Method and device for generating 3D panoramic video streams, and videoconference method and device

• US 8,717,405 B2
• Filed: 06/29/2011
• Issued: 05/06/2014
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Huawei Device Company Limited (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Device Company Limited (Huawei Investment & Holding Co., Ltd.)
• Inventors: Li, Kai, Liu, Yuan, Wang, Jing, Su, Honghong, Zhao, Song
• Primary Examiner(s): Anwah, Olisa
• Application Number:
  US13/172,193
• Publication Number:
  US 20110316963A1
• Time in Patent Office: 1,042 Days
• Field of Search: 379/93.21, 379/158, 379/202.01, 348/14.01, 348/14.08, 348/14.12, 382/285, 382/294, 382/284
• US Class Current: 348/14.08
• CPC Class Codes: H04N 13/243 using three or more 2D image sensors
• CPC Class Codes: H04N 21/42203 sound input device, e.g. microphone
• CPC Class Codes: H04N 21/4223 Cameras H04N23/00 takes precedence
• CPC Class Codes: H04N 21/4788 communicating with other users, e.g. chatting arrangements for providing for computer conferences, e.g. chat rooms, to substation in data switching networks H04L12/1813; distributed application using peer-to-peer [P2P] networks H04L67/104
• CPC Class Codes: H04N 7/15 Conference systems

Abstract

A method and a device for generating 3-dimensional (3D) panoramic video streams, a videoconference method, and a videoconference device are disclosed. The method includes: obtaining depth information of at least two video images; obtaining image data in multiple depth positions from a corresponding video image according to the depth information of each video image; stitching data of the video images according to the obtained image data in multiple depth positions, and generating 3D panoramic video streams. The technical solution of the present invention provides users with high-resolution 3D panoramic seamless telepresence conference video images based on different display modes of different display devices.

Claims

1. In a 3-dimensional depth mapping device, a method for generating overall image data of objects at multiple depths, the method comprising:

obtaining first depth information relative to at least two different focal points of an overall image, which results in at least two different image data views, at a first depth position, to be stitched;

creating first stitched image data by stitching the at least two different image data views at the first depth position, which corresponds to one or more objects within an overall image at the first depth;

obtaining second depth information relative to the at least two different focal points of the overall image, which results in at least two different image data views, at a second depth position, to be stitched;

creating second stitched image data by stitching the at least two different image data views at the second depth position, which corresponds to one or more objects within an overall image at the second depth; and

generating synthesized image data of the one or more objects at multiple depths by combining the first stitched image data with the second stitched image data.

2. The method according to claim 1, wherein the first depth information and the second depth information are obtained simultaneously by at least two depth cameras, which are used to obtain the at least two different image data views at the first death position and the at least two different image data views at the second death position.

3. The method according to claim 1, wherein:

the at least two different image data views at the first and second depth positions are frames of at least two different video streams taken at a same instance in time, the method further comprises;

detecting an image change region of image data in each depth position in a current frame compared with image data in a corresponding depth position in a previous frame of each video stream;

determining that the change region is greater than a set threshold; and

based on the determination, stitching only the image data in the change region.

4. The method according to claim 1, wherein the at least two different image data views at the first and second depth positions are at least two images to be stitched taken at a same instance in time;

before creating the first stitched image data and creating the second stitched image data, the method further comprises;

rectifying the images; and

the rectifying of the images comprises;

obtaining at least two images to be rectified, wherein an overlap region exists between every two adjacent images among the at least two video images to be rectified;

selecting matched feature points of every two adjacent images to be rectified from the overlap region;

generating a color rectification matrix of every two adjacent images to be rectified according to the matched feature points; and

using the color rectification matrix to rectify the images to be stitched.

5. The method according to claim 4, wherein after obtaining the at least two images to be rectified, the method further comprises:

preprocessing the at least two images to be rectified by smooth denoising, and/or distortion rectification.

6. The method according to claim 4, wherein after obtaining the at least two images to be rectified, the method further comprises:

performing color space transformation for the at least two images to be rectified; and

formats of the images before and after the color space transformation comprise;

RGB, HSV, YUV, HSL, CIE-Lab, CIE-Luv, CMY, CMYK, and XYZ.

7. The method according to claim 4, wherein the selecting of the matched feature points of every two adjacent images to be rectified from the overlap region comprises:

detecting Scale-Invariant Feature Transformation (SIFT) feature points in the overlap region, and matching the detected feature points to obtain multiple pairs of matched feature points of two adjacent images to be rectified;

or

detecting the SIFT feature points in the overlap region, matching the detected feature points to obtain multiple pairs of matched feature points of two adjacent images to be rectified, finding regions of the same area by pivoting on the matched feature points, and assigning a mean value of color features of the found regions to the matched feature points;

or

splitting the overlap region, using corresponding regions in the split overlap region of the two images to be rectified as matched feature points, and assigning the mean value of color features of the corresponding regions to the matched feature points;

or

receiving region blocks which are manually selected from the overlap region, using the corresponding selected region blocks of the two video images to be rectified as matched feature points, and assigning a mean value of color features of the corresponding region blocks to the matched feature points.

8. The method according to claim 4, wherein in every two adjacent images to be rectified, one is a source video image, and the other is a destination image;

the generating of the color rectification matrix of every two adjacent images to be rectified according to the matched feature points comprises;

establishing a color space matrix of the source image and a color space matrix of the destination image, wherein each row of the color space matrix represents color space attributes of one of the matched feature points;

establishing a matrix transformation relation between the color space matrix of the source image and the color space matrix of the destination image, wherein the transformation relation is;

the color space matrix of the source image is multiplied by the color rectification matrix, and a multiplication result plus an error amount is the color space matrix of the destination image; and

calculating the color rectification matrix when the error amount is the smallest according to the transformation relation.

9. The method according to claim 4, wherein:

when obtaining two images to be rectified,

the using of the color rectification matrix to rectify the images to be stitched comprises;

receiving the images to be stitched from an inputting apparatus which inputs the source image;

generating a color space matrix of the images to be stitched;

multiplying the color rectification matrix by the color space matrix of the images to be stitched, and using a multiplication result as the color space matrix of rectified images to be stitched; and

generating the rectified images to be stitched according to the color space matrix of the rectified images to be stitched.

10. The method according to claim 4, wherein:

at time of obtaining N images to be rectified that are adjacent in tandem, wherein N is a natural number greater than 2, the N images to be rectified comprise N−

1 pairs of adjacent images to be rectified, and each pair of images to be rectified corresponds to a color rectification matrix;

the using of the color rectification matrix to rectify the images to be stitched comprises;

receiving a image to be stitched from an inputting apparatus, wherein the image to be stitched is a image K among the N images;

generating a color space matrix of the image to be stitched;

multiplying a color rectification matrix 1 to a color rectification matrix K−

1 in tandem to generate a color rectification matrix of the image to be stitched;

multiplying the color rectification matrix by the color space matrix of the image to be stitched, and using the multiplication result as the color space matrix of rectified image to be stitched; and

generating the rectified image to be stitched according to the color space matrix of the rectified image to be stitched.

11. A 3-dimensional (3D) panoramic videoconference method, comprising:

obtaining first depth information relative to at least two different focal points of an overall image, which results in at least two different image data views, at a first depth position, to be stitched;

creating first stitched image data by stitching the at least two different image data views at the first depth position, which corresponds to one or more objects within an overall image at the first depth;

obtaining second depth information relative to the at least two different focal points of the overall image, which results in at least two different image data views, at a second depth position, to be stitched;

creating second stitched image data by stitching the at least two different image data views at the second depth position, which corresponds to one or more objects within an overall image at the second depth;

wherein;

the at least two different image data views at the first and second depth positions are frames of at least two different video streams of the same site taken at a same instance in time from at least two viewpoints;

generating a synthesized frame comprising the one or more objects at multiple depths by combining the first stitched image data with the second stitched image data;

displaying the synthesized frame on a terminal display according to a type of the terminal display.

12. The method according to claim 11, wherein:

before creating the first stitched image data and creating the second stitched image data, the method further comprises;

obtaining at least two images to be rectified, wherein an overlap region exists between every two adjacent images among the at least two images to be rectified;

selecting matched feature points of every two adjacent images to be rectified from the overlap region;

generating a color rectification matrix of every two adjacent images to be rectified according to the matched feature points; and

using the color rectification matrix to rectify the frames.

13. The method according to claim 11, wherein the displaying of the synthesized frame on the terminal display according to the type of the terminal display comprises:

displaying 2-dimensional (2D) image information of the synthesized frame if it is determined that the terminal display is a 2D display;

displaying 3D image information of the synthesized frame if it is determined that the terminal display is a 3D display;

or

displaying image information in multiple depth positions of the synthesized frame if it is determined that the terminal display is a multi-layer display.

14. The method according to claim 11, further comprising:

establishing a mapping relation between gesture information and display control instructions;

obtaining video images of gestures made by persons on the site, and obtaining the gesture information;

obtaining a display control instruction corresponding to the obtained gesture information according to the mapping relation; and

controlling display activities of the terminal display according to the obtained display control instruction.

15. A device for generating overall image data of objects at multiple depths, comprising:

a depth information obtaining apparatus, configured to obtain first depth information relative to at least two different focal points of an overall image, which results in at least two different image data views, at a first depth position, to be stitched, and configured to obtain second depth information relative to the at least two different focal points of the overall image, which results in at least two different image data views, at a second depth position, to be stitched;

a 3D panoramic video stream generating apparatus, configured to create first stitched image data by stitching the at least two different image data views at the first depth position, which corresponds to one or more objects within an overall image at the first depth, create second stitched image data by stitching the at least two different image data views at the second depth position, which corresponds to one or more objects within an overall image at the second depth, and generate synthesized image data of the one or more objects at multiple depths by combining the first stitched image data with the second stitched image data.

16. The device according to claim 15, wherein:

the depth information obtaining apparatus comprises at least two depth cameras; and

the depth cameras are configured to obtain the first depth information and the second depth information simultaneously, and configured to obtain the at least two different image data views at the first depth position and the at least two different image data views at the second depth position.

17. The device according to claim 15, wherein, the at least two different image data views at the first and second depth positions are frames of at least two different video streams taken at a same instance in time, the 3D panoramic video stream generating apparatus comprises an image detecting unit and an image stitching unit:

the image detecting unit, is configured to;

detect an image change region of image data in each depth position in a current frame compared with image data in a corresponding depth position in a previous frame of each video stream; and

output an image stitch instruction after determining that the change region is greater than a set threshold;

the image stitching unit, is configured to;

stitch the image data in the change region according to the image stitch instruction.

18. The device according to claim 15, wherein the at least two different image data views at the first and second depth positions are at least two images to be stitched taken at a same instance in time, and wherein the device further comprises a video image rectifying apparatus which comprises:

an obtaining unit, configured to obtain at least two images to be rectified, wherein an overlap region exists between every two adjacent images among the at least two images to be rectified;

a selecting unit, configured to select matched feature points of every two adjacent images to be rectified from the overlap region;

a generating unit, configured to generate a color rectification matrix of every two adjacent images to be rectified according to the matched feature points; and

a rectifying unit, configured to use the color rectification matrix to rectify the images to be stitched.

19. The device according to claim 18, wherein the video image rectifying apparatus further comprises:

a preprocessing unit, configured to preprocess the at least two images to be rectified, after the obtaining unit obtains the at least two images to be rectified, smooth denoising and/or distortion rectification.

20. The device according to claim 18, wherein the video image rectifying apparatus further comprises:

a transforming unit, configured to perform color space transformation for the at least two images to be rectified, wherein formats of the images before and after the transformation comprise RGB, HSV, YUV, HSL, CIE-Lab, CIE-Luv, CMY, CMYK, and XYZ.

21. The device according to claim 18, wherein the selecting unit comprises at least one of the following units:

a first selecting unit, configured to detect Scale-Invariant Feature Transformation (SIFT) feature points in the overlap region, and match the detected feature points to obtain multiple pairs of matched feature points of two adjacent images to be rectified;

a second selecting unit, configured to;

detect SIFT feature points in the overlap region, match the detected feature points to obtain multiple pairs of matched feature points of two adjacent images to be rectified, find regions of the same area by pivoting on the matched feature points, and assign a mean value of color features of the found regions to the matched feature points;

a third selecting unit, configured to;

split the overlap region, use corresponding regions in the split overlap region of the two images to be rectified as matched feature points, and assign the mean value of color features of the corresponding regions to the matched feature points; and

a fourth selecting unit, configured to receive region blocks which are manually selected from the overlap region, use the corresponding selected region blocks of the two images to be rectified as matched feature points, and assign the mean value of color features of the corresponding region blocks to the matched feature points.

22. The device according to claim 18, wherein:

in every two adjacent images to be rectified, one is a source image, and the other is a destination image;

the generating unit comprises;

a color matrix creating unit, configured to create a color space matrix of the source image and a color space matrix of the destination image, wherein each row of the color space matrix represents color space attributes of one of the matched feature points;

a transformation relation establishing unit, configured to establish a matrix transformation relation between the color space matrix of the source image and the color space matrix of the destination image, wherein transformation relation is;

the color space matrix of the source image is multiplied by the color rectification matrix, and a multiplication result plus an error amount is the color space matrix of the destination image; and

a rectification matrix calculating unit, configured to calculate the color rectification matrix when the error amount is the smallest according to the transformation relation.

23. The device according to claim 18, wherein:

if the obtaining unit obtains two images to be rectified, the rectifying unit comprises;

a video image receiving unit, configured to receive a image to be stitched from an inputting apparatus which inputs the source image;

a color matrix generating unit, configured to generate a color space matrix of the image to be stitched;

a color matrix transforming unit, configured to multiply the color rectification matrix by the color space matrix of the image to be stitched, and use a multiplication result as the color space matrix of the rectified image to be stitched; and

a rectification result generating unit, configured to generate the rectified image to be stitched according to the color space matrix of the rectified image to be stitched.

24. The device according to claim 18, wherein:

if the obtaining unit obtains N images to be rectified that are adjacent in tandem, N is a natural number greater than 2, the N images comprise N−

1 pairs of adjacent images to be rectified, and each pair of images to be rectified corresponds to a color rectification matrix;

the rectifying unit comprises;

a video image receiving unit, configured to receive a image to be stitched from an inputting apparatus, wherein the image to be stitched is a image K among the N images;

a first color matrix generating unit, configured to generate a color space matrix of the image to be stitched;

a rectification matrix generating unit, configured to multiply a color rectification matrix 1 to a color rectification matrix K−

1 in tandem to generate a color rectification matrix of the image to be stitched;

a second color matrix generating unit, configured to multiply the color rectification matrix by the color space matrix of the image to be stitched, and use the multiplication result as the color space matrix of the rectified image to be stitched; and

a rectification result generating unit, configured to generate the rectified image to be stitched according to the color space matrix of the rectified image to be stitched.

25. A 3-dimensional (3D) panoramic videoconference device, comprising:

a depth information obtaining apparatus, configured to obtain first depth information relative to at least two different focal points of an overall image, which results in at least two different image data views, at a first depth position, to be stitched, and obtain second depth information relative to the at least two different focal points of the overall image, which results in at least two different image data views, at a second depth position, to be stitched, wherein;

the at least two different image data views at the first and second depth positions are frames of at least two different video streams of the same site taken at a same instance in time from at least two viewpoints;

a 3D panoramic video stream generating apparatus, configured to create first stitched image data by stitching the at least two different image data views at the first depth position which corresponds to one or more objects within an overall image at the first depth, create second stitched image data by stitching the at least two different image data views at the second death position which corresponds to one or more objects within an overall image at the second depth, and generate a synthesized frame comprising the one or more objects at multiple depths by combining the first stitched image data with the second stitched image data; and

a video image display apparatus, configured to display the synthesized frame on a terminal display according to a type of the terminal display.

26. The device according to claim 25, wherein the device further comprises a video image rectifying apparatus which comprises:

an obtaining unit, configured to obtain at least two images to be rectified, wherein an overlap region exists between every two adjacent images among the at least two images to be rectified;

a selecting unit, configured to select matched feature points of every two adjacent images to be rectified from the overlap region;

a generating unit, configured to generate a color rectification matrix of every two adjacent images to be rectified according to the matched feature points; and

a rectifying unit, configured to use the color rectification matrix to rectify the frames.

27. The device according to claim 25, further comprising:

a display type determining unit, configured to determines a type of a display, and output a display instruction according to a determination result; and

the display, configured to display the synthesized frame according to the display instruction.

28. The device according to claim 25, further comprising:

a gesture instruction storing apparatus, configured to store a mapping relation between gesture information and display control instructions;

a gesture information obtaining apparatus, configured to obtain video images of gestures made by persons on the site, and obtain the gesture information;

a display instruction obtaining apparatus, configured to obtain a display control instruction corresponding to the obtained gesture information according to the mapping relation; and

a display control apparatus, configured to control display activities of the terminal display according to the obtained display control instruction.

29. A computer program product comprising computer executable instructions, which are stored on a non-transitory computer readable medium such that when executed by a computer program processor cause a 3-dimensional (3-D) depth mapping device to perform the following:

obtain first depth information relative to at least two different focal points of an overall image, which results in at least two different image data views, at a first depth position, to be stitched;

create first stitched image data by stitching the at least two different image data views at the first depth position, which corresponds to one or more objects within an overall image at the first depth;

obtain second depth information relative to the at least two different focal points of the overall image, which results in at least two different image data views, at a second depth position, to be stitched;

create second stitched image data by stitching the at least two different image data views at the second depth position, which corresponds to one or more objects within an overall image at the second depth; and

generate synthesized image data of the one or more objects at multiple depths by combining the first stitched image data with the second stitched image data.

30. The computer program product according to claim 29, wherein the first depth information and the second depth information are obtained simultaneously by at least two depth cameras, which are used to obtain the at least two different image data views at the first depth position and the at least two different image data views at the second depth position.

31. The computer program product according to claim 29, wherein the at least two different image data views at the first and second depth positions, which are to be stitched, are frames of at least two different video streams taken at a same instance in time, and wherein the computer executable instructions further cause the 3-D depth mapping device to perform the following:

detect an image change region of image data in each depth position in a current frame compared with image data in a corresponding depth position in a previous frame of each video stream;

determine that the change region is greater than a set threshold; and

based on the determination, stitch only the image data in the change region.

32. The computer program product according to claim 29, wherein the at least two different image data views at the first and second depth positions are at least two images to be stitched taken at a same instance in time, and wherein before create the first stitched image data and create the second stitched image data, the computer executable instructions further cause the 3-D depth mapping device to perform the following:

obtain at least two images to be rectified, wherein an overlap region exists between every two adjacent images among the at least two video images to be rectified;

select matched feature points of every two adjacent images to be rectified from the overlap region;

generate a color rectification matrix of every two adjacent images to be rectified according to the matched feature points; and

use the color rectification matrix to rectify the images to be stitched.

33. The computer program product according to claim 32, wherein after obtaining the at least two images to be rectified, the computer executable instructions further cause the 3-D depth mapping device to perform the following:

preprocess the at least two images to be rectified by smooth denoise, and/or rectify distortion.

34. The computer program product according to claim 32, wherein after obtaining the at least two images to be rectified, the computer executable instructions further cause the 3-D depth mapping device to perform the following:

perform color space transformation for the at least two images to be rectified; and

format of the images before and after the color space transformation comprise;

RGB, HSV, YUV, HSL, CIE-Lab, CIE-Luv, CMY, CMYK, and XYZ.

35. The computer program product according to claim 32, wherein the computer executable instructions that cause the selecting of the matched feature points of every two adjacent images to be rectified from the overlap region further cause the 3-D imaging device to perform one or more of the following:

detect Scale-Invariant Feature Transformation (SIFT) feature points in the overlap region, and matching the detected feature points to obtain multiple pairs of matched feature points of two adjacent images to be rectified;

or

detect the SIFT feature points in the overlap region, matching the detected feature points to obtain multiple pairs of matched feature points of two adjacent images to be rectified, finding regions of the same area by pivoting on the matched feature points, and assigning a mean value of color features of the found regions to the matched feature points;

or

split the overlap region, using corresponding regions in the split overlap region of the two images to be rectified as matched feature points, and assigning the mean value of color features of the corresponding regions to the matched feature points;

or

receive region blocks which are manually selected from the overlap region, using the corresponding selected region blocks of the two video images to be rectified as matched feature points, and assigning a mean value of color features of the corresponding region blocks to the matched feature points.

36. The computer program product according to claim 32, wherein in every two adjacent images to be rectified, one is a source image, and the other is a destination image, and wherein the computer executable instructions that cause the generating of the color rectification matrix of every two adjacent images to be rectified according to the matched feature points further cause the 3-D imaging device to perform the following:

establish a color space matrix of the source image and a color space matrix of the destination image, wherein each row of the color space matrix represents color space attributes of one of the matched feature points;

establish a matrix transformation relation between the color space matrix of the source image and the color space matrix of the destination image, wherein the transformation relation is;

the color space matrix of the source image is multiplied by the color rectification matrix, and a multiplication result plus an error amount is the color space matrix of the destination image; and

calculate the color rectification matrix when the error amount is the smallest according to the transformation relation.

37. The computer program product according to claim 32, wherein when obtaining two images to be rectified, the computer program instructions that cause the use of the color rectification matrix to rectify the images to be stitched further cause the 3-D imaging device to perform the following:

receive the images to be stitched from an inputting apparatus which inputs the source image;

generate a color space matrix of the images to be stitched;

multiply the color rectification matrix by the color space matrix of the images to be stitched, and using a multiplication result as the color space matrix of the rectified images to be stitched; and

generate the rectified images to be stitched according to the color space matrix of the rectified images to be stitched.

38. The computer program product according to claim 32, wherein at time of obtain N images to be rectified that are adjacent in tandem, wherein N is a natural number greater than 2, the N images to be rectified comprise N−

1 pairs of adjacent images to be rectified, and each pair of images to be rectified corresponds to a color rectification matrix, and wherein the computer program instruction that cause the use of the color rectification matrix to rectify the images to be stitched further cause the 3-D imaging device to perform the following;

receive a image to be stitched from an inputting apparatus, wherein the image to be stitched is a image K among the N images;

generate a color space matrix of the image to be stitched;

multiply a color rectification matrix 1 to a color rectification matrix K−

1 in tandem to generate a color rectification matrix of the image to be stitched;

multiply the color rectification matrix by the color space matrix of the image to be stitched, and using the multiplication result as the color space matrix of rectified image to be stitched; and

generate the rectified image to be stitched according to the color space matrix of the rectified image to be stitched.

39. A computer program product comprising computer executable instructions, which are stored on a non-transitory computer readable medium such that when executed by a computer program processor cause a 3-dimensional (3D) panoramic videoconference device to perform the following:

obtain first depth information relative to at least two different focal points of an overall image, which results in at least two different image data views, at a first depth position, to be stitched;

create first stitched image data by stitching the at least two different image data views at the first depth position, which corresponds to one or more objects within an overall image at the first depth;

obtain second depth information relative to the at least two different focal points of the overall image, which results in at least two different image data views, at a second depth position, to be stitched;

create second stitched image data by stitching the at least two different image data views at the second depth position, which corresponds to one or more objects within an overall image at the second depth;

wherein;

the at least two different image data views at the first and second depth positions are frames of at least two different video streams of the same site taken at a same instance in time from at least two viewpoints;

generate a synthesized frame comprising the one or more objects at multiple depths by combining the first stitched image data with the second stitched image data;

display the synthesized frame on a terminal display according to a type of the terminal display.

40. The computer program product according to claim 39, wherein:

before create the first stitched image data and create the second stitched image data, the computer executable instructions further cause the 3D panoramic videoconference device to perform the following;

obtain at least two images to be rectified, wherein an overlap region exists between every two adjacent images among the at least two images to be rectified;

select matched feature points of every two adjacent images to be rectified from the overlap region;

generate a color rectification matrix of every two adjacent images to be rectified according to the matched feature points; and

use the color rectification matrix to rectify the frames.

41. The computer program product according to claim 39, wherein the computer executable instructions that cause the displaying of the synthesized frame on the terminal display according to the type of the terminal display further cause the 3-D mapping device to perform the following:

display 2-dimensional (2D) image information of the synthesized frame if it is determined that the terminal display is a 2D display;

display 3D image information of the synthesized frame if it is determined that the terminal display is a 3D display;

or

display image information in multiple depth positions of the synthesized frame if it is determined that the terminal display is a multi-layer display.

42. The computer program product according to claim 39, wherein the computer executable instructions further cause the 3-D depth mapping device to perform the following:

establish a mapping relation between gesture information and display control instructions;

obtain video images of gestures made by persons on the site, and obtaining the gesture information;

obtain a display control instruction corresponding to the obtained gesture information according to the mapping relation; and

control display activities of the terminal display according to the obtained display control instruction.