JPH06253283A - Data transmitter - Google Patents

Abstract

PURPOSE:To improve the visual characteristic by applying inverse quantization at a decoder with a representative value closer to 0 from its center, converting a time component into a frequency component with respect to the difference between current and preceding picture data for the coding. CONSTITUTION:A coder 1 applies DCT to N difference between current and preceding picture data in the inter mode and an inverse quantizer 106 and an IDCT section 107 convert inverse quantization and frequency component of quantization data into a time component. In the decision of a representative value in the inverse quantizer 106, values closer to zero from a median in input data are selected as representative values. A decoder 2 uses a variable modulation coder 201, an inverse quantization device 202 and an IDCT section 203 to apply variable modulation coding, inverse quantization and IDCT to compressed data and a motion compensation section 205 adds current picture data to preceding picture data subjected to motion compensation to provide an output. Thus, the visual characteristic is improved with simple configuration and the picture quality is enhanced.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a Discrete Cosine Transformation (hereinafter referred to as DCT) for compressing an image in an encoder or a decoder.
The present invention relates to a data transmission device that quantizes or inversely quantizes the coefficient.

[0002]

2. Description of the Related Art Conventionally, in an encoder and a decoder of a data transmission device that compresses an image and transmits data, the quantized data is inversely quantized. When the representative value is determined from, the central value is selected within the range of the quantized input data so that the error with the quantized input data is minimized.

[0003]

However, in the above-mentioned conventional data transmission apparatus, the difference value between the frame / field images is subjected to DCT for image compression, and this D
When the CT coefficient is quantized and dequantized is larger than the true value, that is, when the representative value is positive, the representative value is larger than the true value, and when the representative value is negative, the representative value is true. If it is smaller than the value of, there is a disadvantage that visually noticeable noise is generated and the image quality is deteriorated.

The present invention has been made in view of the above points, and an object thereof is to propose a data transmission apparatus for quantizing or dequantizing DCT coefficients so as to improve visual characteristics and image quality. To do.

[0005]

As shown in FIGS. 1 and 2, for example, a data transmission apparatus of the present invention includes a conversion unit 103 for converting image data from a time component into a frequency component, and an image converted by the conversion unit 103. Quantizing means 104 for quantizing data, and variable length coding means 105 for variable length coding the image data quantized by the quantizing means 104.
And a variable length decoding means 20 for variable length decoding the image data compressed by the encoder 1.
1, dequantizing means 202 for dequantizing the image data variable-length decoded by the variable-length decoding means 201, and image data dequantized by the dequantizing means 202 from frequency components to time components. In the data transmission device including the decoder 2 having the inverse transforming means 203 for performing the inverse transform, the dequantizing means 202 in the demultiplexer 2 is input for quantizing in the quantizing means 104 in the encoder 1. In the range of the obtained data, a value closer to “0” than the central value is used as the representative value for the inverse quantization.

Further, the data transmission apparatus of the present invention comprises a conversion means 10 for converting image data from time components to frequency components.
3, a quantizing means 104 for quantizing the image data converted by the converting means 103, and a dequantizing means 1 for dequantizing the image data quantized by the quantizing means 104.
06, an inverse transforming means 107 for inversely transforming the image data inversely quantized by the inverse quantizing means 106 from a frequency component to a time component, image data inversely transformed by the inverse transforming means 107, and an image to be input next. Subtraction means 111 for subtraction from the data and input to the conversion means 103 as image data
And an encoder 1 having variable length coding means 105 for variable length coding the image data quantized by the quantizing means 104, and variable length decoding the image data compressed in the encoder 1. Variable length decoding means 201, inverse quantization means 202 for inverse quantizing the image data variable length decoded by the variable length decoding means 201, and inverse quantization means 2
In the data transmission apparatus including the decoder 2 having the inverse transforming means 203 for inversely transforming the image data inversely quantized by 02 into the time component from the frequency component, the encoder 1
And the inverse quantization means 106, 202 in the decoder / decoder 2.
Is a range of data input for quantization by the quantization means 104 in the encoder 1, and performs inverse quantization with a value closer to "0" than the central value as a representative value.

Also, in the data transmission apparatus of the present invention, the variable length coding means 105 in the encoder 1 is a Huffman encoder or a run length encoder.

[0008]

According to the present invention described above, when the decoder 2 dequantizes the data compressed by the encoder 1, a value closer to "0" from the center is used as a representative value, and Since it is rounded down and inverse quantization is performed, it is possible to improve visual characteristics and image quality with a simple configuration.

Further, according to the present invention, since the encoder 1 converts the image data of the difference between the current image data and the previous image data from the time component to the frequency component, the visual characteristic is improved. It is possible to improve the image quality.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the data transmission device of the present invention will be described in detail below with reference to FIG.

In the data transmission apparatus of the present invention, in the intra mode, the encoder 1 has the changeover switch 102 selected to the upper side, and the DCT section 103 converts the time component into the frequency component with respect to the inputted frame / field image data. DCT is performed to convert the image data into a quantized value, the resulting coefficient is quantized by a quantizer 104, and a variable length coder 105 applies a variable length code to compress the image data.

In the inter mode, the encoder 1
The changeover switch 102 is selected to the lower side, and the DCT unit 103 performs DCT on the difference value between the current frame / field image data and the previous frame / field image data in order to convert a time component into a frequency component. Here, in order to create and hold the previous frame / field image data, with respect to the data quantized by the quantizer 104, the inverse quantizer 107 and the IDCT unit 108 perform inverse quantization and frequency components on time components. Perform IDCT to convert to. The right side of the changeover switch 108 is selected when the current encoding mode is the intra mode, and the left side is selected when it is the inter mode. As a result, motion detection and motion compensation are performed so that the data is encoded with higher compression, and the data is stored.

Similarly, in the inter mode, the decoder 2
Is the variable length encoder 20 for the compressed data.
1, the inverse quantizer 202 and the IDCT unit 203 perform variable length coding, inverse quantization, and IDCT, respectively, and the lower side of the changeover switch 204 is selected, and the motion compensation unit 205
The current frame / field image data is added to the motion-compensated previous frame / field image data and output.

In such a data transmission device, the inverse quantizer in the inter mode operates as follows. First, in the quantizer 104, the input data is divided into certain widths to determine the quantization level.
As shown in FIG. 2, when the input data is "-7" to "-3", the quantization level is "-1", and when the input data is "-2" to "2", the quantization level is "0"
When the input data is "3" to "7", the quantization level is "1" and the input data is "8" to "1".
When it is "2", the quantization level is "2".

After being quantized in this way, in the inverse quantizer 106, when determining the representative value from the quantization level, it is set to "0" from the central value so that the error with the quantizer is reduced. Choose a close value. For example, the quantization level "-
When the value is "1", the central value "-" from "-7" to "-3"
When "-3" closer to "0" is selected from "5" and the quantization level is "2", the central value "1" of "8" to "12" is selected.
Select "8" closer to "0" than "0".

In this way, when determining the representative value in the inverse quantizer, the value closer to "0" than the central value in the range of the input data to be quantized is used as the representative value. . That is, when the input data includes "0", "0" is the representative value, when the quantized data is positive, the smallest value in the input data is the representative value, and when the quantized data is negative, , The largest value in the input data is selected as the representative value.

Since the quantizer 104 is located in the area for quantizing the DCT coefficient of the difference data of the frame / field image, the inverse quantizer 106 described above dequantizes the DCT coefficient to obtain the visual characteristic. Improvement is planned. Further, according to this example, when the decoder 2 dequantizes the data compressed by the encoder 1, the value closer to “0” from the center is used as a representative value and the other values are truncated. Since the inverse quantization is performed, it is possible to improve visual characteristics and image quality with a simple configuration.

Further, according to the present example, since the encoder 1 converts the image data of the difference between the current image data and the previous image data from the time component to the frequency component, the visual characteristic is improved. Therefore, the image quality can be improved. The above-described embodiment is an example of the present invention, and it goes without saying that various other configurations can be adopted without departing from the scope of the present invention.

[0019]

As described above, according to the present invention, when inversely quantizing data compressed by the encoder by the decoder,
Since a value closer to “0” from the center is used as a representative value and the other values are truncated and inverse quantization is performed, visual characteristics can be improved and image quality can be improved with a simple configuration. Further, according to the present invention, the image data of the difference between the current image data and the previous image data is converted from the time component to the frequency component in the encoder, so that the visual characteristic is improved and the image quality is improved. Can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a data transmission device of the present invention.

FIG. 2 is a diagram for explaining the operation of one embodiment of the data transmission device of the present invention.

[Explanation of symbols]

 1 Encoder 101 Input Terminal 102 Changeover Switch 103 DCT Unit 104 Quantizer 105 Variable Length Encoder 106 Inverse Quantizer 107 IDCT Unit 108 Changeover Switch 109 Motion Detection and Motion Compensation Unit 110 Adder 111 Subtractor 2 Decoding Device 201 Variable length decoder 202 Inverse quantizer 203 IDCT unit 204 Changeover switch 205 Motion compensation unit 206 Adder 207 Output terminal

Claims (3)

[Claims] 1. A conversion means for converting image data from a time component to a frequency component, a quantizing means for quantizing the image data converted by the converting means, and the image quantized by the quantizing means. An encoder having variable-length coding means for variable-length coding data, a variable-length decoding means for variable-length decoding image data compressed by the encoder, and a variable-length decoding means. Dequantizing means for dequantizing the variable length decoded image data, and inverse transforming means for inverse transforming the image data dequantized by the dequantizing means from frequency components to time components In a data transmission device including a decoder, the dequantizing means in the decoding device receives the data input for quantization in the quantizing means in the encoder. In the range, the data transmission apparatus and performing inverse quantization values close to "0" from the value of the center as the representative value. 2. A conversion means for converting image data from a time component to a frequency component, a quantizing means for quantizing the image data converted by the converting means, and the image quantized by the quantizing means. Dequantizing means for dequantizing data, inverse transforming means for inversely transforming the image data dequantized by the inverse quantizing means from frequency components to time components, and inverse transforming means for the inverse transforming means Subtracting means for subtracting the image data from the image data to be input next and inputting the image data to the converting means, and a variable length for variable length encoding the image data quantized by the quantizing means. An encoder having encoding means,
Variable-length decoding means for variable-length decoding the image data compressed in the encoder; dequantizing means for inverse-quantizing the image data variable-length decoded by the variable-length decoding means; And a decoder having an inverse transforming unit for inversely transforming the image data inversely quantized by the inverse quantizer into a frequency component into a time component, wherein the encoder and the decoder are provided. The inverse quantization means in 1 performs inverse quantization with a value closer to "0" than the central value as a representative value in the range of data input for quantization in the quantization means in the encoder. A data transmission device characterized by the above. 3. The data transmission device according to claim 1, wherein said variable length coding means in said encoder is a Huffman encoder or a run length encoder.