DISPLAYING RESIZED VIDEO

FIELD OF THE INVENTION

The present invention relates to a method of operating a video system to display a resized video and also to a video system operable to display a resized video.

BACKGROUND OF THE INVENTION

A number of interactive applications for digital television allow for the display of a resized video in a window (or viewport) of the interactive application. This resized video window is displayed by making a "hole" in an overlay plane (containing the interactive application information, graphics, functions etc.) thus revealing the resized video.

Prior to the advent of high definition TV, the Cartesian coordinates of the resized video window in the overlay plane and the size of the resized video window in the overlay plane were always specified in a frame of reference corresponding to a standard definition (SD) video display format of 4/3 or 16/9, corresponding to a screen resolution of 720x576 pixels (i.e. 720 pixels per column and 576 pixels per line displayed on the screen). Therefore, in standard definition (SD) format, the Cartesian coordinates in the overlay plane of the resized video window as well as the size of the resized video window in the overlay plane required no geometric transformation. In high definition (HD) formatted video, the video image signal could have any one of a plurality of video resolutions when received for display. The coordinates and size of a resized video window for the overlay plane of a received video signal must be adjusted to a desired output resolution in order to obtain an output video size that is consistent with the resized video window and is in the correct position on the screen. In addition, the HDTV label of the European Information, Communications and Consumer Technology Industry Associations (EICTA), which signifies that a device can receive and process HD television

signals, requires support of an automatic mode that preserves the resolution of the received video signal for the output video signal since the resolution of the received video signal is not known in advance (see www.eicta.org, 'EICTA "HDTV" Minimum Requirements for HD Television Receivers ', paragraph 3.2, point 11). For DVB video encoded according to the MPEG standard, this is a consequence of the video resolution not being signaled in the DVB Service Information (SI) or Programme Specific Information (PSI) or in any MPEG signaling packets. Rather, the MPEG video must be decoded in order to discover the video resolution. It is therefore necessary to modify the video according to the resolution of the received video signal on the one hand and according to the desired output resolution on the other hand. This video image modification requires the translation of the resized video window coordinates and a homothetic conversion of size of the resized video window in order to modify it for display in the desired output resolution. One solution to this problem consists of recalculating the coordinates and dimensions of the resized video window each time a new video signal resolution is received. These calculations are typically carried out in the application layer of the decoder. Hence the resolution information for the received video signal passes from the base layer of the decoder, which receives and decodes the video signal and hence discovers the resolution of the received video signal, to the application layer through various drivers/controllers and interfaces. Once the resolution of the received video signal is received by the application layer and the dimensioning and positioning calculations have been carried out, these calculations pass from the application layer back to the base layer, which resizes and repositions the received video image in order to display it correctly inside the resized video window. However, the received video signal is typically displayed immediately after it has been decoded by the base layer and therefore the received video is displayed much more quickly than the time it takes for the position and size information to be processed. When the resolution of the received video signal changes (perhaps suddenly), this results in the incorrect display of the received video inside the resized video window and a visible refraining of the video

displayed inside the resized video window once the position and size information have been calculated and received.

United States patent application of Miura (USSN 11/116,221, published as US 2005/0253950) describes synthesizing on screen display (OSD) data to be superposed on a picture of each resolution by using common OSD data. A video resolution converter converts an HD (High Definition) video signal into an SD (Standard Definition) video signal such as an NTSC or PAL video signal. A memory controller receives a sync signal identical to an SD picture obtained by frequency-dividing an HD video signal, and a sync signal based on an SD video signal, and reads out OSD data (4 bits per pixel) from the memory on the basis of these sync signals. The OSD data read out on the basis of the SD video signal is synthesized with the SD video signal by an SD_OSD_MTX unit, and then output. The OSD data read out on the basis of the SD sync signal synchronized with the HD is multiplied by an integer by an OSD resolution converter, synthesized with an HD video signal by an HD_OSD_MIX unit, and then output.

The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.

SUMMARY OF THE INVENTION

There is provided in accordance with an embodiment of the present invention, a method of operating a video system to display a resized video in a resized video window, the video system including a base layer and an application layer, the method including in the application layer: constructing an overlay plane in a reference resolution, the overlay plane including: one or more layers of graphics; and a window; calculating a size and position for the window in the overlay plane; and transferring the overlay plane and the size and position of the window to the base layer; the method further including in the base layer: receiving an input video; resizing the overlay plane using the overlay plane in the reference resolution to form a resized overlay plane in an output resolution, the resized overlay plane including: one or more layers of graphics; and a resized video

window; calculating a new size and new position for the resized video window using the size and position of the window; resizing the input video using the new size of the resized video window to form the resized video; and displaying the resized video in the resized video window using the new position of the resized video window.

Preferably, the input video has an input video resolution, and the input video resolution is the same as the output resolution.

Alternatively, the input video has an input video resolution, and the input video resolution is different to the output resolution. Preferably the input video resolution is a standard definition video resolution.

Alternatively, the input video resolution is a high definition video resolution and the output resolution is a standard definition video resolution.

Alternatively, the input video resolution is a standard definition video resolution and the output resolution is a high definition video resolution.

Alternatively, the input video resolution is a high definition video resolution.

Preferably, the reference resolution is smaller than the output resolution. Alternatively, the reference resolution is the same as the output resolution.

There is provided in accordance with a further embodiment of the present invention, a video system operable to display a resized video in a resized video window, the video system including: a base layer; and an application layer, where the application layer is operable to: construct an overlay plane in a reference resolution, the overlay plane including: one or more layers of graphics; and a window; calculate a size and position for the window in the overlay plane; and transfer the overlay plane and the size and position of the window to the base layer; where the base layer is operable to: receive an input video; resize the overlay plane using the overlay plane in the reference resolution to form a resized overlay plane in an output resolution, the resized overlay plane including: one or more layers of graphics; and a resized video window; calculate a new size and new

position for the resized video window using the size and position of the window; resize the input video using the new size of the resized video window to form the resized video; and display the resized video in the resized video window using the new position of the resized video window. Preferably, the input video has an input video resolution, and the input video resolution is the same as the output resolution.

Alternatively, the input video has an input video resolution, and the input video resolution is different to the output resolution.

Preferably, the input video resolution is a standard definition video resolution.

Alternatively, the input video resolution is a high definition video resolution and the output resolution is a standard definition video resolution.

Alternatively, the input video resolution is a standard definition video resolution and the output resolution is a high definition video resolution. Alternatively, the input resolution is a high definition video resolution.

Preferably, the reference video resolution is smaller than the output video resolution.

Alternatively, the reference video resolution is the same as the output resolution.

In order to display a resized video in a resized video window of an interactive application, the method according to embodiments of the present invention uses a reference resolution, which is independent of both the input video resolution and the output video resolution, for the various processes and calculations carried out in the application layer, as well as for data exchanges that occur between the application layer and the base layer. The overlay plane, which includes one or more graphics layers and a window, as well as the size and position of the window, are calculated for the reference resolution in the application layer. Following this, the overlay plane as well as the size and position of the window are passed to the base layer in the reference resolution, and the base layer: resizes the overlay plane in accordance with a desired output resolution; calculates a size and position for the resized video window; and resizes the input

video signal in accordance with the desired output resolution and then displays it in the resized video window. Preferably, the reference resolution used by is 960x576 pixels in order to match the legacy SD application video resolution and in order to reduce the amount of graphics calculations that consume lots of RAM and processing (CPU) power. Advantageously, a quality video signal can be provided whilst still maintaining an acceptable level processing power for the various calculations. In addition, various decoder input and output signal resolutions can be handled.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: Figure 1 shows a television broadcasting system according to embodiments of the present invention;

Figure 2 shows the position of a resized video window relative to an overlay plane, according to embodiments of the present invention;

Figure 3 shows a digital decoder architecture according to embodiments of the present invention; and

Figure 4 shows a procedure for managing the display of a resized video image in a resized video window according to embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows a television broadcasting system, and in particular one for HD television. The system comprises, for example, an antenna 1 that broadcasts SD and HD video signals 2. The video signals 2 are received by a decoder 4. These video signals can be in one a plurality of formats: if the video signal is an SD video signal, it can have either a 4/3 or 16/9 format, whereas if the video signal is an HD signal, it has a 16/9 format. An SD video signal has, for

example, a resolution of (720x576), which corresponds to a display consisting of 576 rows and 720 columns of pixels. On the other hand, an HD video signal can have one of two resolutions: (1280x720) and (1920x1080). Therefore, the decoder 4 for the video signal 2 is operable to process at least video signals having a 4/3 format and 16/9 format, as well as video signals having a (720x576) resolution, a (1280x720) resolution and a (1920x1080) resolution. In addition, decoder 4 is operable to output two output video signals 3, 5 whatever the format and resolution of the received video signal. Decoder 4 is operable to transmit output video signal 5, whose resolution is (720x576), to an SD display 7, and operable to transmit video signal output 3, whose resolution is (720x576), (1280x720) or (1920x1080), to an HD display 6, whatever the format and resolution of video signal 2. In addition, in the case of a decoder with an HDTV label, the resolution of the output video signal 3 is the same as the resolution of the received video signal 2. That is to say, when the resolution of the received video signal changes, for example, from (720x576) to (1280x720), the resolution of the output video signal also changes from (720x576) to (1280x720). This is true for both video displayed in full screen and equally true for video displayed in a resized video window. In alternative embodiments of the present invention, various sub- combinations of the system of figure 1 are possible, including (but not limited to) decoder 4 without the other elements.

Figure 2 shows an example of the display of a resized video in a resized video window 23 in an overlay plane 24. The entirety of the original received video 21 is selected and is then resized to the scale of the resized video window that is defined, for example, by width 1 and height h of the resized video window. The resized video window is displayed in a specific position 25, defined according to coordinates (x,y). This position 25 corresponds, for example, to one of the corners of the resized video window 23. A transformation 22 that is proportional to the ratio of the resolution of the output video signal to the resolution of the received video signal is calculated and applied to the received video signal. If the resolution of the received video signal changes, the transformation is recalculated by the decoder in order to correctly display the video in resized video window 23. A "hole" is realised in the overlay plane 24,

the dimensions of the hole being (l,h) and the position of the hole in the overlay plane being (x,y). The overlay plane 24 is then superimposed on the resized video in order to inlay the resized video window in the overlay plane.

Figure 3 shows a high level architecture for digital decoder 4. Decoder 4 processes a received video signal 32, which can contain video data, as well as other digital data such as information relating to the programs being broadcast. A user is also able to access certain interactive applications using decoder 4. Decoder 4 comprises a base layer 34 and an application layer 36. Base layer 34 includes tuner 33, which receives and decodes video signal 32; mixer 38, which composes the output video signal 30 (which may contain only video data but could also contain graphics from interactive applications together with video); drivers/controllers 35; and interface 37, which provides an interface between base layer 34 and application layer 36 of decoder 4. Interface 37 allows information to pass back and forth between base layer 34 and application layer 36. Application layer 36 is loaded with various pieces of software, and in particular, with any interactive applications available to the user.

Video signal 32 received by decoder 4 is decoded by tuner 33, which then transmits a video element 39 to mixer 38 for quasi-instantaneous output and display. Tuner 33 also transmits video and other information (e.g. interactive application data) to application layer 36 via interface 37 and a driver/controller associated with tuner 33. In the present embodiment, application layer 36 supplies mixer 38 (via interface 37 and a driver/controller associated with mixer 38) with an overlay plane in the form of various superimposed planes containing the information to display as part of an interactive application. Mixer 38 then composes a video signal 30 that contains, for example, video in the form of a resized video window inlayed in the graphics of an interactive application.

Figure 4 shows an example of the processing carried out in order to display a resized video window as an inlay in an interactive application overlay plane according to embodiments of the present invention. Video signal 48, which comprises, for example, an HD video signal having a resolution of (1280x720), is received by tuner 52. The video signal 48 is then scaled so as to allow for display with an SD resolution of (720x576), thus providing an SD video signal 47. If

necessary, video signal 48 is also scaled so as to allow for display with a different HD resolution to the HD resolution of video signal 48 (e.g.(1920xl080)), thus providing an HD video signal 53. If no scaling is necessary, video signal 48 is provided as HD signal 53. In parallel, application layer 36 composes an overlay plane using a reference resolution (e.g. (960x576)). The (960x576) reference resolution is equivalent to a (720x576) resolution that is extended for a 16/9 display by adding 120 columns of pixels onto each side of the overlay plane. The various graphic layers for interactive applications are defined in application layer 36 according to this reference resolution whatever the desired output video resolution.

This frees application layer 36 from the constraints associated with having to work with the input video signal resolution (which may not be known until after decoding of the input video signal has commenced) and the output video signal resolution. The various computations carried out in application layer 36 are also simplified. In addition, the fonts used in the graphics layers of the interactive applications can be defined carefully so as to ensure their accurate reproduction during any future resizing processes. However, after any resizing process, the fonts can sometimes appear pixilated and therefore a smoothing algorithm for the various fonts is preferably applied to any text that appears in the various graphics layers. The smoothing algorithm, such as one based in the Freetype 2 font engine of "The Freetype Project" (www.freetype.org), aims to delete the supplementary pixels that can appear after any resizing operation and which pixilate the fonts.

The formation of the overlay plane will now be described in more detail. First a base graphics layer 41 is copied into a buffer memory 44. The buffer memory 44 allows a "hole" 45 to be created in the base graphics layer into which a video window can be inlayed. Following this, various graphics layers 42 comprising the interactive application graphics are copied into buffer memory 44. Hence buffer memory 44 comprises the base graphics layer and various other graphics layers, which comprise a "hole" 45 allowing for the display of the video window. The size and position of the video window are calculated in accordance with the reference resolution (e.g. (960x576)). Buffer memory 44 passes the overlay plane to base layer 34 of decoder 31.

For HD display, base layer 34 then uses the overlay plane in the reference resolution to resize the overlay plane in accordance with the desired HD output resolution to form resized overlay plane 43 having a resolution of either (1920x1080) or (1280x720). This includes calculating the size and position of a resized video window in the resized overlay plane. Mixer 38 then uses the size and position of the resized video window to resize HD video signal 53 to form a resized video and to position the resized video in the resized video window of resized overlay plane 43. The resulting video image 49 contains the received video, which has been resized, embedded in the resized video window of the resized overlay plane. Video image 49 is then passed to the HD output of decoder 4 so as to provide a video signal 50 having an HD resolution.

For SD display, since the reference resolution, in this embodiment, is the same resolution as that used for an SD output video signal, the overlay plane computed by application layer 36 in the reference resolution and held in buffer memory 44 is resized by removing the lateral bands. The size and position of a resized video window in the resized overlay plane are the same as the size and position of the video window as calculated in the reference resolution by application layer 36. Mixer 38 then uses the size and position of the resized video window to resize SD video signal 47 to form a resized video and to position the resized video in the resized video window of resized overlay plane 46. The resulting video image 46 contains the received video, which has been resized, embedded in the resized video window of the resized overlay plane. Video image 46 is then passed to the SD output of decoder 4 so as to provide a video signal 51 having an SD resolution. It will be apparent to the person skilled in the art that the example described above in relation to figure 4 applies analogously to the reception of a video signal having an SD resolution.

In view of the large number of video resolutions that various video systems process, the definition of a reference resolution, which is used as a working or interchange resolution, limits the number of data exchanges that take place between application layer 36 and base layer 34 of decoder 4. In fact, in

order for base layer 34 to compute the various video signals that are outputted by decoder 4, it is sufficient for application layer 36 to pass to base layer 34:

+ the size and position of the video window, which have been calculated in accordance with the reference resolution; and + the overlay plane in the reference resolution.

The resizing of the video signals using different resolutions is therefore limited because the resizing is carried out in base layer 34. This allows for the simplification of the processes carried out in application layer 36 and for the optimisation of the performance of these processes. The reference resolution used in the above described embodiments of the present invention is preferably chosen to achieve a satisfactory compromise between good video signal quality and low processing power cost for the various calculations.

In the above described embodiments, base layer 34 uses enlargement functions only, since the virtual reference resolution is smaller than or equal to the output resolution. This is advantageous because enlargement of graphic information usually provides better image quality results than reduction, depending on the capabilities of the chipset used in decoder 4. In addition, the prior smoothing of the fonts by application layer 36 allows for better text reproduction when the image is enlarged. Hence the resultant video signal is of a good quality. Moreover, the definition of a reference resolution allows the system to dispense with the various conversions that would otherwise be necessary between the various layers of decoder 4, and which result in signal quality loss and increased computation time. In addition, the choice of a smaller reference resolution also reduces computation time for the various signal processing operations.

In alternative embodiments, a reference resolution that is larger than any desired output resolution could be used.

Another advantage of the procedure described above according to embodiments of the present invention is that it enables application layer 36 to carry out its various operations without regard for the various video resolutions employed elsewhere. This is turn allows for the reuse of the various interactive

applications when the resolutions of the input video signal and output video signal are different to those mentioned in the example.

It is appreciated that various features of the invention which are, for clarity, described in the contexts of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable subcombination.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the invention is defined only by the claims which follow: