WO2001019078A1

WO2001019078A1 - Method and apparatus for synchronization of separate digital and analog video streams at a viewer's premise using closed captioning

Info

Publication number: WO2001019078A1
Application number: PCT/US2000/023780
Authority: WO
Inventors: Anand Srinivasan
Original assignee: Hotv, Inc.
Priority date: 1999-09-03
Filing date: 2000-08-29
Publication date: 2001-03-15
Also published as: AU7089000A

Abstract

An interactive video display system has a computerized video display unit (PC/VDU) (33) having a first port for receiving a primary analog video stream (PAVS) with closed caption text strings and a second port for receiving a digital annotation data stream (DADS), a broadcast station (15) delivering PAVS to the first port of the PC/VDU, and an authoring station (11) delivering a DADS to the second port of the PC/VDU. Broadcast station (15) delivers the PAVS to the PC/VDU (33) and the authoring station (11). The authoring station (11) copies the CC into the DADS. The PC/VDU uses the CC in the two data streams to synchronize the two streams in display. The system is particularly adaptable to systems having a cable or satellite port and Internet connection. In some embodiments CC strings are tabled with timing data, and the tables are used for comparison and synchronization. The CC strings may also be used in channel tuning.

Description

Method and Apparatus for Synchronization of Separate Digital and Analog Video Streams at a Viewer's Premise Using Closed Captioning

Field of the Invention

The present invention is in the field of video broadcasting and editing, and pertains more particularly to methods and apparatus for synchronizing analog video with a control stream utilizing known analog closed-caption strings.

Background of the Invention

With continuing development of new and better ways of delivering television and other video presentations to end users coupled with parallel development of computerized information systems such as the Internet, there have been concerted efforts to integrate various systems to provide enhanced information delivery and entertainment systems. For example, developers are introducing integrated systems combining TVs with computer subsystems, so a TV may be used as a WEB browser, or a PC may be used for enhanced and interactive TV viewing.

In some systems, computer elements such as a CPU, memory, and the like, are built into the familiar chassis of a TV set. In such a system, the TV screen becomes the display monitor in the computer mode. In such a system, conventional TV elements and circuitry are incorporated along with the computer elements, and capability is provided for a user to switch modes, or to view recorded or broadcast video with added computer interaction. One may thus, with a properly equipped system, select to view analog TV programs, digital TV programs, conventional cable TV, satellite TV, pay TV from various sources, and browse the WWW as well, displaying WEB pages and interacting with on-screen fields and relational systems for jumping to related information, databases, and other WEB pages. The capabilities are often integrated into a single display, that is, one may view a broadcast presentation and also have a window on the display for WEB interaction.

In some other systems, computer elements are provided in an enclosure separate from the TV, often referred to in the art as a set-top box. Set-top box systems have an advantage for providers in that they may be connected to conventional television sets, so end users don't have to buy a new TV along with the computer elements.

In such integrated systems, whether in a single enclosure or as set-top box systems, user input is typically through a hand-held device quite similar to a familiar remote controller, usually having infra-red communication with the set-top box or a receiver in the integrated TV. For computer modes, such as WEB browsing, a cursor is displayed on the TV screen, and cursor manipulation is provided by buttons or other familiar pointer apparatus on the remote. Select buttons are also provided in the remote to perform the familiar function of such buttons on a pointer device, like a mouse or trackball more familiar to computer users. Set-top boxes and computer-integrated TVs adapted as described above typically have inputs for such as a TV antenna (analog), cable TV (analog or digital), more recently direct-satellite TV (digital), and may also connect to video cassette recorders and to mass storage devices such as hard disk drives and CD-ROM drives to provide a capability for uploading video data from such devices and presenting the dynamic result as a display on the TV screen.

The present inventors have noted that with the coupling of computer technology with TV, many capabilities familiar to computer users have been made available to TV users. For example, ability to provide text annotation for TV presentations is considerably enhanced. Computer techniques such a Pix-on-Pix are now available, wherein separate TV presentations may be made in separate windows, or overlaid windows on the display screen. Separate windows may also support display from separate sources, such as an analog TV program in one window, a computer game in another, and a video conference in a third.

In typical prior art video authoring systems, end users receive a single video stream that contains the video data and any added annotated data such as subtitling, sponsor logos, information blocks, and the like. However, it is desirable to build upon the goal stated in the preceding paragraph above, by having separate streams, one containing video data, and the other containing enhancement data, that may arrive at and end user's location via different delivery media and be displayed synchronously on a suitable display screen. In a system known to the inventors, hyper-video authoring is possible wherein a wide variety of added, often interactive, content is made available to viewers having an active connection to an offered video and an Internet connection for facilitating delivery of interactive results. The system known to the inventors uses separate authoring stations or systems for use in what is termed hyper-video authoring by the inventors. Hyper-video authoring includes creating hot spots (interactive hyperlinks) in a video, providing interactive regions for tracked objects (method known to the inventors), inserting URL's for user interaction, providing interactive banner ads, providing interactive icons for launching instant replays of short video clips, and adding audio/text annotation, and so on. Enhanced content may, in some instances, be delivered via alternate paths

(typically the Internet) and synchronized with a main video stream at the user's end. In other instances, added content is combined (possibly into the VBI of analog feeds, or suitably interleaved in digital feeds) at the provider end and delivered as one stream (typically cable or digital feed) to the viewer. As a viewer interacts with provided content, Internet capability is utilized as a backlink to a server and for the purpose of delivering stored information associated with the viewers interaction that may be viewed on the same display containing the offered video such as by a PIX on PLX method and so on. In some cases users a viewer may elect to save and store Internet- delivered content to suitable data storage facilities associated with their home systems. In other aspects, such material may be saved and stored on-line at a server adapted for the purpose. In this case, a viewer may at a later time retrieve the material at his or her discretion.

One of the capabilities of the authoring system, described above and known to the inventor, is the ability to author live video feeds wherein a separate control stream containing the authoring is created and sent to viewers by an alternate route such as by the Internet. In many instances of this capability, the viewer is receiving an analog video on a suitable cable or satellite connection, and the authored metadata is streamed over a separate Internet connection. At the user's end, synchronization software is applied to cause the main video and the control stream to play in sync on the viewer's display screen. The software in some cases known to the inventor uses a presentation time stamp (PTS) method for synchronizing the separate steams at the viewer's end.

The PTS system assumes that the delay times associated with the delivery of a main video and the separate control stream are near zero which would allow a soft ramping technique to be used with markers in the streams to synchronize both streams within a reasonable amount of time so as to be largely transparent to the viewer. However, in actual practice, delays in receiving the main video or in receiving the metadata may be such that significant time is expended in stream synchronization and is noticeable to a viewer. This is due in part to much varied geographic relationships that may exist between the locations of the source feed, authoring stations and viewers. In a large geographic region, adverse delays may be experienced.

In prior art PC/TV applications general Internet capability is provided to interactive TV viewers, but because the delivery of separate interactive control streams is not available to viewers in such systems, no convention is provided to notify an Internet source of any knowledge of what channel the viewer is tuned to. In these systems, Internet data is sent over a channel contained in the TV cable and is delivered through a cable modem. If a set-top box is used, it is a standard box available from a cable company and not specifically enhanced for Internet communication.

The system known to the inventor, wherein an authored stream may be delivered to a viewer and synchronized to play alongside the main video, uses an Internet path and cable modem capability that is separate from the TV cable for receiving videos. The set-top box and the TV must, in combination, contain suitable software for communication with the Internet including channel notification and requesting capability to the Internet authoring source. The set-top box has a bi- directional communication link to the TV capable of providing input from the TV cable and the Internet as well as output from the TV for initiating requests to the Internet authoring source.

The complexity of the above-described system requires that a separate Internet line be maintained as well as considerable enhancement provided to the set-top box and/or the PC/TV. Therefore, it is desirable to simplify the above system wherein Internet capability including receipt of separate authoring streams and channel notification to the authoring source may be practiced with one cable and a cable modem.

What is clearly needed is a method and apparatus for stream synchronization and channel notification that can compensate for adverse delays in content delivery, and provide correct channel notification to an Internet-based authoring source using the same delivery cable carrying the main videos to the viewer. Such a system would allow for simplification of customer-premise-equipment (CPE) and facilitate a more consistent and transparent synchronization of separately delivered live streams.

Summary of the Invention

In a preferred embodiment of the present invention an interactive video display system is provided comprising a computerized video display unit (PC/VDU) having a first port for receiving a primary analog video stream having multiple instances of closed caption (CC) text strings and a second port for receiving a digital annotation data stream; a broadcast station delivering a primary analog video stream to the first port of the PC/VDU; and an authoring station delivering a digital annotation data stream to the second port of the PC/VDU. The broadcast station delivers the primary analog stream to both the PC/VDU and to the authoring station, wherein the authoring station copies the CC text strings into the digital annotation data stream, and wherein the PC/VDU uses the CC text strings in the two data streams to synchronize the two streams in display. The system is particularly adaptable to the Internet. In some embodiments occurrences of CC text are tabled at both the server and at the PC/VDU, and table entries are used in synchronization. Also in some embodiments the PC/VDU blocks display of annotation data stream received after a threshold delay. In an alternative aspect of the invention, wherein the PC/VDU is in an architecture wherein the VDU is tuned to a constant channel, channel selection is made in a separate PC unit, and the CC text strings in a primary video stream are used in conjunction with stored data at a server to determine the channel. In some embodiments annotation streams are stored at a server associated with the authoring station, and the PC/VDU and the server negotiate based on the CC text strings to associate an annotation stream with a primary video stream.

In another aspect a computerized video display unit (PC/VDU) is provided, comprising a first port for receiving a primary analog video stream having multiple instances of closed caption (CC) text strings, and a second port for receiving a digital annotation data stream over an Internet port, the digital annotation data stream having the multiple instances of CC text strings. The PC/VDU synchronizes the two data streams for display using the CC text strings. In some embodiments the PC/VDU tables data regarding the CC text strings, and uses the tabled data in synchronization, and the PC/VDU may block display of certain material from the annotation data stream received for display beyond a programmable threshold delay time.

In this aspect as well, in cases where PC/VDU is in an architecture wherein the VDU is tuned to a constant channel and channel selection is made in a separate PC unit, the CC text strings in a primary video stream may be used in conjunction with stored data at a server accessed via the Internet port to determine the channel. Also in some embodiments the PC/VDU negotiates with an Internet server based on the CC text strings to associate an annotation stream with a primary video stream.

In another aspect a method for synchronizing, in a computerized video display unit (PC/VDU), a primary analog video stream having multiple instances of closed- captioning text and a digital annotation data stream produced at an authoring station is provided, comprising steps of (a) broadcasting the analog data stream to both the PC/VDU and the authoring station; (b) copying the CC strings into the annotation stream at the authoring station with the same timing as in the analog stream; (c) sending the annotation data stream to the PC/VDU; and (d) using the CC strings in the two streams at the PC/VDU to synchronize the two streams in display.

In some preferred cases of the method, in step (c), the authoring station delivers the annotation data stream on the Internet to the PC/VDU. Also in some cases occurrences of CC text are tabled at both the authoring station and at the PC/VDU, and table entries are used in synchronization. The PC/VDU may block display of annotation data stream received after a threshold delay.

In some instances of this method the PC/VDU is in an architecture wherein the VDU is tuned to a constant channel and channel selection is made in a separate PC unit. In this case the CC text strings in a primary video stream may be used in conjunction with stored data at a server accessible to the authoring station to determine the channel, annotation streams may be stored at a server associated with the authoring station, and the PC/VDU and the server negotiate based on the CC text strings to associate an annotation stream with a primary video stream.

In embodiments of this invention disclosed in enabling detail below for the first time a reliable method is provided for synchronization of analog primary video streams with digital annotation streams, including channel notation and an ability to store and reuse annotation data.

Brief Description of the Drawing Figures

Fig. 1 is a basic overview of a video authoring and delivery system according to an embodiment of the present invention.

Fig. 2 is a chart diagram illustrating closed-caption (CC) detection, tabling and time comparison according to an embodiment of the present invention.

Fig. 3A is a block diagram illustrating a typical CPE scenario wherein CC detection for channel notification is not needed. Fig. 3B is a block diagram illustrating an enhanced CPE scenario using CC detection for channel notification. Description of the Preferred Embodiments

As described in the background section, a system known to the inventor provides a capability for authoring video streams for the purpose of creating separate control streams that are delivered to viewers by an alternate route to the route used to deliver the main video stream. Although that system has broad commercial viability, there are applications wherein the system lacks capability to satisfactorily provide complete synchronization of control streams to analog video streams at the user's end.

Also, in some applications, the known system fails to provide a capability to notify entities responsible for delivering the control streams of the channel to which a viewer may be tuned. Therefore, it is impossible, in those applications, for the sender of the control streams to identify and deliver the appropriate streams that properly associate with the video content being viewed.

The inventors disclose herein a new method and apparatus that will allow accurate synchronization of separate streams regardless of stream format and provide channel notification capability in virtually all conceived applications of interactive TV viewing.

Fig. 1 is an overview of a video authoring and delivery system 9 according to an embodiment of the present invention. System 9 comprises an original source 13 of a video stream, which may be a stored or a live feed, an editing and broadcast station

15, an authoring station 11 and a viewer's premise 33.

Source 13 may be any video source, including stored or live broadcast.

Typically, a presentation from source 13 is acquired by an agent or affiliate of broadcast station 15. In this example, acquisition of an event at source 13 is being performed with analog equipment and viewers will receive an analog video stream, together with a digital annotation data stream to be coordinated with the primary video at the viewer's premise.

The primary video raw is delivered to station 15 for formatting and some editing before being sent to viewers. In the case of analog, editing is generally limited to managing insertion of commercials and other material into the video stream. The managed version of the video stream is delivered, in this example, as an analog stream (available from a cable TV provider) over an analog cable 19 to representative viewer premise 33. A viewer at premise 33, knowing the scheduled time of broadcast and the cable channel carrying the broadcast may tune in to the channel and commence watching the presentation. In this example the primary video stream delivered to user premise 33 is also delivered to authoring station 11 over cable 19. Authoring station 11 comprises substations and servers to enable it to perform different authoring functions simultaneously, multiplex the data and deliver it as a single annotation digital control stream to viewers. For example, substations, substation 27 (A 1) and 29 (A2) are provided and adapted to perform authoring. Substation 27 may provided interactive elements (hyperlinks) such as interactive regions or graphics while substation 29 provides additional audio content and so on. There may be more than the two authoring substations such as those illustrated herein provided and adapted to perform assigned authoring functions without departing from the spirit and scope of the present invention, and, although not specifically shown in Fig. 1, the stream is digitized in the process of authoring.

A server 23 is provided and adapted to receive separately authored control streams from substations such as 27 and 29 and to multiplex them into one control stream that may be delivered to viewer's such as at premise 33. Server 23 is an Internet server in this example, however, such a server may be maintained on a private WAN instead of the Internet. Substations 25, 27 and 29 are preferably on-line modules with a constant connection to server 23.

It is known to the inventors that analog programming whether live or prerecorded, typically has closed-caption (CC) text included for the hearing impaired, which, in this case would be inserted at station 15. The CC text-strings are typically included in line 21 of the vertical blanking interval (VBI) of each analog video frame where CC is needed. In this way, viewers who are hearing impaired may elect to see text captions, which appear during the appropriate sequences in the video.

In a preferred embodiment of the present invention, a substation 25 (P) is provided and adapted to play the analog primary video stream and to note all occurrences of closed-captioning. A unique software application 21 is provided and executable from substation 21 for the purpose. As the primary video is played, software 21 detects CC strings as they occur in real-time, and provides this data to server 23, which prepares a table associated with server time, which is consistent with other time stamps the server may use for other purposes. In this example, software 21 is resident on substation 21 , however, it may be resident on a connected server and made accessible to substation 21.

The data regarding CC text including time of occurrences of each string is digitized and forwarded to server 23, where software 21 tables the text according to a pre-defined format. Substations 27 and 29 feed their digital streams to server 23 in real time. Server 23 includes the CC text data and timing data received from substation 25 to thee annotation data stream during multiplexing performed to combine separate authoring streams. In this way, a consistent and accurate signature is created in the digital control stream that may be used to synchronize the stream with the appropriate analog video being viewed at premise 33. The basis of the subsequent synchronization is the CC text strings.

Typically on request from a viewer at premise 33, server 23 delivers the finished control stream via, in this case, Internet connection 31. Premise 33 comprises in this embodiment a set-top box 37 enhanced with an Internet capability along with a cable port for receiving the analog video. A connected PC/TV is provided and adapted to display video content as well as Internet data including control streams. A client software application 35 detects and tables each occurrence of CC text in the primary analog video and associates each occurrence with a local time as it is playing. When the control stream arrives at premise 33 from Enhancement stream server 23, the tables are used in comparison to synchronize the control stream to the analog video. More detail regarding this unique method is described below.

Fig. 2 is a diagram illustrating closed-caption (CC) detection, tabling and time comparison according to an embodiment of the present invention. In the following example, it is assumed that a viewer at premise 33 (Fig. 1), has elected to view an offered program scheduled to air at 1:00 PM and that the actual start time of the selected program (actual time of display) occurred at exactly 1 :00PM (Local Video Start Time). In embodiments of the present invention occurrences of closed captioning are monitored and tabled both at authoring station 11 and at the viewer's premise, and comparison of the logged text and times can then be used in comparison to synchronize the primary video stream with the annotation data stream sent, in this case, via the Internet as a digital stream. The closed captioning of the analog primary video is also copied into the digital annotation data stream at the authoring station.

Software instance 35 at the viewer's station 33 of Fig. 1 begins detecting and tabling each occurrence and the time of occurrence of the inserted CC text in the analog primary video stream as referenced by time-line 45. Time-line 45 represents the first 20 seconds of the analog program in this example. There are in this example six occurrences of CC text in the 20-second span with the beginning of each occurrence represented by an inverted triangle as a marker with a begin-time of occurrence illustrated below each marker. A table 47 illustrates one example of the compiled data. Each separate occurrence represents a timed sequence in the video during which dialog is being spoken. For the purpose of saving space, only begin times are illustrated in time-line 45 and table 47, however it may be assumed that table 47 will contain the time-duration of the text dialog for each occurrence as well. For the purpose of comparison, assume now that the analog primary video as described in Fig. 1 arrived at station 11 in Fig. 1 at 1 :00:00.5 PM (Arrival of Feed to Author). In this case, a half-second delay occurred before authoring can commence. Software instance 21 of Fig. 1 begins detecting and tabling CC text occurrences and the real local time of each occurrence as the primary video is played at substation 25 as illustrated by time line 49. The data is similarly tabled as illustrated by 51. Again, only begin times are illustrated for the sake of space in the drawing. Although there is a full half-second delay, timing during each CC text occurrence will be identical to the timing of the CC text occurrences at the viewer's end.

In this particular example, an Internet delay associated with delivery of the resulting control stream has added an additional .25 seconds of delay before the viewer receives the control stream, in this case, by separate Internet path. (Local Arrival of Control Stream). Therefore, the arrival of control stream at the viewer's end is 1 :00.00.75 PM, or .75 seconds after the viewer has engaged in watching the - 12 - program. This may be considered a significant time delay in view of the nature (time sensitivity) of some authored data.

There are different cases to be considered. If the video source is a live source, and authoring is live, the CC text is still copied into the digital annotation stream from station 11 to the viewer's premise 33. There is no advantage, however, in sending tabled information from station 11 to the viewer's premise. The table is, after all, being developed as the analog video plays at station 11. In this case the viewer's station synchronizes the two streams by comparing the actual CC strings in the two streams. In the case of pre-recorded primary video streams, now an annotation data stream may be authored and saved, and recalled and sent on request along with a CC table, and the viewing station can synchronize using the tables and the CC strings.

Software 35 at premise 33 (Fig. 1) includes a capability for comparing tabled CC text dialogs and times associated with both the analog stream and the digital control feed. By comparing tables the software notes the delay time of the digital stream and can begin synchronizing the streams by buffering until the CC dialog matches.

Whether to display annotations or not will be a matter of the nature of the delay. That is, some data may be displayable within a very broad window of time, and other material may have to be displayed very close to perfect sync time. In some cases the author may tag certain material to be displayed or not depending on the delay. For example, in some cases a threshold time, such as .75 seconds of delay time, may be tagged to annotated material, such that no annotated material may be displayed if later than the threshold.. An example might be an annotated score- display associated with a basket made in a game of basketball. If too much time passes after a basket has been made before the scorebox appears, another basket may have occurred in the meantime resulting in a false display of the score. Therefore, data arriving past the allowed delay threshold value is discarded or not displayed. Other types of annotation are not as time sensitive and may have a generous threshold value. In some cases threshold may be adjustable at the viewer's premise. Display of the control stream in sync with the analog stream commences with continued tabling and comparison being performed. Further delays that may occur due to jitter or other bandwidth issues may usually be handled by buffering once streams are in sync. If there is a subsequent delay in the control stream that exceeds threshold values applied to the data blocks then that data is simply discarded or not displayed as previously described. If for some reason the digital stream arrives before the analog video, then the digital stream may be cache buffered. Moreover, the digital stream may be stored in server 23 of Fig. 1 and re-streamed if the analog program is replayed. In one embodiment of the present invention, CC detection is also used to determine what channel is being viewed, allowing selectivity as to annotation stream.

Fig. 3A is a block diagram illustrating a typical user's station architecture wherein CC detection for channel notification is not needed. In this example, a PC/TV 53 is provided and contains all of the software and components needed for interactive TV. Note that a set-top box such as set- top box 37 of Fig. 1 is not used in this example. In this example, an analog cable 55 provides a source for analog video to PC/TV 53. A cable modem 57 is provided and connected to analog cable 55 for the purpose of enabling Internet interaction and control stream delivery over a channel provided in cable 55. Internet sourced data arrives at PC/TV 53 through modem 57 and over a short Internet cable 59. Software 35, illustrated resident on PC/TV 53, is used to synchronize a digital control stream arriving through modem 57, over cable 59, to an analog stream arriving over cable 55 as described in Fig.'s 1 and 2. PC/TV 53 is illustrated as being tuned to a cable channel 103 and it is assumed that a viewer is receiving an analog video over that channel. Since the PC/TV selects channels it may negotiate with an Internet server, such as server 23, and request appropriate annotation streams for selected channels.

Fig. 3B is a block diagram illustrating an enhanced user station architecture wherein the PC/TV cannot deduce the channel, so CC detection for channel notification may be needed. In this example, PC/TV 53 is connected to a set-top box 61. Analog cable 55 is connected to set-top box 61 and delivers video according to channel selection. In this case, however, channel selection is performed in set-top box 61. Box 61 is illustrated as tuned to cable channel 103 while PC/TV remains on channel 3 as is known in the art for set-up procedures when connecting cable boxes or VCR's to TVs. The provision of set-top box 61 is the only difference in set-up from Fig. 3 A in this example. In an alternative architecture there may be a separate Internet connection to set top box 61.

In this particular example, PC/TV 53 cannot, without the aid of software 35, determine which channel is being viewed because channel selection is now performed in set-top box 61. However, with the aid of software 35, channel detection is still possible. It is known that CC strings will be unique to each and every primary video stream. If, as is done in embodiments of the present invention, the CC strings are tabled and also copied into annotation streams, the CC strings can be matched to select correct annotation streams for primary video streams.

In this way, a source of digital control streams such as server 23 of Fig. 1 may receive proper notification of the proper channel when the viewer selects a channel and content arrives. A slight delay in delivery of Internet sourced data will occur in this embodiment due to the fact that a request for a proper control stream may not be made until the analog program begins streaming. However, such delays will still be less than those experienced with a separate Internet connection.

It will be apparent to one with skill in the art that, the method and apparatus of the present invention may be used to synchronize any digital enhancement stream authored from any associated analog video to the analog video at the viewer's premise. It will also be apparent to one with skill in the art that now digital enhancement streams may be stored and latter synchronized with a re-telecast of a same analog presentation such that re-authoring of a pre-authored video need not be performed.

It will also be apparent to one with skill in the art that the channel detection option may or may not be required depending on CPE equipment and set-up parameters. In an example wherein a PC/TV is adapted to contain all of the channels available by section from the PC/TV, no channel detection is required. However, CC text detection is used in every instance wherein a digital control stream needs to synchronize to an analog main video at the viewer's end. Therefore the spirit and scope of the present invention should be afforded the broadest scope. The spirit and scope of the present invention is limited only by the claims that follow.

Claims

What is claimed is:

1. An interactive video display system comprising: a computerized video display unit (PC/VDU) having a first port for receiving a primary analog video stream having multiple instances of closed caption (CC) text strings and a second port for receiving a digital annotation data stream; a broadcast station delivering a primary analog video stream to the first port of the PC/VDU; and an authoring station delivering a digital annotation data stream to the second port of the PC/VDU; wherein the broadcast station delivers the primary analog stream to both the PC/VDU and to the authoring station, wherein the authoring station copies the CC text strings into the digital annotation data stream, and wherein the PC/VDU uses the CC text strings in the two data streams to synchronize the two streams in display.

2. The system of claim 1 wherein the authoring station delivers the annotation data stream on the Internet, and the second port is an Internet port.

3. The system of claim 1 wherein occurrences of CC text are tabled at both the server and at the PC/VDU, and table entries are used in synchronization.

4. The system of claim 1 wherein the PC/VDU blocks display of annotation data stream received after a threshold delay.

5. The system of claim 1 wherein the PC/VDU is in an architecture wherein the VDU is tuned to a constant channel and channel selection is made in a separate PC unit, and wherein the CC text strings in a primary video stream are used in conjunction with stored data at a server to determine the channel.

6. The system of claim 1 wherein annotation streams are stored at a server associated with the authoring station, and wherein the PC/VDU and the server negotiate based on the CC text strings to associate an annotation stream with a primary video stream.

7. A computerized video display unit (PC/VDU) comprising: a first port for receiving a primary analog video stream having multiple instances of closed caption (CC) text strings; and a second port for receiving a digital annotation data stream over an Internet port, the digital annotation data stream having the multiple instances of CC text strings; wherein the PC/VDU synchronizes the two data streams for display using the CC text strings.

8. The PC/VDU of claim 7 wherein the PC/VDU tables data regarding the CC text strings, and uses the tabled data in synchronization.

9. The PC/VDU of claim 7 wherein the PC/VDU blocks display of certain material from the annotation data stream received for display beyond a pre-stored delay time.

10. The PC/VDU of claim 7 wherein the PC/VDU is in an architecture wherein the VDU is tuned to a constant channel and channel selection is made in a separate PC unit, and wherein the CC text strings in a primary video stream are used in conjunction with stored data at a server accessed via the Internet port to determine the channel.

11. The PC/VDU of claim 7 wherein the PC/VDU negotiates with an Internet server based on the CC text strings to associate an annotation stream with a primary video stream.

12. A method for synchronizing, in a computerized video display unit (PC/VDU), a primary analog video stream having multiple instances of closed-captioning text and a digital annotation data stream produced at an authoring station, comprising steps of:

(a) broadcasting the analog data stream to both the PC/VDU and the authoring station;

(b) copying the CC strings into the annotation stream at the authoring station with the same timing as in the analog stream;

(c) sending the annotation data stream to the PC/VDU; and

(d) using the CC strings in the two streams at the PC/VDU to synchronize the two streams in display.

13. The method of claim 12 wherein, in step (c) the authoring station delivers the annotation data stream on the Internet to the PC/VDU.

14. The method of claim 12 wherein occurrences of CC text are tabled at both the authoring station and at the PC/VDU, and table entries are used in synchronization.

15. The method of claim 12 wherein the PC/VDU blocks display of annotation data stream received after a threshold delay.

16. The method of claim 12 wherein the PC/VDU is in an architecture wherein the VDU is tuned to a constant channel and channel selection is made in a separate PC unit, and wherein the CC text strings in a primary video stream are used in conjunction with stored data at a server accessible to the authoring station to determine the channel.

17. The system of claim 1 wherein annotation streams are stored at a server associated with the authoring station, and wherein the PC/VDU and the server negotiate based on the CC text strings to associate an annotation stream with a primary video stream.