number Ji = 4
Becomes "1010" and is output in the bit serial format. The one-bit data “0” added last is a flag G indicating the positive / negative of the category number, indicating that the category number is positive.

In the encoding circuit 110, the lower-order Mi = 3 bits of the remainder data Ei = 6 are output in a bit serial format to become encoded data CEi "110".
In the multiplexing circuit 111, the encoded data CJi "1
After the 010 ", the coded data CEi" 110 "is added to make the coded data Ci =" 1010110 ", which is output from the terminal 118 in a bit serial form from the left end (most significant bit).

In the decoding device, the encoded data from the terminal 112 is temporarily stored in the buffer memory 119 in a bit serial format. The decoding has been completed up to the current data D _i-1 = 35, and the data Di
Is to be decrypted.

The decoding circuit 120 reads the encoded data Ci in the bit serial format from the memory address indicated by the pointer in the buffer memory 119. The decoding circuit 120 can detect that the code length LJ of the coded data CJi is 4 bits at the time of reading from the first bit of the coded data Ci to “101”, and if Ji is not 0, the added 1 bit Is read. That is, 4
All the encoded data bits CJi = "1010" are read. Since the flag G = 0 indicates that the category number Ji is positive, the decoding circuit 120 sets the category number Ji
= 4 is output.

Subsequently, the decoding circuit 121 receives the decoded category number Ji = 4 and obtains M according to (Table 1).
By reading data from the buffer memory 119 for i = 3 bits, coded data CEi = “110” is obtained. This is converted into a parallel format, and 0 is added to upper bits to obtain remainder data Ei = 6. ,Output.
The pointer of the buffer memory 119 is updated to indicate the head memory address of the next encoded data Ci _{+ 1} .

The conversion circuit 114 calculates the divisor data OU which is the upper limit value SXi of the prediction error range in the category of the category number Ji = 4 and which is a power of 2 according to (Table 1).
Output the exponent part Mi of i.

The quotient data calculation circuit 115 includes the prediction circuit 11
Predicted value from _{8 Pi = D i-1 =} 35 and the upper limit value SXi
Then, the remainder data Ei = 6 is subtracted and further divided by the divisor data OUi = 2 ^Mi = 8 to obtain and output quotient data Ni = 5.

The combining circuit 116 multiplies the quotient data Ni = 5 by the divisor data OUi = 2 ^Mi = 8 to obtain an offset Fi, and adds the remainder data Ei = 6 to the decoded data Di = 46. And output from the terminal 117. Thus, the decoding of the data Di is completed.

Since the divisor data OUi is a power of 2, the division circuit 124 does not need to perform ordinary division, and the quotient data Ni is obtained by removing the lower three bits Mi = 3 of the data Di. The circuit 125 does not need to perform normal multiplication, and Mi is placed below the quotient data Ni.
The offset Fi, which is the result of the multiplication, can be obtained simply by adding 0 to the bit. Further, in the adder 126, the remainder data Ei, which is one input, is 0 except for the lower Mi bits, and the offset Fi, which is the other input, has lower Mi bits of 0. Therefore, it is not necessary to perform normal addition.
It is only necessary to replace the lower Mi bits of the offset Fi with the lower Mi bits of the remainder data Ei. Therefore, divider 1
24, the multiplier 125, and the adder 126 are implemented by a very simple circuit, that is, a circuit that replaces the lower Mi bits of the output of the adder 123 with the lower Mi bits of the remainder data Ei and outputs this as decoded data Di. it can.

Next, decoding in the case where the immediately preceding data D _i-1 = 36 has been decoded to a value 31 with a relatively small error due to a transmission error will be considered. Since the predicted value Pi = D _i−1 , error propagation always occurs in the case of conventional predictive coding.
However, when the high-efficiency encoding method of the present invention is actually decoded, a correct result of Di = 46 is obtained. That is, no error propagation occurs. This means that the quotient data Ni is obtained by using equation (7), equation (5) or equation (6) for decoding, and the predicted value P used in these equations is obtained.
This is because correct quotient data Ni can be obtained even if i has a certain range of error from the prediction value at the time of encoding. Equation (Equation 7)
According to this, when Di = 46 and the predicted value Pi is 31 or more and 38 or less, correct quotient data Ni = 5 can be obtained.

As described above, according to the present embodiment, error propagation does not always occur, so that transmission error resistance can be greatly improved. Further, by setting the divisor data to a power of 2, the encoding apparatus of the present invention can be realized with a circuit size as small as that of a conventional predictive encoding apparatus.

In the above embodiment, the residual data is cut out and coded by converting the lower-order Mi bits into a simple binary code. However, if the data is coded after being converted into a gray code, the error resistance can be further improved. This is because the gray code can reduce an error due to a one-bit error to one level. Exceptionally, the upper limit of the remainder data becomes the lower limit,
In the case where the quotient data Ni is corrected by +1 or -1, the correction can be made.

When a decoded value used for prediction has a considerably large error due to a transmission error, only the predicted value Pi having a large error can be obtained by the same prediction method as used for encoding, and a correct decoded value can no longer be obtained. However, if a prediction value Pi ′ having a small error can be obtained by a prediction method using another decoded value that is not affected by a transmission error, that is, a prediction method different from that at the time of encoding, correct decoding is possible. This is because the encoding method of the present invention encodes and transmits upper bit information (category number Ji) of prediction error and lower bit information (remainder data Ei) of data to be encoded. This is because if the quotient data Ni, which is one unknown, is obtained, correct decoded data Di can be obtained. In particular, when the divisor data OUi is large, the range of the quotient data Ni is narrowed, so that the determination is easy.

The decoding method using the predicted value Pi ', that is, the decoding apparatus of the second embodiment using the first high-efficiency code decoding method of the present invention will be described. First, this decoding method will be described. The coded data is coded data Ci output from the coding apparatus according to the first embodiment.

The input data in the first embodiment is
The image signal is used to predict the previous value in the horizontal direction of the image during encoding.
To obtain the predicted value Pi. Image signal is two-dimensional
(3D direction including the time axis direction for moving images)
For example, the data Di is one line before the decoded
Data D_iH (However, H represents the number of pixels in one line.
Is strong, that is, if the vertical correlation is strong,
Pre-value prediction (predictive method different from encoding) in the direct direction
By doing so, the predicted value Pi '(= D
_iH ) Is possible. Therefore before the error is small
When the predicted value Pi 'is obtained, the data Di and the predicted value P
The quotient data Ni is determined so that the error from i ′ is small,
That is,

[0077]

(Equation 9)

Ni that satisfies the following equation is obtained, and this is calculated by the equation (Equation 3).
, The correct data Di can be reproduced with a high probability.

Therefore, a circuit is provided for detecting that a large error has occurred in the decoded data due to a transmission error and for detecting that the vertical correlation of the data Di is strong, and generating a control signal. At the normal time when no control signal is generated, decoding is performed using the predicted value Pi by the same prediction method as at the time of encoding, as in the decoding device of the first embodiment. By performing the decoding method using the prediction value Pi 'using a different prediction method, a decoding device that is more resistant to transmission errors can be realized.

Next, a description will be given of a decoding apparatus according to a second embodiment using the high-efficiency code decoding method of the present invention. This decoding device includes a prediction circuit 118 and a quotient data calculation circuit 115 in the decoding device of FIG. 1 (FIG. 2).
And the quotient data calculation circuit shown in FIG. 3 (FIG. 3), so that the overall configuration of the decoding device is omitted.

In FIG. 2, reference numeral 201 denotes a delay circuit which is composed of one register for holding the immediately preceding decoded data and generates a one-stage data delay.
1 is an input, and a delay circuit for generating (H-1) -stage data delay, 203 outputs the output of the delay circuit 201 as the predicted value Pi when the control signal is not generated, and outputs the output only when the control signal is generated. This switch outputs the output of the delay circuit 202 as the predicted value Pi ′.

In the normal state where the control signal is not input, the switch 203 sets the same horizontal predicted value Pi = D as in the encoding.
_i-1 is output, and the same operation as the prediction circuit 118 in FIG. 1 is performed. When the control signal is generated, a prediction different from that at the time of encoding, that is, a previous value prediction in the vertical direction is performed, and a predicted value Pi '= _DiH is output.

In FIG. 3, reference numeral 301 denotes the upper limit value SXi of the prediction error range and the prediction value P from the prediction circuit shown in FIG.
i, an addition circuit for selecting the output of the addition circuit 301 when the control signal is not generated, and a switch for selecting and outputting the predicted value Pi ′ when the control signal is generated. A subtraction circuit for subtracting the remainder data Ei from the output of the switch 303;
305 is a rounding circuit that performs a rounding process on the output of the dividing circuit 303 when the control signal is not generated, and performs a rounding process on the output of the dividing circuit 303 when the control signal is generated.

When the control signal is not generated, the predicted value of the input is the same Pi as that at the time of encoding, the output of the adding circuit 301 is input to the adding circuit 303 via the switch 302, and the rounding circuit 305 Is performed, the same processing as in quotient data calculation circuit 115 in FIG. 1 is performed. When the control signal is generated, the predicted value of the input is a predicted value Pi ′ obtained by performing a prediction in the vertical direction.
02, the predicted value Pi ′ is input through the rounding circuit 305
Rounds off, the error between the decoded output data Di and the predicted value Pi ′ is minimized, that is, the quotient data Ni that satisfies the equation (Equation 9) is output.

Using the obtained quotient data Ni, the combining circuit 116 (FIG. 1) obtains the decoded data Di by performing the operation of the equation (Equation 1) and outputs this. As described above, according to the present embodiment, decoded data having a large error is generated due to a transmission error, and only when a predicted value Pi ′ having a small error is obtained by a prediction method different from that at the time of encoding, the first embodiment is not used. Since the decoded data is obtained by a decoding method different from that of the decoding device, that is, by determining and decoding the quotient data Ni so that the correlation with the predicted value Pi 'is high, the decoded data can be correctly decoded with a higher probability. Thus, the error resilience can be greatly improved as compared with the related art.

The data Dr between the data Dm in which the transmission error has occurred and the data Di decoded by the control signal.
(However, m <r <i) can be correctly decoded by decoding in the direction in which r decreases, that is, in the reverse direction, using the data Di. If this decoding method is used together, the error propagation area can be made smaller. It is possible to

The decoding in the reverse direction, that is, the decoding of data Di from data Di _{+ 1} can be performed by the following method. That is,

[0088]

(Equation 10)

The quotient data Ni is obtained so as to satisfy the condition, and the quotient data Ni and the category number Ji obtained by the equation (Equation 3) are obtained.
Divisor data OUi obtained from the transmitted remainder data E
Data Di is obtained by substituting i.

FIG. 4 shows an encoding apparatus (FIG. 4) according to a third embodiment using a second high-efficiency encoding method of the present invention and a second high-efficiency code decoding method which is an inverse transform thereof.
FIG. 5A is a block diagram of a decoding device (FIG. 4B). As in the first and second embodiments, the input data V is obtained by sampling and quantizing an analog video signal obtained by raster-scanning an image.

In FIG. 4A, reference numeral 401 denotes an input terminal of the data V to be encoded, and 402 denotes a rectangular area obtained by rearranging the input data and dividing the image into eight pixels in the horizontal direction and eight pixels in the vertical direction. Data DDi for each block
(H) (where h is an integer from 0 to 63) is a blocking circuit that outputs an octal DCT to the data DDi (h) in the horizontal and vertical directions to obtain one DC coefficient DCi (h). Subscript i represents block number i), and 63 AC coefficients ACi (k) (where k
Is an integer from 1 to 63).
A CT circuit 404 is a quantization circuit which quantizes the DC coefficient DCi by a predetermined quantization step size Qd (that is, divides by Qd and rounds) to obtain data Di, and 405 is equivalent to the encoding device of FIG. An encoding circuit that encodes the data Di to obtain encoded data Ci;
A quantization circuit quantizes the coefficient ACi (k) at a predetermined quantization step size to obtain data Bi (k). A quantization circuit 407 encodes the data Bi (k) from the quantization circuit 406 by two-dimensional Huffman coding. An encoding circuit that outputs data Ai, 408 is a multiplexing circuit that outputs encoded data CCi obtained by multiplexing the encoded data Ci and the encoded data Ai, and 409 is a terminal that outputs the encoded data CCi. is there.

In FIG. 4B, reference numeral 410 denotes an input terminal of the coded data CCi, and 411 denotes an input terminal of the coded data CCi.
a separating circuit 412 for separating the coded data Ci and the coded data Ai from i, a decoding circuit 412 for decoding the coded data Ci to obtain data Di, and a 413 for decoding the coded data Ai to obtain data Di. A decoding circuit 414 for obtaining Bi (k) performs inverse quantization by multiplying the data Di by the quantization step size Qd to obtain decoded data DCi ′ of DC coefficients.
An inverse DCT circuit 416 for performing an inverse transform of the DCT circuit 403, and an inverse quantization circuit 416 for multiplying the output data Bi (k) by 3 with each predetermined quantization step size to obtain a decoded value ACi ′ (k) of the AC coefficient. 417 is a delay circuit for adjusting timing, 418 is an addition circuit that adds the inverse DCT output passed through the delay circuit and the decoded data DCi ′ to obtain data DDi ′ (h) of a block unit, and 419 is a block unit. A deblocking circuit 420 that rearranges the image data DDi 'to obtain image data having the same data sequence as before encoding, and 420 is an output terminal of decoded image data V' from the deblocking circuit.

The operation of the encoding apparatus and the decoding apparatus of the present embodiment configured as described above will be described below.

In the encoding device, the image data V from the terminal 401 is input to the blocking circuit 402. The blocking circuit 402 rearranges the image data and outputs data DDi (h) for each block. DCT
The circuit 403 performs an eight-dimensional two-dimensional DCT on the data DDi (h) for each block to obtain one DC coefficient DCi.
And ACi (k) composed of 63 AC coefficients.
The quantization circuit 404 quantizes the DC coefficient DCi by a predetermined quantization step size Qd (ie, divides the DC coefficient DCi by Qd and rounds it) to output quantized data Di. Encoding circuit 40
5 encodes the data DCi and outputs encoded data Ci, as in the encoding device of FIG. The difference from the coding apparatus of FIG. 1 is that the input is not the quantized value of the image data but the data obtained by quantizing the DC coefficient (equal to the average value) of a block composed of 64 pixels of 8 × 8. The same symbol Di as in FIG. 1 is used to clarify the correspondence. The quantization circuit 406 converts the AC coefficient ACi (k) into a predetermined quantization step size Qa determined for each coefficient.
Quantize with i (k). The encoding circuit 407 subjects the output Bi (k) of the quantization circuit 406 to two-dimensional Huffman encoding and outputs encoded data Ai. The multiplexing circuit 408 multiplexes the coded data Ci and the coded data Ai and outputs coded data CCi from a terminal 409.

The decoding device can be realized by a block configuration for performing an inverse transform of the encoding circuit shown in FIG. 4 (a). However, correct decoding can be performed with a higher probability even when a transmission error that causes a decoded value having a large error occurs. (FIG. 4B).

In the decoding device, the encoded data CCi from the terminal 410 is input to the separation circuit 411. The separation circuit 411 separates the coded data CCi into coded data Ci and coded data Ai. The decoding circuit 413 decodes the coded data Ai that has been subjected to the two-dimensional Huffman coding to obtain quantized AC coefficients Bi (k). The inverse quantization circuit 415 performs inverse quantization by multiplying the data Bi (k) by a predetermined quantization step Qai (k) determined for each coefficient to obtain an AC coefficient ACi ′ (k). The inverse DCT circuit 416 performs an inverse DCT with the DC coefficient input as the provisional value 0 and the AC coefficient input as ACi ′ (k) to obtain provisional decoded data (AC component data) DTi of the block.

The decoding circuit 412 is basically the same as the decoding device of the second embodiment, and
It decodes i and outputs data Di which is a quantized DC coefficient. The difference from the decoding circuit of the second embodiment is that the configuration of the prediction circuit is not shown in FIG. 2 but is shown in FIG.
This is shown in FIG. This predicting circuit is used for predicting circuit 11 in FIG. 1 during normal decoding without transmission errors.
8 or (FIG. 2), that is, the same prediction value Pi = D _i-1 as that at the time of encoding (this is the DC coefficient of the already decoded i-th block, and this block (i -1) is output to the left of block i in the image), but when a large error is detected and a control signal is input from the outside, prediction different from that at the time of encoding is performed. The prediction value Pi 'is output.

The predicted value Pi ′ is obtained from the data of the block (iH) immediately above the block i currently being decoded. The predicted value P as in the second embodiment
i ′ = D _iH ′ (where H is the number of blocks in the horizontal direction of the image), but in this embodiment, the prediction value Pi is calculated from the decoded image data _{D iH} ′ in order to improve the accuracy of the prediction value. 'Seeking. This quantized DC coefficient D
A method for obtaining the predicted value Pi ′ for i will be described.

The eight pixel data DDi '(q) of the block i which is in contact with the block (i-H) (where q = q
1, q2,. . . , Q8) have a short distance from the block (i-H), so that the predicted value pi (q) for them can be obtained more accurately than the pixel data _DDiH ′ in the block (i-H). The pixel data DDi ′ (q) includes a DC component DCi ′ = Di · Qd of a block and a DT that is an AC component.
i (q), the pixel data DDi ′
The difference between (q) and the predicted value pi (q),
Then

[0100]

[Equation 11]

Is satisfied. By making the error d small and setting it to 0, an approximate value of the quantized DC component Di, that is, a predicted value Pi ′ is obtained.

[0102]

(Equation 12)

Is established. In the present embodiment, the prediction value pi (q) is obtained by performing pre-prediction in the vertical direction in order to simplify the circuit configuration. 8 of block i
Pixel data DDi ′ (q) (where q = q1, q
2,. . . , Q8).
If the decoded data of 8 pixels in H) are represented by DD _iH ′ (q), they are the predicted values pi (q) in the pre-prediction.
be equivalent to. The predicted value Pi ′ can be obtained only by calculating the equation (Equation 12) for one q, but the average value of (pi (q) −DTi (q)) is obtained for eight qs in order to further improve the accuracy. , Which is divided by the quantization step size Qd to obtain a predicted value Pi ′. The configuration and operation of the prediction circuit for obtaining the predicted value Pi 'will be described with reference to FIG.

In FIG. 5, reference numeral 501 denotes a delay circuit which receives data Di and inputs the immediately preceding data Di _-1 to a predicted value Pi.
Output as Reference numeral 502 denotes a delay circuit which receives the decoded data DDi 'as an input and calculates the predicted value pi (q) = DD.
_{Output iH} ′ (q). 503 is a subtraction circuit for predicting the value p
The difference between i (q) and data DTi (q) is obtained. 504
Is an averaging circuit, which outputs an average value of the difference for the eight qs, and a quantization circuit 505 divides the average value by a quantization step size Qd (that is, performs quantization) to obtain a prediction value P
Output i '. Reference numeral 506 denotes a switch which outputs the predicted value Pi during normal times when the control signal is not input, and outputs the predicted value Pi 'when the control signal is input.

As a result, the decoding circuit 412 outputs decoded data Di having a small error even when a transmission error occurs. In order to obtain the predicted value Pi ′, decoding of the AC coefficient and inverse DCT must precede decoding of the DC coefficient.
Reference numeral 12 internally has a delay circuit for adjusting timing. The inverse quantization circuit 414 multiplies the data Di by the quantization step size Qd and outputs DC coefficient data DCi ′. The addition circuit 418 adds the data DCi ′ passed through the delay circuit 417 for timing adjustment and the data DCi ′ to output decoded image data DDi ′ for each block. The inverse block circuit 419 is connected to the image data DD.
The data i ′ (h) is rearranged, and the data before encoding and the decoded image data V ′ are output from the terminal 420.

As described above, according to this embodiment, even if decoded data Di having a large error occurs due to a transmission error, a decoded value of correct image data can be obtained with a high probability by using the correlation of pixel data between blocks. Thus, error resilience can be greatly improved as compared with the related art.

In the above embodiment, lossless encoding is performed. However, for example, where the prediction error is large, an irreversible encoding method is possible by rounding and transmitting lower bits of the remainder data Ei. In this case, it is necessary to provide a local decoding device in the encoding device and create a prediction value from the decoded data in order to match the prediction values in the encoding device and the decoding device. It is a matter of course that a configuration in which the local decoding device is provided can be used in the reversible encoding as in the present embodiment.

The present invention is not limited to these embodiments, and various prediction methods can be applied, and arithmetic coding can be applied as an entropy coding method. In addition to DCT, various transform methods and various encoding methods such as quantization of average value separation vectors can be applied.

[0109]

According to the present invention, a high-efficiency encoding method characterized by transmitting high-order bit information of a prediction error and low-order bit information of input data and a decoding method for performing inverse transform thereof reduce the encoding efficiency. Without this, transmission error tolerance can be greatly improved, and its practical effect is great.

[Brief description of the drawings]

FIG. 1 is a block diagram of an encoding device and a decoding device according to a first embodiment using a first high-efficiency encoding method and a decoding method thereof according to the present invention.

FIG. 2 is a block diagram of a prediction circuit in a decoding device according to a second embodiment using the first high-efficiency code decoding method of the present invention.

FIG. 3 is a block diagram of a quotient data calculation circuit in a decoding apparatus according to a second embodiment using the first high-efficiency code decoding method of the present invention.

FIG. 4 is a block diagram of an encoding apparatus and a decoding apparatus according to a third embodiment using a second high-efficiency encoding method according to the present invention and a second high-efficiency code decoding method according to the present invention, which is the inverse transform thereof; It is a block diagram.

FIG. 5 is a block diagram of a prediction circuit in a decoding device according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 101 Input terminal of data Di to be encoded 102 Prediction circuit 103 Subtraction circuit 104 Classification circuit 105 Conversion circuit 106 Remainder arithmetic circuit 107 Encoding circuit 108 Output terminal of encoded data Ci 112 Input terminal of encoded data Ci 113 Decoding circuit 114 Conversion Circuit 115 quotient data calculation circuit 116 synthesis circuit 117 output terminal of decoded data Di 118 prediction circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03M 7/38 H04N 1/41 H04N 7/13 G06F 15/66 330

Claims (7)

(57) [Claims] A step of obtaining a prediction value of the input data, obtaining a prediction error which is a difference between the input data and the prediction value, using the sampled and quantized signal as input data; Outputting a category number representing a corresponding category by classifying according to the size; and a predetermined value larger than a difference between a predetermined upper limit value and a predetermined lower limit value defining a range of the corresponding category as a divisor. A high-efficiency encoding method, comprising: dividing input data to obtain a remainder; and encoding and outputting the category number and the remainder. 2. The method according to claim 1, wherein the divisor is a value obtained by adding 1 to the difference between the upper limit and the lower limit, and the upper limit and the lower limit of each category are set so that the divisor is a power of 2. The high-efficiency encoding method according to claim 1. 3. The step of encoding and outputting the category number and the remainder includes entropy encoding the category number and converting the remainder into a variable-length code according to the divisor size. 2. The high-efficiency encoding method according to claim 1, wherein: 4. The high-efficiency encoding method according to claim 1, wherein the step of encoding and outputting the category number and the remainder includes a step of converting the remainder into a gray code. 5. A prediction error, which is a difference between data D to be encoded and a predicted value thereof, the prediction errors are classified into categories according to their magnitudes, a category number is obtained, and a divisor determined by a corresponding category is obtained. Decoding the data to be coded to obtain a remainder, decoding the high-efficiency code using the coded data obtained by the high-efficiency coding method for obtaining the coded data by coding the category number and the remainder as input data A method of decoding the encoded data to obtain the category number and the remainder; obtaining a predicted value from output data that has already been decoded; and calculating a prediction error of the category indicated by the category number. Using at least one of the upper and lower limits of the range, the divisor obtained from the category number, and the predicted value, generating an offset that is an integral multiple of the divisor And obtaining the new output data by adding the offset and the remainder, and when a control signal is input from the outside, the step of obtaining a predicted value includes the steps of: Obtaining a predicted value by performing a prediction method different from the above, and generating an offset, wherein the offset is generated such that output data obtained by decoding by the control signal has a high correlation with the predicted value. A decoding method for a high efficiency code. 6. A step of forming data as a sampled and quantized signal as an encoding input, forming a block by combining a predetermined number of the input data, and performing a predetermined conversion on the data of the block to obtain a DC component and an AC component. And quantizing each of them, encoding the data D of the quantized DC component and outputting DC encoded data, encoding the quantized AC component to generate AC encoded data And the step of outputting the DC encoded data obtains a prediction error that is a difference between the data D and a predicted value thereof, classifies the prediction error into a category according to its magnitude, and Number, and divides the data D by a divisor determined by a corresponding category to obtain a remainder, and encodes the category number and the remainder to obtain D.
A highly efficient encoding method characterized by obtaining C encoded data. 7. A step of constructing a block by assembling a data which is a sampled and quantized signal as a coded input and combining the input data by a predetermined number, and performing a predetermined conversion on the data of the block to obtain a DC component and an AC component. And quantizing each of them, encoding the data D of the quantized DC component and outputting DC encoded data, encoding the quantized AC component to generate AC encoded data And the step of outputting the DC encoded data obtains a prediction error that is a difference between the data D and a predicted value thereof, classifies the prediction error into a category according to its magnitude, and Number, and divides the data D by a divisor determined by a corresponding category to obtain a remainder, and encodes the category number and the remainder to obtain D.
What is claimed is: 1. A method for decoding a high-efficiency code using coded data of a high-efficiency coding method characterized by obtaining C-coded data as input data, comprising: decoding an AC component quantized by decoding the AC-coded data. And decoding the DC encoded data to obtain a quantized DC component;
Dequantizing the quantized AC component to obtain an AC component; performing inverse transform on the AC component and the DC component to obtain decoded data in a block; A deblocking step of obtaining and outputting decoded data having the same arrangement as the encoded input data, wherein the step of obtaining the quantized DC component comprises: decoding the DC encoded data to obtain the category number and the remainder. Obtaining a predicted value from the already decoded quantized data, at least one of an upper limit or a lower limit of a range of a prediction error of a category indicated by the category number, and a divisor obtained from the category number, Generating an offset that is an integral multiple of the divisor using the predicted value and adding the offset and the remainder to form a new Obtaining a decoded data D, wherein, when a control signal is input from the outside, the step of obtaining the predicted value performs a different prediction method from that at the time of encoding by the control signal, and the step of generating the offset Generating an offset such that the decoded data of the block being decoded is adjacent to the block being decoded by the control signal and has the highest correlation with the decoded data of the block in which no error has occurred. Decoding method of efficiency code.