# Patent

## Title
Method and system for encoding and transmitting high definition 3-D multimedia content

## Abstract

One particular implementation of the present invention may take the form of a method and system for encoding and/or transmitting high definition 3-D multimedia content. In one embodiment, the frames for each eye of a viewer may be transmitted in a frame sequential manner to a display device, with an occasional null frame included in the frame stream. The null frame may be ignored by the display device and not presented to the viewer. In another embodiment, a synchronization signal may be presented to the display device to instruct the display device on how to display the frame-sequenced frames such that the 3-D effect of the content may be achieved. The synchronization signal may be presented to the display device embedded within the frames of the content or embedded within the null frames. The synchronization signal may also be provided out of band, such as on a high definition multimedia interface (HDMI) cable.

## Background
FIELD OF THE INVENTION
Aspects of the present invention relate to display of 3-D multimedia content. More particularly, aspects of the present invention involve a system and method for encoding and transmitting high definition 3-D content to a display device.
BACKGROUND
Three dimensional (3-D) imaging, or stereoscopy, is a technique used to create the illusion of depth in an image. In many cases, the 3-D effect of an image is created by providing a slightly different image of a scene to each eye of a viewer. The slightly different images may present two perspectives of the same object, where the perspectives differ from each other in a manner similar to the perspectives that the viewer's eyes may naturally experience when directly viewing a three dimensional scene. When the two images are viewed at the same time, the image is perceived as having depth.
Several methods exist to provide a 3-D effect to an image. An anaglyph image may present the two images for each of the viewer's eyes in different colors, such as red and blue-green. To achieve the 3-D effect, the viewer wears glasses with color filter lenses that filter the color(s) so as to present only one of the images for each eye. Thus, the viewer's right eye receives the red image while the viewer's left eye receives the blue-green image. When the left-eye image and the right-eye image are viewed at the same time, the viewer perceives a 3-D effect. In another example, left-eye and right-eye image are superimposed through polarizing filters such that one image is clockwise polarized and the other image is counter-clockwise polarized. The viewer wears glasses with polarized lenses such that each eye receives only one of the images. In a third example, the 3-D images are presented in a time-multiplexed fashion, such as alternating between images meant for the viewer's right eye and the viewer's left eye. The viewer wears glasses that shutter between the viewer's eyes, allowing the right eye to receive the right eye image and the left eye to receive the left eye image.
To transmit 3-D or “stereo” multimedia content (such as 3-D video or film), both left-eye and right-eye images are sent to a display device in a manner that allows the left-eye and right-eye images to be separately presented to the user's left eye and right eye, respectively. Conventional digital interfaces and transmission standards are not designed to support 3-D content that involves transmitting twice as many video frames as non-stereo video. This is a particular problem for high definition video which requires significantly more data for each frame as compared to standard definition video. Techniques have been developed, however, to squeeze a left-eye frame and a right-eye frame into the space of a single video frame allowing a stereo video to be communicated using conventional digital interfaces and transmission standards. For example, one method transmits the images for both eyes of a 3-D image by fitting the images for the right and left eye into a single frame, in a side-by-side arrangement (e.g., dividing the conventional frame into a left half and right half) or over-under arrangement (e.g., dividing the conventional frame into an upper half and a lower half). In another example, anamorphic squeeze techniques are used to squeeze each of the left-eye and the right-eye images into the smaller space for transmission as a single frame. The two images may then be separated, expanded and presented to the viewer in a manner consistent with 3-D techniques by the display device. Another method involves transmitting both images in a checkerboard fashion in a single frame. Thus, the pixels of the images for each eye are interleaved into a single frame on a pixel-level basis. These methods may provide the data for the two images needed for a single 3-D image at the same rate as 2-D images may be transmitted. However, because two images are being presented in a single frame, the resolution of each image is less than if each frame contained a single image. Thus, the images provided in these schemes may not meet the high resolution requirements of high definition video.
High definition video generally refers to multimedia content presented in a display resolution of 720p or higher. A resolution of 720p indicates that each frame of the image presented has a vertical resolution of 720 pixel lines and that each pixel line of the image is refreshed when the image is updated. A high definition television mode specified as 720p typically has an aspect ratio of 16:9 and, therefore, has a horizontal resolution of 1280 pixels, resulting in 921,600 (720×1280) pixels in each frame. Further, high definition video is often transmitted at 60 frames per second, meaning that the entire image is updated 60 times per second in progressive modes. Video with higher resolutions and frame rates may also satisfy the high definition standard.
Since 3-D content is often transmitted by squeezing or interleaving the images for the left and right eye into a single frame, each of the left-eye and right-eye images can use only half of the pixels available in the frame. For example, a 720p frame can be vertically divided but such a division allows only 360 vertical lines for each image. While some methods exist to improve the appearance of the squeezed or combined images, the transmitted images may no longer satisfy the quality expectations of a high definition image. Thus, what is needed, among other things, is a method and system for encoding and transmitting 3-D multimedia content that meets the resolution expectations of high definition video and is at the same time compatible with existing digital interfaces and transmission standards.
SUMMARY
One implementation may take the form of a method for encoding 3-D content. The method may comprise the operation of receiving 3-D content having a plurality of frames and having a source frame rate. The plurality of image frames comprises at least a first kind of image frames and a second kind of image frames. The method may also comprise the operations of modifying the plurality of frames by including a synchronization signal distinguishing the first kind of frames from the second kind of frames and organizing the plurality of frames in a frame-sequential manner including the synchronization signal, wherein the organized frames have a frame rate that is at least twice the source frame rate.
Another implementation may take the form of a method for displaying 3-D content. The method may comprise the operation of receiving the 3-D content having a plurality of frames from a source. The plurality of frames comprises at least a first kind of image frames, a second kind of image frames and a plurality of null frames. The method may also comprise the operations of reading a synchronization signal that distinguishes the first kind of frames from the second kind of frames included in the plurality of frames and presenting the plurality of image frames in a frame-sequential manner in response to the synchronization signal.
A third implementation may take the form of a method for providing 3-D content over a distribution channel. The method may comprise the operation of receiving the 3-D content having a plurality of frames having a source frame rate and comprising at least a first kind of image frames, a second kind of image frames and a plurality of null frames. The plurality of frames may also include a synchronization signal distinguishing the first kind of frames from the second kind of frames. The method may also comprise the operations of organizing the plurality of frames in a frame-sequential manner including the synchronization signal, wherein the organized frames have a frame rate that is at least twice the source frame rate and transferring the organized plurality of frames over the distribution channel.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a system for transmitting high definition 3-D content to a display device.
FIG. 2 is a diagram illustrating a system for transmitting a high definition 3-D content to a source device.
FIG. 3 is a diagram illustrating a first embodiment of a series of frames containing 3-D content and null frames.
FIG. 4 is a diagram illustrating a second embodiment of a series of frames containing 3-D content and null frames.
FIG. 5 is a diagram illustrating pixels of a 3-D multimedia frame including an in-line synchronization signal contained within the first line of pixels.
FIG. 6 is a block diagram illustrating a system for encoding high definition 3-D multimedia content to a computer-readable medium.
FIG. 7 is a flowchart of a method for encoding high definition 3-D content to a computer-readable medium.
FIG. 8 is a high-level block diagram illustrating a particular system for providing high definition 3-D multimedia content.



DETAILED DESCRIPTION
Implementations of the present invention involve methods and systems for encoding and/or transmitting high definition 3-D multimedia content, such as 3-D video. The frames of the 3-D video may be encoded or transmitted in a frame-sequential fashion, with some image frames intended for the viewer's right eye and other frames intended for the viewer's left eye. To account for the addition of frames intended for each eye of the viewer, one embodiment may encode and/or transmit the frames at a frame rate about twice that of a source content or higher. For example, a 30 frame per second 3-D video may be encoded and transmitted at 60 frames per second to account for the separation of the right-eye images and the left-eye images into separate frames. Further, in some implementations, null frames may be inserted into the transmitted or encoded frame stream to accommodate a mismatch between the increased frame rate in accordance with the present invention and an industry standard frame rate. In such an implementation, the null frames may be recognized and discarded by downstream image processing and/or display devices. Such downstream image processing devices may include, but are not limited to, a digital video disc (DVD) player, a digital video recorder (DVR), set-top box (STB) for a satellite or digital cable system, a television, and a personal computer, and such.
In some implementations, a synchronization signal is transmitted in-band or out-of-band to downstream image processing and/or display devices. The synchronization signal instructs the display device on how to distinguish between left-eye and right-eye frames in the frame sequenced stream. Such a synchronization signal may describe the sequence at which each transmitted frame is to be displayed to the viewer. The synchronization signal may be presented to the display device embedded within the content frames (i.e., “in-band”) of the multimedia content or, in cases including null frames, embedded within the null frames themselves. Synchronization signals may also be provided out-of-band, such as on a high definition multimedia interface (HDMI) cable or other communication channel to the display device.
In one arrangement, the sequence of image frames and null frames may act as a synchronization signal. In such an arrangement, a display device or other downstream image processing device is configured to automatically determine a cadence to the transmitted frames upon receipt of an initiation signal and use the determined cadence to distinguish and separately display left-eye and right-eye images to a viewer.
FIG. 1 is a diagram illustrating a system for transmitting high definition 3-D content between a source 110 and a display 120. The embodiment of FIG. 1 may provide the 3-D content at a resolution that satisfies a high definition video standard by transmitting right-eye frames 180 and left-eye frames 190 in a frame-sequential fashion. The frames 140 may be transmitted to a display device 120 such that the display device 120 presents the frames 140 to the user utilizing a technique to provide the images with a 3-D effect. For convenience, the content is portrayed as a series of frames 140 transmitted from the source 110 to the display 120 in FIG. 1.
Generally, video content may be transmitted by a source device 110 to a display device 120 for display to the viewer. The source device 110 may take many forms, including but not limited to, a Blu-ray Disk® compatible optical disc player, a laptop computer, a personal computer, a set-top box (STB) of a satellite or digital television system and a video game console. Any device that may provide high definition content through an electrical, wireless or optical connection, such as an I/O port, may be a source device 110 and may be used with the embodiments as set forth herein.
In some embodiments, a computer readable data storage medium 130 may be associated with the source device 110 to store the high definition 3-D content. The source device 110 may access the storage medium 130 to retrieve the 3-D content and transmit the content to the display device 120. The data storage medium 130 may take many forms, including but not limited to, an optical disc (such as a Blu-ray Disk® compatible optical media); magnetic storage medium; magneto-optical storage medium; read only memory (ROM); random access memory (RAM); or other types of tangible medium suitable for storing electronic data. Generally, any tangible computer-readable medium capable of storing high definition content may be used with the embodiments described herein and/or store video encoded pursuant to techniques described herein. In one example, the source device 110 is a Blu-ray Disk® compatible player. The 3-D video content is stored on optical disks such that the player retrieves the content from the disk. Upon retrieval, the player transmits frames 140 to a display device 120, such as a television, to display the content to a viewer.
The display device 120 may be any device that may access frames 140 from the frame buffer 150 and present the accessed frames 140 to a viewer. Examples of display devices 120 include, but are not limited to, a liquid crystal display (LCD) or plasma television, a cathode-ray tube (CRT) television, a computer monitor and various types of projection arrangements. To receive the frames 140, the display device 120 may include an interface port that may receive the frames 140 from the source device 110 for display and storage in the frame buffer 150. The interface port may be any port that supports a frame transfer rate of at least 2× the frame rate of the content. Examples of interface ports include those ports conforming to industry standard interface specifications, such as HDMI, Digital Visual Interface (DVI), DisplayPort, etc.
In another embodiment, depicted in FIG. 2, the source device 110 may be a STB 210 associated with a distribution system 200, such as a cable, satellite, broadcast, network or other available digital distribution system. In the example of a satellite distribution system 200, the content is transmitted to the STB from a provider, such as a headend 250 of the distribution system 200. The headend 250 transmits the content to the STB 210 through a satellite 240 to a dish antenna 230 electrically connected to the STB 210. Alternatively, the headend 250 may transmit the content directly to the STB 210 through a dedicated cable, such as in a digital cable example. In other embodiments, the content may be provided to the source device 110 from a server through a network connection, such as over the internet.
Returning to FIG. 1, once the high definition content is received by the source device 110, the content is transmitted to a display device 120 that displays the content to a viewer. To transmit the content, the source 110 may be connected with the display device 120 through an electrical, wireless or optical connection. For example, the content may be provided to the display device via a high definition multimedia interface (HDMI) cable. Generally, any communication channel that transfers the data of each frame 140 of the content at a rate sufficient to meet current transmission standards or faster may be used to transmit the content to the display. The video content is transmitted in frames 140 containing the pixels of each discrete image, which when shown consecutively provide moving video. The received frames 140 may then be placed into a frame buffer 150 associated with the display device 120 for access by the display device 120. Frame buffer 150 comprises a computer-readable addressable memory, such as a dual-ported random access memory (RAM). The frame buffer 150 should have sufficient capacity and bandwidth to receive, store and forward at least two frames (one left-eye frame 190 and one right-eye frame 180) at an industry-standard frame rate or higher. The frame buffer can be accessed by display 120 while also loading frames 140 from the frame buffer 150 input such that the frames can be displayed without a perceivable delay when presented to the viewer. To display the content, the display device 120 retrieves the frames 140 from the frame buffer 150 and displays the frames 140 at the correct time and in the correct sequence. Displaying the sequence of frames 140 then appears as a motion video. For example, film is generally presented at 24 frames per second (fps) and television and video are generally presented at 30 fps.
To present the continuous motion effect for 3-D content, the frame rate of the 3-D content may be increased to at least two times (2×) the frame rate of the content source to include both the frames for the viewer's right-eye and the viewer's left-eye. For example, the frame rate for non-stereo video is generally presented at 30 fps. To transmit both the right-eye image and left-eye image for the 3-D content, the separate eye images may be encoded and/or transmitted to the display device 120 in different frames. One frame may include a left-eye image while another frame may include the corresponding right-eye image. The separated frames may then be encoded and/or transmitted at a rate of 60 fps, with a sequence of 30 frames containing the images for the viewer's right eye and a sequence of 30 frames containing the images for the viewer's left eye for every second of the content. Similarly, 3-D film content is provided at a rate of 48 fps, with 24 frames for the viewer's right eye and 24 frames for the viewer's left eye.
As shown in FIG. 1, the content transmitted to the display device 120 is shown as a series of frames 140. However, the display device 120 may not necessarily receive all of the data corresponding with a single frame 140 from the source device 110 at once. Rather, the source device 110 may provide a stream of digital data to the display device 120 that represents the pixels of each frame 140 of the content. Such is the case, for example, if the content is compressed or encrypted. The display device 120 or other downstream image processing device may then decompress, decrypt or otherwise decode the incoming data, build or compile each frame 140 of the image to be displayed from the provided data and store the compiled frames 140 in the buffer 150 for display at the appropriate time. Thus, the content may be transmitted to the display device 120 in any manner that enables display device 120 to access and/or reconstruct frames 140 at a frame rate that is a least twice the frame rate of the content source.
In one implementation, the frames 140 are transmitted to the display device 120 in a frame-sequential fashion, such that the content frames 140 are provided in a sequence of left-eye and right-eye frames that is recognized by the display device 120 for proper display to a viewer. In the embodiment depicted in FIG. 1, for example, right-eye frames 180 and left-eye frames 190 are transmitted in an alternating, interleaved, frame-sequential fashion. Thus, a single left-eye frame 160 containing an image intended for the viewers left eye is transmitted, followed by a single right-eye frame 170 containing an image intended for the viewers right eye. This pattern of transmitting the frames of the content may be repeated, alternating left-eye frames (“L”) 190 and right-eye frames (“R”) 180, while the source device 110 is providing the content to the display device 120. Alternatively, the frames may be transmitted to the display device 120 such that two right-eye frames 180 are transmitted to the display 120, followed by two left-eye frames 190, and so on. In yet another example, several right-eye frames (e.g., 24 or 30 right eye frames) may be followed by several left-eye frames (e.g., 24 or 30 right eye frames). Generally, the frames 140 may transmitted to the display 120 in any order, as long as the display device 120 may place the frames 140 in the proper order for presentation to the viewer without a perceivable delay in the presentation of the content to the viewer.
To maintain the desired frame rate for the 3-D content, the frames 140 are transmitted at a frame rate of at least two times (2×) compared to the frame rate of the content source. For example, in a conventional arrangement, video is often rendered at 30 fps, with each frame containing resolution-compromised (e.g., compressed, squeezed or the like) versions of both the left-eye image and the right-eye image. In accordance with aspects of the present invention, the left-eye and right eye images are transmitted in different frames 140 such that each image has the full resolution available in the entire frame 140. Thus, each 3-D image comprising a left-eye image and a right-eye image is transmitted in two frames 140, a single frame 160 for the left-eye image and a single frame 170 for the right-eye image. Therefore, 3-D video content may be encoded and/or transmitted at a rate of 60 fps. Similarly, 3-D film content is provided at a rate of 48 fps, which is twice the frame rate (24 fps) of conventional film content. Further, by transmitting the frames at a higher rate, the high definition resolution of each image is maintained since there is no need to compress or squeeze the right-eye and left-eye images for transmission.
Broadcast and electrical interface standards exist for transmitting high definition content at 60 fps with a resolution of 720p. Conventional film content at 24 fps and video content at 30 fps require less than or equal to half the bandwidth available in the existing transmission infrastructure and electrical interface standards. Aspects of the present invention take advantage of the available bandwidth to transmit at least twice as many frames as compared to the conventional content, allocating substantially half of the frames for left-eye and half for right-eye. In this manner, aspects of the present invention enable 3-D multimedia to be transmitted as high definition without the loss of resolution to the images.
For 3-D video content, which is shown at a rate of 30 fps, transmitting alternating left eye and right eye frames requires 60 fps and thus fits within the 60 fps available for high definition video. However, 3-D cinema content, provided at 24 fps requires 48 fps to handle left-eye and right-eye frames and so does not fit neatly within the 60 fps rate. In the case of film content, additional frames are used in implementations of the present invention to adapt the 48 fps rate into the 60 fps transmission rate of high definition video transmission and interface conventions.
FIG. 3 is a diagram illustrating a series of frames including 3-D content frames 310 and null frames 320 encoded pursuant to aspects of the invention. This embodiment illustrates how high definition 3-D cinema multimedia content may be transmitted using a 60 fps transmission rate. A greater or lesser number of null frames 320 may be provided within the transmission stream 300 so as to adapt to other transmission rates and/or other source content frames rates. For convenience, the content is portrayed as a stream of frames 300 in FIG. 3. The stream 300 includes content frames 310 (including both left-eye image frames (“L”) and right-eye image frames (“R”) and null frames 320, shown in black.
3-D cinema content with a source frame rate of 24 fps is produced with separate left-eye and right-eye frames at a rate of 48 fps. In one embodiment, the right eye frames and left eye frames are transmitted in a frame-sequential fashion, alternating between left and right frames. However, for 3-D cinema content, the content frames 310 including the images of the content only require 48 fps of the 60 fps capacity, leaving 12 fps in the transmission stream 300 to account for. Thus, null frames 320 are included within the stream 300 to occupy the 12 fps capacity that is not used to transmit content frames 310.
The null frames 320 included in the stream of frames 300 may include any information, image, pattern or other indicia recognized by the display device 120 as a null frame 320. Generally, the display device 120 is configured to identify the null frames 320 within the stream of frames 300 either implicitly (e.g. a frame that does not bear characteristics of a content frame 310 is deemed to be a null frame 320) or explicitly (e.g., indicia within a frame identifies the frame as a null frame 320). For example, the null frames 320 may include only black pixels that signal the display device 120 to ignore the null frames 320 or otherwise handle the frames as null frames 320. The occurrence of a null frame 320 may also signal display device 120 that the next subsequent frame is a left-eye frame 190 or a right-eye frame 180, for example. In this manner, the null frames 320 can be used to convey signaling information that can be used by display device 120 to properly sequence playback.
Null frames 320 are inserted into the frame stream 300 as every fifth frame, in one possible arrangement. Thus, four content frames 310 may be transmitted for each null frame 320, alternating between left-eye images and right-eye images in the embodiment illustrated in FIG. 3. However, the null frames 320 of the frame stream 300 may be placed anywhere within the frame stream 300. For example, in the embodiment of FIG. 4 null frames 420 are placed after ten content frames 410 are transmitted. Further, to ensure that twelve null frames are included in the stream 400 (to transmit 48 frames in a 60 fps transmission rate), two consecutive null frames 420 may be included in the stream 400.
In conventional 2D content, every frame is essentially similar to every other frame in that there is no left-eye or right-eye separation at the display device 120. When displaying 3D content it is important to ensure that the display remains able to properly pair left-eye 190 and right eye images 180 and to accurately determine whether a particular image is a left-eye image or a right-eye image. To assist the display device 120 in presenting the content correctly, a synchronization signal typically provided to the display device 120 to instruct the display device 120 as to which frames 140 are to be presented and in which order the images are to be displayed to create the 3-D effect.
FIG. 5 is one embodiment for providing a synchronization signal by including an in-band synchronization signal contained within a frame 500. FIG. 5 illustrates several pixels of a frame 500, such as the pixels of the upper rightmost corner of the frame image. Signal pixels 520 designated by “S” represent synchronization pixels embedded within the frame 500 while pixels designated by “P” represent data pixels. Frame 500 may be a content frame (310, 410) or a null frame (320, 420).
In this example, the synchronization signal takes the form of data embedded within a line of pixels 510 of the frame 500, such as the first line 510 of the frame 500. Alternatively, the synchronization signal may be embedded within any pixels of the frames of the content in a manner that allows display device 120 to identify the pixels used for the synchronization signal. The synchronization signal is read by the display device 120 from the frame 500 when the frame 500 is received and processed.
As shown in FIG. 5, the content frame 500 is composed of a set of pixels. For example, in one embodiment the frame 500 may be 1280 pixels wide and 720 pixels tall. Each pixel of the frame 500 may include a small part of the overall image presented by the frame 500. However, the pixels of each frame 500 may also be utilized to transmit a synchronization signal to the display device 120 by altering the color of the signal pixels 520 representing the synchronization signal within the frame 500. For example, signal pixels 520 may be all black to signal the display device 120 that the frame is a left-eye frame. Generally, the signal pixels 520 may be any color that signals to the display device 120 the proper sequence or type of the frame 500. Further, the synchronization signal pixels 520 may be any number of the pixels or in any location within the frame 500. For example, a single black pixel in the upper right corner of the frame 500 may indicate a left-eye image frame while a single white pixel in the same position may indicate a right-eye image. In this manner, the 3-D content provider has control over the sequence of the content by controlling the color of the signal pixels 520.
Upon receipt, the synchronization signal provides an indication enabling the display device 120 to determine whether a particular frame 500 or group of frames 140 are left-eye or right-eye frames. For example, the synchronization signal may inform the display device 120 that the frame 500 is intended for the left eye of the viewer. The display device 120 then processes the frame 500 accordingly, such as placing the frame 500 in the proper order in the frame stream being displayed. In other embodiments, the synchronization signal enables the display device 120 to pair a particular left-eye frame 160 with a matching right-eye frame 170 to create the 3-D image. Generally, the synchronization signal may include any information that may assist the display device 120 in compiling and displaying the 3-D content.
In the embodiment shown in FIG. 5, the synchronization signal is a four-pixel signal contained within the first line of pixels 510 of the image frame 500. Thus, pixels 1-4 of the first line of pixels 510 of the frame 500 contain the signal pixels 520 of the synchronization signal. However, the synchronization signal pixels 520 are not required to be transmitted on the first line of pixels 510 of the frame 500. Rather, the synchronization signal pixels 520 may be included anywhere within the frame 500. Other embodiments may instruct the display device 120 to look in a particular area within the frame 500 to locate and read the synchronization signal pixels 520.
The display device 120 is configured to recognize when synchronization signal pixels 520 are embedded within the frame 500 and adjust the display of the frame 500 accordingly. Further, the display device 120 may be configured to not present the synchronization signal pixels 520 to the viewer. Thus, in the example where the synchronization signal pixels 520 are located in the first line of pixels 510 of the frame 500, the display device 120 may be configured to not display the first line of pixels 510 to the viewer. Instead, the display device 120 may convert the first line of pixels 510 into an all black line for presentation to the viewer or may disregard the line altogether. In this manner, a synchronization signal may be embedded within the transmitted frames 140 that may instruct the display device 120 on how to compile the frames 140 and, in some cases, the sequence in which the frames 140 should be displayed.
One disadvantage to including the synchronization signal in-band is that the viewer may detect or otherwise recognize the altered pixels of the image. Thus, other embodiments may provide the synchronization signal to the display device 120 without embedding the signal within the content frames 140 of the content. In such embodiments, the synchronization signal may be provided to the display device 120 out-of-band over an existing broadcast/interface specification. For example, the synchronization signal may be provided to the display device 120 via an HDMI cable or similar interface. Generally, any communication channel may be used to transmit the synchronization signal to the display, including wireless channels or coaxial cable. The synchronization signal may be a single bit or several bits transmitted to the display device 120 over the out-of-band interface to indicate the sequence and/or type of frame being transmitted. The synchronization signal may be transmitted in an allowed space within the specification of the standard interface, such as in a header within the information being transmitted over the interface. The display device 120 may then interpret and process the synchronization signal in a similar manner as described above.
it is not required that a synchronization signal be provided to the display 120 for every transmitted frame. Rather, a synchronization signal may be provided to the display device 120 to set a cadence for the incoming frames 140. For example, the display device 120 may be configured to recognize a left eye or right eye designation for the incoming frames 140 based on a synchronization signal that begins the cadence. Null frames (320, 420) are inserted into the transmitted frame stream 300 in some embodiments. In the embodiments shown in FIG. 3 with a null frame 320 after every four content frames 310, the display device 120 may be configured to recognize a left eye designation for the frame 310 that immediately follows the null frame 320 and alternate designations for every frame 310 that follows until another null frame 320 arrives. Thus, the display device 120 may then recognize a right eye designation to the next frame and continue alternating between a left eye designation and right eye designation until the next null frame 320 is detected. The display device 120 may also be configured to recognize a right eye designation for the frame 310 following the null frame 320 and alternate with a left eye designation. However, in this embodiment, the null frames 320 of the frame stream 300 would likely be set up in such a manner that the frames 310 that follow the null frames 320 would always be intended for the same eye and thus receive the same designation. Generally, however, the display device 120 may recognize any arbitrary pattern of left-eye and right-eye images that follows a null frame 320.
In a similar embodiment, the null frames 320 themselves may carry the synchronization signal information for the frame 310 that follows the null frame 320. In this example, the display device 120 may receive and recognize a null frame 320 as described above. However, in this example, the null frame 320 may include a synchronization signal to instruct the display or initiate a cadence. The synchronization signal may instruct the display device 120 to recognize a left-eye or right-eye designation for the frame 310 following the null frame 320. Further, the synchronization signal may instruct the display device 120 to alternate between left and right designations as described above on all incoming frames 310 until the next null frame 320 is received.
FIG. 6 is a block diagram illustrating a system for encoding high definition 3-D multimedia content to a computer-readable medium. The system may include a telecine or similar apparatus to convert and encode 3-D multimedia content from film or video onto a computer-readable medium.
The system of FIG. 6 may include an encoder 630 that may be configured to encode a stream of frames 620 from a 3-D source 610 to a computer-readable medium 650. In one embodiment, the 3-D source 610 may be a 3-D film or video involving multiple frames 620. The frames 620 may be structured and presented to a viewer as described above to create a 3-D image or series of 3-D images. In other embodiments, the 3-D content is a digital data file containing information representing the frames 620 of the multimedia source 610. Generally, any source involving a series of frames may be used with the embodiment. The frames 620 of the source 610 may be transmitted to the encoder 630 for encoding and storage on a memory medium 650.
The encoder 630 may receive the frames 620 and encode the 3-D content in a similar manner as described above with reference to FIGS. 1-4. The frames 620 may be encoded in an frame-sequential fashion 640, alternating between the left-eye frame and a right-eye frame. Further, the frames 620 of the content may be encoded to provide a particular frame rate to the content, such as 60 fps. For sources with frame rates below 30 fps, the encoder 630 may insert several null frames into the frame-sequential frames 640 to ensure that the content is encoded at a particular frame rate.
To insert the null frames into the frame stream 640 of the content, the encoder 630 may ascertain the frame rate of the source content 610. If the encoder 630 determines that the frame rate of the source 610 is less than 30 fps, the encoder 630 inserts null frames into the frame stream 640 of the content to provide a 60 fps frame rate to the encoder 630, including the added null frames. For example, a typical frame rate of 3-D film is 24 fps which results in 48 fps when left-eye and right-eye frames are transmitted separately in accordance with the present invention. A source 610 rendered at 24 fps may include 12 null frames to provide a 60 fps frame rate of the content (48 frames of content and 12 null frames). In this manner, 3-D content may be encoded at a frame rate and resolution that satisfies broadcast interface standards.
The encoder 630 may also include the synchronization signal into the encoding of the content 610. The synchronization signal may be encoded within each frame of the multimedia content, within the null frames of the frame stream 640 or provided out-of-band to the display, such as an available HDMI interface.
Once encoded, the high definition 3-D content may be recorded on a computer-readable medium or otherwise distributed. The memory medium 650 may take many forms, including but not limited to, an optical disc (such as a Blu-ray Disk® compatible optical disc); magnetic storage medium; magneto-optical storage medium; read only memory (ROM); random access memory (RAM); external hard drive; flash memory or other types of medium suitable for storing electronic data.
FIG. 7 is a flowchart of a method for encoding high definition 3-D content to a computer-readable medium in accordance with the present invention. The method may be practiced by the encoder 630 of FIG. 6 or a similar device to encode 3-D content to a computer-readable medium or otherwise distribute the 3-D content.
In operation 710, the frame rate of a 3-D multimedia source is determined, typically because the source is provided with an indication of the frame rate used by the content creator. Once the frame rate of the 3-D source is determined, the encoder ascertains which of the images of the 3-D content are those images intended to be viewed by the left eye of the viewer and the images intended to be viewed by the right eye of the viewer in operation 720.
In operation 730, null frames may be inserted into the frame stream encoded in operation 730. As explained in more detail above, the null frames may be used to increase the frame rate of the encoded content to 70 fps. The null frames may be inserted into the stream as desired to ensure the 70 fps frame rate.
A synchronization signal may be encoded with the frame stream in operation 740. The synchronization signal may be used to instruct a display device on the manner in which the frames of the content are to be presented. The synchronization signal may be encoded within each frame of the content, within the null frames of the frame stream inserted in operation 730 or provided out-of-band on a separate input to the display.
It should be noted that the flowchart of FIG. 7 is illustrative only. Alternative embodiments of the present invention may add operations, omit operations, or change the order of operations without affecting the spirit and scope of the present invention.
FIG. 8 is a high-level block diagram illustrating a particular system for providing high definition 3-D multimedia content in accordance with the present invention. In this particular embodiment, the 3-D content is encoded and stored on Blu-ray Disk® 810. The disk is encoded to include digital information representing the image frames of the 3-D content, including the left-eye and right-eye frames for each image of the content. The information stored on the disk 810 is accessed and read by the Blu-ray Disk® player 820 and transmitted to a decoder device 830.
Blu-ray Disks® 810 generally provide encoded content. Encoding represents a difference in the formats that are typically used for storing or transmitting multimedia content and the formats used for intermediate processing of the multimedia content. The decoder 830 translates between the storage and intermediate formats. For example, stored MPEG content is both compressed and encrypted. Prior to being played at an output device, the stored MPEG content is decrypted and uncompressed by a decoder 830. The decoder 830 may comprise hardware, software, or some combination of hardware and software. Further, decoder 830 may be integrated within the Blu-ray Disk( Player 820, may be a stand-alone device, or may be integrated in the output device or other downstream image processing device.
Once decoded, the content is transmitted to a high definition television (HDTV) 840 over a suitable cable or other electrical connection for display to a viewer. For example, the content may be transmitted to the HDTV 840 over a HDMI cable. Generally, the HDTV 840 is capable of displaying the high definition quality content (i.e., a display resolution of 720p or higher). Once the content is received, the HDTV 840 presents the content to the viewer. In the example, shown, the HDTV 840 includes a video display 850 for presenting the frames of the content and speakers 870 to provide the sound of the content. In this manner, the 3-D content stored on the Blu-ray Disk® 810 is presented to the viewer for the viewer's entertainment.
The foregoing merely illustrates the principles of the invention. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements and methods which, although not explicitly shown or described herein, embody the principles of the invention and are thus within the spirit and scope of the present invention. From the above description and drawings, it will be understood by those of ordinary skill in the art that the particular embodiments shown and described are for purposes of illustrations only and are not intended to limit the scope of the present invention. References to details of particular embodiments are not intended to limit the scope of the invention.

## Claims

1. A method for encoding three-dimensional multimedia content comprising:
receiving three-dimensional content having a plurality of frames and having a source frame rate wherein the plurality of image frames comprises at least a first kind of image frames and a second kind of image frames;
modifying the plurality of frames by including a synchronization signal distinguishing the first kind of frames from the second kind of frames; and
organizing the plurality of frames in a frame-sequential manner including the synchronization signal, wherein the organized frames have a frame rate that is at least twice the source frame rate.

2. The method of claim 1 wherein the organized frames have a frame rate that is less than a display frame rate at which the organized frames will be presented to a viewer.

3. The method of claim 1 wherein the act of modifying comprises embedding signal information in at least some of the first kind of frames to indicate their kind.

4. The method of claim 1 wherein the act of modifying comprises embedding signal information in all of the first kind of frames and all of the second kind of frames to indicate their respective kind.

5. The method of claim 1 wherein the act of modifying comprises inserting a null frame amongst the plurality of image frames such that the relative position of the null frame with respect to the first kind of image frames and the second kind of image frames provides the synchronization signal.

6. The method of claim 1 further comprising configuring the organized plurality of frames for a distribution channel having a distribution channel frame rate that is greater than the source frame rate by at least a factor of 2.

7. The method of claim 1 wherein the act of organizing the plurality of frames comprises inserting null frames within the plurality of frames to substantially match the frame rate of the organized frames to a distribution channel frame rate.

8. The method of claim 1 wherein the first kind of frame comprises left-eye images and the second kind of frame comprises right-eye images.

9. The method of claim 1 wherein each left-eye image is paired with a particular one of the right-eye images.

10. The method of claim 1 wherein the act of organizing comprises placing the synchronization signal in a channel that is out of band with respect to image information contained in the plurality of image frames.

11. A method for displaying three-dimensional multimedia content comprising:
receiving three-dimensional content having a plurality of frames from a source, wherein the plurality of frames comprises at least a first kind of image frames, a second kind of image frames and a plurality of null frames;
reading a synchronization signal included in the plurality of frames, wherein the synchronization signal distinguishes the first kind of frames from the second kind of frames;
organizing the plurality of frames in a frame-sequential manner including the synchronization signal, wherein the organized frames have a frame rate that is at least twice the source frame rate; and
presenting the plurality of image frames in a frame-sequential manner in response to the synchronization signal.

12. The method of claim 11 wherein the image frames have a frame rate that is less than a display frame rate at which the image frames will be presented to a viewer.

13. The method of claim 11 wherein the synchronization signal is embedded in at least some of the first kind of frames to indicate their kind.

14. The method of claim 11 wherein the synchronization signal is an embedded signal in all of the first kind of frames and all of the second kind of frames to indicate their respective kind.

15. The method of claim 11 wherein the first kind of frame comprises left-eye images and the second kind of frame comprises right-eye images.

16. The method of claim 11 wherein each left-eye image is paired with a particular one of the right-eye images.

17. The method of claim 11 wherein the synchronization signal is in a channel that is out of band with respect to image information contained in the plurality of frames.

18. A method for providing three-dimensional multimedia content over a distribution channel comprising:
receiving three-dimensional content having a plurality of frames having a source frame rate and comprising at least a first kind of image frames, a second kind of image frames and a plurality of null frames including a synchronization signal distinguishing the first kind of frames from the second kind of frames;
organizing the plurality of frames in a frame-sequential manner including the synchronization signal, wherein the organized frames have a frame rate that is at least twice the source frame rate; and
transferring the organized plurality of frames over the distribution channel.

19. The method of claim 18 further comprising configuring the organized plurality of frames for a distribution channel having a distribution channel frame rate that is greater than the source frame rate by at least a factor of 2.

20. The method of claim 18 wherein the act of organizing the plurality of frames comprises inserting null frames within the plurality of frames to substantially match the frame rate of the organized frames to a distribution channel frame rate.

21. The method of claim 18 wherein the first kind of frame comprises left-eye images and the second kind of frame comprises right-eye images.

22. The method of claim 18 wherein each left-eye image is paired with a particular one of the right-eye images.