JPH0479590A - Moving image encoder - Google Patents

Abstract

PURPOSE:To suppress a quantize noise at an edge part by performing quantization by a value less than that in a quantization step quantizing the same block last time when it is decided that an edge exists by a quantization means, and it is decided that a block is a still block by a motion detecting means. CONSTITUTION:The edge detecting function of an image is attached on the quantization means 3 which performs the inter-compensation frame prediction or in-frame prediction of an input image at every block, and performs the quantization in the processing unit of the block for a predictive error in a constant quantization step. When it is decided that the edge exists exceeding a threshold value to decide the edge, and also, it is decided that the block is the still block by the motion detecting means 7, the quantization means 3 is controlled so as to perform the quantization by the value less than that in the quantization step quantizing the same block last time. Thereby, it is possible to suppress the quantizing noise at the edge part.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a moving picture encoding device that is applied to television signals and is capable of transmitting high-quality images.

Conventional technology In a video encoding device that performs motion compensated inter-frame prediction or intra-frame prediction and then performs quantization, the quantization step is determined depending on the amount of data remaining in the transmission buffer, and the quantization result is converted into a Huffman run-length code. data, and sent it to the transmission buffer, and from the transmission buffer it was output to the line as line data. A video encoding device incorporating this method will be described below with reference to the drawings.

FIG. 5 shows the configuration of a conventional video encoding device.
FIG. 6 shows an example of the distribution of quantization step values in one encoded frame 1/- frame. In FIG. 5, 5 is an input image frame memory for storing input images, 52 is an input image frame memory 5, and the image read out from the 5 input image frame memory and the reproduced image read out from the frame memory 55 (between frames 53 is a quantization circuit that quantizes the calculation result of the calculation unit 52, and 54 is a quantization circuit. An arithmetic unit for performing addition between the quantization result at 53 and the reproduced image or "0" stored in the frame memory 55 and storing a new reproduced image in the frame memory 55; 56 is an input image frame memory It is determined for each block whether or not there is a correlation between the input image 51 and the reproduced image stored in the frame memory 55, and if there is a correlation, interframe coding is performed, and if there is no correlation, the 57 is a coding method determination circuit that controls the coding method selection switch 61 to perform intra-frame coding, and 57 is a circuit for determining each block of the input image stored in the input image frame memory 5 or stored in the frame memory 55. A motion detection circuit 58 determines whether a block at the same position in the reproduced image is a static area or a moving area for each block. A variable length encoding circuit receives the output and creates variable length encoded data, and 59 is a transmission buffer that stores the variable length encoded data created by the variable length encoding circuit 58 and sends it to the transmission path at a constant speed. , 60 is a quantization step transmission line for transmitting the quantization step updated every certain number of blocks according to the residual amount of data in the transmission buffer 59 and driving the quantization circuit 53; 61 is a quantization step transmission line for the encoding method determination circuit 56; This is an encoding method selection switch that selects an encoding method based on judgment. In such a moving image encoding apparatus, as shown in FIG. 6, the quantization step is updated for every fixed number of blocks, and quantization is performed using quantization steps from 01 to Q1.

Problems to be Solved by the Invention However, in the conventional video encoding device described above, the control unit of the quantization step is always a fixed number of blocks, so that the quantization step is performed in order to prevent the transmission buffer 59 from overflowing. When this becomes large, blocks containing edges where the image level changes rapidly are quantized roughly, resulting in a problem in that quantization noise appears conspicuously at the edges.

The present invention solves these conventional problems, and provides an excellent video encoding device that can suppress quantization noise in edge portions by improving the quantization control unit. With the goal.

Means for Solving the Problems In order to achieve the above object, the present invention performs motion compensated inter-frame prediction or intra-frame prediction, and quantizes prediction errors at a constant quantization step within a processing unit of a block. When performing image processing, if the quantization means equipped with an edge detection function of the image within the block determines that an edge exists exceeding the edge determination threshold, and the motion detection means determines that the block is a stationary block. Furthermore, if the amount of data remaining in the transmission buffer is smaller than a certain threshold, quantization is performed using a smaller value than the quantization step used to previously quantize the same block.

Operation The present invention has +7)i as described above, so that it is possible to detect static blocks in which edges are noticeably present using the threshold value for determining edges of the quantizer having an edge detection function and the motion detection means. , when the amount of data remaining in the buffer when quantizing that block falls below a threshold, the quantization means is controlled to perform quantization with a smaller value than the quantization step used to previously quantize the same block. This has the effect of suppressing quantization noise at the edge portion.

EXAMPLES The present invention will be explained below using FIGS. 1 to 4. FIG. 1 shows the configuration of an embodiment of the present invention, and FIG. 2 shows the detailed configuration of the quantization circuit of FIG. 1. FIG. 3 is an explanatory diagram of a method for detecting blocks in which edges appear prominently and finally determining the quantization step, and FIG. 4 is a diagram showing an example of the distribution of quantization steps in one encoded frame.

In Figure 1, 1 is an input image frame memory that stores input images, and 2 is an image read out from the input image frame memory 1 and a reproduced image read out from the frame memory 5 (interframe encoding). case) or “0” (
(in the case of intra-frame encoding), a computing unit 3 calculates the difference between the quantization step transmission line KO, the residual data amount transmission line 1] and the static motion block determination line 12, as will be described later.
It is an edge detection quantization circuit that quantizes the calculation result of the arithmetic unit 2, and as shown in FIG. The final quantization step is determined based on the quantization circuit 3b which quantizes the output of the output by the quantization step from the final quantization step transmission line 3e, and the frequency component transmission line 3d to which the result of the frequency component conversion circuit 3a is transmitted. The final quantization step determining circuit 3c includes a final quantization step determining circuit 3c. 4 is an operation for adding the quantization result in the edge detection quantization circuit 3 and the reproduced image or "0" stored in the frame memory 5, and stores a new reproduced image in the frame memory 5. The unit 6 determines for each block whether or not there is a correlation between the input image in the input image frame memory 1 and the reproduced image stored in the frame memory 5, and if there is a correlation, performs interframe encoding. An encoding method determination circuit 7 is stored in the input image frame memory 1 and controls the encoding method selection switch 13 so as to perform intra-frame encoding when there is no correlation. A motion detection circuit determines whether each block of the input image is a static area or a moving area for each block at the same position of the reproduced image stored in the frame memory 5; A variable length encoding circuit that receives the static motion area information and the output from the edge detection and quantization circuit 3 to create variable length encoded data; 9 stores variable length encoded data created by the variable length encoding circuit 8; 10 is a quantization step transmission line for transmitting quantization steps that are updated every certain number of blocks according to the residual amount of data in the transmission buffer 9; 11 is a transmission line; 12 is a static and moving block determination line through which the determination result of the motion detection circuit 7 is transmitted for each block; 13 is a transmission line for the encoding method determination circuit 6; A coding method selection switch selects interframe coding or intraframe coding for each block based on the judgment; 14 is a prediction error transmission line to which the output of the arithmetic unit 2 is transmitted; 15 is the edge detection quantization circuit 3; This is the quantization result transmission line through which the results are transmitted.

Next, the operation of the above embodiment will be explained. In FIG. 3, among the prediction errors converted by the frequency component conversion circuit 3a of FIG. If the quantization step is unconditionally reduced and quantized finely, the transmission buffer 9 may overflow, so the final quantization step determination circuit 3c is a transmission buffer 9 using the remaining data transmission amount transmission skill ball 1
The residual amount of data and the static motion information based on the static motion block determination line 12 are monitored, and the residual data amount is below a certain threshold,
In addition, when the encoded block is in a static region, the quantization step is determined to be smaller than the value for the same encoded block last time, and the quantization noise of the block where edges are clearly recognized can be reduced. .

In FIG. 4, the quantization step is updated every certain number of blocks, from Ql to Q. When performing quantization with a quantization step of
,Q,is smaller than,Q,1. Q3゜, Q51. Q5
2 indicates that it is quantized. Note that Ql to Q are updated with a fixed number of locks shown in FIG. The manner in which the quantization steps are distributed is shown as an example, and of course the distribution is not limited to this.

Effects of the Invention As is clear from the above embodiments, the present invention performs motion-compensated inter-frame prediction or intra-frame prediction, and quantizes the prediction error at a constant quantization step within a processing unit of a block. In addition, if the quantization means equipped with an edge detection function of the image in the block exceeds the threshold for determining an edge, and the motion detection means determines that the block is a stationary block, the amount of data remaining in the transmission buffer is further reduced. If the value is smaller than a certain threshold, the quantization step is configured to perform quantization with a smaller value than the quantization step used to previously quantize the same block, which can reduce quantization noise in blocks where noticeable edges appear. It has this effect.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing the configuration of a video encoding device in one embodiment of the present invention, FIG. 2 is a schematic block diagram showing the configuration of a quantization circuit in the same embodiment, and FIG. 3 is a schematic block diagram showing the configuration of a quantization circuit in the same embodiment. FIG. 4 is an explanatory diagram of a method for detecting blocks in which edges appear prominently in the final determination of the quantization step, and FIG. Image frame memory, 2... Arithmetic unit, 3... Edge detection quantization circuit, 4... Arithmetic unit,
5... Frame memory, 6... Encoding method determination circuit, 7... Motion detection circuit, variable length encoding circuit for 8, 9...
... Transmission buffer, 10... Quantization step transmission line,
Data residual amount transmission line 2, ]-2...Static motion block determination line, 13...Encoding method selection switch, 14.
...Prediction error transmission line, ]-5...Quantization result transmission line,
3a...frequency component conversion circuit, 3b...quantization circuit,
3c... Final quantization step determination circuit, 3d... Frequency component transmission line, 3e... Final quantization step transmission line.

Claims (2)

[Claims] (1) A quantization unit that performs motion-compensated inter-frame prediction or intra-frame prediction on an input image for each block, and quantizes the prediction error at a constant quantization step within the processing unit of the block; If the quantization means is equipped with an image edge detection function, and it is determined that an edge exists exceeding the edge determination threshold, and the motion detection means determines that the block is a stationary block, it is determined that the same block was previously quantized. A video encoding device characterized in that quantization is performed in smaller quantization steps than quantization steps. (2) quantization means for performing motion-compensated inter-frame prediction or intra-frame prediction on an input image for each block, and quantizing the prediction error at a constant quantization step within the processing unit of the block; The image processing means has an image edge detection function, and it is determined that an edge exists by exceeding a threshold value for determining an edge, and the motion detection means determines that the block is a stationary block, and furthermore, the amount of data remaining in the transmission buffer exceeds the threshold value. A video encoding device characterized in that when the quantization step is smaller than the quantization step of the previous quantization step of the same block, the quantization step is smaller than the quantization step of the previous quantization step of the same block.