JP2002176652A - Video-encoding method and video encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video encoder that will not execute encoding of an image according to a B picture, in the case of encoding the image in compliance with the MPEG 2 system and that suppresses increase in a code quantity by an I picture, so as to avoid delays with respect to decoding of the B picture, thereby obtaining a reproduced image with high image quality, even when transmission bit rate is low. SOLUTION: Part or parts in frames of a P picture, generated at encoding of image in compliance with the MPEG 2 system, is subjected to intra- processing. Furthermore, inserted position of an intra macro block of frames of consecutive P pictures is controlled, so that the intra-processed position in the frames will not be in duplicated until the time the intra macro blocks are inserted uniformly within the entire frames of the consecutive P pictures.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video coding method and a video coding apparatus for coding a video according to the MPEG2 system, and more particularly to a system which needs to transmit an MPEG2 stream through a network such as light or satellite. Also, the present invention relates to an apparatus used for a monitoring application such as a train monitoring system and a system requiring real-time communication such as two-way communication.

[0002]

2. Description of the Related Art FIG. 11 is a schematic diagram showing an example of a general frame configuration in image coding according to the conventional MPEG2 system. In MPEG2, for the purpose of storage or transmission,
I picture (Intra coded picture: intra-coded picture), P picture (Predictive coded picture: inter-frame forward predictive coded picture), B picture (Bidirectional
ypredictive coded image: bidirectional predictive coded image)
Video is encoded by a combination of these pictures, defined as two types of frames (hereinafter also referred to as images).

[0003] An I picture is an image encoded from original image information. The P picture is an image that has been encoded by prediction using past I and P pictures as information sources. The B picture uses past and future I and P pictures as information sources,
This is an image encoded by prediction. The periods of the I, P, and B pictures are various. For example, as shown in FIG. 11, the period of the I picture is set to 15, and the period of the P picture is set to 3. In the drawings, an I picture, a P picture, and a B picture are represented as I, P, and B, respectively.

On the other hand, MPEG2 image data is composed of a sequence layer, a GOP (Group of Pictures).
(Pictures) layer, picture layer, slice layer, macro block layer, and block layer.

The structure of each layer is as follows. The sequence layer is composed of a sequence header and a GOP, and is a screen group having a series of the same attributes such as an image size and an image rate. The GOP layer is composed of three encoded pictures of an I picture, a P picture, and a B picture, and is a minimum unit of a screen group serving as a unit of random access. The picture layer is composed of small screens (macroblocks) obtained by dividing one screen into arbitrary lengths, and has attributes common to macroblocks, such as an image encoding mode (picture type). The slice layer is composed of small screens obtained by dividing one screen into arbitrary lengths, and has information common to macroblocks such as quantization characteristic values.

The macroblock layer has information common to pixel blocks (macroblocks) obtained by further dividing a slice layer such as a motion vector. One macro block includes a luminance block including a luminance signal (Y) of 16 × 16 pixels and a color difference block including a color difference signal (Cb, Cr) of 8 × 8 pixels. The block layer is composed of blocks of 8 × 8 pixels, and has transform coefficients such as DCT coefficients.

[0007] Further, in the conventional image coding of the MPEG2 system, it is determined which type of image is to be coded, i-picture, P-picture or B-picture, and all the macroblocks included in the same picture are the same. Encoded by image type. That is, for example, when the image type is determined to be an I picture, all image data belonging to the one image are intra-type macroblocks (intra macroblocks) encoded based on the original image data.
Will be constituted by

[0008] The MPEG2 image coding technique is used in various places, for example, in a train monitoring system. This train monitoring system is to install a camera on the platform, image the train or platform, and monitor the image on a monitor by a driver or station staff to confirm the safety of train operation. It is used in one-man trains where only the driver opens and closes doors and checks safety. At this time, the captured image is encoded into an image according to the MPEG2 system, transmitted as an MPEG2 stream via an optical network, and decoded to display the image on a monitor. In order to configure such a monitoring system, real time performance is required for displaying images on the monitor.

[0009]

However, the presence of a B picture that generates an encoded image by future prediction increases the compression rate of image data and reduces the amount of code, but it takes time to decode the B picture. There is a problem that the delay amount increases.

[0010] The present invention eliminates the delay associated with decoding a B picture by not encoding a B picture when encoding an image according to the MPEG2 system and suppressing an increase in the amount of code due to an I picture. It is an object of the present invention to obtain a high-quality reproduced image even when the rate is low.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention encodes a video by the MPEG2 system,
A video encoding method for creating a plurality of temporally continuous frames, wherein the frames created at the time of the encoding are configured to be only I pictures and P pictures. With the above configuration, it is possible to suppress a delay when decoding a B picture frame.

Further, the present invention is configured such that a part or a plurality of parts in the frame of the P picture created at the time of the encoding is intra-structured. With the above configuration,
It becomes possible to partially make the P-picture intra, and it is possible to improve the image quality.

Further, according to the present invention, only the first frame created at the time of the encoding is defined as an I picture, and all subsequent frames are defined as the P picture. According to the above configuration, it is possible to select the improvement of the image quality or the reduction of the delay amount related to decoding by an application or the like according to the network environment.

Further, according to the present invention, only the first frame created at the time of the encoding is defined as an I picture, and the subsequent frames for an arbitrary time or an arbitrary number are defined as the P picture. The frame subsequent to the time or an arbitrary number of consecutive frames is set as the I picture. According to the above configuration, when the transmission bit rate is high in accordance with the network environment, it is possible to improve the image quality by forcibly inserting the frame of the I picture in order to give priority to the delay.

In the present invention, a part or a plurality of parts of the frame of the P picture to be intra-structured are configured in macroblock units. With the above-described configuration, the M-block created by the video encoding method of the present invention is processed by the conventionally performed processing in units of macroblocks.
It becomes possible to decode the PEG2 stream.

Further, the present invention is configured such that a portion or a plurality of portions of the frame of the P picture to be intra-structured has a width of the frame in which a plurality of macroblocks are gathered in a band shape. According to the above configuration, it is possible to increase the area of the inserted intra macroblock in accordance with the network environment, and it is possible to shorten the cycle for uniformly distributing the intra macroblock throughout the frame. Become.

Further, the present invention relates to a position in the frame between the frames of the consecutive P pictures,
Until the whole of the continuous P picture in the frame is uniformly intra-transformed, the position of the continuous P picture to be intra-transformed in the frame is controlled so as not to overlap. With the above-described configuration, until the whole of a continuous P-picture frame is uniformly intra-processed, the positions of the intra-frames to be intra-processed are prevented from overlapping, and the image quality of only a part of the image is prevented from being deteriorated. It becomes possible.

Further, according to the present invention, an intra-portion or a plurality of portions of the frame of the P-picture is divided by α in the horizontal direction with respect to positive integers α and β which are relatively prime relations. , Composed of vertically divided cells, randomly assigning numbers to the array of the cells in the horizontal direction and the array of the cells in the vertical direction, and referring to the numbers, the consecutive P pictures Is controlled so that the positions of the intra conversion within the frame do not overlap. With the above-described configuration, until the whole of a continuous P-picture frame is uniformly intra-processed, the positions of the intra-frames to be intra-processed are prevented from overlapping, and the image quality of only a part of the image is prevented from being deteriorated. It becomes possible.

According to the present invention, an MP
What is claimed is: 1. A video encoding device that encodes a video according to the EG2 method to create a plurality of temporally continuous frames, and includes a part or a plurality of parts in the frame of a P picture created at the time of the encoding. It was configured to be intra. According to the above configuration, it is possible to partially convert a P picture into an intra picture, thereby improving the image quality.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a video encoding method and a video encoding device according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment according to the video encoding device of the present invention. In addition, the embodiment according to the video encoding apparatus corresponds to a first video encoding method described later.
The third embodiment can be used in common. The control means 1 is a means for holding parameters required for each means determined by the image parameter determining means 9 in a register, and supplying parameters to each means as needed. Also,
It outputs I / F and encoded data with an external host, and also controls the operation of each means. The data I / F (interface) 2 is a means for performing data transfer between each means and the external SDRAM 3, and is a means for temporarily holding original images and encoded data. The external SDRAM 3 is an external memory in which an original image and encoded data are temporarily stored.

The image conversion means 4 is a means for outputting a format-converted image from an input image. The original image macroblock data memory 5 is a memory that holds the original image and supplies the held original image to the predicted image generation unit 6 and the DCT transform / quantization unit 7. The predicted image generation unit 6 is configured to perform the following operations according to the parameters set in the control unit 1.
This is a means for generating a predicted image from an original image. The DCT transform / quantization unit 7 determines the image parameter determining unit 9 based on the difference image in the case of a non-intra (Non-Intra) macroblock and on the basis of the original image in the case of an Intra macroblock.
Is a means for performing DCT transform and quantization processing (arithmetic processing for data compression) according to the parameters determined in (1).

The encoding means 8 applies a fixed length (variable length) to the quantized data processed by the DCT transform / quantization means 7.
It is means for encoding. Image parameter determining means 9
Is a means for determining in advance parameters required for input images (macroblocks) for those images (macroblocks). External host / encoded data output I
/ F10 is an I / F (external) for outputting I / F with the control means of the external host and encoded data to the outside.

FIG. 1 also shows data input and output between each means. The data I /
The data A output to each of the F2, the image converting means 4, the predicted image generating means 6, the DCT transform / quantizing means 7, and the encoding means 8 are required for the image processing of each means, and the image parameter determining means 9 Is the image parameter determined by Data B input to the image conversion means 4 from an external memory or another processing device is image data input to the MPEG2 image encoding device.

The data C output from the image conversion means 4 to the data I / F 2 is original image data which is converted by the image conversion means 4 and output. Data I / F2
Is output from the original image macroblock data memory 5 or from the original image macroblock data memory 5 to the predicted image generation means 6 and the DCT transform / quantization means 7, respectively. The original image data in macroblock units used by the quantization means 7.

The data E output from the predicted image generation means 6 to the DCT transform / quantization means 7 is difference image data in macroblock units between the original image data and the predicted image.
Data F output from the DCT transform / quantization unit 7 to the encoding unit 8 is quantized data in units of macroblocks that have been subjected to DCT transformation and quantization processing. The data G output from the encoding unit 8 to the data I / F 2 is encoded data in units of macroblocks after encoding. Data I / F2
H which is input and output between the external SDRAM 3 and
Is original image data or encoded data.

Data I / F 2 to control means 1 or control means 1 to external host / encoded data output I / F 10
Is coded data in macroblock units output to the outside. Data J input / output between the control means 1 and the external host / encoded data output I / F 10 is communication data input / output between the external host and the MPEG2 image encoding apparatus. The data K output from the control means 1 to the image parameter determination means 9 is an image parameter determination command. The data L output from the image parameter determining means 9 to the control means 1 is an image parameter determined by the image parameter determining means 9.

<First Embodiment> Next, the basic concept of the first embodiment according to the video encoding method of the present invention will be described. FIG. 5 is a schematic diagram showing an arrangement of frames after encoding an image according to the MPEG2 method according to the first embodiment of the video encoding method of the present invention. In the encoding according to the first embodiment of the video encoding method of the present invention, the arrangement of frames is determined as follows: I = I picture (encoded based on original image information) and P = P picture (past I and P pictures are (Encoding with prediction as an information source). As a result, the encoded picture is composed of an I picture and a P picture. The array of frames includes
Basically, it is preferable that an I picture is used for only the first picture and a P picture is used for a subsequent frame.

In a P picture, an intra type macro block (intra macro block) encoded based on original image information or an intra macro macro which is a group of a plurality of intra macro blocks is provided in a part of the picture. Make sure blocks are inserted. One or more intra macroblocks can be inserted at a time. Also, it can be inserted into all P pictures, or can be inserted into any P picture.

In each P picture, it is preferable that the insertion position of the intra macroblock is set at random. Further, as described later, P
It is also possible to insert an I picture between the arrangement of pictures (second embodiment), and to set the size of an intra macroblock to be inserted arbitrarily (third embodiment).

FIG. 2 is a flowchart showing a processing operation in the first embodiment according to the video encoding method of the present invention. Here, it is assumed that the original image data is already stored in the original image macroblock data memory 5.
First, in step S101, the original image data (data D) to be encoded is read from the original image macroblock data memory 5, and in step S103, the control unit 1 causes the image parameter determination unit 9 to generate image parameters for the original image data. Parameter determination command (data K) is issued. In step S105, the image parameter determination means 9 determines various parameters (data L) for the original image data, and outputs various parameters to the control means 1.

Here, in step S107, the control means 1 determines whether or not the parameter of the image type is an I picture, that is, the original image data is encoded as an I picture or as a P picture. To determine If it is determined in step S107 that the parameter of the image type is an I picture, step S10
In step 9, the DCT transformation / quantization means 7 extracts macroblock data (data D) one by one from the original image macroblock data memory 5, and the DCT transformation / quantization means 7 and the encoding means 8 set the set parameters. According to (Data A), DC is applied to each of the original image data.
Performs T-transform, quantization, and encoding. In this case, the type of the macro block is an intra type. Then, in step S111, the control means 1 determines whether or not the processed macroblock is the last macroblock in the original image data. If the processed macroblock is the last macroblock, the processing is terminated, and the processing is not the last macroblock. In this case, a different macro block is read out again and the processing of step S109 is performed.

On the other hand, if it is determined in step S107 that the image type parameter is not an I-picture, in step S113, the image parameter determining means 9
The position where the intra macroblock is to be inserted is specified, and the position information of the specific macroblock is held in the memory (register) of the control means 1 or the like. The position of the macro block specified by the image parameter determining means 9 may be specified by control of an external host or the like, or a pseudo random pattern may be created by the image parameter determining means 9 and the insertion position may be specified. It is. Then, in step S115, the control means 1 determines whether or not the position of the currently read macroblock (current macroblock) is equal to the position specified in step S113.

If the position of the current macroblock is equal to the position specified in step S113 in step S115,
In step S117, the DCT transform / quantization means 7
Extracts the macroblock data (data D) one by one from the original image macroblock data memory 5,
The transform / quantization means 7 and the coding means 8 perform DCT transform / quantization and coding on the original image data according to the set parameters (data A). In this case, the type of the macro block is an intra type (intra macro block).

On the other hand, if the position of the current macroblock is not equal to the position specified in step S113 in step S115, the predictive image generating means 6 determines in step S119 the macroblocks from the original image macroblock data memory 5 one by one. The data (data D) is taken out, and the predicted image generation means 6, DCT transform / quantization means 7, and encoding means 8 perform the following processing according to the set parameters (data A).
For this original image data, a predicted image generation, DC
Performs T-transform, quantization, and encoding. In this case, the type of the macro block is a non-intra type.

Then, step S117 or step S117
After step 119, in step S121, the control unit 1
Determines whether the processed macroblock is the last macroblock in the original image data, terminates the processing if it is the last macroblock, and reads another macroblock again if it is not the last macroblock Step S115 is performed.

Through the above processing, it becomes possible to encode only the macroblock designated in step S113 into the P type picture so as to be of the intra type (intra macroblock). Note that any number of intra macroblocks can be inserted at any position in the image. Therefore, it is also possible to insert intra macroblocks sequentially or randomly, for example, to always intra into a macroblock corresponding to the vicinity of the door in the image to improve the image quality near the door in the train monitoring system, It is also possible to insert intra macroblocks according to certain rules. In addition, since the P picture is partially intra-structured, the image quality of the P picture can be improved. A method of specifying the insertion position of the intra macro block will be described later in detail.

<Second Embodiment> Next, the basic concept of the second embodiment according to the video encoding method of the present invention will be described. FIG. 6 is a schematic diagram showing an arrangement of frames after encoding an image according to the MPEG2 system according to the second embodiment of the video encoding method of the present invention. In the encoding according to the second embodiment of the video encoding method of the present invention, the forced I picture flag is controlled by an external host or the like, the control by the image parameter determining means 9, the timer control related to time or the number of images, or the like. , For example, a fixed number of P
It can be inserted for each picture. This forced I
The picture flag makes it possible to forcibly change the parameter indicating the picture type from the P picture to the I picture among the parameters set in the control means 1 from the image parameter determination means 9, and as a result, P = P picture It is possible to forcibly interrupt an I picture in the array.

FIG. 3 is a flowchart showing a processing operation in the second embodiment according to the video encoding method of the present invention. The flowchart shown in FIG. 3 corresponds to step S107 of the flowchart of the first embodiment shown in FIG.
Step S123 is added between step S113 and step S113. Since the operation is basically the same as the operation shown in the flowchart of FIG. 2, only the operation related to the added step S123 will be described below.

In step S107, the control means 1 determines whether or not the parameter of the image type is an I picture.
If it is determined that the picture is not an I picture, step S12
In step 3, with reference to the host I / F and the like,
It is determined whether or not there is a forced I-picture flag that is an instruction to insert a picture. If the forced I picture flag exists, step S109 is performed, and if the forced I picture flag or the like does not exist, step S113 is performed.

<Third Embodiment> Next, the basic concept of the third embodiment according to the video encoding method of the present invention will be described. FIG. 7 is a schematic diagram showing an arrangement of frames after encoding an image according to the MPEG2 system according to the third embodiment of the video encoding method of the present invention. In the encoding according to the third embodiment of the video encoding method of the present invention, a forced intra slice flag is inserted under the control of an external host or the like, or is inserted by the image parameter determining means 9 for every fixed number of P pictures, for example. It is possible to By the forced intra slice flag, the first
In the same manner as the insertion of a macroblock in the embodiment of
It becomes possible to insert an intra slice (for example, a slice-type intra-type macroblock band arranged in one row in the horizontal direction). Further, it is preferable to insert the intra slice at a different position in a continuous P picture.

FIG. 4 is a flowchart showing a processing operation in the third embodiment according to the video encoding method of the present invention. The flowchart shown in FIG. 4 corresponds to step S107 of the flowchart of the first embodiment shown in FIG.
Step S125 and step S127 are added between step S113 and step S113. Since the operation is basically the same as the operation shown in the flowchart of FIG. 2, only the operation related to the added steps S125 and S127 will be described below.

In step S107, the control means 1 determines whether or not the image type parameter is an I picture.
If it is determined that the picture is not an I picture, step S12
5, the external host / encoded data output I / F 10
It is determined whether or not there is a forced intra-slice flag that instructs to insert an intra-slice with reference to the above. If the forced I-picture flag exists, in step S127, the image parameter determination unit 9 specifies a position where an intra slice is to be inserted,
The position information of a specific macroblock is held in a memory (register) of the control means 1 or the like. On the other hand, if the forced I picture flag or the like does not exist, step S113 is performed.

Next, a method of enabling an intra macroblock to be uniformly inserted into an image in the first embodiment will be described. In the first embodiment, one or more intra-type macroblocks (intra macroblocks) are inserted into one P picture. However, for example, in a mode in which one intra macroblock is inserted into one P picture, if an intra macroblock is completely randomly inserted, long-term (a large number of P pictures)
In this case, intra macroblocks are uniformly inserted on the image, but in the short term (relatively few P pictures)
Has a position where an intra macroblock is inserted a plurality of times, while a position where an intra macroblock is not inserted exists, which may affect the image quality.

As a method of uniformly inserting an intra macroblock on an image even in a short term, there is a method of creating a pseudo random pattern and inserting an intra macroblock according to the pattern, for example. FIG. 8 shows that, in one image divided into α in the horizontal direction and β in the vertical direction, the numbers 1 to α are assigned to each square in the horizontal direction, and the numbers 1 to β are assigned to each square in the vertical direction. It is a figure showing an example allocated at random. In FIG. 8, α = 11 and β = 8, but α and β can be arbitrary positive integers. It is assumed that a plurality of macroblocks exist in one divided cell, and the number of macroblocks present in each cell is equal.

With respect to one image, only one of these cells is regarded as an intra-type cell (consisting of an intra-type macro block group). When the insertion position of the macroblock group is changed and the process advances to α × β images,
A method will be described in which the insertion positions are not overlapped and the intra type is uniformly inserted in all the cells (the process proceeds to α × β images). .., α in the horizontal direction and 1 in the vertical direction
2,..., Β are assigned. At this time, for example, as shown in FIG. 8, it is preferable to randomly sort in both the horizontal and vertical directions.

Next, the relationship between the horizontal and vertical numbers assigned to the image and the positions where the intra macroblock groups are inserted will be described. FIG. 9 is a graph for explaining a relationship between horizontal and vertical numbers assigned to an image and an insertion position of an intra macroblock group. In the graph of FIG. 9, the horizontal axis represents the image number n (the number indicating the n-th image (frame) that advances with time:
n is a positive integer), and the vertical axis is a number x _n allocated in the horizontal direction and a number y _n allocated in the vertical direction. Further, a solid line in the graph represents a position in the horizontal direction, and a dotted line represents a position in the vertical direction. Horizontal grid position x
_n (solid line in FIG. 9) and vertical grid position y _n (FIG. 9
Is represented by the following equation by the image number n.

[0047] With respect to the horizontal direction, x _n = n in the case of 1 ≦ n ≦ α, in the case of α + 1 ≦ n ≦ 2α is, x _n = n-
When α, 2α + 1 ≦ n ≦ 3α, x _n = n−2α, and when αβ + 1 ≦ n <(αβ + 1) + α−1, x
_n = n-αβ. Also, regarding the vertical direction, 1 ≦
y _n = n in the case of n ≦ beta, in the case of β + 1 ≦ n ≦ 2β y n = n-β, in the case of 2β + 1 ≦ n ≦ 3β is, y _n =
n−2β, and αβ + 1 ≦ n ≦ (αβ + 1) + β−
A y _n = _n-αβ in the case of 1.

According to the above equation, the insertion position of the intra macroblock group in each image is determined as follows. (X ₁ , y ₁ ) for the image with image number n = 1
= The position of the (1,1), the image number n = 2 of the image to insert the intra-macro blocks in the position of (x _2, y ₂₎ = (2, 2) (Intra of macroblocks).
Then, an intra macroblock group is similarly inserted until n = β. That is, in the image with the image number n = β, the intra macroblock group is inserted at the position of (x _β , y _β ) = (β, β).

[0049] Then, the image number n = beta + 1 of the image, inserting the intra-macro blocks in the position of _{(x β + 1, y β} +1) = (β + 1,1). That is, the value of the vertical position is returned to 1 again, and the value of the horizontal position and the value of the vertical position are increased by one for each ( _{xβ + 1} , _{yβ + 1} ) every time the image number n increases. .

Further, when the image number n = α + 1, an intra macroblock group is inserted at the position of (x _{α + 1} , y _{α + 1} ) = (1, α + 1−β). That is, the value of the horizontal position is returned to 1 again, and this (x _{α + 1} , y _{α + 1} )
, Each time the image number n increases, the values of the horizontal position and the vertical position are increased by one. When referred to generalize the above equation _{(x γ, y γ) =} (γ-pα, γ-qβ) it can be written as. Here, p is the number of turns in the horizontal direction, and q is the number of turns in the vertical direction. Here, the number of turns p or q is set to 0 when (x ₁ , y ₁ ),
When the image number becomes a multiple of α or β and ascends to the next value (when one round), it is defined as a value that increases by one.

Since there are α × β positions where the intra macroblock group can be inserted, the image number n = α ×
Until β, it is necessary to insert an intra macroblock group into every cell. The conditions of α and β are shown below so that the insertion positions of the intra macroblock groups do not overlap until the image number n = α × β. In the case of α> β, referring to the graph of FIG.
Within the range of n ≦ α, the horizontal position changes every screen, so there is no overlap. Similarly, α + 1 ≦ n ≦ 2α, 2α +
Also, if 1 ≦ n ≦ 3α,..., (Β−1) α + 1 ≦ n ≦ αβ, the insertion positions of the intra macroblock groups will not overlap if they are limited to the respective ranges.

Here, attention is paid when x _n = 0.
n = α × to β, because it is β times of the x _n = 0, one of the β times, if at all different positions of the y _n position,
The insertion positions of the intra macroblock group do not overlap, and α
× β positions can be designated. For example x
position of y _n when the _n = 0 is determined as shown in equation shown below.

That is, when _n = 1, y _n = 1, n
= In the case of α + 1 is _{y n = (α + 1)} -k 1 β ( where k
₁ = integer portion of the alpha / beta), in the case of _n = 2α + 1 y n =
(2α + 1) (integer part of provided that _{k 2 = 2α / β) -k} 2 β, n = y n = in the case of 3α + 1 (3α + 1) -k 3
β (where k ₃ = an integer part of 3α / β), and n =
a _{y n = (βα + 1)} -kβ ( although k = alpha) in the case of .alpha..beta + 1.

[0054] When the n = αβ + 1, because after the alpha × beta number of intra macroblocks are inserted, always returns to y _n = 1 is the first condition. On the other hand, y _n the other must be 1 than an integer _{(1 <y n ≦ β)} . This condition is satisfied when the least common multiple of α and β is α × β (α and β are relatively prime relations). If the least common multiple is a value smaller than α × β, n is set at a position of x _n = 0 before n = βα + 1.
= 1 and duplication occurs. Therefore, as a condition necessary to create this pseudo random pattern,
It is necessary to select a value of (α, β) such that the least common multiple of α and β is α × β.

Although the above method of inserting an intra macroblock group has been described for the case where α> β and α <2β, any α and β values satisfying the above conditions, ie, any α
And β, it is possible to set a value of (α, β) such that the least common multiple is α × β.

Next, an example of inserting an intra macroblock group into an actual P picture will be described. FIG.
In one image divided into 1 and divided into 5 vertically,
FIG. 11 is a diagram showing an example in which numbers 1 to 11 are randomly assigned to each square in the horizontal direction, and numbers 1 to 5 are randomly assigned to each square in the vertical direction. Consider the case where one image has 44 × 30 macroblocks. Considering a 4 × 6 macroblock as one macroblock group and an image as a set of 11 × 5 macroblock groups, a macroblock group that can be intra-processed (a cell into which an intra macroblock group can be inserted) is shown in FIG. As shown in FIG.
There are a total of 55 locations, including 5 locations and 5 vertical locations.

Numbers are randomly assigned to this image in the horizontal and vertical directions as shown in FIG. 10, and an intra macroblock group is inserted in the pseudo random pattern. At this time, the group of intra macroblocks is inserted into each P picture in the order indicated by the circled numbers.
That is, for example, in the case of the image with the image number n = 1, the intra macroblock group is inserted at the position shown in the figure, and with the image with the image number n = 2, the intra block is inserted at the position shown in the figure. Since the least common multiple of 11 and 5 is 55, the positions do not overlap. Therefore, as a result, it is possible to randomly and uniformly determine the insertion position of the intra macroblock group in the arrangement of the P pictures.

Further, since the number of I-picture frames is reduced, it is possible to prevent the transmission time from being lengthened when the transmission bit rate is low, thereby preventing the quality of the reproduced image from deteriorating. Specifically, the transmission rate of the MPEG2 stream is 30 frames / second, and in the video encoding method of the present invention, the I picture 2
It is possible to reduce the delay amount (1/15 second) for one sheet. The delay time of 1/15 second is a delay amount that can be visually recognized, and is particularly applied to a system that requires real-time performance, such as a train monitoring system that needs to confirm opening and closing of a train door instantaneously. Doing so has a further effect.

According to the present invention, it is possible to insert an arbitrary number of intra macroblocks at an arbitrary position in an image, and to forcibly insert a frame of an I picture or Since it is possible to insert a slice, when the transmission bit rate is high, the frame of the I picture is forcibly inserted to give priority to the delay, and when the transmission bit rate is low, It is possible to insert an intra slice in order to prioritize image quality, increase the number of intra macroblocks to be inserted in one P-picture frame, and widen the insertion range. In addition, it is possible to select the improvement of the image quality or the reduction of the delay amount related to decoding by an application or the like.

Further, according to the present invention, the position at which an intra macroblock is inserted in a continuous P-picture frame is controlled. Since the positions to be intra-processed are not duplicated, it is possible to prevent the image quality from being deteriorated only in a part of the image.

Further, according to the present invention, according to the stream data structure having the six-layer hierarchical structure described in the prior art, the image is encoded by the MPEG2 system in accordance with the conventional standard. It is possible to transmit an MPEG2 stream encoded by the video encoding method of the present invention by a transmission method. In addition, the conventional MPE
The G2 image decoding device can decode the MPEG2 stream encoded by the video encoding method of the present invention.

[0062]

As described above, according to the present invention,
Since the number of B-picture frames is reduced when encoding an image according to the MPEG2 system, it is possible to provide a video encoding method and a video encoding device that can reduce the amount of delay in decoding time related to future prediction.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a video encoding device according to the present invention.

FIG. 2 is a flowchart illustrating a processing operation in the video encoding method according to the first embodiment of the present invention;

FIG. 3 is a flowchart showing a processing operation according to a second embodiment of the video encoding method of the present invention;

FIG. 4 is a flowchart showing a processing operation in a third embodiment according to the video encoding method of the present invention;

FIG. 5 is a schematic diagram showing an arrangement of frames after encoding an image according to the MPEG2 system according to the first embodiment of the video encoding method of the present invention;

FIG. 6 is a schematic diagram showing an arrangement of frames after encoding an image according to the MPEG2 system according to the second embodiment of the video encoding method of the present invention;

FIG. 7 is a schematic diagram showing an arrangement of frames after encoding an image according to the MPEG2 method according to the third embodiment of the video encoding method of the present invention;

FIG. 8 shows 1 obtained by dividing an image horizontally into α and vertically into β.
FIG. 3 is a diagram showing an example in which, in a single image, numbers 1 to α are randomly assigned to each square in the horizontal direction, and numbers 1 to β are randomly assigned to each square in the vertical direction.

FIG. 9 is a graph for explaining a relationship between horizontal and vertical numbers assigned to an image and an insertion position of an intra macroblock group.

FIG. 10 shows one image divided into 11 in the horizontal direction and 5 in the vertical direction.
Is a diagram showing an example in which numbers 1 to 5 are randomly assigned to each square in the vertical direction.

FIG. 11 is a schematic diagram showing an example of a general frame configuration in encoding an image according to the MPEG2 method.

[Explanation of symbols]

Reference Signs List 1 control means 2 data I / F (interface) 3 external SDRAM 4 image conversion means 5 original image macroblock data memory 6 predicted image generation means 7 DCT transformation / quantization means 8 encoding means 9 image parameter determination means 10 external host Encoded data output I / F A Image parameter required by image processing of each means and determined by image parameter determining means B Image data input to MPEG2 image coding apparatus C Format converted by image converting means and output Original image data D Predicted image generating means, original image data in macroblock units used in the DCT transform / quantization unit E Difference image data in macroblock units between the original image data and the predicted image F DCT transformation, quantization processing Macroblock quantized data G Macroblock after encoding Encoded data H Original image data or encoded data I Encoded data in macroblock units output to outside J Communication data input / output between external host and MPEG2 image encoding device K Image parameter determination command L Image parameters determined by the image parameter determining means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Naoki Okawa 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa F-term (reference) in Matsushita Communication Industrial Co., Ltd. 5C059 KK00 MA00 MA23 MC11 MC31 PP05 PP06 SS00 SS06 UA02 UA28 UA38 5J064 AA01 BA09 BB06 BC01 BC16 BD02

Claims (9)

[Claims] 1. A video encoding method for encoding a video according to the MPEG2 system to create a plurality of temporally continuous frames, wherein the frames created at the time of the encoding are I pictures and P pictures Video encoding method to be only. 2. The video encoding method according to claim 1, wherein a part or a plurality of parts in the frame of the P picture created at the time of the encoding are intra-processed. 3. The video according to claim 1, wherein only the first frame created at the time of encoding is an I picture, and all subsequent frames are P pictures. Encoding method. 4. The method according to claim 1, wherein only the first frame created at the time of encoding is an I-picture, and the subsequent frame is an arbitrary time or an arbitrary number of consecutive frames as the P-picture. 3. The video encoding method according to claim 1, wherein the frame subsequent to the number of consecutive frames is the I picture. 5. The video code according to claim 1, wherein a part or a plurality of parts of the frame of the P picture to be intra-structured are configured in macroblock units. Method. 6. The P-picture according to claim 1, wherein a portion or a plurality of portions of the frame of the P picture to be intra-structured has a width of the frame in which a plurality of macroblocks are gathered in a band shape. The video encoding method according to any one of the above. 7. With respect to a position in the frame between the frames of the consecutive P pictures, the consecutive P pictures are repeated until the whole of the continuous P picture is uniformly intra-framed. 7. The video encoding method according to claim 1, wherein control is performed such that the positions of the intra conversion within the frame do not overlap. 8. The frame is divided into α in the horizontal direction and α in the vertical direction by dividing a part or a plurality of parts of the P picture to be intra-processed into positive integers α and β which are disjoint relations. It is composed of β divided cells,
A number is randomly assigned to the array of the cells in the horizontal direction and the array of the cells in the vertical direction so that the positions of the continuous P pictures to be intra-processed in the frame do not overlap while referring to the numbers. The video encoding method according to claim 7, wherein the method is controlled. 9. A video encoding apparatus that encodes a video according to an MPEG2 system to create a plurality of temporally continuous frames, wherein a part of a P picture created in the encoding is included in the frame. Alternatively, a video encoding device having a control unit that converts a plurality of parts into the intra.