JPH11196418A - Video signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an appropriately contour-corrected video signal by appropriately performing contour correction while controlling the degree of contour correction corresponding to the degree of quantization in image compression, and lowering the degree of contour correction at a border part composed of block/macro block units. SOLUTION: Video data are sent to a transmission buffer 10, and audio and output data are respectively outputted to an audio output terminal 13 and a text data signal output terminal 14. Next, a contour correct signal is generated by a contour correct signal generator 17 by sampling the specified frequency of a contour pre-corrected video signal, which is inputted from an information source decoder 12, through a secondary differentiation circuit. Then, the border of required macro block units is detected based on encoding control data by an encoding data operating part 16. On that border, a signal is outputted for lowering a gain in gain control based on the degree of a code amount. Thus, a luminance signal and a color difference signal are corrected on the border of blocks or macro blocks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the field of video signal processing technology, and particularly to compression and compression of digital video signals.
It belongs to the technical field of a signal processing device for performing expansion.

[0002]

2. Description of the Related Art Conventionally, when a video signal is transmitted or recorded in a recording device, a compression process is performed on a digitized signal in order to shorten a transmission time or increase a recording time, and then transmit or convert the signal. A method is used in which recording is performed and decompression is performed during reproduction.

[0003] When thinning data such as quantization is performed during the compression / expansion processing of the video, the outline of the image is blurred due to the lack of high frequency components and the image quality is deteriorated.
There is a process of performing contour correction after image compression / expansion processing and correcting image contours to prevent image degradation.

However, in such contour correction, the frequency at which the contour is emphasized by the contour correction circuit and the degree of contour enhancement are constant irrespective of the degree of quantization. In this case, it is necessary to keep the amount of data after compression to a fixed value or less.

In order to keep the data amount of the compressed image constant, a method of adjusting the data amount by changing the degree of quantization to a variable speed has been adopted.

[0006] Generally, an image having a complicated content or a moving image having a fast motion is coded at a high bit rate (a degree of quantization), while an image having a simple content or an image having a small motion has a low bit rate. .

In this case, the ambiguity of the contour and the frequency component of noise generated by the quantization change depending on the degree of quantization.

Therefore, there is a problem that proper contour correction cannot be performed depending on the degree of quantization, and in some cases, noise is emphasized by performing contour correction, thereby deteriorating image quality.

As described in Japanese Patent Application Laid-Open No. 9-81104, a frequency at which a contour is enhanced and a gain of a contour correction signal are controlled in accordance with a degree of quantization by controlling a microcomputer by inputting a digital video signal. However, this method also emphasizes block-like noise at the boundary between a block that is a unit when performing orthogonal transform (DCT) and a macroblock that is a unit for frame prediction and field prediction, and this method requires contour correction. There is a problem that image quality is deteriorated.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in view of the fact that noise is emphasized at boundaries between image processing units such as blocks or macroblocks involved in digital video signal processing by contour correction. It is a technical object to prevent image quality deterioration due to the above.

[0011]

According to the present invention, there is provided a video signal processing apparatus for performing discrete cosine transform for each signal processing unit, correcting the contour of a compressed digital video signal, and reproducing. Detecting means for detecting the boundary of the signal processing unit and gain control means for controlling the gain of the video reproduction signal, wherein the gain is controlled by the gain control means at the boundary of the signal processing unit detected by the detecting means. It is characterized by lowering.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a video signal processing apparatus according to the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of a video signal processing apparatus according to the present invention. This video signal processing device
The video signal is compressed and recorded on the storage medium by the encoder unit composed of the components (1) to (8), and (11) to (1)
The recorded data is decompressed and reproduced by the decoder unit constituted by the component 7).

In FIG. 1, (1) is a video input terminal to which a digitized video signal is input.

An information source encoder (2) performs discrete cosine transform (DCT), quantization, motion compensation, and bidirectional prediction on a digital video signal.

A format generator (3) performs hierarchical structure coding and variable length coding.

(4) is a transmission buffer, which comprises a memory for keeping the amount of transmission data constant.

Reference numeral (5) denotes a system multiplexing encoder for synchronously multiplexing voice data, text data, and coding control data.

Reference numeral (6) denotes an audio input terminal for inputting a digital audio signal to the system multiplexing encoder (5).

Reference numeral (7) denotes a text information input terminal, which inputs a video of text data to the system multiplexing encoder (5).

An encoding controller (8) controls the encoding speed based on the complexity of the video contents and the area and speed of the moving part.

(9) is a system multiplex decoder, which separates audio data, text data and encoding control data.

(10) is a reception buffer, which comprises a memory for temporarily storing received data.

Reference numeral (11) denotes a format decoder which performs hierarchical structure decoding and variable length decoding of output data of the reception buffer (10).

An information source decoder (12) converts the output data of the format decoder (11) into inverse DCT, inverse quantization,
Performs reverse motion compensation and reverse bidirectional prediction.

An audio signal output terminal (13) outputs an audio signal separated and output from the system multiplexing decoder (9).

(14) is a text signal output terminal,
A text signal separately output from the system multiplexing decoder (9) is output.

Reference numeral (15) denotes an encoding control data output terminal, which outputs the encoding control data separated and output from the system multiple duplication unit (9).

Reference numeral (16) denotes an encoded data arithmetic unit, which outputs a signal for decreasing the gain of the gain control based on the encoded control data.

(17) is a contour correction signal generator,
A specific frequency is extracted by the next differentiating circuit.

(18) is a gain controller,
Based on the output result of the encoding control data operation unit (16),
The gain of the contour correction signal is controlled.

A delay circuit (19) delays the input signal and matches the phase with the contour correction signal output from the gain controller (18).

Thus, the encoder units (1) to (8)
By the following processing, the video data is synchronized with the audio data, the text data, and the encoded control data, and is recorded on the storage medium.

When a digital video signal is input to the video input terminal (1), the information source encoder (2) divides the video signal into blocks (for example, 48 blocks), performs DCT conversion, and converts the value of the spatial coordinates into a frequency. Convert to

Further, the coefficients converted into the frequency components by the DCT by the quantization are compressed.

If the video signal is a moving image, motion detection and motion compensation frame prediction are performed.

That is, the two frames to be transmitted are divided into blocks, the consistency of each block is taken in consideration of the passage of time, the distance in the moving direction is expressed as a motion vector, and the previously transmitted frame is used. Then, the current frame is predicted by shifting by the newly moved amount, and only the prediction error is sent.

Next, hierarchical format coding and variable length coding (VLC) are performed by the format generator (3).

The signal is written into the transmission buffer (4), and is synchronized with the audio data, text data and encoding control data by the system multiplex encoder (5), and is recorded on the storage medium.

The encoding control data is information used for the above-mentioned hierarchical structure encoding, variable length encoding or compression of the video signal, and the decoding section decodes the video data based on this data. . Specifically, it is information such as the number of vertical and horizontal pixels of the image, the DCT coefficient, the quantization size of the macroblock or block, the position of the macroblock of the image, and the like.

Next, when reproducing the video data recorded on the storage medium, the following processing is performed by the decoder units (11) to (17).

First, the system multiplex decoder (9)
Voice data, text data and encoding control data are separated.

The video data is sent to the transmission buffer (10), and the audio data and output data are output to the audio output signal terminal (13) and the text data signal output terminal (14), respectively.

The output of the transmission buffer (10) is subjected to hierarchical structure decoding and variable length decoding by a format decoder (11).

Further, the information source decoder (12) performs inverse DCT, inverse quantization and inverse motion compensation based on the encoded control data.

A contour correction signal generator (17) extracts a specific frequency from a video signal before contour correction input from the information source decoder (12) by a secondary differentiating circuit to generate a contour correction signal.

The generated contour correction signal is input to a gain controller (18).

The gain controller (18) controls the gain of the next contour correction signal based on the output result of the encoding control data calculator (16).

Based on the coding control data, the coded data arithmetic unit (16) is a block composed of 8 pixels horizontally and 8 pixels vertically and 16 blocks horizontally and 16 pixels vertically arranged two each in the horizontal and vertical directions. The boundary of the unit of the macro block of the pixel is detected.

FIG. 2 shows the relationship between pixels on one screen and macroblocks.

At the boundary, a signal for decreasing the gain of the gain control based on the code amount is output.

Therefore, the gain controller (1)
In 8), the luminance signal and the color difference signal are corrected at the boundary of the block or the macroblock and output.

Further, the video signal before contour correction expanded by the information source decoder (12) is subjected to a contour correction signal generator (17) and a gain controller (18) by a delay circuit (19).
Is delayed by the same amount as the delay amount of the signal generated in step (1), and the phase is matched with the contour correction signal output by the gain controller (18).

Thereafter, the adder (20) adds the contour correction signal output from the gain controller (18) and the video signal before contour correction whose phase has been matched by the delay circuit (19), and outputs it as a video signal. .

Thus, according to the degree of the coding amount,
It is possible to obtain a video signal whose contour is appropriately corrected by controlling the boundary portion in units of blocks and macroblocks.

[0056]

As described above, according to the present invention, the degree of contour correction is controlled in accordance with the degree of quantization of image compression, and appropriate contour correction is carried out. By reducing the degree of contour correction, it is possible to obtain a video signal whose contour has been appropriately corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram of a video signal processing apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between pixels on one screen and macro blocks.

[Explanation of symbols]

 1. Video signal input terminal 2. Information source encoder 3. Format generator 4. 4. Transmission buffer 5. System multiplex encoder 6. Audio signal input terminal 7. Text signal input terminal 8. Coding controller System multi-duplication unit 10. Receive buffer 11. Format decoder 12. Information source decoder 13. Audio data signal output terminal 14. Text signal output terminal 15. Encoding control data output terminal 16. Encoded data arithmetic unit 17. Contour correction signal generator 18. Gain controller 19. Delay circuit 20. Adder 21. Video signal output terminal after contour correction

Claims (1)

[Claims] 1. A video signal processing apparatus for performing contour correction and reproducing a digital video signal which has been subjected to discrete cosine transform for each signal processing unit, comprising: detecting means for detecting a boundary between the signal processing units; Gain control means for controlling the gain of the signal, wherein the gain control means reduces the gain of the video reproduction signal at the boundary of the signal processing unit detected by the detection means. Processing equipment.