JPH11112993A - Device and method for dynamic image encoding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable calculation amount reduction by setting a detection range according to a size and encoding type of a storage motion vector for each unit area, so that the range is small when a storage motion vector value is small and large, when the value is large. SOLUTION: A motion detection range setting part 12 decides the range of a motion vector in a horizontal/vertical direction from the size of a storage motion vector of a motion vector memory 12 and a macroblock type. A setting part 12 sets, according to the size and an encoding type of the stored motion vector for each unit area, a detection range to be small when a motion vector value is small and at be large, when the value is large. A motion vector detection part 11 detects the motion vector within the range set by the setting part 12, and sends it out to a motion compensation part 14 and the motion vector memory 13. The compensation part 14 prepares a reference image from the motion vector transmitted by the detection part 11 and a stored image of a frame memory 17. The memory 13 stores the size and the macroblock type of the motion vector of a P picture for the first two frames.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving picture coding apparatus used for efficient coding of moving picture signals.

[0002]

2. Description of the Related Art The detection of a motion vector has been performed within a certain fixed range through one sequence. In order to reduce the prediction error, the motion vector detection range is set to be wide. The greater the motion vector detection range, the greater the amount of computation. In general, a motion vector takes a small value in a scene with a small motion, and takes a large value in a scene with a large motion.

If a motion detection range is widened for a scene with a small motion, a large vector may be accidentally obtained. In an encoding standard such as MPEG, a difference value is encoded for a motion vector, and a code having a shorter run length is assigned as the difference value is smaller. Therefore,
The occurrence of a large vector by accident leads to the selection of a long run-length code, which reduces the coding efficiency.

[0004]

The greater the motion vector detection range, the greater the amount of computation. Also,
Generally, a motion vector takes a small value in a scene with a small motion, and takes a large value in a scene with a large motion. If a motion detection range is widened for a small motion scene, a large vector may be accidentally obtained. For example, in a coding standard such as MPEG, a difference value is coded for a motion vector, and a code having a shorter run length is assigned as the difference value is smaller.

[0005] Accordingly, the occurrence of a large vector by accident means that a long run-length code is selected, which means that the coding efficiency is reduced. Conversely, if the motion vector detection range is narrow in a scene with a large motion, an appropriate motion vector cannot be detected, and the prediction error may increase.

[0006]

According to a first aspect of the present invention, there is provided a moving picture coding apparatus for performing motion compensated predictive coding of moving picture data. Means for encoding, means for supplying the moving image data and detecting a motion vector for each unit area, and output of means for detecting the motion vector are supplied and the magnitude of the motion vector for each unit area and Means for storing the coding type of the unit area, and the size of the motion vector of the storing means and the coding type, for each unit area, the motion detection range is reduced when the value of the stored motion vector is small. And a means for setting the motion detection range to be large when the motion vector is large.

According to a second aspect of the present invention, in the moving picture coding method for performing motion compensated predictive coding of moving picture data, the step of coding the moving picture data includes the step of: Detecting the motion vector for each unit, storing the detected output of the motion vector, storing the magnitude of the motion vector for each unit area and the coding type of the unit area, Depending on the size and the encoding type,
Setting, for each of the unit regions, a motion detection range when the value of the stored motion vector is small, and a motion detection range when the motion vector is large. It provides a method.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, the encoding method is MPEG
Method shall be used. In the MPEG system, there are three types of pictures: an I picture that performs only intra-frame coding, a P picture that performs forward motion prediction and intra-frame coding, and a B picture that performs bi-directional motion prediction and intra-frame coding.

The respective prediction directions are shown in FIG. The detection of a motion vector is performed for a P picture and a B picture, and is performed in units called macroblocks (hereinafter abbreviated as MBs). As shown in FIG. 3, one picture is divided into 16 × 16 MBs.

Next, an embodiment of the moving picture coding apparatus according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the moving picture coding apparatus according to the present invention. The video encoding device 10 includes a motion vector detecting unit 11, a motion detecting range setting unit 12, a motion vector memory 13, a quantizer 14, a variable length encoder 15, a dequantizer 16, an inter-picture predictor 17, It comprises a local decoding unit 18 and an adder 19.

The motion vector detecting section 11 detects a motion vector within the range determined by the motion detecting range setting section 12, and sends the value to the motion vector memory 13, the motion compensating section 14, and the encoding section 16. I do.

[0012] The motion compensating unit 14 includes a motion vector detecting unit 1
A reference image is created from the motion vector sent from the image memory 1 and the image stored in the frame memory 17. The motion vector memory 13 stores the size of the motion vector of the P picture for the two latest frames and the macroblock (MB) type, which is the coding type, respectively.

There are two types of MB types, a type that performs motion compensation (hereinafter, this type of MB is called an inter MB) and a type that does not perform motion compensation (hereinafter, this type is called an intra MB). There are two types. MPE
In the G system, use of an intra MB is permitted even for a P picture or a B picture. This intra MB
Is an MB type selected when a motion prediction does not hit and a prediction error increases.

Next, the motion detection range setting section 12 will be described. The motion detection range setting unit 12 calculates the magnitude MVmem of the motion vector stored in the motion vector memory 13.
From (k) [k = 1,2] and MB type Mbtype (k) [k = 1,2], a range in which a motion vector is detected in each of the horizontal and vertical directions is determined. The motion detection range setting unit 12 reduces the motion detection range for each unit area when the value of the motion vector stored in the motion vector memory 13 is small, based on the size of the stored motion vector and the coding type. If it is larger, the motion detection range is set larger.

Next, the vectors stored in the motion vector memory 13 will be described below with reference to FIG. Now, it is assumed that at time Tm, the motion vector of Pn and the information of the MB type are stored in the memory 2 and the information of Pn + 1 is stored in the memory 1, respectively. The reference vector Mvref of Pn + 2 contains Pn
MVmem (1) in memory 1 which is a vector of +1
Mbtype (1) is used for each type. When the encoding of Pn + 2 is completed, the information of Pn + 1 is supplied to the memory 2 and the information of Pn + 2 is supplied to the memory 1.

Next, the reference vector MVref of Bj + 2 and Bj + 3
(1), MVref (2) is MVmem in memory 1 which is information of Pn + 1.
(1), MVm in memory 2 which is information of Mbtype (1) and Pn + 2
Use em (2) and Mbtype (2). At the end of the encoding of the B picture, the memory information is not updated.

The reference vector MVref is divided into P and B pictures based on the size of the motion vector MVmem in the memory, and is set as shown in Equation 1.

[0018]

(Equation 1)

Here, TRb is the distance between the reference picture and the B picture in the forward direction as shown in FIG. 2, for example, TRb = 1,2
Where TRd is the forward reference picture (I picture)
And a distance between the reference picture (P picture) in the backward direction and TRd = 3, for example. The horizontal and vertical ranges of the motion vector detection are obtained from Table 1 corresponding to the horizontal and vertical components of the reference vector. However, when the MB type, which is the encoding type, is an intra MB, level 8 is always selected.

[0020]

[Table 1]

The encoding unit 16 converts the transmitted data into M
The encoded output is supplied according to the PEG standard, and the encoded output is supplied to the local decoding unit 18. The local decoding unit 18
The encoded data is decoded, and the image data motion-compensated by the motion compensator 14 is added to the decoded output by the adder 19 and stored in the frame memory 17.

[0022]

The present invention provides means for encoding moving image data, means for detecting a motion vector for each unit area to which the moving image data is supplied, and output from the means for detecting the motion vector. Means for storing the magnitude of the motion vector for each unit area and the coding type of the unit area; and for each unit area according to the magnitude of the stored motion vector and the coding type, When the value is small, the motion detection range is set small, and when the motion vector is large, the motion detection range is set to be large. Therefore, the amount of calculation of the video encoding device is reduced. I can do it.

Further, according to the present invention, it is possible to prevent a long run-length code from being selected due to an accidental generation of a large motion vector in a scene having a small motion, thereby preventing the encoding efficiency from being lowered.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a moving image encoding apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an MPEG prediction direction and a motion vector memory according to the present invention.

FIG. 3 is a diagram illustrating a macroblock according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Video encoding apparatus 11 Motion vector detection part (means for detecting a motion vector) 12 Motion detection range setting part (means for setting a motion detection range) 13 Motion vector memory (means for storing) 14 Motion compensation part 15 Subtraction part 16 Encoding unit (means for encoding moving image data) 17 Frame memory 18 Local decoding unit 19 Addition unit

Claims (2)

[Claims] 1. A moving picture coding apparatus for performing motion compensated predictive coding of moving picture data, comprising: means for coding the moving picture data; and detecting the motion vector for each unit area supplied with the moving picture data. Means for receiving the output of the means for detecting the motion vector, means for storing the magnitude of the motion vector for each unit area and the coding type of the unit area, and the magnitude of the motion vector of the means for storing. Means for setting the motion detection range if the value of the stored motion vector is small, and increasing the motion detection range if the value of the motion vector is large, for each unit area according to the encoding type. A moving picture coding apparatus comprising: 2. A moving picture coding method for performing motion compensated predictive coding of moving picture data, comprising the steps of: coding the moving picture data; Performing a detection, storing the motion vector magnitude for each unit area and the coding type of the unit area supplied with the detection output of the motion vector, and storing the magnitude of the stored motion vector and the encoding. Depending on the type, a step of setting a small motion detection range when the value of the stored motion vector is small and a large motion detection range when the value of the stored motion vector is large is set for each unit area. A moving picture coding method characterized by the following.