Interactive video distribution systems – Video distribution system with local interaction – Interactive data transmitted in video signal band
Reexamination Certificate
1999-10-05
2002-07-02
Faile, Andrew (Department: 2611)
Interactive video distribution systems
Video distribution system with local interaction
Interactive data transmitted in video signal band
C725S029000, C725S032000, C725S051000, C725S146000
Reexamination Certificate
active
06415438
ABSTRACT:
BACKGROUND INFORMATION
FIG. 1
(Prior Art) is a simplified diagram of an interactive television system
100
. System
100
includes a receiver unit
101
, a receiving antenna
111
, and a remote control unit
102
. A viewer uses the remote control unit
102
to control the receiver unit
101
and/or to interact with interactive television content via the receiver unit
101
. A video link
103
couples receiver unit
101
to an ordinary analog television set
104
so that the receiver unit can use the screen of the television set as a display device. The receiver unit
101
receives broadcast television video
105
on receiving antenna
111
and displays it as television video
106
on the screen of the television set
104
.
In interactive television, information
107
from an information resource
108
is displayed along with television video
106
in a synchronized fashion. When the information
107
is to be displayed at a particular point in the television video, a communication called a “trigger”
109
is broadcast along with the television video
105
and is received on receiving antenna
111
. Trigger
109
includes a Uniform Resource Identifier (URI) that identifies the information resource
108
. Receiver unit
101
uses this URI to retrieve the information resource
108
from the Internet
110
. Receiver unit
101
then displays the information
107
from the information resource
108
along with the television video
106
to provide an enhanced television viewing experience.
Each frame of the television video
106
includes two fields of 262.5 horizontal scan lines each in accordance with the National Television Standards Committee (NTSC) broadcast television format standard. The first twenty-one scan lines of each frame are commonly referred to as the “vertical blanking interval” (VBI lines). This interval is used to synchronize television receiver electronics and to return the electron beam of the television to the top of the screen among other things. The electron beam is therefore disabled (i.e. “blanked”) during the scan time of the first twenty-one scan lines so that the electron beam does not scribe a visible line from the bottom of the screen to the top of the screen when it is being returned to the top of the screen. The entire vertical blanking interval is, however, generally not required for vertical synchronization and vertical beam retrace. Only VBI lines
1
-
9
of a field are generally required. The other twelve lines
10
-
21
of the field are therefore available for the communication of other information.
VBI line
21
, for example, provides a low speed communication sub-channel. The Federal Communications Commission (FCC) mandates that part of this sub-channel be reserved for closed captioning services as specified by EIA-608. Text subtitles are encoded into this VBI line
21
sub-channel such that a television receiver that receives the signal can decode the information encoded into VBI line
21
and display it as a text subtitle along with the television video to assist the hearing impaired. Spare bandwidth available in this VBI line
21
sub-channel after the encoding of the closed captioning information may be used to transport the interactive television triggers such as trigger
109
to the receiver unit
101
at an appropriate time with respect to the broadcast television video
105
.
FIG. 2
illustrates a problem associated with the use of the VBI line
21
sub-channel for the transport of trigger
109
. Trigger
109
is desired to be transmitted to receiver unit
101
at time
200
with respect to broadcast television video
105
. There is in this example, however, particularly heavy closed captioning use of the VBI line
21
sub-channel during period
201
. Accordingly, there is not adequate bandwidth left for the communication of the trigger
109
at time
200
.
A conventional method of solving this problem involves sending the trigger
109
beforehand (out of synchronization) with respect the point in the associated broadcast television video
105
where the trigger
109
is to be executed. In the example illustrated, trigger
109
is sent via the VBI line
21
sub-channel at time
202
before period
201
. Receiver unit
101
, rather than executing trigger
109
immediately upon receipt, executes a script on the information resource
108
to which the trigger
109
is addressed. The script involves a delay loop that delays the execution of trigger
109
until time
200
.
The use of such a delay loop, however, introduces several complexities. The magnitude of the delay of such a delay loop is generally somewhat unrepeatable and difficult to control. The magnitude of the delay may, for example, vary from receiver unit to receiver unit due to hardware differences. The magnitude of the delay may also be affected by the particular software processes running on a receiver unit. Moreover, the coding required to realize such a delay loop involves effort on the part of the author of the interactive content and this is undesirable. Solutions to one or more of these problems are desired.
Moreover, in a current interactive television implementation, if trigger
109
executes in the context of a channel, and the viewer then changes channels to a different channel, and the viewer then changes channels back, the trigger is not reexecuted automatically. If, for example, trigger
109
initially caused stock ticker tape information
107
to be displayed along with video of a given channel, and if the viewer switched channels and then switched back, the stock ticker tape information
107
would not reappear because its trigger
109
would not automatically be reexecuted. A solution to this problem is also desired.
SUMMARY
In a first aspect of the invention, a trigger includes a time attribute indicative of a time in the future when the trigger is to be executed. Providing a time in the future when the trigger is to be executed allows the trigger to be sent in advance when there is adequate transport bandwidth to transport the trigger to the receiver unit. The receiver unit receives the trigger but knows from the future time attribute that the trigger is not to be executed yet, but rather is to be executed at the indicated future time. The receiver unit therefore waits until the indicated future time to execute the trigger. This future time attribute therefore eliminates the need for the script and delay loop described above.
In a second aspect of the invention, a trigger includes a time attribute indicative of a particular frame when the trigger is to be executed. In one embodiment, each frame of video is numbered with a frame number that is embedded in the video in accordance with a standard. The receiver unit monitors these frame numbers (or otherwise keeps track of the number of the current frame) and waits to execute the trigger until the frame identified by the time attribute of the trigger has been received. This future time attribute therefore eliminates the need for the script and delay loop described above.
In a third aspect of the invention, a receiver unit receives a trigger with an attribute indicating that the trigger is to be executed at some time in the future or some frame in the future. The receiver unit determines whether the receiver unit has enough time to retrieve an information resource identified by the trigger (this may involve establishing a connection to the Internet and retrieving the information resource from the Internet). If the receiver unit determines that there is enough time, then the receiver unit pre-fetches the information resource so that it is available at the future time or future frame when the trigger is to be executed. Triggers are therefore sent well before they are to be executed so that receiver units will pre-fetch associated information resources. Such pre-fetching is used in some embodiments to have receiver units access the Internet at off-peak (low cost) times and retrieve information resources needed for subsequent interactive television viewing at peak (high cost) times.
In a fourth aspect of the invent
Blackketter Dean J.
Park Timothy F.
Zigmond Daniel J.
Faile Andrew
Tran Hai V.
WebTV Networks Inc.
Workman & Nydegger & Seeley
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