JP2000224594A - Method and device for displaying picture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve display quality for a period till a whole screen is refreshed in the case of decoding and displaying a video stream where an I picture does not exist. SOLUTION: In this picture display method, a P picture is continuously displayed in place of the B picture without displaying the B picture during a period till the whole screen is refreshed after obtaining the clear picture where the whole screen is constituted of a clear slice when the video stream consisting of the P and B pictures without including the I picture is decoded and displayed. The P picture being high in picture quality compared with that of the B picture is continuously displayed during the period till picture quality being the same as that of the I picture is obtained so that the quality of the display picture can be improved in comparison with a case where the P and B pictures are coexisting and displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display method and a display device for transmitting coded image data, decoding the coded image data and displaying the image.

[0002]

2. Description of the Related Art As a technique for reducing the data amount of a digital image, there is a pixel coding method by MPEG.
In particular, when coding a moving image, the prediction of the picture is performed from a previous / future (previous and / or future) picture (also referred to as a frame). Is encoded. When the coded image is decoded and displayed, the image of the previous / future picture is used as a reference image, and the moving image portion is decoded and displayed on the reference image. Can be displayed. Therefore, it is possible to reduce the amount of image data of the picture. FIG. 3 (a) is a conceptual diagram of a video stream of such a system.
It consists of a picture and a B picture. In the same figure, encoding is performed by taking the difference of the image data between the pictures indicated by the arrows.

[0003] For example, an NTSC image is shown in FIG.
As shown in (a), one picture is 720 pixels wide,
It is composed of 480 pixels vertically, which is divided into blocks (macroblocks) each having 16 pixels in the horizontal and vertical directions. In particular, a set of macroblocks in one horizontal line is called a slice. That is, one picture is 3 in the NTSC image.
It is composed of 0 slices S. And in MPEG,
There are two slices, an intra slice and an inter slice. The intra slice is obtained by encoding only image data in the picture, and the inter slice is obtained by encoding a difference from previous / future picture data. is there. A picture composed only of the intra slices, that is, a picture composed of intra slices in which all slices in the picture are coded only with image data in the picture, is referred to as an I picture. In addition, a picture composed of an inter slice obtained by encoding a difference with respect to an I picture is referred to as a P picture, and a picture composed of an inter slice obtained by encoding a difference with respect to a P picture is referred to as a B picture.

Accordingly, a P picture and a B picture are
It is difficult to display a target image only with these pictures because the image data is a difference from an I picture or a P picture. However, once an I picture is decoded to obtain an image, By using the image as a reference image, the image can be displayed by decoding the P picture and the B picture. However, if the display with the P picture and the B picture is repeated, the error component included in the difference is accumulated, and the image is not displayed correctly. Therefore, an I-picture is periodically inserted, and the entire picture is refreshed with the I-picture to obtain a clear picture, thereby correcting the picture. However, since the I picture is composed of only intra slices as described above, the data amount is extremely large as compared with the P picture and the B picture. Therefore, when transmitting or recording image data, it is not appropriate to transmit and record the I picture as it is. Therefore, as shown in FIG.
At the time of encoding, a part of slices in the P pictures P1 to Pn is composed of intra slices, and by changing the vertical position of the intra slice for each picture, the P picture is decoded over n pictures. In the process, P _m is decoded with reference to P _m−1 , so that when the n-th Pn picture is decoded, the intra slices S1 to S1 included in the first to n-th P pictures are decoded. It is possible to refresh the picture of Pn by Sn. This eliminates the need for transmission and recording of I-pictures, which is preferable for reducing the data amount.

[0005] When decoding and displaying such a video stream composed of a P picture and a B picture that do not include an I picture, in order to refresh the entire screen with the P picture, an intra slice of the P picture must be displayed. It is necessary to wait for a few pictures before refreshing the whole. Therefore, in the meantime, the slice part that is not refreshed decodes and displays the P picture or the B picture. As described above, the P picture is an image of difference data from the I picture, and therefore, the image quality of a portion that is not refreshed by the intra slice is poor, and the B picture is an image of difference data from the P picture, so the image quality is even worse. . For this reason, simply displaying the pictures of the P picture and the B picture that constitute the stream, until the entire screen is refreshed by the intra slice, the P picture having a poor image quality and the P picture having a further higher quality than this. The bad B picture is displayed while switching. As a result, in the display screen during that time, the image quality is improved while a part of the screen is gradually refreshed by the intra slice, while the poor image quality of the P picture and the B picture is continuously displayed in the non-refreshed part. This is problematic in terms of display quality.

[0006]

To solve such a problem, Japanese Patent Laid-Open Publication No. Hei 8-163575 discloses a method for decoding and displaying a video stream having no I-picture.
A technique has been proposed in which a part other than an intra slice of the first P picture is replaced with a predetermined image, for example, a gray image, and is decoded. However, in this technique, only the first P picture is replaced with gray color, and subsequent P and B pictures are decoded using the gray P picture as a reference image. Thus, it can be said that it is effective in reducing noise, but since the displayed image is an image in which the difference between subsequent pictures is superimposed on gray color, it is displayed as an image far from the original image and displayed As a result, the balance with the gradually refreshed image is poor, and it is not always preferable in terms of display quality.

[0007] It is an object of the present invention to provide a display method and a display device in which, when decoding and displaying a video stream having no I picture, the display quality until the entire screen is refreshed is improved.

[0008]

According to the image display method of the present invention, when a video stream composed of a P picture and a B picture is decoded and displayed, the B picture is not displayed until a clear picture is obtained. It is characterized in that only P pictures are displayed. Here, until a clear picture is obtained, the decoding is performed by sequentially referring to the intra slice data included in the P picture, and as a result, when one picture is decoded, all the slices of the picture have the intra This is when the information of the slice data is referred to. When the intra slice data constitutes one picture, the image data obtained from the first decoded P picture is stored in the memory as reference image data, and subsequently obtained from sequentially decoded P pictures. This is when each intra slice data included in the image data is written into the memory, and the intra slice data is written into all the slices constituting one picture. Further, while the B picture is not displayed, image data is obtained from the first decoded P picture, the obtained image data is displayed, and the next P picture is decoded until new image data is obtained. The B picture during that time is not decoded. Further, in the present invention, image data other than the intra slice data included in the P picture may be replaced with desired color data.

[0009] The image display device of the present invention comprises a P picture and a B picture.
An image display device that decodes and displays a video stream composed of pictures; a decoding unit that can decode the P picture and the B picture; a display unit that displays image data obtained by decoding the P picture; Storage means for storing, from the image data obtained by decoding the P-picture, intra slice data included in the image data; and determination of outputting a required signal when it is determined that the stored intra slice data constitutes one picture. Means for stopping decoding of the B picture by the decoding means until the signal is output from the determination means. For example, the determination means includes a plurality of registers corresponding to a plurality of slices constituting one picture, and recognizes a register corresponding to intra-slice data included in the decoded P-picture image data. When the register reaches all of the plurality of registers, the required signal is output.
Means for replacing image data other than the intra slice data with the desired color image data in the decoded image data of the P picture;
It is preferable to include means for determining whether to display all of the image data of the picture or to replace and display the image data with the color image data.

According to the present invention, a B picture is not displayed until a clear picture in which the entire screen is composed of clear slices based on a plurality of P pictures is obtained and the entire screen is refreshed. Instead, only P-pictures are displayed, so that P-pictures with higher image quality are displayed continuously compared to B-pictures. To improve the quality of the displayed image. Further, by replacing a part of the image of the P picture with a desired color image, the quality of the displayed image can be improved from another viewpoint.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the display device of the present invention. A PES decoder unit 1 that converts an input stream from PES data to elementary data, or separates audio data and image data, and converts each picture of the converted or separated video stream into an I picture, a P picture, and a B picture. A VLD unit 2 for determining which one of them, an IQ unit 3 for inversely quantizing the image data of each determined picture, an IDCT unit 4 for inverse orthogonal transform decoding of the inversely quantized image data, and decoding. An MC unit 5 for converting the converted image data into a vector and a display control unit 6 for displaying an image on a display device such as a CRT or a liquid crystal display device (not shown) based on the converted image data. Have. Each of the above sections is controlled by the decoding control section 10. The decoding control unit 10 includes the display control unit 6.
And a clear picture determination device 11 for determining that the entire screen of the displayed image data has been refreshed and turned into a clear picture. Further, a memory 20 connected to the respective units via the data bus 7 is provided. The memory 20 includes an input buffer unit 21 for temporarily storing the input video stream, and a memory for storing decoded image data. A decoded image data section 22 for temporarily storing and a reference image data section 23 for storing image data used as a reference image are sectioned.

The general flow of processing in this display device will be described. The input stream is decoded by the PES decoder 1 into elementary data, and is temporarily stored in the input buffer unit 21 of the memory 20. Then, the image data of the input buffer unit 21 is sequentially read out, and the VLD unit 2 determines whether the image data is an I picture, a P picture, or a B picture. Based on this determination result, the decoding control unit 10 determines whether or not to decode the picture. When decoding, the decoding control unit 10 decodes the image data via the IQ unit 3 and the IDCT unit 4. The decoded image data is stored in the decoded image data section 22 of the memory 20. Also, at this time, when the I picture is determined and decoded, all slices of the I picture are composed of intra slices, that is, clear slices and become clear pictures. Data part 2
3 and used as a reference image for subsequent display images. Decoding is also performed when a P picture is determined. If an I picture exists, the picture is output as an image to be displayed using the reference picture data of the I picture and its own picture data. If there is no reference image data, the first determined P picture is decoded and stored in the decoded image data unit 22, and the decoded image data is subjected to coordinate conversion by the MC unit 5 to perform the reference image data unit 23 To memorize. Further, when the B picture is determined, the details of the B picture will be described later.
Decoding of the picture is stopped, but when it is determined that the current image data of the display control unit 6 is a clear picture, the decoding stop of the B picture which has been stopped until then is canceled, and the same decoding and display of the B picture are performed. To start.

Next, the display method of the present invention will be described in detail with reference to the flowchart of FIG. First, FIG.
A case where an I picture is present in an input video stream as shown in FIG. The VLD unit 2 performs picture determination on the input stream. If an I picture exists in the stream as described above, the I picture is determined (S101). Since the I picture is composed of all slices of image data, ie, clear slices, the I picture is cleared. All the flags of the register R as a frame memory incorporated in the picture determination unit are set to "1" (S102, S1
03). Thus, it is determined that the entire screen of the image is a clear picture composed of clear slices (S1).
04). At the same time, the IQ picture 3 and the IDCT section 4 decode the I picture and store the decoded picture data in the decoded picture data section 22. Is stored in the reference image data unit 23 as reference image data, and based on this, the display control unit 6 displays an image on the display device. At this time, since the flags of the register R are all “1”, the clear picture determination device 10 decodes and displays all the subsequent P pictures and B pictures (S105). When decoding and displaying the P picture and the B picture, the clear picture is used as reference image data to form a display image, so that high quality image display is realized.

On the other hand, FIG.
As shown in (b), when there is no I-picture in the stream, the clear picture described above cannot be obtained immediately, so that the display quality up to that point is reduced as described above. It is. In this case, in the present embodiment, the VLD unit 2 performs a picture determination, and when the P picture P1 is first determined (S106), the flag of the register corresponding to the clear slice existing in the P picture P1 is set to “1”. (S107). At this time, all the flags of the register R are initialized to “0”. At the same time, the P picture P1 is decoded via the IQ section 3 and the IDCT section 4, and the decoded picture data section 22 is decoded.
To memorize. Then, the stored decoded image data is MC
The coordinates are converted by the unit 5 and stored as reference image data in the reference image data unit 23, and are read by the display control unit 6 and displayed on the display device.

Next, when the VLD unit 2 determines the B picture B1 following the P picture P1 of the stream (S108), it determines whether or not the B picture B1 is to be decoded (S109). At this time, since no clear slice exists in the B picture B1, another flag of the register R is not set to “1”. Therefore, at this time, all of the flags of the register R have not yet become "1", that is, since the clear picture state is not yet reached, the clear picture determination device 11
Without outputting a signal for decoding picture B1, B
The decoding of the picture B1 is stopped (S110). Therefore, the image data of the decoded image data unit 22 remains the image data of the previous P picture P1, and the image data of the reference image data unit 23 also becomes the image data of the previous P picture P1, so that the display control unit 6 Determines whether to display all the images of the P picture P1 (S11).
1) The image of the same P picture P1 is continuously displayed (S112). Subsequently, the next B picture B2 is determined.
1, the decoding is stopped, and the same P picture P1 is continuously displayed during that time. As a result, as shown in FIG. 4, display is performed in a state where the B pictures B1 and B2 of the stream in FIG. 3B are replaced with the P picture P1.

Subsequently, when the next P picture P2 is determined (S106), the flag of the register corresponding to the clear slice existing in the P picture P2 is set to "1" (S106).
107). At the same time, the P picture P2 is
Unit 3, decodes the data through the IDCT unit 4,
Stored in 2. Then, after reading out the stored decoded image data and performing coordinate conversion in the MC unit 5, the reference image data stored in the reference image data unit 23 is updated, and the updated reference image data is transmitted to the display device control unit. 6 and displayed on a display device. At this time, the image to be displayed is an image in which the clear slice included in the new decoded image data is added in addition to the clear slice of the reference image data, as described with reference to FIG. The clear slice portion is refreshed to improve the image quality.

Next, the B pictures B3 and B4 are sequentially determined again (S108). At this point, since all the flags of the register R have not yet been set to "1", the clear picture determination device 11 changes this state. If it is determined (S1
04), decoding is stopped here as well as the B pictures B1 and B2 (S110), and these B pictures B3
Since the decoded image of B4 cannot be obtained, the image of the P picture P2 is continuously displayed on the display device in place of the B pictures B3 and B4 as shown in FIG.

In this way, a plurality of P pictures are determined, decoded and displayed, and the flag "1" of the register is incremented each time. When all the flags of the register become "1" at the time when a predetermined number of P pictures, in FIG. 4, the P picture P4 is determined, decoded and displayed, the clear picture determination device detects this and forms a clear picture. It is determined that it has occurred (S104). That is, in the decoding of P4, the clear slice of P4 itself and the clear slices of P3, P2,..., P1 decoded earlier are referred to as a result. Are all refreshed by the clear slice. In addition, the clear picture determination device 11 cancels the suspension of the decoding of the B picture that has been continued until the clear picture is determined.
As a result, after the P picture P4, not only the P picture but also the B picture are decoded (S11).
3) The decoded image data of the decoded B picture is sequentially stored in the decoded image data section in the same manner as the P picture, and a display image is sequentially formed with the reference image data of the reference image data section. It will be displayed on the display device. As a result, the display screen on the display device is displayed with an improved image quality equivalent to the case where the stream including the I picture is decoded and displayed.

As described above, in the above embodiment, all the flags of the register R do not become "1" until a clear picture is obtained based on a plurality of P pictures and the entire screen is refreshed. , Clear picture determination device 1
1 stops the decoding of the B picture,
A picture is displayed, but no B picture is displayed. Therefore, although the picture quality is poor compared to the I picture, the P picture having the high picture quality compared to the B picture is continuously displayed, and the P picture and the B picture are mixed as in the related art. It is possible to improve the image quality of the display as compared with the case where it is displayed. Further, in the above-described embodiment, in order to continuously display a series of mutually related P-pictures, a portion other than the clear slice of the first P-picture is replaced with a gray image as in the technique described in the above-mentioned publication. In this case, no extreme change occurs in the displayed image, and the display quality can be improved in that sense. FIG. 5A is a diagram schematically showing one form of display in which a clear picture is obtained halfway through the screen.

Here, in the above embodiment, P pictures are sequentially displayed until a clear picture is obtained, so that the displayed image has a high image quality in a portion which is set as a clear picture by a clear slice. , And other portions are displayed with a lower image quality, and the area of the clear slice gradually increases with time. At this time, since the low image quality part is a P picture image, the image quality is higher than that of the B picture mixed as described above. However, even in this display mode, the presence of a portion having lower image quality than the clear slice may lower the impression of the overall display quality. In such a case, a part of the image of the P picture may be replaced with another image.

That is, in the case of this embodiment, FIG.
In the flowchart of (1), the P picture is decoded to obtain decoded image data, and at the same time, it is determined whether to display all the P pictures (S111). In order to make this determination, whether or not to display all of the P pictures is set in the clear picture determination device 11 in advance. When displaying all the P pictures, the display according to the above embodiment is performed. On the other hand, if it is determined that not all of the P pictures are to be displayed, the area other than the clear picture in the decoded picture data of the P picture is replaced with a desired color image (S114). This color image replacement process can be easily realized in the MC unit 5. Thereafter, the P picture replaced with the color image becomes reference image data, and display on the display device is performed based on the reference image data.
Therefore, in the case of this embodiment, as shown in FIG. 5B, the display screen of the display device displays a clear slice part as a clear picture, while the other parts are displayed as shown in FIG. Will be displayed as a color image. For this reason, it is possible to eliminate the display in a state where the image quality is low in the area other than the clear slice, and it is possible to prevent the fear in the above-described embodiment.

[0022]

As described above, according to the present invention, when decoding and displaying a video stream composed of a P picture and a B picture, only the P picture is displayed without displaying the B picture until a clear picture is obtained. Since it is characterized by displaying, a clear picture is obtained based on a plurality of P-pictures, and until the entire screen is refreshed, P-pictures having higher image quality than B-pictures are continuously displayed. As a result, the quality of the displayed image can be improved as compared with the case where the P picture and the B picture are mixedly displayed. Further, by replacing a part of the P picture image with a desired color image, the quality of the display image can be improved from another viewpoint.

[Brief description of the drawings]

FIG. 1 is a block diagram of a display device of the present invention.

FIG. 2 is a flowchart illustrating a display method according to the present invention.

FIG. 3 is a schematic diagram illustrating an example of a picture configuration of a video stream.

FIG. 4 is a schematic diagram of a display picture according to the display method of the present invention.

FIG. 5 is a schematic diagram showing a display mode according to the display method of the present invention.

FIG. 6 is a diagram for explaining a clear slice and a clear picture.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PES decoder part 2 VLD part 3 IQ part 4 IDCT part 5 MC part 6 Display control part 7 Data bus 10 Decoding control part 11 Clear picture determination device 20 Memory 21 Input buffer part 22 Decoded image data part 23 Reference image data part R register (Frame memory) I picture P1 to Pn P picture B1 to B10 B picture S slice S1 to Sn clear slice (intra slice)

Claims (8)

[Claims] 1. An image display method for decoding and displaying a video stream including a series of code data of a P picture and a B picture and including intra slice data in the code data of the P picture, wherein a clear picture is obtained. The B picture is not displayed until the P
An image display method characterized by displaying only a picture. 2. The method according to claim 1, wherein the time until the clear picture is obtained is a time when intra-slice data included in the P-picture is sequentially accumulated, and one picture is composed of the accumulated intra-slice data. Image display method. 3. When the intra slice data constitutes one picture, the image data obtained from the first decoded P picture is stored in the memory as reference image data, and the P picture which is sequentially decoded thereafter is stored. 3. The image display method according to claim 2, wherein each intra-slice data included in the obtained image data is written into the memory, and the intra-slice data is written into all slices constituting one picture. 4. While not displaying the B picture, image data is obtained from the first decoded P picture, the obtained image data is displayed, and the next P picture is decoded to obtain new image data. 4. The method according to claim 1, wherein the B picture is not decoded until the following is obtained.
The image display method according to any one of the above. 5. The apparatus according to claim 1, wherein, while the B picture is not displayed, image data other than the intra slice data included in the decoded P picture is replaced with desired color data and displayed. The image display method according to any one of the above. 6. An image display device configured to decode and display a video stream including a series of code data of a P picture and a B picture and including intra slice data in the code data of the P picture. Decoding means capable of decoding a B picture, display means for displaying image data obtained by decoding the P picture, and storage for accumulating intra slice data contained in the image data obtained by decoding the P picture Means, a determination means for outputting a required signal when it is determined that one picture has been composed of the accumulated intra slice data, and the B means in the decoding means until the signal is output from the determination means. Means for stopping decoding of a picture. 7. The determining means includes a plurality of registers corresponding to a plurality of slices forming one picture,
Recognizing a register corresponding to intra slice data included in the decoded P picture image data, and outputting the required signal when the recognized register reaches all of the plurality of registers. The image display device according to claim 6. 8. A means for replacing image data other than the intra slice data with desired color image data in the decoded image data of the P picture, and displaying all of the decoded image data of the P picture. 8. The image display apparatus according to claim 6, further comprising: means for determining whether to display the color image data.