3d display handling of subtitles

[0001] The present invention relates to the creation and transmission of a three-dimensional (3D) image signal. In one embodiment of the invention, a method is provided for automatically, optimizing the positioning of subtitles on a 3D display, reducing viewer fatigue.

BACKGROUND OF THE INVENTION [0002] Currently, interest in 3D television has returned, which is associated with recent groundbreaking display technology solutions that allow good reproduction of three-dimensional video for many viewers. One of them is the 3D autostereoscopic lens display - but there are also other types of displays, such as barrier autostereoscopic displays and time-multiplexed stereoscopic displays using rear projection technique. Usually, displays of this type use one of the two basic video formats as the basis for creating a three-dimensional impression for the viewer. Stereoscopic displays use time interlacing sequencing and eyepieces to display two separate views - one for each eye; therefore they require a stereoscopic video signal. An example of such displays can be stereoscopic displays multiplexed in time and using rear projection - such systems are also used in 3D cinemas. Their main alternative are multi-view autostereoscopic displays, which do not require the use of glasses, and use the image and depth as the input format to create a three-dimensional impression. For more information on 3D display technology, see chapter 13 of the publication "3D video communication - Algorithms, concepts and real time systems in human centered communication" by Oliver Shrer et al. (Wiley 2005).

[0003] The stereoscopic video format is simple because it uses two images, one for each eye. Usually, these two images are interlaced, spatially or sequenced in time, before being displayed. The alternative format, called image and depth, differs in that it combines a two-dimensional image with the so-called "Depth" or dispatch map. It is usually a grayscale image, where the pixel gray value indicates the degree of dispersion (or depth in the case of depth maps) of the corresponding pixel in the associated two-dimensional image. The display for 3D rendering uses dispersion or depth maps to calculate additional views using the input 2D image. This can be accomplished in many ways, in the simplest implementation, moving the pixels to the left or to the right, depending on the value of the degree of dispersion corresponding to these pixels. A review of this technique is described in an article by Christoph Fen entitled "Depth image based rendering, compression and transmission for a new approach on 3D TV".

[0004] The problem associated with three-dimensional autostereoscopic and stereoscopic displays (using time sequencing) is a matter called accommodation mismatch and convergence. In this case, the viewer's eye converges on the virtual position of the displayed object, while at the same time the eyes accommodate (to see a sharp image) on the surface of the display itself. This mismatch can cause headaches and other symptoms associated with the disease

EP 2 362 671 B1. In addition, any differences in geometric parameters (especially any vertical parallax) as well as electrical parameters (brightness, contrast, etc.) between the left and right eye images may cause additional eye strain. However, if the size of the difference is low, i.e. less than one degree, these problems are less serious and users can view the content without experiencing significant problems. More details are included in the article "Two factors in visual fatigue caused by stereoscopic HDTV images", Sumio Yano et al. Displays 2004, pp. 141-150, Elsevier.

[0005] A problem similar to those described above arises when the rendering device displays text, such as subtitles or coded subtitles. If the text is not properly positioned on the screen - which depends on the type and settings of the display, it may appear blurred, for example due to cross-views between the left and right eye views, which may result in the viewer feeling tired. In this case, blur may also affect the readability of the text. According to E. Legge (see "Psychophysics of Reading: I. Normal Vision", Gordon E. Legge et. al. Vision Research, vol. 25, No. 2, pp. 239-252, 1985) reading deteriorates if the throughput for the text is less than 2 cycles per character. Blurring is also a problem with autostereoscopic displays, where usually creating multiple views is done at the expense of resolution. For stereoscopic displays, there is a general problem of suboptimal separation between two views, which can aggravate image blur. Moreover, according to Yano (cited above), depth of movement increases eye strain.

[0006] Another anticipated problem is the possibility for viewers to adjust the degree of dispersion (difference) and relative position of the depth of the plane in the case of 3D television (using, for example, the buttons on the television remote control). Such regulations may cause the text to become blurred as it moves away from the neutral depth position or its "depth" may increase in a way that causes eye strain.

[0007] US Patent Application No. US 2005/0140676 includes a method of displaying multi-level text data on a three-dimensional map. In the system described in this Application, the three-dimensional map is displayed on the screen, and text data with different levels of density are displayed according to the distance from the point of view of the displayed three-dimensional map to the nodes where the text is to appear, which increases the readability of the text data. What's more, it is possible to display text data by locally adjusting the text density on the screen. The three-dimensional map is displayed on the display panel screen by converting the map data containing two-dimensional coordinates into three-dimensional coordinates using the perspective projection method. The text data to be displayed together with the three-dimensional map are converted into a coordinate system for three dimensions, with the origin specified by the point of view for the three-dimensional map. The converted text data is projected onto a two-dimensional plane, where it is to be converted to those that contain the coordinates for the screen. Next, the distances from the viewpoint for the displayed three-dimensional map are classified to the nodes where the text data are to be displayed. Classified distances are determined for converted text data with screen coordinates. Text data with levels corresponding to the specified distances are displayed on the display panel screen, which displays a three-dimensional map.

[0008] While in the context of the mapping of the three-dimensional map on a two-dimensional display device, the handling of text data in accordance with this document is carried out by positioning and scaling in a manner suitable for the user. This does not apply to any of the problems listed above when displaying text on a three-dimensional display device.

[0009] Patent JP 2004-274125 describes the generation of a 3D signal. The multiplexer multiplexes two image components and text data that are superimposed on the end device. The 3D image signal contains a single stream of text data (component D). The appropriate depth parameter (E component) is included in the signal to enable positioning of the text stream in the terminal device.

[0010] Patent WO2008 / 044191 describes the creation of three-dimensional graphic data. A multiplexed data stream containing video and graphic signals has been described. The data stream consists of two different graphic data streams (presentation graphics stream and interactive graphics stream), which are rendered in the decoder on respective, separate graphic planes. In the stream for each graphic object (object definition segment containing 2D graphics) there is a corresponding data structure containing information about the depth map.

[0011] Patent US2008 / 043095 A1 describes an LFC apparatus table where the maximum disparity between two adjacent images is calculated by an encoder and transmitted to the receiver via SEI messages - however, this information is not used for video decoding.

SUMMARY OF THE INVENTION [0012] The object of the present invention is to improve the state of the art.

[0013] According to a first aspect of the present invention, there is provided a method as defined in claim 1, methods as defined in claim 3, devices as defined in claim 5, devices as defined in claim 6, a three-dimensional image signal as defined in claim 8, a disk for a three-dimensional playback system as defined in claim 10 and a computer program on a computer readable medium, for creating a three-dimensional image signal as defined in claim 11. It is preferred that the position Z of both text subtitles and presentation graphics is the same, and can be stored individually per stream (i.e., the subtitle language). Practical embodiments, e.g., the use of a BD disk to record these shared positions. From subtitles are specified in the dependent claims.

[0014] Thanks to the invention, it is possible to improve the readability of text, such as subtitles on a 3D display. Improved readability uses the fact of passing additional parameters to the 3D display so that it treats the part of the image containing subtitles separately from the rest of the image. The display can then ensure that the subtitles are positioned automatically, in the best way and taking into account the depth, sharpness and overall readability of the text. The invention will find application in systems such as a Blu-Ray disc player and a DVD or HD-DVD player connected to a 3D display that displays 3D content and relevant subtitles

EP 2 362 671 B1. It will be obvious to those skilled in the art that the image signal can also be transmitted partly or completely via a digital network such as the Internet or an intranet.

[0015] The text, and especially the subtitles, should be displayed within a limited depth range from the screen and throughout the presentation the depth cannot change. Since the depth of the text must remain constant, this is an additional problem for positioning, because the depth of the video can be variable and may include parts of the text in some scenes. In summary, the following factors must be taken into account when displaying subtitles or subtitles coded on a 3D stereoscopic display: the level of disparity (difference) should be less than one degree, the throughput for the text should be higher than two cycles per character, the text must have a constant depth relative to the screen and the text should not be obscured by video objects.

[0016] To meet bandwidth constraints, the player must provide sufficiently high text resolution that the ghosting is kept to a minimum and the text speed is not too high. The reproduction apparatus must transmit subtitles or coded subtitles in a resolution sufficient for the display and adjust the depth to minimize the afterimage so that the above factors are met. This means that usually the text depth should be neutral (as close to the screen as possible). However, this can raise the problem of video encompassing some of the text because the depth of the video changes dynamically. This is done by dynamically adjusting the depth of the text to ensure that it stays in front. However, this means that the depth of the text will change, which - according to Yano's work - can cause eye strain. These problems can be eliminated by passing information about the position of the text and adjusting the 3D parameters of the 3D image in the place of the text.

[0017] Although the depth of the text should be constant over longer intervals, changes may be allowed, e.g. to achieve specific 3D effects.

BRIEF DESCRIPTION OF THE DRAWINGS [0018] Embodiments of the present invention are described below, using only examples and with reference to the accompanying drawings, in which reference numerals are used to identify similar elements or functions:

Figure 1 is a diagram illustrating the formation of a 3D image,

Figure 2 shows a diagram of the 3D playback system,

Figure 3 shows a diagram indicating the content and flow of data in the 3D playback system,

Figure 4 shows the diagram of the playback device of the 3D playback system, Figure 5 shows the diagram of the use of planes in creating the output,

Figure 6 shows a 3D image signal diagram,

Figure 7 is a diagram of an improved 3D image signal,

Figure 8 is a diagram of another enhanced 3D image signal,

Figure 9 shows a diagram, similar to the one in Figure 4, of another embodiment of the reproduction apparatus and

Figure 10 is a diagram of the text placed on the 3D image.

DETAILED DESCRIPTION

[0019] The formation of the three-dimensional image is shown schematically in Figure 1. Indeed, regardless of whether the final rendering display device is autostereoscopic or uses stereoscopic pairs (requiring the user to wear special glasses) , the process is the same. The first image component 10 and the second image component 12 are used to create a three-dimensional image 14. The second component 12 together with the first image component 10 are processed together, resulting in image 14. In all systems, the first component of image 10 is a typical, two-dimensional image frame in a convenient standard. In a system using stereoscopic pairs, the second component 12 is also an image, and in autostereoscopic systems the second component 12 is a depth map or a dispersion (difference) map.

[0020] It is important to understand that the final image 14 is not necessarily a single frame. For example, in a system using stereoscopic pairs (where image 10 is for the left eye, and image 12 - for the right) these two components 10 and 12 can be displayed in order. In autostereoscopic sequential systems that do not use time dependencies, image 10 and density map 12 are used to create many similar image views 10, while the density map is used to make changes to image 10 that are necessary to create separate views. These views are then combined into a single frame 14. For example, the final rendering display device may be set to display four individual views, generated from the same image 10. These views are then combined, each of them having a resolution equal to a quarter of the resolution of the display device.

[0021] The first component of the image 10 may consist, for example, of a two-dimensional array of pixels or an image consisting, for example, of RGB or YUV data, reflecting the view of the scene, as is the case with the contents for stereoscopic display, on multi-view displays or using the image and depth. As mentioned above, the second component 12 may be a two-dimensional pixel array or an image. In the case of stereoscopic or multi-view content, it can still be a view of the same scene, while in the case of content constituting the image + depth it can be called dispersion or depth map, containing information about dispersion or depth. The output image 14 may consist of a video image signal, for example using multiple frames reflecting the course of one or more scenes in time.

[0022] Figure 2 shows a 3D reproduction system, wherein the disc 16 includes carriers for the first and second components 10 and 12, e.g. a 3D film. Disc 16 may be, for example, a standard Blu-Ray DVD. Disc 16 is played by a playback device 16, such as a Blu-Ray DVD player. The video interface 20 is used to transfer components 10 and 12 to the 3D TV 22. Television 22 includes a rendering stage 24 that processes components 10 and 12 in real time, generating a 3D output image 14 (as shown in Figure 1 above). User 26 watches the rendering display device 22 and can enter settings 28 into the device 22 using the appropriate user interface and remote control (not shown).

[0023] In systems of this type, the use of subtitles (or any text, such as menus) is supported by the reproduction device 18. For example, disc 16 typically includes subtitles, such as subtitles in a foreign language, recorded in sectors

The data information stored on disc 16. They can be selected by the user through the on-screen menu, before playing the movie recorded on disc 16. These subtitles are then displayed by the display device 22, overlapping the rendered 3D content. As stated above when discussing the current state of the art, in many situations displaying subtitles by 3D display systems can cause a strain on the viewer's eyesight and fatigue. The system of the present invention provides a method of displaying subtitles (or also any text) in a manner that reduces the problems known to the prior art.

[0024] The solution is to enable text (e.g., subtitles) to be detected in the incoming video stream by display 22 and to treat it in a different way than the rest of the video signal. The display 22 can, for example, ensure that the text stays in front of the video or compress and reduce the depth of the video signal to prevent the text from sticking out (as described in International Patent Application No. WO 2008/038205). Display 22 may additionally provide a screen section that will be designed to display text, which will be switchable, or have a different lens arrangement (in the case of a display with lens), supporting, for example, fewer views. Because the readability of the text on the 3D autostereoscopic display is a problem inherent in the autostereoscopic display technology, further, currently unknown, display improvements are expected that may result in the identification of subtitles in the incoming video signal.

[0025] One way to separately transfer the text of subtitles to the display is to send them as information in the form of coded subtitles, which is contained in line 21 of the analog video signal in the case of NTSC, used in Europe (PAL) to Ceefax or teletext. Transmission of information in the form of coded subtitles is not supported during high-definition video transmission via HDMI. Currently, to overcome this problem, playback devices, such as DVD or BluRay players, decode the encoded subtitles present in the MPEG stream and superimpose them on the video signal before sending it to the display. Therefore, to use this solution, it would be necessary to extend the specification of the HDMI standard to include information in the form of coded subtitles. It will be apparent to those skilled in the art that the above described issues may also apply to other digital display interfaces.

[0026] Another solution is to provide a two-way communication link between the reproduction apparatus 18 and the display 22 to inform the reproduction apparatus 18 that the user adjusts the display depth settings 22. As a result, the reproduction apparatus 18 can adjust the position of the subtitles. In a preferred embodiment, the reproduction apparatus 18 is allowed to support positioning and superimposing subtitles on the video and indicating to the display 22 that subtitles are present and determining their location. Display 22 can then ensure that the "depth" value associated with the subtitles will be mapped to the depth that is best for the particular display 22 and user settings 28 entered. The advantage of this solution is that the display 22 does not need to have a subtitle decoder or subtitles encoded in the rendering degree.

[0027] In one embodiment, an improvement has been achieved in the system in which the reproduction apparatus 18, as shown in Figure 2, adjusts the position of the subtitles so that the text is in front of the video image, while maintaining the disposition at a level less than one degree. Preferably, the reproduction apparatus 18 should include in the output metadata stream information enabling the display apparatus 22 to identify if and where the subtitles are located - taking into account the coordinates of the position x, y and z ("depth") for the volumetric display. In this case, the rendering degree 24 in the display device 22 adjusts the position of the subtitles in the projection area of ​​the display, depending on the aforementioned information in the form of metadata and the user's preferred settings 28 (in terms of dispersion amount and relative position), while maintaining a position ensuring minimal afterimage (ghosting) and disposition size below one degree. In addition, if the display 22 is equipped with such a function, it positions the subtitles on a special part of the display surface that can be switched between 2D and 3D display, or which supports less ghosting and higher optical resolution (for example, supporting fewer views or a limited level dysparycji).

[0028] In one embodiment, the textual component 30 is actually flat and / or when the depth range is associated with the text 30, the range is limited by the threshold, in a way that limits the disparity between individual views to a specific range, which may be a range initially fixed, for example one or two pixels. In a preferred embodiment in which the text component 30 is actually flat, the text component is a text-based component rather than a bit-based text component; so that a particularly compact mapping of the text component is possible 30.

[0029] The data and their flow in the system according to Figure 2 are shown in Figure 3. Plate 16 contains the first image component 10 and the second component 12 and the text component 30, constituting subtitles. User command 32 is received by reproduction apparatus 18, which indicates that the user wishes to display subtitles 30 for the 3D movie he is about to watch. The reproduction apparatus 18 transmits components 10 and 12 together with subtitles 30 and data component 34, which contains position information describing the position of the text component 30 in the final 3D image 14, to the rendering engine 24. The reproduction apparatus comprises a receiver for receiving various components from respective sources and a multiplexer which combines such four elements 10, 12, 30 and 34 into a three-dimensional image signal 36, which is received by the rendering engine 24.

[0030] The subtitle information 34 can be sent to the rendering engine 24 separately from the image data 10 and 12, i.e. it may not be transmitted in the active area of ​​the image, but in the header or in the data islands or as part of a frame that does not contain data image. For example, a video stream can be transmitted at twice the frame rate, where one frame contains image data 10 and 12, and the other depth information (optionally also with de-occlusion) and the area where 30 subtitles and location information are transmitted .

[0031] The rendering engine 24 is adapted to render the three-dimensional image 14, using the first image component 10 and the second component 12, for rendering (including

Rendering of the text component 30 in the three-dimensional image 14), rendering of the text component 30, including adjustment of one or several parameters of the three-dimensional image 14 at the location of the rendered text component 30. The text component 30 itself can be completely changed by the adjustments made by the engine render 24. An important factor is that the rendering engine adjusts the parameters of the image portion 14 to be displayed at the position of the text 30. This may include reducing the subjective depth of the 3D image in such image area 14 or including reducing the number of views (in autostereoscopic display devices) or a combination of two or more regulation. It is also possible for the rendering engine 24 not only to be able to change the depth of the area in which the subtitles are to be displayed 30, but also to be able to change the offset to move the entire depth range forward or backward. The offset for subtitles 30 can be controlled independently of the other image data 14.

[0032] In an embodiment employing an autostereoscopic display, the second component 12 includes a depth map, and the method of rendering the 3D image 14 may then include scaling the second component 12 before rendering the three-dimensional image 14 to allow the text component 30 to be positioned in the position specified in data component 34. In this case, the rendering engine may then receive a recommendation component, including recommended scaling of the second component 12, so that the position information remains the same for many subsequent images. As a result of using the recommendations component, it becomes possible to maximize the depth of the scene when subtitles / graphics are turned off and when subtitles / graphics are turned on using the previously specified scaling component introduced into the image signal to render content containing subtitles / graphics.

[0033] An example of a reproduction apparatus 18 is shown in Figure 4, showing a Blu-Ray decoder 18 along with decoding and using presentation plans. The ROM 38 drive contains disc 16 and reads its contents, which is demodulated and decoded by element 40. The set of parallel buffers 42 stores various components of the decoded signal that pass through the set of parallel decoders 44 to form the output signal that will be displayed by the display 22, it consists of standard video 46 and superimposed content 48 (constituting subtitles, menus, etc.).

[0034] In the Blu-Ray system, the subtitles on the disc may be in bitmap or text based format and appropriate fonts. The player 18 additionally supports information containing encoded subtitles. Technically speaking, both systems are somewhat similar, however, coded subtitles usually contain more information and are provided specifically for people with hearing impairment. Both text subtitles as well as bitmap based or coded subtitles are decoded and presented on one of the presentation planes on a Blu-Ray disc. Figure 4 shows the decoder 18 and planes, showing an example of the text connected to the video. The text is always presented on the plane of presentation graphics (PG), this plane is superimposed on the video player 18 on the (plane) video and sent to the output as one combined presentation. Figure 5 shows an example of a combined presentation 50. Such an output presentation 50 consists of a main movie plane 52, a presentation plane 54 and an interactive plane 56. The output presentation according to Figure 5 is sent to the display 22 via the video interface 20 (as shown in Figure 2). In the preferred one

In embodiment, the reproduction apparatus 18 has the ability to send additional information to the display 22, this information, in addition to the output presentation 50, includes 3D image data 34. This enables the 3D display 22 to display three-dimensional representation of the combined output video, text and graphics of the reproduction apparatus 18. .

[0035] Figure 6 shows an example of such a combined image transmitted to a 3D display 22. The 3D system used is an example of using image output and depth. The first image component 10 and the second component 12 (which is a depth map) will be combined to display the 3D image by the display device 22. The text component 30 is contained in the first component 10, and indeed all content (three components 10, 12 and 30) can be constructed as a single high-definition frame.

[0036] Figure 7 illustrates the addition of a header indicating the position of the subtitles 30. The header contains the data component 34 containing location information 58, describing the position of the text component within the three-dimensional image, shown here as x and y coordinates, although the z component will also be present based on the content depth maps 12. The header allows the final rendering device to adjust the 3D output, taking into account the presence of subtitles 30.

[0037] Additional transmitted parameters may be included in the header above the image data as described in "3D interface Specifications - white paper", Philips 3D solutions, <a href="http://www.business-sites.philips.com/shared/assets/global/Downloadablefile/Philips-3D-">http://www.business-sites.philips.com/shared/assets/global/Downloadablefile/Philips-3D-</a>

Interface-White-Paper-13725.pdf, in accordance with international patent application No. WO 2006 / 137000A1, or - for example - in the data islands of the HDMI standard. These parameters include an indication of whether subtitles are present and their position in the video input, as shown in Figure 7. The display device 22 can then ensure that the disposition of a portion of the image positioned here is not higher than one stage and remains constant, even if the user, through an input command, increases the amount of disposition used by the display device 22.

[0038] The quality of the final result can be improved if the player's output 18 also contains occlusion or background information. This is shown in Figure 8. To prevent artifacts, subtitles should be placed outside the most active part of the image, for example at the top or bottom. Figure 8 shows the image, depth, and background output format. The background components 60 and 62 are provided for the first image component 10 and the second component image 12, respectively.

[0039] The location of subtitles 30 within the final image 14 may include a reference to the Z position of the subtitles. For example, it is possible to extend the Blu-Ray disc subtitle text decoder model and related information about the components (especially the set of dialogue styles, section 9.15.4.2.2) with the location Z in such a way that the author of the original content can indicate the location Z - within the 3D projection area - where subtitles should be positioned. The Blu-Ray disc standard has a defined subtitle text decoder and associated stream. The text subtitle decoder is defined in section 8.9 and consists of various processing elements and buffers. Figure 9 shows a simplified image of the decoder model extended with support for 3D images with related text components, such as subtitles 30.

[0040] Figure 9 shows a decoder model of 3D text subtitles. Starting from left to right, segments of the text subtitles enter into the decoder 18, where they are processed and decoded by the text stream processor 64. The decoded text data is placed in the dialog buffer 66, while information about the components of the decoded text subtitles are placed in the component buffer 72. Controller 74 interprets component information and applies it to the text after it has been rendered by the text rendering engine 68 (using font file 80) and places the result in bitmap buffer 70. In the last step, bitmap images are assembled by player 18 into appropriate graphic planes. User input 78 is also received by controller 78, for example, affecting display depth parameters.

[0041] In addition to text-based subtitles, the Blu-ray Disc (BD) also supports subtitles based on bitmap images, so-called Presentation Graphics (PG). Similarly, the location of PG subtitles must be specified on the disc, preferably near the already defined information about the position X and Y. As the latter are stored in the composition_object () structure, it is logical to extend it to the location of Z subtitles, e.g. by using reserved bits starting with offset bit 26. The term textual component used in the context of this application refers to text-based subtitles and / or bitmap-based subtitles.

[0042] The decoder 18 has been extended with an additional bitmap buffer 76, which stores a depth or disposition map, which indicates where - with respect to the Z direction - the text of the subtitles 30 is to be located. Depth or disposition information can be included in the style set dialogue as specified in the Blu-Ray specification. One way to do this is to extend the set of dialogue styles with the region_depth_position parameter. The region_depth_position parameter is an 8-bit field containing values ​​from 0 to 255, but this may expand in the future. Controller 74 determines the proper pixel values ​​for the depth map or disposition based on the region_depth_position field value. The translation of this value into the color value of the depth map or disposition depends on the 3D metadata placed in the 3D_metadata field of the playlist or placed in the Program Map Table [Program Map Table] MPEG-2 (ISO / IEC 13818-1). The syntax for this information is defined by MPEG in ISO / IEC 23002-3.

[0043] The Z position of the subtitles 30 is then transmitted to the rendering engine 24, which takes into account the position Z of the subtitles 30 when rendering the 3D image 14 to be displayed by the 3D display device 22. Figure 10 shows an example of 3D space with depth positioning via use of region_depth_Position. Image 14 contains subtitles 30 which are located on plane 82. Plane 82 indicates location in space at zero depth, the other lines indicate the three directions x, y and z in 3D space.

[0044] In addition to including the depth area indicating the area in the space in which the subtitles are to be positioned, it is even possible to add a separate depth value for the text itself and specify the area not as a plane, but as a cube in space. This can be done, for example, by expanding the location area fields in the dialog style set with the region_depth_position and region_depth_length parameters. The same can be done for the position of the text box, which will indicate the exact position of the text in the area.

[0045] Font file 80 can be used to include an embossed font style because it has been proven that using this style increases the readability of the resulting 3D text. Font styles are described in Table 9-75 of the BluRay specification, for this purpose the external font thickness field may be used, as described in Table 9-76 of the Blu-Ray specification. Both tables contain reserved fields at the end that can be used for this purpose. The extruded font style corresponds to the value 0x08 in Table 9-75, and the external thickness of the extruded font corresponds to the value 0x04 in Table 9-76.

[0046] Preferably, the position on the Z axis of both text subtitles and those consisting of PG is the same and can be stored individually per stream (i.e. per subtitle language). It is clear to those skilled in the art that there are many alternative locations on a BD disc in which a common Z-subtitle location can be stored. Examples of such alternative locations are described below. The document "White paper Blu-ray Disc Format 2.B Audio Visual Application Format Specifications for BD-ROM March 2005" available via the Internet resource http: //<a href="http://www.blu-raydisc.com/Assets/Downloadablefile/2b_bdromaudio-visualapplication0305-12955-">www.bluraydisc.com/Assets/Downloadablefile/2b_bdromaudio-visualapplication0305-12955-</a>

15269.pdf contains further basic information about the BD format and the above-mentioned format structures.

[0047] The common position of the subtitles may for example be stored in a new table, defined as the PlayList extension. The Play List in the BD specification is a list specifying the sequence of elements of the Audio Visual content that together form the presentation of a title, for example a Movie. The structure of the Playlist provides a mechanism for its further expansion through extension data. The "Z" position of the subtitle plane (PG plane) for streams with different languages ​​can be included in a new table called the metadata shift table. Table 1 details the table.

In addition, if the Play List contains PlayItems for playing stereoscopic multi-angular video data, the "Z" position for applying graphics such as subtitles may be different for each stereoscopic multi-angular video clip. Therefore, the table offset_metadata should allow different "Z" positions for each stereoscopic, multi-angle video clip associated with the Playback Element. In this case, the offset_metadata table contains different "Z" positions for overlaying subtitles for each stereoscopic, multi-angle video clip. These different "Z" positions can then be associated with an identifier for each stereoscopic, multi-angle video clip requiring different "Z" positions for overlaying Table 2 shows how to extend Table 1 with support for different "Z" positions for various stereoscopic, multi-angle video clips. The StreamID and AngleID parameters in Tables 1 and 2 serve as unique identifiers for respectively elemental streams on the disk (containing subtitles) and a stereoscopic (multi) angular video clip.

[0049] Instead of using the extension data, it is also possible to define a new structure of the Play List table in particular for reproducing 3D streams and including "Z" position parameters in it. Playback problems on existing players can be prevented by using a new index table (title list selected by the user) on the disk or use of extended array data

EP 2 362 671 B1 index containing a list of titles that can only be played on players with the 3D function.

[0050] Alternatively, if the information is to be provided in an existing Play List table, it may be included in the table STN_Table_SS (). This is an array containing video streams and graphics associated with the Playback Element. For each Playback Element it contains a loop with stream coding information (attributes) for each text and bitmap subtitle stream. It is suggested to place information about the "Z" position in the same loop as the information about stream attributes.

[0051] The problem of using a Play List to store "Z" parameters for each subtitle stream is duplication of data. Many Play Lists can refer to the same subtitle streams. This limitation can be overcome by including "Z" position metadata in the information file about the Clip. The Clip information file collects MPEG Transport Stream related metadata that includes A / W content and subtitle streams. The Clip information file can be extended with an array similar to that proposed for the playlist extension data. However, since the Clip information file is associated with MPEG Transport Stream, it ranks the Subtitle Basic Streams based on the Package Identifier (PID). Therefore, it is proposed to provide metadata with the "Z" position for each PID list that indicates the PID of the subtitle stream.

[0052] Alternatively, instead of defining a new table in the extension data, the "Z" location is stored in the Program Information table [ProgramInfo] in the clip information file. The Program Information Table provides a list of Basic Streams that together form a presentation of the A / W content. Contains similar information as the PMT table defined in MPEG ISO / IEC 13818-1 systems. It is proposed that for each Basic Stream containing information about subtitles provide "Z" position metadata. The metadata can be included in the Program Information table itself or in the Program Information table sub-table - Stream Coding Information Table [StreamCodingInfo]. It provides details about coding and language codes for subtitles present in Transport Stream. The Stream Coding Information Table also contains several reserved fields, it is suggested to use these reserved fields to transfer the "Z" position parameters associated with the subtitle stream for a given language code.

[0053] If a "Z" position change is required every few seconds, use the CPI table () in the clip information file. CPI information is a table that collects information about the input points of video streams for playback when paused or scrolling. List of input points it can be extended with the "Z" position parameter, which - for each entry point - indicates the "deep" position or situation when it is necessary to apply any graphic, such as subtitles.

Alternatively, if the "Z" position information is accurate about the frame, it should be included in the SEI messages of the dependent video stream. SEI (Supplemental Enhancement Information, called character messages) are packets embedded in the MPEG Basic Stream that carry parameters can be used by the decoder to support content decoding. MPEG also allows embedding of private SEI messages of user data; they will be ignored by typical

Decoders, but can be used by a modified decoder. The user data SEI message can be defined as the "Z" position carrier of overlay elements to be superimposed on the video - such as subtitles. To provide "Z" information for each stream (language), it is proposed to calculate "Z" values ​​for all subtitle streams present on the disc.

EP 2 362 671 B1

<td>offsetmetadata () - Syntax</td>

<td>offset metadata () {</td>

<td>length</td>

<td>for (i = 0; i &lt;number of playitem; i ++) {</td>

<td>number of Plane offsets [i]</td>

<td>for (j = 0; j &lt;number of Plane offsets [i] \ j ++) {</td>

<td>PG Plane offset [pts]</td>

<td>Other fields not related to 1</td>

<td>Other fields not related, i.e.</td>

<td>is PG Offsets</td>

<td>if (is_PG_Offsets == 1_b&gt;) { number_of_streams [n] for (k = 0; k &lt;number of Streams [n] _id; k ++) { streamIDList [k]</td>

<td>PG Z position metadata</td>

<td>(depth or dispatch data)</td>

<td> }</td>

<td> }</td>

<td> }</td>

<td> }</td>

<td> }</td>

Table 1. Example of an array for storing shifted metadata [0055] It will be clear to those skilled in the art that processing steps, such as rendering 3D images, or multiplexing steps can be implemented in many different processing platforms. Such processing platforms may include dedicated semiconductor devices and / or devices, programmable logic devices, digital signal processors or even general purpose processors. Similarly, combined software and hardware implementations can be used.

[0056] Although the invention has been illustrated and described in detail by means of the drawings and the above description, such illustrations and description should be considered illustrative or exemplary and not limiting. The invention is not limited to the disclosed embodiments.

EP 2 362 671 B1

<td>offset metadata () - Syntax</td>

<td>offset metadata () {</td>

<td>length</td>

<td>for (i = 0; i &lt;number of playitem; i ++) {</td>

<td>number of Plane offsetsli]</td>

<td>for (j = 0; j &lt;number of Plane offsets [i]; j ++) {</td>

<td>PG Plane offset [pts)</td>

<td>Other fields not related to 1</td>

<td>Other fields not related, i.e.</td>

<td>is PG Offsets</td>

<td>if (is_PG Offsets— 1 b) { number_of_Z_values for (k - 0; k &lt;number of Z values k ++) { numer_of_streams numer_of_angles For (int m = 0; m &lt;number_of_streams; m ++) {StreamID; } For (int o = 0; o &lt;number_of_angles; o ++) {anglelD; }</td>

<td>PG Z position metadata</td>

<td>(depth or dispatch data)</td>

<td> }</td>

<td> }</td>

<td> }</td>

<td> }</td>

<td> }</td>

Table 2. An example of a table for storing shifted metadata extended with position metadata "Z" of various subtitles for each segment of stereoscopic, multi-angle video.

[0057] Other examples of disclosed embodiments may be understood and utilized by those skilled in the art for practicing the claimed invention based on the analysis of the drawings, disclosed and appended claims. In the claims, the phrase "comprising / consisting of" does not exclude other elements or steps, and the use of the singular does not exclude the plural. A single processor or other entity may perform the functions of several elements specified in the claims. The mere fact that some measures are listed in several different dependent claims does not indicate that a combination of these measures cannot be used. The computer program may be stored or distributed on a suitable medium, such as an optical medium or a semiconductor medium supplied with or as part of other equipment; it may also be distributed in other forms, for example via the Internet or other wired or wireless telecommunications systems. Any references present in the claims should not be construed as limiting the scope of the invention.

EP 2 362 671 B1