WO2004036903A2

WO2004036903A2 - Display for variable aspect ratio signals

Info

Publication number: WO2004036903A2
Application number: PCT/IB2003/005340
Authority: WO
Inventors: Roger Dominik Bozzini; Severin Werner Engeli
Original assignee: Thomson Licensing S.A.
Priority date: 2002-10-18
Filing date: 2003-10-18
Publication date: 2004-04-29
Also published as: AU2003283625A8; WO2004036903A3; AU2003283625A1

Abstract

The invention provides an apparatus and method for displaying video pictures. The apparatus comprises a picture display screen (630) having a first aspect ratio and a picture decoder (610) for decoding a video signal including at least one picture. The picture has a second aspect ratio. In one embodiment of the invention, the second aspect ratio is different than the first aspect ratio. A picture aspect ratio detector (622) is coupled to the picture decoder. A border generator (620) is coupled to the picture aspect ratio detector. The border generator provides a border for the picture. The dimensions of the border are based, at least in part, on the detected picture aspect ratio.

Description

DISPLAY FOR VARIABLE ASPECT RATIO PICTURES

.BACKGROUND OF THE INVENTION

The present invention relates to image display devices and in particular to television receivers and other picture display devices.

Despite many advances in technology, the conventional television set continues to present an appearance of a "big black box". While providing a wide variety of entertainment choices, the television set contributes little to the decor of the home. Mechanical television frames have been devised and constructed of attractive woods, plastics, metals and other materials. These are often available in a variety of colors and styles. However, these choices are limited and can become unsuitable when a homeowner moves the television set, or when the area surrounding the television set is painted, remodeled or otherwise redecorated.

Recently, flat panel displays have become available. Such displays are capable of hanging on a wall. However, the color, texture and other attributes of such displays are frequently inappropriate for the surrounding decor. This mismatch detracts from the overall appearance of a room.

The above mentioned decorating problems are especially evident when a television picture with a given aspect ratio is displayed on a television screen having a screen aspect ratio different than the picture aspect ratio. The term "aspect ratio" refers to the ratio between the horizontal measurement and the vertical measurement of a display screen, image or picture. Most movies are filmed in a process that provides an image suitable for display on a movie theatre screen. The width of a typical movie theatre screen is between 1.85 to 2.4 times greater than the height. Therefore, for every inch of screen height, the visual portion of the movie is between 1.85 to 2.4 times as wide. This results in a panoramic view that can enhance the imagery and mood of a movie.

Unfortunately, most modern television screens are only 1.33 times as wide as they are high. As a result of the difference in aspect ratio between the theatre screen and the television screen, many movies have much of the visuals removed from the screen for home display. This is to match the dimensions of the movie so the picture fills the TV screen.

As a result of this so called "pan and scan" technique, many movies lose story information and depth when presented on a television screen. This loss of information is unacceptable to some viewers. The widescreen or "letterbox" process is a linear processing method that overcomes the problems associated with pan and scan techniques. The letterbox format presents the full, wide picture on the middle of the television screen, with black bars above and below it. This maintains the movie's original theatrical aspect ratio, so a viewer sees everything the movie's director intended. Because they preserve the original cinematography of the movie, letterbox, or widescreen, videos have become more and more popular in recent years. The format is particularly common on DVDs.

An undesirable effect of the letterbox technique is the presence of "black bars". Black bars are unused areas of the screen. A 16:9 image displayed on a 4:3 screen will appear centered on the screen with vertical black bars ('gray' on some models) on both sides. On the other hand, an image that is transmitted with a 4:3 aspect ratio and displayed on a 16:9 screen will appear "window-boxed". Horizontal bars will appear across the top and bottom of the screen. Some viewers regard black bars as unsightly and distracting. This is particularly so when the television set has a visible mechanical frame. In that case the viewer sees two frames. One frame is the mechanical frame of the TV set. The other frame is created by the black bars, or the area of the screen resulting from the letterbox or window box process and not used for the picture. What is needed is a method and system for providing a pleasing presentation regardless of the aspect ratio of the picture or television screen, while matching the television set to the decor of the home.

SUMMARY OF THE INVENTION: The invention provides a method and apparatus for displaying video pictures.

The apparatus comprises a picture processor and a display. The display has a first aspect ratio. The picture processor comprises a decoder for decoding a video signal including at least one picture. The at least one picture has a second aspect ratio. In one embodiment of the invention, the second aspect ratio is different than the first aspect ratio. A picture aspect ratio detector is coupled to the decoder. A border generator provides a border for the picture. The border geometry is based at least in part, on the detected picture aspect ratio. BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 illustrates a display apparatus and a displayed picture, useful for understanding the terms presented herein.

Figure 2 illustrates a display apparatus 200 having a substantially non- visible mechanical frame 205.

Figure 3 illustrates an alternative embodiment of the invention including a picture and a border.

Figure 4 illustrates an alternative embodiment of the inventive arrangements providing an alternative display. Figure 5 is a flow chart illustrating a method according to an embodiment of the invention.

Figure 6 is a block diagram of a signal processing circuit in accordance with an embodiment of the invention.

DETAILED DESCRIPTION:

For purposes of this specification the following terms are used as defined herein. The term "Source Aspect Ratio" refers to the aspect ratio of the picture comprising the source video signal, e.g., about 4:3 or about 16:9. The term

"Display Aspect Ratio" refers to the aspect ratio capability of the display device, e.g., television screen or projection equipment. This is typically about 4:3 , or about 16:9 . The term "picture" refers to a visual scene or series of scenes intended to be viewed by a human viewer, e.g., a video image, or a series of video images as would comprise a motion picture, television show, video game, commercial, home movie, etc. The term "picture" also includes still images. Figure 1 illustrates a picture display device 100 comprising a picture display area 110 and a mechanical frame 105. Picture display device further comprises circuits for providing a picture 120 for display in at least a portion of display area 110. Display apparatus 100, for purposes of illustration, is situated within a room 130, for example, a room in the home of a television viewer, a professional office or other decorated living space. Picture display device 100 is capable of displaying motion, still or other pictures from a variety of broadcast and non- broadcast sources.

In one embodiment of the invention, frame 105 is generally rectangular in shape and includes a plurality of frame segments 15, 16, 17 and 18 that are typically constructed from U-shaped channels in accordance with conventional methods. While one embodiment of frame 105 is shown as a rectangular structure, a variety of display devices having different mechanical frame shapes and sizes are commercially available. For purposes of discussion of the example illustrated in Fig. 1 , picture display area 110 has an aspect ratio of about 16:9. That is, display 100 is capable of displaying pictures having a source aspect ratio of dimension x to dimension y of 16:9 so as to substantially fill display area 120.

Figure 1 illustrates a picture 120 having a source aspect ratio of about 4:3 as it appears displayed within display area 110. The ratio of dimension x of picture 120 to dimension y of picture 120 is about 4:3 as transmitted from a source. As a result of the difference in aspect ratio between picture 120 and display area 110, and to preserve the source aspect ratio of picture 120, "black bars" 115 appear on both sides of picture 120. The black bars 115 are areas of display area 110 not filled by picture 120. A "two frame effect" is caused by the appearance of black bars 115 adjacent to picture 120. The black bars 115 present a first frame, or picture border, to a viewer. A second frame is presented to t he viewer by mechanical frame 105. Figure 2 illustrates a display apparatus 200 in accordance with an embodiment of the invention. A substantially frameless picture display apparatus 200 is provided. That is, the visible part of mechanical frame 105 is sufficiently narrow so as to be substantially not visible to a viewer when display apparatus 200 is viewed from a normal viewing distance. This reduces the contribution of mechanical frame 105 to the "two-frame" effect. Further reducing the two-frame effect, picture 220 fills substantially all of display area 210. This allows a brilliant frameless picture to fill display area 210 and presents an aesthetically pleasing option for a viewer.

Figure 3 illustrates an alternative embodiment of the invention. A border 315 fills at least a portion of display area 320 instead of the black bars 115 illustrated in Fig. 2. At least one of color, frame, texture, dimensions and other attributes of border 315 are selectable by a viewer. In one embodiment of the invention, a menu of viewer selectable border attributes is presented to the viewer and at least one selection option is provided to the viewer via a remote control device. Alternatively, viewer operable attribute selection means are provided as an integral part of a housing (not shown) of display device 300.

Regardless of the user selection device employed, at least one of a color palette, texture palette, and other attribute choices are stored in a memory of display device 300 and provided to a border generator (illustrated in Fig. 6) such that a viewer may match border 315 with the decor of a room. In this way the subjective appearance of the picture display device is greatly enhanced.

In one embodiment of the invention, the positioning of border 315 is selectable by a viewer. The position of the border is selectable to appear, not only in place of black bars 115 (illustrated in Fig. 1 ), but adjacent picture 320 at the top and bottom (and, alternatively, left and right) of display area 310. The overall appearance and impression of such a closed frame is, in some cases, preferable to a viewers over single frames on top and bottom or left and right, of display area 320. Such a border is illustrated in Figure 3. In order to provide the border 315 illustrated in Fig. 3 (i.e., adjacent to all sides of display area 320) display apparatus 300 reduces the size of picture 320. In one embodiment of the invention, size reduction is accomplished by linearly down-scaling the picture so as to preserve aspect ratio and to avoid possible distortions. In an alternative embodiment of the invention, border 315 is selectable to surround picture 320 active even when the source picture aspect ratio and the format and the display aspect ratio are similar.

Figure 4 illustrates an alternative embodiment of a picture display device 400 of the invention implemented when display 400 is in a "stand by" mode (i.e., video from a program or other content source is not displayed). As illustrated in Fig. 4, frame 415 is substantially not visible to a viewer from a typical viewing distance. Furthermore, a complete integration of the border area illustrated in Fig. 3 at 315, with the picture display area 320 is achieved by displaying a full size image. In one embodiment of the invention, the full size image is customizable by a viewer by selecting from a menu of choices. In one embodiment of the invention, display 400 is operable by a viewer to download a picture from a source such as the Internet, a camera, or a home or other computer.

Figure 5 is a flow chart useful for explaining implementation of the inventive arrangements. In an initial step 505 the resolution of the video transmitted by the source is detected by a detecting means. In one embodiment of the invention, the aspect ratio of the video transmitted by the source is also detected in initial step 505. A number of circuits capable of resolution detection and aspect ratio detection are readily commercially and need not be described in detail herein.

Once the picture aspect ratio and resolution are detected, they are compared to a reference criteria. In one embodiment of the invention the reference criteria includes at least the display aspect ratio. In the case that the source picture aspect ratio and the display aspect ratio are similar, processing proceeds with step 520. If the source picture aspect ratio and the display aspect ratio detected in step 505 are different, the method proceeds with step 515. Step 520 is to determine if a border is to be displayed with the picture.

If no border is to be displayed, the picture is displayed on the display without carrying out other steps of the method. If a border is to be displayed, the method proceeds with step 525. Step 515 is to resize the source image to fit the display area of the display. That is, to provide a picture of a size that will substantially fill the display area of the display. In one embodiment of the invention, the resizing step is selectable such that the picture can be resized in the horizontal direction or in the vertical direction, or in both directions. After step 515 the method proceeds with step 525. Step 525 is to provide a viewer selection means enabling a viewer to select attributes of the border in accordance with the attributes described above. Further examples of viewer selectable attributes include a user selected aspect ratio. Other examples of viewer selectable attributes are picture dimensions, border dimensions, border color, texture, border shading, border stippling, border hue and other border attributes and characteristics.

Once at least one of the selectable attributes are selected by a viewer the method proceeds with step 530. In step 530 a resize factor for the source picture is determined. The resize factor is the amount by which the picture dimensions must be changed to achieve the dimensions corresponding to at least one viewer selection. Once the picture resize factor and other viewer selectable attributes are known a final step of providing a border in accordance with the selected attributes is carried out.

In one embodiment of the invention, border attributes are selected by a viewer via a remote user interface device such as a remote control device or an on-screen user interface means. In one embodiment of the invention, user selected attributes are stored in a memory and are recallable according to a predefined storage schema.

If step 510 determines the source picture aspect ratio and the display aspect ratio are the same, the next step, 520, determines if a viewer has selected a border. If not, the picture is displayed on display screen 310. If a viewer has selected a border, the characteristics of the border are determined in step 525. In one embodiment of the invention this step is carried out by presenting an on-screen menu of characteristics to the viewer for selection. Such border characteristics include, but are not limited to, color, texture, border width and other attributes as described in detail herein. Further attributes include the placement on the screen of the border segments. For example, the border may appear adjacent the top and bottom sections of the viewing area of the display as in a letter box display. Alternatively, the border may appear only adjacent to the side sections as in a window box display. In the case where the video is sized such that black box areas surround the picture, the viewer may choose a border that appears on top, bottom and both sides. Thus the border is selectable to be viewable instead of at least one black bar.

In step 530, the resize factor for the picture is calculated. The resize factor is determined based on the viewer selected attributes. Also in step 530 the border is added to the displayed video presentation by a border generator (illustrated in Fig. 6). In step 535, the resulting picture is displayed to the viewer.

Figure 6 shows a block diagram of a video receiving and display apparatus 600 in accordance with an embodiment of the invention. The functions illustrated in Fig. 6 are capable of implementation, at least in part, in a television receiver, e.g. a digital television receiver, a set top box, or other video signal receiving apparatus. In one embodiment of the invention, video receiving and display apparatus 600 includes the usual amplifying, tuning, intermediate frequency detection and demodulation circuits for receiving a video signal and providing a composite video and blanking signal for a display.

Apparatus 600 is capable of receiving, processing and displaying video from a variety of video signal sources 607. Video sources suitable for use in the invention signal source include broadcast video source, broadcast and cable television sources, satellite sources, and the Internet. Further, video recording, playing and memory devices such as VCRs, DVD players and recorders, PDAs and the like are suitable sources for providing a video signal for use in the present invention. For purposes of discussion, picture processor 614 is depicted as comprising a decoder 610 and two signal processing sections 615 and 620 . While these are illustrated as separate functional blocks, this grouping is for purposes of discussion only. It will be understood by those of ordinary skill in the art that the functions performed by the various blocks and circuits discussed herein are capable of implementation in hardware or in software and can reside in a number of possible physical locations, either singly or distributed among a plurality of physical components. Thus, the present invention is not limited to any particular hardware implementation. In one embodiment of the invention signal source 607, comprises an antenna or cable television distribution network, providing a radio frequency (RF) signal comprising a plurality of television signals modulated according to a vestigial sideband (VSB), quadrature amplitude modulation (QAM) or other suitable modulation scheme. The provided RF television signals are coupled to e.g., a DTV front end comprising, e.g., an antenna, a tuner, a demodulator, and a transport demultiplexer (not shown).

In one embodiment of the invention, signal source 607 provides an MPEG- like system stream containing one or more MPEG-like program transport streams. The MPEG-2 standard, for example, describes an encoding method suitable for use with the invention. The MPEG standard results in substantial bandwidth reduction by a subjective lossy compression followed by a lossless compression. The encoded, compressed digital data is subsequently decompressed and decoded in decoder 610, which, in one embodiment of the invention is an MPEG-2 compliant decoder. The signal from decoder 610 is processed by signal processing circuits 615 and 620, formatted for display by output by display driver 625 and displayed on a display device 630. In one embodiment of the invention, display device 630 is a CRT display device and the processed video signal is displayed according to horizontal and vertical timing signals produced by a raster generator. However, the invention is not limited to CRT display devices. Other display devices such as projection type devices, Liquid Crystal Diode (LCD) and other display types are suitable for use in accordance with the principles of the present invention.

In one embodiment of the invention, decoder and signal processor 614 includes a normal video mode and at least one scaled video mode. In scaled video mode, a video scalar 624 scales the decoded stream of video data when picture processor 614 is in the scaled video mode. When in the normal video mode, full size frames are output from picture processor 614 for display on display 630. When in the scaled video mode, scaled frames comprising a fractional size of the full size frames are output from picture processor 614 for display on display 630. System 600 includes a user operable selection means 670, for example, a remote control device. Remote control device 670 cooperates and communicates with a controller 606 to cause apparatus 600 to operate in a manner that facilitates the processing of the video signal in accordance with the invention as described herein PicturepProcessor 614 further comprises an aspect ratio discriminator 622 for discriminating an aspect ratio from the video signal provided by signal source 607. Aspect ratio discriminator 622 provides pictures to display 630 that correspond to predetermined criteria, or to user selected criteria.

In one embodiment of the invention, aspect ratio detector 622 includes a plurality of user selectable modes for converting between 4:3 and 16:9 aspect ratios. In one embodiment of the invention, aspect ratio detector 622 provides additional user-selected pre-set modes. In one embodiment of the invention aspect ratio detector 622 is capable of continuously compressing and/or expand a picture from about 50% to about 200% normal size. In one embodiment of the invention, controller 620 cooperates with remote control device 670 user to provide a user selectable first option for 16:9 sources to be shown on a 4:3 monitor with the geometry of the 16:9 source picture preserved. In an embodiment of the invention controller 620 is operable to cause conversion of a 4:3 aspect ratio video signal to a 16:9 signal for display and vice versa. Therefore, apparatus 600 is operable by a viewer to select display of an entire picture with a border, less than an entire picture with more narrow border, or even less picture with virtually no border.

In one embodiment of the invention, pre defined selections of at least one of attributes comprising aspect ratio, resolution, scaling, frame color, and scale are stored in Memory 605. Also stored in memory 605 is at least one of a color and texture palette 601.

In accordance with the principles of the present invention, picture processor 614 includes an image sealer 623. Image sealer 623 receives a digitized image at its input and converts the image to adapt to the signal characteristics and attributes selected by the user according to a predefined scaling factor, e.g., 2 and/or 4 in both either the horizontal and vertical axis.

In that manner, picture processor 614 is operable to scale the size of an MPEG-2 video presentation by a predetermined, user selected reduction factor. Sealer 623 of video decoder signal processor 614 reduces the size of the decompressed digital video from decoder 607 to a fractional picture display size for producing a reduced size, decompressed video signal for display on display 630.

According to one embodiment of the invention, in order to upscale, sealer 623 generates a higher number of scanning lines (NV) and/or horizontal pixels (NH) by a process of interpolation. The interpolation simulates image positions that do not correspond to available samples. Sealer 623 upscales by reducing the number of scanning lines (NV) and/or horizontal pixels (NH) by a process of decimation. In one embodiment of the invention the interpolation is achieved by performing mathematical operations on the number of samples representing the original imagein accordance with conventional image processing techniques applied in the digital domain. In typical applications the mathematical operation is a multiplication complemented by a division. In the analog domain this multiplication process can be performed by an analog multiplier and is a continuous process. In the digital domain a digital multiplier operating on each sample of the image performs it. Resizing the image affects the sampled spectrum, resulting in aliasing. In one embodiment of the invention Finite-impulse-response (FIR) digital filters are used to avoid aliasing.

According to one embodiment of the invention, images can be adapted to aspect ratios ranging from traditional 4:3 aspect ratios of conventional computer monitors and televisions to the 16:9 format used in wide screen HDTVs. Apparatus 600 includes external memory 605 and 602 for storing attributes, for example, a color palette. Memory 605 cooperates with border generator 620 of picture processor 614 to provide border attributes in accordance with viewer selections.

The present invention can be included, for example, in an article of manufacture (e.g., one or more computer program products) having, for instance, computer usable media. This media has embodied therein, for instance, computer readable program code means for providing and facilitating the capabilities of the present invention. The articles of manufacture can be included as part of the computer system or sold separately. Additionally, at least one program storage device readable by machine, tangibly embodying at least one program of instructions executable by the machine, to perform the capabilities of the present invention, can be provided.

The flow diagrams depicted herein are provided by way of example. There may be variations to these diagrams or the steps (or operations) described herein without departing from the spirit of the invention. For instance, in certain cases, the steps may be performed in differing order, or steps may be added, deleted or modified. All of these variations are considered to comprise part of the present invention as recited in the appended claims.

While the invention has been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art. Accordingly, it is intended by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.

Claims

1. A display apparatus comprising: a picture display area having a first aspect ratio; a video decoder for decoding a video signal including at least one picture to be displayed by said display, said at least one picture having a second aspect ratio; an aspect ratio detector coupled to said video decoder for detecting said second aspect ratio; a border generator coupled to said aspect ratio detector; said border generator providing a border to be displayed with said picture, the dimensions of said displayed border based, at least in part, on said second aspect ratio.

2. The device of claim 1 further comprising: memory means for storing attributes for said border; user operable means for selecting said border attributes from said stored attributes; said border generator providing a displayed border based, at least in part, upon said user selected border attributes.

3. The device of claim 2 wherein said attributes are selected from the group comprising color, texture, dimension and pattern.

4. The device of claim 3 wherein said border dimension attribute is selectable such that said border fills substantially the whole screen display.

5. A video receiving apparatus comprising: means for decoding a video signal, said video signal including at least one picture to be displayed; means for determining an aspect ratio of said at least one picture; means for displaying said at least one picture, said means for displaying characterized by a first aspect ratio, said displayed picture characterized by a second aspect ratio; means for generating and displaying a border for said displayed picture; user operable means for selecting display attributes of said displayed border.

6. The video receiving apparatus of claim 5 wherein said display attributes are selected from the group comprising color, texture, pattern, and dimension.

7. The video receiving apparatus of claim 5 wherein said user operable means is operable to select a display aspect ratio for said displayed picture.

8. The video receiving apparatus of claim 5 wherein said user operable means is operable to select display dimensions/resolution of said displayed picture

9. A method for displaying a video signal including at least one picture, the method comprising the steps of: receiving a video signal including said at least one picture to be displayed; detecting an aspect ratio of said at least one picture; generating and displaying a border for said at least one picture based on said detected aspect ratio of said picture.