JP3427659B2 - Adaptive quantization for orthogonal transform coding - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a predictive coding method in which a television signal is digitized, a prediction error signal is quantized, data compression coded and transmitted, and an orthogonal transform method in which an image signal is orthogonally transformed and coded. In particular, the present invention relates to a quantization method used when orthogonally transforming a prediction error signal and then performing quantization to code and transmit.

[0002]

2. Description of the Related Art Conventionally, the one shown in FIG. 5 is known as an encoding system (prediction error orthogonal transform encoding system) that combines differential encoding (predictive encoding) and orthogonal transform encoding. Then, as an example of a typical method for orthogonally transforming the prediction error signal, quantizing the transformed signal, and encoding and transmitting the signal, for example, TTC standard JT-H261 (published by the Telegraph and Telephone Technical Committee, hereinafter referred to as Reference 1). There is.

Referring to FIG. 5, in this method, the subtracter 4
In 1, the 8-bit image signal and the 8-bit motion-compensated inter-frame prediction signal are subtracted to obtain a 9-bit difference signal (prediction error signal).
Block, performs orthogonal transform by DCT (discrete cosine transform) to obtain 64 types of 12-bit transform coefficients.
Then, the transform coefficient is set to a predetermined quantization characteristic (maximum 1
2-bit dynamic range with a range of -2048 to 2
047) to quantize, and the quantized transform coefficient is code-converted by the code converter 44 and transmitted.

The quantized transform coefficient is also given to the inverse orthogonal transformer 45, where it is subjected to inverse orthogonal transform and given to the adder 46. The adder 46 adds the inverse orthogonal transformer 45 and the prediction signal and gives the result to the predictor 47. Then, the predictor 47 generates a motion-compensated interframe prediction signal according to the output of the adder 46.

On the other hand, conventionally, the adaptive quantization system for predictive coding shown in FIG. 6 is known, and this system is described in, for example, Japanese Patent Laid-Open No. 6-343047.

With reference to FIG. 6, in this system, an 8-bit input signal X is supplied to a subtracter 51 and an adder 52.
The subtractor 51 performs an 8-bit modulo operation, subtracts the prediction signal P from the input signal X to obtain an 8-bit prediction error signal E, and sends it to the quantizer 53.

The quantizer 53 has a quantization characteristic of a dynamic range of 8 bits, quantizes the prediction error signal E to output a temporary quantized output Q, and outputs the temporary quantized output Q by one. Quantization level Q ₊ and the tentative quantization output Q of
The quantization level Q ₋ which is one level lower than that is output.

The subtractor 24 subtracts the temporary quantized output Q and the prediction error signal E to obtain the quantized noise qn, and the adder 52 adds the quantized noise qn and the input signal X. A temporary local decoded signal Yt is obtained. Then, the switch 54 determines whether the locally decoded signal Yt exceeds or falls below the 8-bit dynamic range, and if it is within the range, outputs the temporary quantized output Q as the quantized output Qs. When the range is exceeded, the quantization level Q _- is output as the quantization output Qs, and when the range is exceeded, the quantization level Q ₊ is output as the quantization output Qs. Then, the quantized output Qs is encoded by the code converter 55 and transmitted.

The adder 56 outputs the quantized output Qs and the prediction signal P.
And modulo addition are performed to obtain the locally decoded signal Y. Then, the predictor 57 generates the next predicted signal P according to the locally decoded signal Y.

On the receiving side, the code inverse converter 58 performs inverse conversion to reproduce a signal having the same quantization level as the quantization output Qs. This quantized signal is modulo-added with the prediction signal by the adder 59 to obtain a locally decoded signal. The predictor 60 generates a prediction signal according to this locally decoded signal.

[0011]

By the way, the dynamic range of the quantization characteristic is set to 1 while keeping the image quality at the same level.
In order to reduce the coding transmission bit rate using a quantizer with a smaller bit size, apply the predictive coding adaptive quantizer to the quantizer of the prediction error orthogonal transform coding method described above. However, in this case, in the prediction error orthogonal transform coding method, the prediction error transform coding is performed for each 8 × 8 block, and
The orthogonal transform / inverse orthogonal transform is performed later. Therefore, in the temporary local decoded signal of 64 pixels decoded for each block, each pixel is affected by the quantization noise of 64 transform coefficients. For this reason, the quantization error and the pixel signal do not have a one-to-one correspondence, and the determination method in the predictive coding adaptive quantization method cannot be directly applied to the determination method of the prediction error orthogonal transform coding.

When a pixel signal exceeds the dynamic range in one block, to determine which transform coefficient exceeds the dynamic range due to the influence of the quantization noise of the transform coefficient, for example, a simple brute force method is used. , 6
It is necessary to obtain the effect of quantization noise for the combination of four types of transform coefficients, and in the worst case, the amount of brute force calculation becomes enormous and the decision circuit cannot be practically realized in real time. There is a problem.

An object of the present invention is to quantize an image having the same image quality as conventional quantization without deterioration of overload noise with a quantization characteristic whose dynamic range is smaller by 1 bit than before without increasing the device scale. It is to provide the system.

Another object of the present invention is to provide a quantization method capable of performing transmission with a smaller number of quantization levels (number of allocated bits), that is, with a smaller number of coded transmission bits than in the past. .

[0015]

When a predictive coding adaptive quantizer is directly applied to a prediction error orthogonal transform coding system, a transform coefficient which greatly affects a pixel signal exceeding a dynamic range is obtained, Adaptive quantization is determined by a method of checking whether the temporary local decoded signal can be prevented from exceeding the dynamic range by reducing the temporary quantization output level of the transform coefficient by one.

The transform coefficient which greatly affects the dynamic range over of the decoded signal can be estimated from the amplitude value of the transform coefficient of the out-of-range signal and the magnitude of the quantization noise of the quantized output.

Here, as the out-of-range signal, the pixel point within the dynamic range is 0, and the pixel exceeding the upper part has the positive amplitude value of the exceeded part as the amplitude value of the pixel point, and exceeds the lower part. , The signal value of one block is obtained by using the negative amplitude value of the exceeded portion as the amplitude value of the pixel point.

Next, the out-of-range signal is subjected to inverse orthogonal transformation to obtain the amplitude value of the transformed signal, and it is assumed that the transform coefficient having a large amplitude has a great influence of the quantization noise, and the quantization step is decreased by one. The value is increased to determine whether the temporary local decoded signal exceeds the dynamic range. If it exceeds the dynamic range, the judgment is repeated. By this procedure, by forcibly changing the quantization level of the transform coefficient that has a large influence, the quantization noise works in the opposite direction to the pixel signal of the range over, and the temporary local decoding is performed. Since the signal does not exceed the dynamic range, it is possible to quickly determine that the signal does not exceed the dynamic range by this determination method.

According to the configuration of the present invention, the orthogonal transformation signal of the prediction error signal can be quantized and coded and transmitted with the quantization characteristic of the dynamic range which is smaller by 1 bit than the conventional one, and the reproduced image is equivalent to the conventional one without overload. Will be able to decode the image.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings.

Referring to FIG. 1, an 8-bit digital input signal X (-128 to 127) is supplied to a subtractor 1 having an 8-bit dynamic range, and the subtractor 1 outputs a prediction signal P from a predictor 7. Is subtracted from the input signal X by a modulo operation to obtain an 8-bit prediction error signal E, which is supplied to the orthogonal transformer 2.

In the orthogonal transformer 2, "8 samples" × "8 samples"
The prediction error signal E is orthogonally transformed for each block with 64 pixels (Eij = E11 to E88) of "line" as one block, and 64 types of transform coefficients (Et11 to Et88) are output as one block. The 64 types of transform coefficients have a dynamic range of 11 bits and are supplied to the adaptive quantizer 3.

The adaptive quantizer 3 comprises a quantizer 10 and a selector 1.
1, inverse orthogonal transformer 12, adder 13, range determiner 1
5, an orthogonal transformer 16, a control decision unit 17, and an output switch (SW) 18. The quantizer 10 has a dynamic range of 11 bits, quantizes each transform coefficient block by block with a quantization characteristic corresponding to each transform coefficient, and supplies each temporary quantized output Q to the selector 11. Further, the quantizer 10 also outputs a quantized output at a level one level above (Q ⁺ ) and one level below (Q ⁻ ) from each temporary quantized output Qij and supplies the quantized output to the selector 11.

The selector 11 is controlled determiner provisional in response to the control signal from 17 Qij a quantized output, Q ^+, and Q ^- provisionally for each block to select one of the quantization output Qt Is obtained and supplied to the inverse orthogonal transformer 12 and the output SW 18.

The inverse orthogonal transformer 12 has the inverse transform characteristic of the orthogonal transformer 2, and inversely orthogonally transforms the tentative quantized output Qt for each block and tentatively quantized the prediction error signal having an 8-bit dynamic range. Eq is reproduced and supplied to the adder 13.

The adder 13 adds the prediction signal P supplied from the predictor 7 and the temporary quantized prediction error signal Eq by an 8-bit modulo operation to obtain an 8-bit temporary local decoded signal Y, which is obtained. It is supplied to the range determiner 15.

The range determiner 15 first compares the input signal X with the temporary local decoded signal Y to determine whether the local decoded signal Y exceeds the dynamic range. For comparison, a 9-bit subtracter (not shown) subtracts the temporary local decoded signal Y from the input signal X to obtain a noise signal. When the noise signal N is larger than half the dynamic range, the temporary local decoded signal Y overflows or underflows the 8-bit dynamic range due to the influence of quantization noise, and a correct local decoded signal is not obtained. Then, a value exceeding the range boundary of each pixel is obtained for each block as an out-of-range signal. The out-of-range signal has a positive value in the case of overflow and a negative value in the case of underflow. If the pixel is determined to be within the range, the out-of-range signal has a value of 0.
The out-of-range signal consisting of 64 pixels in one block thus obtained is supplied to the orthogonal transformer 16 and the control decision unit 17.

The orthogonal transformer 16 has the same conversion characteristic as that of the orthogonal transformer 2, and orthogonally transforms the out-of-range signal block by block to obtain a transform coefficient and supplies it to the control decision unit 17. The control determiner 17 first performs control so that the temporary quantized output Q output from the quantizer 10 is selected. In the first comparison judgment, when the out-of-range signal supplied to the control judgment unit 17 is all 0 in one block, the control judgment unit 17
Sends a control signal to the output SW 18 to output the temporary quantized output Q output from the selector 11 as the finally selected quantized output.

When the out-of-range signal is not 0, the quantization output Q ⁺ or Q ⁻ is selected as the level of the temporary quantization output corresponding to the conversion coefficient having the largest out-of-range signal conversion coefficient. A control signal is sent to the container 11. As a result,
The above-described comparison determination control process is repeated for the newly output temporary quantized output.

From the second time onward, this comparison / judgment / control process is repeated until the range signal becomes 0 for all blocks.

As a method of controlling the quantized output based on the transform coefficient, a method of performing the quantized adaptive control only by the transform coefficient of the DC component will be described.

Quantization noise N (f (x, y)) obtained by inverse orthogonal transforming the quantization noise Nt of the transform coefficient is given by the equation 1 described later, and transform coefficient quantization noise Nt (F (u, v) ) Is multiplied by a coefficient of 1/8. Therefore, when overflow occurs, the quantization level of the DC component of the transform coefficient is decreased by one, and when underflow occurs, the quantization level is increased by one.

When the magnitude of the out-of-range signal is small, it is possible to make a complicated determination by only correcting the DC component and make a correction so as not to exceed the range easily. When the amplitude is large, the coefficient of ⅛ is applied, so that the correction may not be effective for the fluctuation of one level, and the correction of two or more levels may be necessary. However, since the quantization noise of the DC component is easily noticeable as block distortion,
When the amplitude is large, it is necessary to perform selective control of the quantization level of the temporary quantized output including the conversion coefficient of the AC component.

The output SW 18 outputs the quantized output supplied from the selector 11, and supplies it to the code converter 4 and the inverse orthogonal converter 5. The code converter 4 code-converts each level of the quantized output into a transmission code for each block, multiplexes it with other information, and sends out to the transmission line. The inverse orthogonal transformer 5 has the inverse transform characteristic of the orthogonal transformer 2, and inversely transforms the quantized output to obtain the quantized prediction error signal Eq and supplies it to the adder 6.

The adder 6 has a dynamic range of 8 bits, and modulo-adds the quantized prediction error signal Eq and the prediction transform coefficient P to obtain an 8-bit locally decoded signal Y and supplies it to the predictor 7. To do. The predictor 7 obtains the next predicted signal P for each block from the locally decoded signal Y according to the prediction characteristic, outputs the block, and supplies it to the subtractor 1, the adder 6, and the adder 13.

The predictor 7 has a function of performing motion compensation prediction, finds an optimum motion vector for the next input block for each block by a matching method, and outputs a motion-corrected prediction signal P. The motion vector is encoded together with the quantized output signal and sent to the receiving side.

Next, the characteristics of the orthogonal transformers 1 and 16 and the inverse orthogonal transformers 5 and 12 will be described.

In the DCT transform of 8 rows and 8 columns in the orthogonal transformer, a two-dimensional discrete cosine transform that can be separated into an 8 × 8 one-dimensional transform is performed. The signal of 1 block of 8 rows and 8 columns is f
(x, y) (corresponding to X11 to X88) and the conversion output coefficient of 8 rows and 8 columns is F (u, v) (corresponding to Xt11 to Xt88), the conversion output F (u, v) is TTC. The one given by the number 1 shown in the standard JT-H261 is used.

[0039]

[Equation 1] For the converted block, x = 0 corresponds to the left end of the block, and y = 0 corresponds to the upper end of the block.

On the other hand, the inverse transform characteristic of the inverse orthogonal transformer is as shown in Equation 2.

[0041]

[Equation 2] When this conversion is performed, the conversion coefficient F becomes a signal whose dynamic range is expanded by 3 bits. That is, when the signal f has 8 bits, the conversion coefficient F has a dynamic range of 11 bits.

In the conventional differential encoding, since the difference signal E obtained by subtracting the 8-bit prediction signal P from the 8-bit input signal X is 9 bits, the transform coefficient obtained by orthogonally transforming the 9-bit difference signal is obtained. Has a dynamic range of 12 bits. In other words, in the conventional example, the difference conversion coefficient is 12
It has a dynamic range of bits, and the quantization characteristic requires a dynamic range of 12 bits in order to quantize this transform coefficient.

On the other hand, in the present invention, the 8-bit input signal X
Then, the 8-bit prediction signal P is subtracted by a bit modulo operation to obtain an 8-bit difference signal (prediction error signal). The transformation coefficient obtained by orthogonally transforming the 8-bit difference signal is 11
It becomes a bit conversion coefficient, and the quantizer 10 quantizes the signal of the conversion coefficient of the 11-bit dynamic range, and the dynamic range of the quantization characteristic is half (one bit less) the 11-bit range than the conventional one. You can do it.

Next, the operation of the range determiner will be described.

In predictive coding, Y = X × N, where X is the input signal, Y is the locally decoded signal, and N is the quantization noise.
Have a relationship. In the present invention, the prediction error signal is obtained by the modulo arithmetic unit having the same dynamic range as that of the input signal (n = 8 bits), and the locally decoded signal is also obtained by the modulo addition of the same dynamic range. Therefore, the locally decoded signal is represented by Ym = MOD (X + N, n (value modulo n bits), and -2 ** (n-1) to 2 ** (n-
The value is in the range of 1) -1.

Therefore, for example, X is the upper limit value of the range T =
For a value close to 2 ** (n-1) -1, if the quantization noise N is larger than XT-X, the locally decoded signal Y = X + N overflows and exceeds the dynamic range, and the actual locally decoded signal is obtained. The value Ym of is Ym = MOD (X + N, n)
= X + N-2 ** n, and the lower limit B = -2 ** (n-
It is a negative value close to 1).

When an underflow is caused by the quantization noise N, similarly, the locally decoded signal that overflows due to the influence of the quantization noise with respect to the input signal close to the lower limit takes a value close to the upper limit.

The judgment of overflow or underflow is made by subtracting the local decoded signal Ym from the input signal X and noise N.
It can be judged from. Quantizer noise is usually 2 **
Since it is set smaller than half of (n-1), overflow occurs in the case of X-Ym> 2 ** (n-1), underflow occurs in the case of X-Ym <-2 ** (n-1), and otherwise. The correct local decoded signal is obtained within the range.

A simple decision is to make a subtraction value (X
-Ym) is judged by looking at the upper 2 bits. If the upper 2 bits are "01", an overflow occurs, if "10", an underflow occurs, and in the other cases, "11" or "00", a correct local decoded signal is obtained.

As described above, the range determiner 15 compares and determines the ranges of the signals and obtains and outputs the out-of-range signal.
For a locally decoded signal that exceeds the dynamic range due to the influence of quantization noise, the transform coefficient that affects the signal that exceeds the range is obtained. Then, in order to prevent the locally decoded signal from exceeding the dynamic range due to the influence of the quantization noise of the quantized output of the transform coefficient, instead of the selected quantization level, one level above or one level below that level is used. Select and output the quantization level of.

A signal that does not exceed the range is set to 0, and a signal that exceeds the range is set to a value that exceeds the range, and an out-of-range signal indicating an out-of-range signal is obtained for each block. The out-of-range signal has a positive value in the case of overflow and a negative value in the case of underflow.

Next, an example of the operation of the control determiner will be described.

When the local decoded signal of one block exceeds the dynamic, it is determined which transform coefficient has a large influence of the quantization noise. An out-of-range signal indicating a signal of a portion exceeding the dynamic range is orthogonally transformed for each block to obtain a transform coefficient. Of the obtained conversion coefficients, the one with the largest amplitude is obtained.

In the case of overflow, when the transform coefficient having the largest amplitude is a positive value, the quantization level one level below is controlled to be selectively output instead of the temporary quantization output corresponding to the transform coefficient. When the value is negative, control is performed such that the next higher quantization level is selected instead of the temporary quantization output corresponding to the transform coefficient.

In the case of underflow, when the transform coefficient with the largest amplitude has a positive value, control is performed so that the next higher quantization level is selectively output instead of the temporary quantization output corresponding to that transform coefficient. However, when the value is negative, control is performed so that the next lower quantization level is selected instead of the temporary quantization output corresponding to the transform coefficient.

Another example of the operation of the control determiner will be described.

When the dynamic range of the locally decoded signal of one block exceeds the dynamic range, it is determined which transform coefficient has a large influence of quantization noise. An out-of-range signal indicating a signal of a portion exceeding the dynamic range is orthogonally transformed for each block to obtain a transform coefficient. Among the obtained conversion coefficients, the one with the largest amplitude is obtained.

When an overflow occurs, a positive conversion coefficient having the largest amplitude is searched for. Instead of the provisional quantization output corresponding to the transform coefficient, the next lower quantization level is selectively output.

The limitation to the positive transform coefficient is that when the transform coefficient has a negative value, if the control is performed so that the next higher level is selected instead of the temporary quantized output corresponding to the transform coefficient, A positive value will be added to the quantization noise of the coefficient, and for a component close to DC, the quantization noise will be added to the pixel in the further positive direction, and in some cases, overflow is prevented. This is because it will not be possible.

When underflow occurs, a conversion coefficient having the largest amplitude among positive conversion coefficients is searched for. Control is performed so that the next higher quantization level is selectively output instead of the temporary quantization output corresponding to the transform coefficient. The limitation to the positive transform coefficient is that when the transform coefficient has a negative value, when the control is performed so that the next lower level is selected instead of the temporary quantized output corresponding to the transform coefficient, As for the quantization noise, a negative value is added, and for a component close to DC, the quantization noise is added to the pixel in a more negative direction, and underflow can be prevented in some cases. Because it will disappear.

A second example according to the present invention will be described with reference to FIG.

In the example shown in FIG. 1, the adaptive quantizer 3 obtains a temporary local decoded signal, whereas in this example, the quantized prediction error signal Eq is subtracted from the prediction error signal and quantized. The configuration is such that the noise N is obtained (in the illustrated example, the same components as those in the example shown in FIG. 1 are designated by the same reference numerals).

The subtracter 21 subtracts the quantized prediction error signal from the prediction error signal to obtain the quantization noise N, and supplies it to the range determiner 22. In the range determiner 22, when the input signal X and the quantization noise N are added by the 8-bit adder,
A provisional local decoded signal Y is obtained.

The comparison judgment as to whether the dynamic range is exceeded or not is made by using a 9-bit adder with the input signal X and the quantization noise N.
When adding and and looking at the upper 2 bits of the 9-bit output,
It is possible to determine whether the temporary local decoded signal exceeds the dynamic range. That is, the input signal X (-128 to
If the quantization noise N is added to 127) and the dynamic range of 8 bits is exceeded, overflow or underflow will occur, and the upper 2 bits will be “01”.
In case of (128 or more), overflow has occurred,
In the case of "10" (-129 or less), underflow has occurred.

Another specific example of the adaptive quantizer will be described with reference to FIG.

In the illustrated example, the same components as those of the adaptive quantizer shown in FIG. 1 are designated by the same reference numerals.
In the illustrated example, the determination controller 32 performs control in consideration of the magnitude of the quantization noise Nt added to the transform coefficient by the quantizer 10 in addition to the transform coefficient of the out-of-range signal.

The subtractor 31 subtracts the quantized transform coefficient from the transform coefficient supplied from the orthogonal transformer 2 to obtain quantization noise and supplies it to the decision controller 32. Judgment controller 32
Is the transform coefficient of the out-of-range signal and the quantization noise N of the transform coefficient.
The quantization step selection control is performed based on the information of t. For 64 types of transform coefficients, it is determined that the quantization noise due to the coefficient of the two products has a large effect on the overflow or underflow of the temporary local decoded signal, and the temporary quantum of the corresponding transform coefficient is determined. Control is performed so as to select a quantization level one level up or one level down instead of the quantization output.

If the corresponding quantization noise is written beforehand in the ROM (read-only memory), the ROM alone does not require the subtractor, and if it is shared with the ROM of the quantizer, it becomes H.
/ W configuration becomes simple.

Still another specific example of the adaptive quantizer will be described with reference to FIG.

Although the illustrated example is almost the same as the configuration shown in FIG. 3, in this example, in the subtractor 31, the temporary coefficient output from the selector 11 from the transform coefficient supplied from the orthogonal transformer 2 is used. The quantization output is subtracted to obtain the quantization noise. When the selector 11 selects an alternative temporary quantization level according to the control signal, the temporary quantization output changes. With the configuration of the illustrated example, the selected temporary quantized output is obtained, and accurate transform coefficient quantization noise is obtained.

Although different quantization characteristics may be prepared for each transform coefficient, the control becomes complicated. For example, there is a method of dividing the DC component quantization characteristic for intra-frame encoding and other transform coefficients. Then, the same quantization characteristic is applied in a predetermined range (macroblock).

The following method is used as another method. In the high frequency component, the component of the transform coefficient becomes small, so that it is visually coarse and quantized to make it inconspicuous, and the gain is increased in advance by bit shifting etc. according to the transform coefficient, and then quantized with the same quantization characteristic. . This equivalently coarsely quantizes the transform coefficients of the high frequency components.

When each quantization level variable length coding (entropy coding) is performed, if a variable length code corresponding to the frequency of occurrence of each level is used, efficient coding can be performed even if the number of levels increases. Although possible, the limitation of the number of quantization levels is necessary for efficient coding when a large amount of information is generated in the scene chain and too much information is generated.

[0074]

As described above, according to the present invention,
Since the transform coefficient of the orthogonal transform can be quantized by using the half of the quantization characteristic that the dynamic range of the quantizer is 1 bit smaller than the conventional one, it is possible to reduce the number of bits for coding the quantized output, and to improve the efficiency. There is an effect that general coded transmission can be performed.

Further, according to the present invention, when the prediction difference signal of the predictive coding method is orthogonally transformed and the transform coefficient is quantized and coded and transmitted, the dynamic range of the quantization characteristic can be improved with a small number of bits, and the transient response characteristic can be improved. Can be good.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a first example of an adaptive quantization method for orthogonal transform coding according to the present invention.

FIG. 2 is a block diagram illustrating a second example of an adaptive quantization method for orthogonal transform coding according to the present invention.

FIG. 3 is a block diagram showing another example of the adaptive quantizer shown in FIG. 1.

4 is a block diagram showing still another example of the adaptive quantizer shown in FIG. 1. FIG.

FIG. 5 is a block diagram for explaining conventional inter-frame prediction orthogonal transform coding.

FIG. 6 is a block diagram for explaining DPCM (predictive coding) using conventional adaptive quantization.

[Explanation of symbols]

1,21 Subtractor 2 Orthogonal transformer 3 Adaptive quantizer 4 Code converter 7 Predictor 10 Quantizer 11 selector 12.5 Inverse orthogonal transformer 13,6 adder 15,22 Range judgment device 16 Orthogonal transformer 17,32 Control decision device 18 Output SW

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03M 7/38 H04N 7/32

Claims (6)

(57) [Claims] 1. The same dynamic range as the input signal
Transform obtained by orthogonal transforming the prediction error signal for each block
When the coefficient is quantized and encoded, the transform coefficient is blocked.
Quantization is performed for each
Depending on the quantized prediction error signal obtained by inverse orthogonal transform of the force
To obtain a temporary local decoded signal and the temporary local decoded signal
The temporary local decoded signal compared to the dynamic signal.
If the dynamic range is exceeded, the dynamic range will be exceeded.
The conversion coefficient obtained by orthogonally converting the obtained signal
Output method that adaptively quantizes and outputs as quantized output
A stage, said output means and said quantized prediction error signal
The prediction signal obtained based on the temporary quantized output and the
Modular addition in the dynamic range and the temporary local restoration
Orthogonal transform code characterized by obtaining the signal
Adaptive quantization method for optimization. 2. The same dynamic range as the input signal
Transform obtained by orthogonal transforming the prediction error signal for each block
When the coefficient is quantized and encoded, the transform coefficient is blocked.
Quantization is performed for each
Depending on the quantized prediction error signal obtained by inverse orthogonal transform of the force
To obtain a temporary local decoded signal and the temporary local decoded signal
The temporary local decoded signal compared to the dynamic signal.
If the dynamic range is exceeded, the dynamic range will be exceeded.
The conversion coefficient obtained by orthogonally converting the obtained signal
Output method that adaptively quantizes and outputs as quantized output
The output means has a step from the prediction error signal.
Quantization noise is obtained by subtracting the child prediction error signal
The temporary local decoded signal is obtained by adding the input signal to noise.
Adaptation for orthogonal transform coding characterized by being obtained
Quantization method. 3. The same dynamic range as the input signal
Transform obtained by orthogonal transforming the prediction error signal for each block
When the coefficient is quantized and encoded, the transform coefficient is blocked.
Quantization is performed for each
Depending on the quantized prediction error signal obtained by inverse orthogonal transform of the force
To obtain a temporary local decoded signal and the temporary local decoded signal
The temporary local decoded signal compared to the dynamic signal.
If the dynamic range is exceeded, the dynamic range will be exceeded.
The conversion coefficient obtained by orthogonally converting the obtained signal
The adaptively quantizes output hands to output as the quantization output
And outputting the quantized prediction error signal to the quantized prediction error signal.
Accordingly, the temporary local decoded signal is obtained and the input signal and the
The temporary local decoded signal is compared by comparing with the temporary local decoded signal.
If the dynamic range is exceeded, the temporary amount
The quantization level next to the temporary quantized output is used instead of the childized output.
Means for outputting the temporary quantized output as an alternative
And repeatedly executing the first means to perform the temporary local decoding.
Temporary quantized output where the signal does not exceed the dynamic range
An orthogonal transformation characterized in that it has a second means for obtaining a force.
Adaptive quantization method for transcoding. 4. The same dynamic range as the input signal
Transform obtained by orthogonal transforming the prediction error signal for each block
When the coefficient is quantized and encoded, the transform coefficient is blocked.
Quantization is performed for each
Depending on the quantized prediction error signal obtained by inverse orthogonal transform of the force
To obtain a temporary local decoded signal and the temporary local decoded signal
The temporary local decoded signal compared to the dynamic signal.
If the dynamic range is exceeded, the dynamic range will be exceeded.
The conversion coefficient obtained by orthogonally converting the obtained signal
Output method that adaptively quantizes and outputs as quantized output
A signal obtained by performing inverse orthogonal transform on the temporary quantized output
From the temporary local decoded signal to obtain the input signal and the temporary
Compared with the local decoded signal, the temporary local decoded signal is
If the dynamic range is exceeded, the dynamic range
A signal that has undergone orthogonal transformation of a signal that exceeds
The tentative amount according to the quantization noise generated by the quantization output of
Instead of the child output, the quantization level next to the temporary quantization output
Means for outputting the temporary quantized output as an alternative
And repeating the first means to repeat the temporary local decoding signal.
Signal is a temporary quantized output that does not exceed the dynamic range
And a second means for obtaining
Adaptive quantization method for encoding. 5. The same dynamic range as the input signal
Transform obtained by orthogonal transforming the prediction error signal for each block
When the coefficients are quantized and encoded, the dynamic range
The modulo subtraction of the predicted signal from the input signal
First means for obtaining a prediction error signal, and the prediction error signal
Is orthogonally transformed for each block and the transform coefficient is output.
2 means and the above-mentioned change according to a predetermined quantization characteristic.
Quantize the substitution coefficient block by block to obtain a temporary quantized output.
Together with the temporary quantized output obtained by inverse orthogonal transform
Said input signal to obtain a local decoded signal of the provisional using the conversion signal
And the temporary local decoded signal as compared with the temporary local decoded signal.
If the number exceeds the dynamic range,
It is obtained by orthogonally transforming the signal of the part exceeding the Mick range.
Selected variable as a result of performing selection control according to the converted signal
Instead of the temporary quantized output corresponding to the replacement coefficient,
Outputs the next lower quantization level as an alternative temporary quantization output.
The temporary local decoded signal is within the dynamic range.
To obtain the quantized output by performing the selection control until
And means for converting the quantized output into a transmission line code.
Signal conversion means and quantization by performing inverse orthogonal transform on the quantized output
Fourth means for obtaining a prediction error signal, the prediction signal and the
Quantized prediction error signal is added locally by modulo operation
A fifth means for obtaining a decoded signal, and
And a fifth means for obtaining the predicted signal.
An adaptive quantization method for orthogonal transform coding. 6. The adaptive quantizing method for orthogonal transform coding according to claim 5 , wherein the third means, in addition to the transform signal in the selection control, has a magnitude of quantization noise of the transform signal. An adaptive quantization method for orthogonal transform coding, which is characterized in that information representing is used.