KR20010080591A - Scalable system for video-on-demand - Google Patents

Abstract

Emulate VOD services in the NVOD structure. The content information is made available to the end user in the NVOD structure. The opening part of the content information is stored in the end user's device, for example by downloading overnight. While the opening part is played out at the end user, the possible content information supplied in the NVOD structure is buffered at the end user's device. The device is controlled to switch the playing out of the stored opening portion to playing out the buffered content information.

Description

Scalable system for video-on-demand

A VOD delivery system is a system for giving program information through bidirectional transmission paths between a supply center and subscribers. In a broad sense, the VOD delivery system handles multimedia information including still images, high definition TV images, computer software and the like. However, the term "VOD delivery system" is usually used in a narrow sense as a system for dealing with movies, TV programs and the like. Thus, the term Video-on-demand (VOD) typically refers to a service that allows subscribers to select videos from a central server to watch a TV or PC monitor. Since the data required by video is very large, VOD over a data network, such as the Internet, is not scaled to many users. VOD requires huge network bandwidth and many servers. Near-VOD (NVOD) is a solution to the scalability problem of VOD. But users can't really control the video: they can't control the start time, stop the program or rewind the video. In NVOD programming, an interactive entertainment system broadcasts different time-shifted versions of an interactive application to all of its subscribers via shared communication paths (ie, each Broadcast the duplicated versions of the application by uniquely offsetting the start time of the version by a predetermined time increment. Typically, interactive systems use NVOD services that provide multiple presentations for a movie, where the start times of the presentation are staggered so that the two presentations do not start at the same time.

Published European patent application EP 0 749 242 A1 describes a VOD system with a server operating in near-video-on-demand (NVOD) mode. The server transmits multiple copies of each program on multiple, separate transport NVOD channels. The transmission of a particular program on one NVOD channel is time offset by a certain time interval in relation to the transmission of the same program on another NVOD channel. As a result, different NVOD channels show different steps in running the same program. When a client makes a request to receive a particular program, the server sends the beginning of the program through the VOD channel rather than the NVOD channel to the requesting client. The start portion provided has a duration equal to or shorter than the stagger time interval. The client is controlled to start recording the program in progress on a particular one of the NVOD channels. The particular NVOD channel is the channel from which the transfer of the program began before the shortest time period associated with the request. This ensures an overlap in the information content between the recording of the beginning and the play-out, from a particular moment. In principle, the overlap enables a seamless transition in switching from a VOD channel to a particular NVOD channel.

A disadvantage of the known system is that it cannot be standardized on the number of users. Each requirement for the beginning requires a separate VOD channel for the end user, in addition to the number of NVOD channels to implement the NVOD mode.

The present invention relates in particular to a system and method for implementing video-on-demand (VOD) services using certain transmission networks, such as cable TV and the Internet.

1 is a block diagram of an NVOD server system in the present invention.

2 and 3 are block diagrams of clients for connecting to the system shown in FIG.

4 is a detailed block diagram of the client.

Throughout the drawings, the same reference numerals indicate similar or corresponding features.

It is an object of the present invention to provide a new method for emulating a VOD service in an NVOD structure. Another object is to provide a method that allows scalability. With the method of the present invention, the content information is made available to the end user in the NVOD structure. An introductory portion of the content information may be stored on the end user's device. While the opening part of the end user is playing out, the content information supplied via the NVOD structure can be buffered to the devices. The method further makes it possible to switch from playing out the stored opening portion to playing out the buffered content information. In a more detailed embodiment, the content information includes a plurality of programs, and the opening portion includes respective opening portions of the plurality of opening portions associated with each of the plurality of programs. The transition includes changing from playing out a particular opening portion to playing out a particular program associated with that particular opening portion.

The present invention is intended to store the beginnings of all the different programs available in NVOD mode on the user's client. The user can thus navigate through the various channels in his storage device, preferably including a hard disk, and select a program based on the stored portions. Once a portion has been selected and played out, recording starts from the closest relevant NVOD channel in time for that particular program. Local storage of the openings makes the system referenceable. The openings may be stored, for example, over night recording from any TV channel or downloaded over a data network such as the Internet, for example a card of solid state semiconductor memory such as a flash memory card. It may be provided stored in a physical device such as a DVD or a DVD.

Video streaming over an IP network requires buffering of the data. Such buffering is required to minimize the adverse effects of low quality of IP network services. This slows the start time. The present invention uses NVOD services to emulate VOD services, for example, by means of large local storage capabilities on a set-top box (STB). Data broadcasting collects and stores the beginning of all movies in a mass local storage device of a set-top box. When the user chooses to watch a particular movie, the STB starts showing the movie from local storage. At the same time, the STB tunes to the appropriate NVOD channel and begins to buffer the rest of the movie. The locally stored movie portion need not be longer in duration than the staggering interval of the NVOD service. The STB can immediately start playing the movie. Because the STB buffers the video stream, the user can freeze or rewind the movie as if adjusting the VCR. Of course, it is not possible to fast forward past the current buffer contents. If the buffer is a recirculating buffer, that is, overwriting the new contents every time the buffer is full, it is also impossible to fast rewind beyond the overwritten contents.

User profiling and personalization services can be used to automate the manner of selection of movies stored on mass local storage.

The device of the user equipment storing the opening portion may be a device such as, but not necessary, that buffers content information supplied via NVOD. If they are two separate devices, they are required to cooperate to minimize the perceived effects of interruption when switching from one to the other to play out. If they are one and the same storage device, it is required to be able to perform read and write operations simultaneously.

First, the environment for analog video is discussed in detail. After that, a system for digital video is discussed.

1 is a block diagram of an NVOD server system 100 for the delivery of analog video and audio. System 100 includes, for example, an audio / video (A / V) source 102, a frame counter 104, a data insertion sub-system 106 and storage, such as a video tape recorder (VTR). Sub-system 108. A / V source 102 supplies analog A / V program content. The counter 104 counts the number of frames in the opening portion of the A / V content, and the sub-system 106 adds the number of frames as data to the vertical blanking interval (VBI) following the relevant frame. Instead, a flag is inserted in the VBI just after the last frame or one of the last frames of the beginning of the A / V program content. The flag indicates that a switchover will occur. Having a flag after the frame preceding the last frame has the advantage of taking into account the latency in the process of controlling switching. The A / V content, which includes labeled frames of the opening portion of each A / V program, is then stored in storage system 108. The system 100 may include a program information generator 110, a download scheduler 112, a sub-system 114 for inserting data into the VBI, and an interface 116 to a delivery network 118. It further includes. The generator 110 generates program information under the control of the download scheduler 112. The program information includes the number of frames at the beginning, i.e. the number of labeled frames and, for example, the title of the program, the name of the content owner, and the name of the author. The scheduler 112 determines how often and when the beginning portion of each program will be made available to the delivery network 118 for storage at the client (not shown here) (eg, 3am every night). Until 4am). Sub-system 114 inserts the information generated by generator 110 into the VBI at the beginning of the beginning of each program to be downloaded to the client via network 118.

2 is a block diagram of a client 200 for receiving introductory portions of A / V content programs, downloaded from system 100 for local storage. Client 200 includes interface 202, VBI parser 204, memory 206, A / D converters 208, 210, MPEG encoders 212, 214, multiplexer 216. ) And memory 218.

The interface 202 connects the client 200 with the delivery network 118 to supply the audio path and the video path. Parser 204 is coupled to the video path to analyze the VBI information. The parser 204 extracts program information generated by the generator 110, such as the title of the program, the name of the content owner and author, and the like. The parser 204 further extracts the number of labeled video frames and the number of frames currently received at the beginning of the program. The total number of program information and frame labels is stored in a database in memory 206. The A / D converter 208 converts the analog video signal received through the network 118 into a digital video signal. The digital video signal is fed to an MPEG encoder 212 to compress it. The A / D converter 210 converts the analog audio signal received through the network 118 into a digital audio signal. The digital audio signal is compressed by the MPEG encoder 214. The compressed digital audio and video signals are then stored in memory 218 via multiplexer 216.

3 is a block diagram of the client 200 of FIG. 2, illustrating configurations for playing out content. In addition to the configurations introduced in FIG. 2, the client 200 includes a buffer 302, a switch 304 with an output device 306, a controller 308 and a frame counter 310. When the user begins to play out the opening portion of a particular A / V content program stored in local storage 218, switch 304 is in a position at which output device 306 is coupled to storage 218. The counter 310 stores the frames supplied by the storage device 218. The controller 308 receives a signal indicating the number of frames supplied by the storage device 218. The controller also receives from database 206 the total number of frames included in the stored opening portion. The controller 308 compares the number of frames received from the counter 310 with the total number of frames stored for the opening portion. If the controller determines that the numbers are equal, the switch 304 is controlled to connect to the buffer 302.

The buffer 302 receives the digitally compressed content supplied by the system 100 in NVOD mode and is received at the client 200 via the A / D converters 208, 210 and the encoders 212, 214. It is done. The size of the buffer 302 is determined by the stagger time interval of the NVOD which in turn determines the length needed for the opening portion. When a user starts playing out the opening portion of a program from local storage 218, the system 100 starts the NVOD programs on a particular channel, i. Choose one. Information for controlling the selection can be obtained, for example, from the database 206. Assume that the last frame of the opening portion is being supplied from local storage 218. Since overlap is required in the content, the same frame may now be available anywhere in the buffer 302. All frames in the beginning are tagged or labeled. Therefore, the controller 308 controls the buffer 302 to start feeding the frame after the last tagged frame.

4 shows the switch 304 in more detail. The switch 304 is a demultiplexer 402, 404, an audio decompressor 406, 408, an audio mixer 410, a D / A converter 412, a video path switch. a switch 414, a decoder 416, and a D / A converter 418. Demultiplexer 402 is connected to input A of switch 304 and demultiplexer 404 is connected to input B of switch 304 (see FIG. 3). Demultiplexers 402 and 404 generate a video stream and an audio stream, respectively.

The audio stream generated from demultiplexer 402 is fed to decompressor 406. The audio stream generated from demultiplexer 404 is fed to decompressor 408. The outputs of the decompressor 406, 408 are connected to the data inputs of the mixer 410. Mixer 410 is controlled by controller 308. The output of the mixer 410 is connected to a D / A converter 412 that supplies an analog audio output. The mixer 410 is, for example, glitch-free by phase in the signal received from the buffer 302 and phase out the audio signal from the local storage 218. Is controlled to produce an audio signal.

The video stream is switched at switch 414 between two frames from input A to input B. The switch 414 is also controlled by the controller 308. This produces a continuous bitstream of digital video decoded at decoder 416, which is then converted to analog at D / A converter 418 for analog playout. Preferably, the video encoding is that the last frame is not a B-frame (bi-directional frame). That is, decoding the last frame of the opening part does not require the next frame. The encoding is also preferably an I-frame (intra frame), where the first frame supplied by buffer 302 does not require a previous frame to decode. These restrictions ensure that the output of the switch 414 is a continuous video stream.

The example above relates to analog content. Digital content is relatively simple. Digital video bitstreams have time stamps. Therefore, the digital video bitstreams may be truncated at any frame transition and followed using appropriate time stamps as a reference to recreate exactly the same bitstream. To implement the VOD concept, the time stamps at the end of the beginning of the program need to communicate with the client at the time of download. To connect the program contents, the client compares the current time stamp of the bitstream being played out from the local storage device with the stored time stamp (which indicates the end of the preamble). If the comparison signals that the time stamps are the same, the client switches the video source from local storage to a buffer. The configuration of the system for digital content is, for example, functionally similar to the analog case discussed above, but does not include the A / D and D / A converters 208, 210, 412, 418 and the compressor 212. 214 and decompressors 406 and 408, no configuration for processing frame numbers, and no audio mixer 410 is needed.

Within the context of the present invention, reference is made to the following patent documents:

-Attorney docket PHA 23,633, filed by Yevgeniy Eugene Shteyn and filed April 1, 1999, "Time- and location-driven presonalized TV". The document relates to a server system that allows a subscriber to select a particular broadcast program for recording and to select a specific location and time frame for playing out the recorded program.

-US Patent Application No. 09 / 149,950 (Attorney docket PHA 23,495), invented by Raoul Mallart, filed on September 9, 1998, "Real-time video game uses an emulation of streaming over the Internet in broadcast events. emulation of streaming over the internet in a broadcast event). In broadcast applications, on a client-server network, streaming of animated data is emulated over the Internet to a large number of clients. The animation is considered a series of states. Status information is sent to clients instead of the graphic data itself. The client generates the animation data itself under the control of the state information. Servers and clients communicate with each other using a shared object protocol. Therefore, streaming works just as well as broadcast without falling into serious network bandwidth problems. This is the approach used to represent real-life events (e.g. car racing) in a virtual environment to encourage the user to participate in a virtual race rather than a real professional athlete. The dynamics of the virtual environment are driven by changes in the state sent to the user. Is determined.

-Attorney docket PHA 23,491, invented by Raoul Mallart and Atul Sinha, filed Aug. 24, 1998, "Emulation of streaming over the internet in broadcast applications. a broadcast application ". The document relates to a broadcast application on a client-server network, in which animation data streaming is emulated over a large number of clients over the Internet. The animation is considered a series of states. Status information is sent to clients instead of the graphic data itself. The client generates the animation data itself under the control of the state information. Servers and clients communicate with each other using a shared object protocol. Therefore, streaming does not fall into serious network bandwidth problems and works just as well as broadcast.

-US Patent Application No. 09 / 053,448 (Attorney docket PHA 23,383), invented by Raoul Mallart and Atul Sinha, filed April 1, 1998 "Group-wise video conferencing using a three-dimensional graphical model of a broadcast event. uses 3D-Graphics model of broadcast event). The document relates to TV broadcast services for end users distributed in different regions configured in conferencing mode. For any event in the broadcast, certain groups of end users are put into conference mode under software control so that the group can discuss the event. The conference mode is enhanced by a three-dimensional graphical model of the graphical representation of the events downloaded to the groups. End users can interact with the model to alternately discuss events.

The present invention relates in particular to a system and method for implementing a video on demand (VOD) service using a transmission network, such as cable TV and the Internet. The present invention also overcomes the disadvantage that the known system cannot standardize on the number of users, and provides a method of allowing standardization for a large number of users. With the method of the present invention, the content information is made available to the end user in the NVOD structure.

Claims (11)

A method of emulating a VOD service in an NVOD structure 108, Making the content information available to the end-user 200 in the NVOD structure; Enabling storage (218) of the beginning portion of the content information on an end-user's device; Enabling the end-user's device to buffer (302) content information supplied in the NVOD structure during playout at the end-user; Enabling to transition (304) from playing out the stored opening portion to playing out the buffered content information. The method of claim 1, The content information includes a plurality of programs; The opening portion includes respective opening portions of the plurality of opening portions associated with respective ones of the plurality of programs; Also Enabling the switch to include switching from playing out a particular opening portion of the opening portions to playing out a particular program among a plurality of programs associated with the particular opening portion. . The method of claim 1, The content information is broadcasted via the data network 118; And the opening portion is supplied via the data network. The method of claim 1, The content information is broadcasted through a TV network; And the opening portion is supplied through the TV network. The method of claim 1, The content information is broadcasted through a TV network; The preamble portion is supplied via a data network. The method of claim 1, Wherein the opening portion is provided to an end-user and stored on a physical device. The method of claim 2, The content information includes frames in analog format; Enabling the switching includes labeling consecutive ones of the frames of the opening portion in the VBI signal (104/106); Also The conversion is controlled by the labeling. The method of claim 2, The content information includes frames in digital format with time stamps; The conversion is controlled by the timestamps. In a client device 200 for use in a client-server system that emulates a VOD service in an NVOD structure, The system has a server 108 that makes content information available to clients in NVOD mode; The client has a storage device (218) for storing an opening portion of the content information; The client has a buffer (302) for buffering the content information supplied in NVOD mode during playout of the opening portion; Also And the client has a switch (304) that controls switching from playing out an opening portion from the storage device to playing out the content information from the buffer. The method of claim 9, The server makes the content information available in analog format; The opening portion has frames with labels; The client has a parser 204 for extracting information about the labels; The client has a controller (308) for controlling the transition under control of the information. The method of claim 9, The server makes the content information in digital format having timestamps available; And the client has a controller for controlling the transition under control of the timestamps.