JP2762712B2 - Encoding device and decoding device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the amount of data required to transmit and store image signals in order to reduce communication costs and extend recording time. And an encoding device and a decoding device.

2. Description of the Related Art FIG. 7 shows a block diagram of a conventional encoding device. In the figure, 1 is an input signal, 2 is an orthogonal transformer that outputs an orthogonal transformation signal 3, 4 is a quantizer that quantizes the orthogonal transformation signal 3 and outputs a quantization value 5, and 6 is a quantization step selection signal. , 7 is a selector for selecting one of the quantized values 5 and outputting it as a quantized value 8, and 9 is an encoder for encoding the quantized value 8 and outputting a coded signal 10.

The operation of the conventional encoding apparatus configured as described above will be described below. The input signal 1 is orthogonally transformed by the orthogonal transformer 2. In general, the orthogonally transformed signal has a bias in the energy distribution as compared with the input signal 1, and it is supported by information theory that if the bias occurs, the data amount can be easily reduced. Therefore, the orthogonal transform is a method for reducing the data amount. Often used. In particular, DCT (discrete cosine transform), which is a component corresponding to frequency, is known as one of orthogonal transforms with the highest data amount reduction efficiency. The orthogonally transformed data is quantized by the quantizer 4, and the importance of the orthogonally transformed component is corrected. That is, quantization is performed such that the data amount of components having visually low importance is further reduced. From the quantized values 5 calculated by the quantizers 4 as described above, the one indicated by the constant selection signal 6 is selected by the selector 7. The constant selection signal is controlled by the buffer occupancy or the like. If the average data amount is large, the quantization value 5 that reduces the data amount is selected, and if the average data amount is small, the quantization value 5 that increases the data amount is selected. . One of the quantized values 5 of the plurality of quantizers 4 selected in this manner is converted by the encoder 9 into a quantization step selection signal 6.
And is encoded with The encoder 9 performs fixed-length coding or variable-length coding.

FIG. 8 shows a block diagram of a conventional decoding device. In the figure, reference numeral 10 denotes an encoded signal encoded by the encoding device, 20 denotes a decoder that outputs a decoded signal 21 obtained by decoding the encoding performed by the encoder 9, and 23 denotes the decoder. Inverse quantization value obtained by inverse quantization in the quantization step of the quantizer 4
24 is an inverse quantizer that outputs 24, 22 is a decoded version of the quantization step selection signal 6, and 27 is an inversely quantized value 24 that is inversely quantized in the quantization step selected by the encoding device.
Is a selector for selecting and outputting as an inverse quantization value 28, and an orthogonal transformer 29 for performing an inverse transformation of the orthogonal transformer 2 in the encoding device and outputting a reproduced signal 30.

The operation of the conventional decoding device configured as described above will be described below. The decoder 20 is a decoding means of the encoder 9, and the inverse quantizers 23 are inverse quantizers having the same quantization steps as the quantizer 4, respectively.
The orthogonal transformer 29 is an inverse orthogonal transform of the orthogonal transformer 2.
Therefore, the encoded signal 10 encoded by the encoding device is correctly decoded by the above configuration.

Problems to be Solved by the Invention However, in the conventional encoding apparatus and decoding apparatus as described above, quantizers and inverse quantizers are required by the number of possible values of the quantization step selection signal 6. . Therefore, a large number of quantizers and inverse quantizers are required to perform fine data amount control, and the hardware scale becomes large. Conversely, if the number of quantizers and inverse quantizers is reduced, fine data amount control cannot be performed, which causes deterioration in image quality.

Means for Solving the Problems The encoding device of the present invention divides an input signal into blocks,
Orthogonal transform means for orthogonally transforming each block, quantizing means for dividing the orthogonally transformed block into at least two fixed regions, and performing scalar quantization for each region in the same quantization step; Parameter control means for controlling the value of the quantization step, and coding means for performing fixed-length coding or variable-length coding of the scalar quantization value of the quantization means, wherein the quantization means comprises a plurality of quantization steps. And a configuration in which one quantization step is selected from the plurality of quantization steps for each fixed region to perform quantization.

Operation In the present invention, the region is divided into n (n is 2)
Above integer) and having m quantizers
By creating ^mn combinations and selecting a data set to be encoded by the encoding means from the combinations, it is possible to control m or more finer data amounts than the conventional m with the same number m of quantizers. Accordingly, there is little fluctuation in image quality, and the image quality is improved on average compared with the conventional encoding device and decoding device.

Embodiment FIG. 1 (a) is a block diagram of an encoding apparatus according to a first embodiment of the present invention. In the figure, 1 is an input signal, 2 is an orthogonal transformer that outputs an orthogonal transform signal 3, 4 is a quantizer that outputs a quantized value 5 obtained by quantizing the orthogonal transform signal 3, 11 is a compression parameter control signal, 12 is a parameter controller that outputs a control signal 13 for switching the quantization value 5, 14 is a selector that selects one of the quantization values 5 for each component of the orthogonal transform and outputs it as a quantization value 8, 9 Is an encoder that encodes the quantized value 8 and outputs an encoded signal 10.

The operation of the encoding apparatus of the present invention configured as described above will be described below. The input signal 1 is orthogonally transformed by the orthogonal transformer 2. The orthogonally transformed data is quantized by the quantizer 4. From the quantized values 5 calculated by the quantizers 4 as described above, the one indicated by the control signal 13 for each component of the orthogonal transform is selected by the selector 14.
The control signal 13 is generated from the compression parameter control signal 11 for each area of the orthogonal transform block. FIG. 2 shows an example of region division of the orthogonal transform block. The components are arranged such that the upper left corresponds to a low frequency and the lower right corresponds to a high frequency. The quantization step for each region
T ₁ , T ₂ , T ₃ , and T _4, and L ₁ and L ₂ (L ₁ > L ₂ ) for each area
There are five possible combinations that satisfy the condition of T ₁ ≧ T ₂ ≧ T ₃ ≧ T ₄ , and the quantization steps are shown in FIGS. 3 (a ₁ ) to (a). _{See 5} ).

The control signal 13 selects a quantization value 5 corresponding to the quantization step T _i (1 ≦ i ≦ 4) of the position of the orthogonally transformed component.
Order to select at 14. Thus although the pattern of five types is performed in quantization of two types of L ₁ and L ₂ each component,
Conventional method (FIG. 3 _{(b 1) ~ (b 5} )) In the quantization of five different for each component is required. Therefore, in the present method, the number of selection candidates of the selector 14 can be significantly increased without increasing the number of quantizers. Switching of the quantization step is used to increase or decrease the amount of data. To adjust the increase or decrease, finer control can be performed when the number of candidates switched by the selector 14 is larger. As a result, visually favorable image quality can be obtained with little local fluctuation in image quality. The control signal 13 is encoded by the encoder 9 together with the selected quantization value 8. The encoder 9 performs fixed-length coding or variable-length coding.

As described above, according to the present embodiment, the orthogonally transformed data is divided into several regions by using the parameter controller 12 and the selector 14, and fine data is obtained by a combination of quantization steps for each divided region. By performing the amount control, the fluctuation of the image quality can be reduced. In the case where the quantizer 4 is implemented by a multiplier in FIG. 1A, the number of quantizers can be reduced to one by switching the multiplier. FIG. 1 (b) shows a block diagram.

FIG. 4 is a block diagram of an encoding apparatus according to another embodiment of the present invention. In the figure, 1 is an input signal, 2 is an orthogonal transformer that outputs an orthogonal transformation signal 3, 11 is a compression parameter control signal, 12 is a parameter controller that outputs the number of bits 13 for shifting the orthogonal transformation output 3, and 15 is A shift register 9 outputs a quantized value 8 obtained by shifting the orthogonal transform signal 3 by the number of bits 13, and 9 denotes an encoder that encodes the quantized value 8 and outputs an encoded signal 10.

The operation of the encoding apparatus of the present invention configured as described above will be described below. In the embodiment of FIG. 4, all the quantization steps in the embodiment of FIG. If the quantization steps are all powers of two, the quantization can be performed only by the shift register,
Hardware is simplified. The input signal 1 is the orthogonal transformer 2
Are orthogonally transformed. The number of bits 13 to be shifted for each area is generated from the parameter control signal 11, and the shift register 15
Shifts the orthogonal transform signal 3 by the number of bits 13. The shifted quantized value 8 is encoded by the encoder 9 together with the parameter control signal.

As described above, according to the present embodiment, the orthogonally transformed data is divided into several regions by using the parameter controller 12 and the shift register 15 and fine data is determined by a combination of the number of shifts for each divided region. By performing the amount control, the fluctuation of the image quality can be reduced.

FIG. 5A is a block diagram of a decoding device according to the first embodiment of the present invention. In the figure, reference numeral 10 denotes a coded signal coded by the coding apparatus, 20 denotes a decoder that outputs a decoded signal 21 obtained by decoding the coding performed by the coder 9 of FIG. 1, Reference numeral 23 denotes an inverse quantizer which performs inverse quantization at the quantization step of the quantizer 4 shown in FIG. 1 and outputs an inversely quantized value 24. Reference numeral 22 denotes a signal obtained by decoding the compression parameter control signal shown in FIG. , 31 are parameter controllers for outputting a control signal 32 for selecting, for each region, an inversely quantized value 24, which has been inversely quantized in the quantization step selected by the encoding apparatus of FIG. 1, and 27 is a control signal 27. A selector 29 for switching the inverse quantization value 24 for each region and outputting it as an inverse quantization value 28. A selector 29 performs an inverse transformation of the orthogonal transformer 2 in the encoding apparatus of FIG.
Are output from the orthogonal transformer.

The operation of the decoding apparatus of the present embodiment configured as described above will be described below. This embodiment is a decoding device for the encoding device of the embodiment shown in FIG. The coded signal 10 is decoded by a decoder 20 into a decoded signal 21 and a compression parameter control signal 22. Decoded signal 21 is inverse quantizer
Dequantized at 23. The parameter controller 31 controls the control signal for each region of the orthogonal transformation signal from the compression parameter control signal 22.
The control signal 32 is the same as the control signal 13 used for that area by the selector 14 of the encoder of FIG. In the selector 33, the inverse quantization value 24 is selected for each region by the control signal 32, and the quantization value 28 is formed. Finally, the orthogonal transformer 29 performs an orthogonal transformation, which is an inverse transformation of the orthogonal transformer 2 of FIG.
Generate

As described above, according to the present embodiment, the parameter controller 31
Using the selector 33, the orthogonally transformed data is divided into several regions, and fine data amount control is performed by a combination of quantization steps for each of the divided regions to reduce fluctuations in image quality. When the inverse quantizer 23 is implemented by a multiplier in FIG. 5 (a), the number of quantizers can be reduced to one by switching the multiplier. FIG. 5 (b) shows a block diagram.

FIG. 6 is a block diagram of a decoding device according to the first embodiment of the present invention. In the figure, reference numeral 10 denotes an encoded signal encoded by the encoding device, 20 denotes a decoder that outputs a decoded signal 21 obtained by decoding the encoding performed by the encoder 9, and 22 denotes a decoder. 5 is a decoded version of the compression parameter control signal shown in FIG. 5, and 31 is a shift number for shifting the decoded signal 21.
Parameter controller that generates 32, 28 is shift register 34
The inverse quantized value 29 shifted by the above is an orthogonal transformer which outputs the reproduction signal 30 by performing an inverse transformation of the orthogonal transformer 2 in the encoder shown in FIG.

The operation of the decoding apparatus of the present embodiment configured as described above will be described below. This embodiment is a decoding device for the coding device of the embodiment shown in FIG. The coded signal 10 is decoded by a decoder 20 into a decoded signal 21 and a compression parameter control signal 22. The parameter controller 31 generates a control signal 32 for each area of the orthogonal transform signal from the compression parameter control signal 22, and this control signal 32 is used by the shift register 15 of the encoding apparatus shown in FIG. This is the same as the shift number 13 used. Shift register 34
In the above, an inverse quantization value 28 in which the decoded signal 21 is shifted for each region by the shift number 13 is formed. Finally, the orthogonal transformer 29 performs an orthogonal transformation, which is an inverse transformation of the orthogonal transformer 2 shown in FIG. 4, on the inverse quantization value 28 to generate a reproduction signal 30.

As described above, according to the present embodiment, the parameter controller 31
Using the shift register 34, the orthogonally transformed data is divided into several regions, and fine data amount control is performed by a combination of the number of shifts for each of the divided regions, so that a change in image quality can be reduced.

In this embodiment, the quantization is performed using either the quantizer or the shift register. However, the quantizer and the shift register are connected in cascade to reduce the number of quantizers or to reduce the number of powers of two. Data amount control using a fine quantization level may be performed. Similarly, the inverse quantizer and the shift register can be cascaded.

Effect of the Invention As described above, according to the present invention, it is possible to perform fine data amount control without increasing the number of quantizers,
Visually favorable image quality with little local fluctuation can be obtained, and its practical effect is great.

[Brief description of the drawings]

1 (a) and 1 (b) are block diagrams of an encoding apparatus according to an embodiment of the present invention, FIG. 2 is a diagram of block area division, FIG. 3 is a diagram of a change in quantization level due to block division, FIG. 4 is a block diagram of an encoding apparatus according to another embodiment of the present invention, FIGS. 5A and 5B are block diagrams of a decoding apparatus according to one embodiment of the present invention, and FIG. FIG. 7 is a block diagram of a conventional encoding device, and FIG. 8 is a block diagram of a conventional decoding device. 4 Quantizer, 12, 31… Parameter controller, 14, 33…
... selector, 15,34 ... shift register, 23 ... inverse quantizer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Journal of the Institute of Television Engineers of Japan, 39 [10] (1985) Aizawa et al. 920-925 IEEE Trans. Commun. Vol. COM-32 [3] (1984) 225-232 IEICE Technical Report, IE85-59, P.E. 105-112 IEEE ICASSP (1989) 1890-1893 1988 IEICE Spring National Convention, D-115 (58) Fields studied (Int.Cl. ⁶ , DB name) H04N 7/24-7/68 H04N 1/41-1/419

Claims (6)

(57) [Claims] 1. An orthogonal transformation means for dividing an input signal into blocks and orthogonally transforming each block, and dividing the orthogonally transformed blocks into at least two fixed regions to perform the same quantization step for each region. And a parameter control means for controlling the value of the quantization step, and a coding means for performing fixed-length coding or variable-length coding on the scalar quantization value of the quantization means. Wherein the quantizing means has a plurality of quantization steps, and performs quantization by selecting one quantization step from the plurality of quantization steps for each of the fixed regions. Device. 2. A method as claimed in claim 1, wherein said quantizing means comprises a cascade of quantizers having only powers of two and quantizers having quantization steps other than powers of two.
An encoding device according to claim 1. 3. An input signal is divided into blocks, orthogonally transformed for each block, and the orthogonally transformed block is divided into at least two fixed regions, and scalar-quantized by the same quantization step for each region. A fixed-length coding or a variable-length coding of the scalar-quantized value, comprising a plurality of quantization steps, wherein each of the fixed regions includes a plurality of quantization steps. An encoding method comprising selecting one quantization step and performing quantization. 4. A decoding method which receives a coded signal coded by the coding method according to claim 3 and decodes the fixed-length code or the variable-length code of the coded signal to obtain a decoded signal. Means, inverse quantization means for performing inverse quantization in the quantization step of the scalar quantization performed when encoding the decoded signal for each region, and an inverse quantization value of the inverse quantization means. And an orthogonal transformation means for performing an orthogonal transformation which is an inverse transformation of the orthogonal transformation means performed at the time of the encoding. 5. A quantization means in which an inverse quantizer having only a power of 2 as a quantization step and an inverse quantizer having a quantization step other than a power of 2 are cascaded.
The decoding device according to claim 1. 6. A coded signal coded by the coding method according to claim 3 is input, a variable length code or a fixed length code of the coded signal is decoded, and the decoded signal is converted into each area. Inverse quantization in a quantization step of scalar quantization performed in each encoding, and performing an orthogonal transform, which is an inverse transform of the orthogonal transform, on the inversely quantized dequantized value. The decoding method to use.