News Column

Patent Issued for 3D Authoring Tool Ensuring No Buffer Underrun upon Jumps

May 7, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Takashima, Yoshikazu (Los Angeles, CA); Thompson, Michael (Los Angeles, CA), filed on November 17, 2011, was published online on April 22, 2014.

The assignee for this patent, patent number 8705946, is Sony Corporation (Tokyo, JP).

Reporters obtained the following quote from the background information supplied by the inventors: "In the Blu-ray.RTM. specification, 3D stream files can be played by both 2D players and 3D players. A 3D player will read the entire 3D stream, while a 2D player reads only the 2D portion of the stream, which includes 2D video as well as audio streams.

"The above specification defines two types of 3D streams: 1TS and 2TS. The 1TS stream includes both base view video and dependent view video in a single transport stream. This transport stream is maximum bit rate limited to 48 Mbps, so in general this type does not have a high enough bit rate to multiplex high quality 3D video with multiple high-quality audio streams. The 2TS stream files have a maximum total bit rate for the base and dependent transport streams of 64 Mbps and thus has enough bit rate to carry high-quality 3D video and audio.

"The 2TS stream includes base view video and audio streams in one transport stream file, and includes dependent view video in another transport stream. As a result, the base view video is often larger in extent, and often has a higher bit rate. In fact, the dependent view bit rate may approach zero if the view varies very little from the base view, because of the way MVC encodes data.

"The 2TS stream files are interleaved, and as noted incorporate base view blocks and dependent view blocks. Such stream files are stored as one hybrid file termed an SSIF file in the Blu-ray.RTM. specification, where SSIF refers to a stereoscopic interleaved file.

"In more detail, in one implementation, and referring to prior art FIG. 1, an architecture 10 includes a 2TS 3D stream file 16 that includes a base view transport stream (TS) file 12 and a dependent view TS file 14. The 3D stream file 16 is broken into a set of base view blocks 22j and a set of dependent view blocks 18i. Both are employed for 3D playback, e.g., base view for left eye and dependent view for right eye, or vice-versa, and just the base view 22j is used for 2D playback.

"When a player performs a drive seek to read the blocks of the AV (audiovisual) stream, the player needs to buffer enough AV stream data to a read buffer to continue smooth playback, at least until the drive starts reading new AV stream data after a jump.

"Two situations require special handling: playback over an optical media layer jump and play back in a multi-story branching situation (FIGS. 2-4). Referring first to the layer break jump illustrated by the sequence 20 in prior art FIG. 2, a 3D stream file 24 is multiplexed into a base view and dependent view of the 3D stream, and a number of base view blocks 26i and dependent view blocks 28j are defined. A layer break 32k is established where desired, and the same may be estimated using time codes or file sizes. The layer break 32, which usually constitutes a long jump, is typically set at the block boundary closest to the requested timecode or file size. In many cases, current authoring systems employ 'parameters-A' to determine the jump point. These may include AV stream maximum bit rate, drive jump performance, and jump distance, or a sub combination of these. In many cases, the target jump point is determined by stream file size, then evaluated based on the parameters-A.

"The Blu-ray.RTM. specification then sets a number of conditions that must be established for seamless playback, and these are checked, for a proposed jump point, in step 34. If seamless playback does not occur, the layer break is moved, i.e., a different layer break point is attempted. If seamless playback is achieved, a layer size check 36 is performed to ensure the layer size does not exceed the maximum size set for the medium and further such that the first layer size is larger than or equal to the second layer size as required in the Blu-ray.RTM. specification. Finally, a file system image is created, e.g., a master disc is created in step 38.

"FIG. 3 illustrates a prior art method 30 for a medium including 2D multi-story branching. The 2D stream is shown with a multi-story playback path set up including chapters A (42), B (44/46), and C (48), where B has two alternative branches B1 (44) and B2 (46). In the case where the size of B1 or B2 is larger than a maximum jump distance, B1 and B2 are interleaved to keep the jump distance less than the maximum. For example B1 (44) and B2 (46) may be further broken up into (for B1) B1[1]=44(1) and B1[2]=44(2); and (for B2) B2[1]=46(1) and B2[2]=46(2). That is, the components of B1 and B2 are interleaved such that the maximum jump distance is less than a predetermined maximum, e.g., 640,000 sectors or 1.28 Gb for a current Blu-ray.RTM. disc to cap the drive seek time. Sample playback paths are illustrated, both for branch A-B2-C (bottom path) and for branch A-B1-C (top path).

"As in FIG. 2, a seamless playback check is performed in step 52. If seamless playback does not occur, the interleaving is performed again in a different way. As above, a layer size check 54 is performed to ensure the layer size does not exceed the maximum size set for the medium and that the first layer size is larger than or equal to the second layer size as required in the Blu-ray.RTM. specification. Finally, a file system image is created, e.g., a master disc is created in step 56.

"FIG. 4 illustrates a prior art method 40 for a medium including 3D multi-story branching. The 3D stream is shown as set up with a multi-story playback path having chapters A (62), B (64/66), and C (68), where B has two alternative branches B1 (64) and B2 (66). All of the chapters or 3D stream files are shown divided into base and dependent view blocks 62i, 62j, 64i, 64j, 66i, 66j, 68i, and 68j. Where B1 or B2 are larger than a maximum jump distance, the two may be interleaved to keep the jump distance less than a maximum. Again, this maximum jump distance is currently about 1.28 GB. As an example of interleaving, B1 (64) and B2 (66) are further broken up into (for B1) B1[1] and B1[2]; and (for B2) B2[1] and B2[2]. The interleaving is such that the maximum jump distance is less than the predetermined maximum. Sample playback paths are illustrated, both for branch A-B2-C (bottom path) and for branch A-B1-C (top path).

"Again, a seamless playback check is performed in step 72. Following the seamless playback check, a layer size check 74 is performed to ensure the layer size does not exceed the maximum size set for the medium. Finally, a file system image is created, e.g., a master disc is created in step 76."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "Systems and methods are provided to implement techniques for providing 3D content, such as on optical media like Blu-ray.RTM. discs. In one exemplary implementation, a 3D authoring tool executing on a computer system manages how to construct an image for replication where the image is constructed to handle jumps without buffer underruns, the jumps caused by, e.g., layer switching or by moving from or to branches in a multi-branch story line.

"In one embodiment of the system and method, a feature is provided to an optical medium authoring tool that controls where jumps (to another layer or to another point on the same layer) may be made without the danger of a buffer underrun, such resulting in unacceptable playback quality.

"In certain implementations of the system and method, instead of using the 'parameters-A' as noted above in prior art systems, a different group of parameters, 'parameters-B', and especially AV stream local bit rate and jump distance, are employed to determine all the acceptable jump points for a given 2D or 3D stream. Jump capability flags are set at these points, and if a jump is required, the same is made at these points, which eliminates the chance for a buffer underrun. Accordingly, there is no need to perform seamless playback condition checks as was previously required. While jump capability flags are disclosed as a convenient way to identify appropriate points, it will be understood by one of ordinary skill in the art that any way of noting such points may be employed, and that the use of flags is merely exemplary.

"In one exemplary method, for a given 3D stream file, a first step may be to define base view blocks and dependent view blocks. When defining these, parameters such as local bit rate and jump distance may be employed to determine where to set jump capability flags, these flags determining whether a long jump could be placed after a given base or dependent view block. In essence, the jump capability flags determine where long jumps can be made without buffer underrun, ensuring seamless playback. In the 3D situation, the local bit rates of 3D block (sequence of both the base and dependent view blocks) and 2D block (base view block) both may be employed to determine if a point is jump capable.

"In more detail, a common reason why such buffer under runs may occur is because a long jump is attempted when the local bit rate before the long jump point is too high. In particular, if each block before a long jump is larger than the minimum extent size, seamless playback will be guaranteed because buffered data from a minimum extent block will be sufficient to provide data for display while the jump is being made. However, the bit rate cannot be too high, or else too much data will be demanded. Consequently, the minimum extent size can be calculated by the bit rate of each block, i.e., the block bit rate leads to a determined minimum extent size. As in the 2D case, a 3D block bit rate leads to a minimum 3D extent size and a 2D block bit rate leads to a minimum 2D extent size. Put another way, if a block is too short, a jump cannot be made after it.

"The system and method may be employed in a number of different specific scenarios. Particularly pertinent situations include where playback occurs over an optical medium layer jump, i.e., one where an optical layer is being read and the reading continues onto another optical layer. In general, for multilayer recording, at least one such layer jump will occur. In many cases, for layer jumps, at most 40,000 sectors may be jumped, because of the time necessary to refocus the reading laser on the new layer. Another situation involving long jumps is where a title includes multi-story branches, and the jump occurs at a branching point of the stories. Still another is where a title includes multiple angles, and the user may be enabled to switch from one angle to another. In these cases, if the same layer is being read, i.e., no layer jump is required, a long jump may be over more sectors, e.g., 640,000.

"The system and method may be employed in the authoring of both 2D and 3D media streams. Where the two are linked, e.g., in the Blu-ray.RTM. specification, the feature would be generally applied to both.

"In one aspect, the invention is directed to a method of preparing a 3D media stream such that long jumps do not result in buffer underruns, including: a) receiving a 3D media stream; b) dividing the 3D media stream into a set of base view blocks and dependent view blocks; c) for a first base view block, employing at least a local bit rate in a calculation to determine if a long jump during 2D playback may be made to a second block without the occurrence of a buffer underrun; d) for a first 3D block, which is a pair of base view block and dependent view blocks, employing at least a local bit rate in a calculation to determine if a long jump during 3D playback may be made to a second block without the occurrence of a buffer underrun; e) if a long jump may be made to the second block without the occurrence of a buffer underrun, then configuring the media stream to allow long jumps following the first base view block; and f) creating a file system image or master disc image from the divided and configured media stream.

"Implementations of the invention may include one or more of the following areas the configuring may include setting a jump capability flag at the first block, and where each block has a temporal beginning and a temporal end, and where the setting includes setting the jump capability flag at the temporal end of the first block. The local bit rate may be an average bit rate of a block. The method may further include, for a first dependent view block, using at least a local bit rate to determine if a long jump may be made to another block without the occurrence of a buffer underrun, and if so, then setting a jump capability flag following the first dependent view block. The employing may further include employing a jump distance in the calculation to determine if a long jump can be made to a second block without the occurrence of a buffer underrun. The 3-D media stream may have a beginning base view block and an ending base view block, and the ending base view block may have an extent that is as large as possible while maintaining the size requirement satisfied for the base view blocks that precede it. The ending base view block may have an extent that is larger than all of the base view blocks that precede it in the 3D media stream. The average local bit rate of the base view blocks may be between two and four times the average local bit rate of the dependent view blocks. The method may further include configuring the file system image or master disc image for a Blu-ray Disc.RTM.. The local bit rate may be employed in a calculation of a minimum block size, and if a given base view block size is greater than the minimum block size, and if a given 3D block size is greater than the minimum block size, then the method may further include allowing a long jump at the given base view and 3D block. The long jump may be associated with a media layer jump. The configuring may include setting a jump capability flag at the first block, and the method may further include selecting a layer break from among the long jump capable points, the layer break selected to keep a layer size less than a maximum layer size. The selecting may further include selecting the layer break such that layers created thereby have a layer size within a predetermined range of sizes. The long jump may be associated with a multi-story branching point. The set of base view blocks and dependent view blocks may be further organized into story chapters, at least one story chapter divided into a plurality of branches, and the method may further include: a) subdividing at least one branch into two or more groups of base and dependent view blocks; and b) interleaving at least one group of base and dependent view blocks associated with one branch into a point between two groups of base and dependent view blocks associated with another branch, the point chosen where a long jump is allowed, and where a jump distance associated with the long jump is less than a maximum jump distance. The maximum jump distance may be between 320000 sectors and 640000 sectors.

"In another aspect, the invention is directed towards a non-transitory computer-readable medium, including instructions for causing a computing device to perform the above method.

"In another aspect, the invention is directed towards a system for preparing a media stream for seamless playback over a jump, the seamless playback ensuring a minimum of offer underruns, including: a) memory bearing computer readable instructions capable of analyzing a 3D stream file and dividing the 3D stream file into a series of base view and dependent view blocks; and b) memory bearing computer readable instructions capable of selecting one or more points between the blocks in the series, the points chosen as long jump capable points, the long jump capable points representing locations where a long jump may be made without the occurrence of a buffer underrun.

"Implementations of the invention may include one or more of the following. The long jump may be for a layer jump, and the system may further include memory bearing computer readable instructions capable of choosing a layer break, the layer break chosen at a location where a long jump may be made, and where the layer break is chosen such that the layer size is less than a predetermined maximum. The long jump may be for a multi-story branching point, the multi-story including at least two chapters, at least one of the chapters having at least two branches, at least two of the branches each having at least two groups of base and dependent view blocks, and further including memory bearing computer readable instructions capable of interleaving at least one group of base and dependent view blocks associated with one branch into a point between two groups of base and dependent view blocks associated with another branch, the point chosen where a long jump is allowed, and where a jump distance associated with the long jump is less than a maximum jump distance. The system may further include memory bearing computer readable instructions capable of creating a final base view block associated with the media stream, the final base view block larger than preceding base view blocks of the media stream.

"Advantages of the invention may include one or more of the following. Authoring tools may be provided that have a highly useful feature of reducing or eliminating the occurrence of buffer underruns during media playback. The feature may be applied to reduce buffer underruns during layer jumps, during jumps within multi-story branching, or in other scenarios.

"Other advantages will be apparent to one of ordinary skill in the art given the teaching herein."

For more information, see this patent: Takashima, Yoshikazu; Thompson, Michael. 3D Authoring Tool Ensuring No Buffer Underrun upon Jumps. U.S. Patent Number 8705946, filed November 17, 2011, and published online on April 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=41&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2034&f=G&l=50&co1=AND&d=PTXT&s1=20140422.PD.&OS=ISD/20140422&RS=ISD/20140422

Keywords for this news article include: Sony Corporation.

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Source: Journal of Engineering


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