Receiving an information resource from the internet if it is...

Details Receiving an information resource from the internet if it is... Receiving an information resource from the internet if it is...

1999-04-20

2003-05-27

Miller, John (Department: 2614)

Interactive video distribution systems

Video distribution system with upstream communication

Having link to external network

C725S109000, C725S134000

Reexamination Certificate

active

06571392

ABSTRACT:

BACKGROUND INFORMATION
Broadcast television in the United States is broadcast in accordance with the NTSC (National Television Standards Committee) broadcast television format standard. Approximately, thirty image frames are transmitted each second. The NTSC signal for a single frame consists of two interlaced fields of 262.5 horizontal scan lines each.
FIG. 1
(Prior Art) is a simplified diagram of an NTSC field l
00
having 262.5 horizontal scan lines. Only a viewable portion
101
of the field communicates the image.
Broadcast and display of field
100
is described in connection with a conventional analog television set having a cathode ray tube (CRT) with an electron beam. Receiver electronics in the television receives the broadcast NTSC signal and controls the electron beam-so that the electron beam is scanned across a screen of the CRT to form the image. The first nine horizontal scan lines
102
of the NTSC field
100
are used to synchronize the television receiver electronics and to return the electron beam to the top of the screen. The electron beam is 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. These first twenty-one horizontal scan lines are therefore commonly referred to as the “vertical blanking interval” lines (VBI lines).
The odd scan lines of the frame (frame line
1
, frame line
3
, frame line
5
, and so forth) are received first and in order. These odd scan lines are called the “odd field”. The first twenty-one of these odd lines are VBI lines. These first lines are used, among other things, to synchronize. the television receiver for the subsequent scanning of the horizontal scan lines of the viewable portion
101
. For each horizontal scan line, the electron beam in the television scans from left to right across the screen. After the beam has reached the right edge of the screen, the electron beam is returned to the left edge of the screen in preparation for the scanning of the next scan line. After the scanning of each odd scan line in viewable portion
101
, the electron beam is “blanked” for an appropriate period of time so that the beam can be returned to the left edge of the screen in preparation for the next scan. The sum total of the time of these blankings is referred to as a horizontal blanking interval of the field. Region
103
of field
100
corresponds to the sum of the horizontal blanking interval times of all the scan lines.
Next, the even scan lines of the frame (frame line
2
, frame line
4
, frame line
6
, and so forth) are received in order. As with the odd field, the first twenty-one scan lines of the even field are VBI lines. The electron beam is “blanked” during the scanning of these even VBI lines so that the electron beam can be returned to the top of the screen without scribing a line on the screen. After the scanning of the even VBI lines, the even scan lines of viewable portion
101
are then scanned in similar fashion to the scanning of the odd scan lines. The viewable horizontal scan lines of the odd and even fields together cause the electron beam to scan across the screen of the television to create the viewable television image.
The entire vertical blanking interval is generally not, however, required for vertical synchronization and vertical beam retrace. Only VBI lines
1
-
9
of a field are generally used for these purposes. The other twelve VBI lines
10
-
21
of the field are therefbre available for the communication of other information.
VBI line
21
, for example, provides a low speed communication sub-channel (hereinafter referred to as the “line 21 sub-channel”). Data is encoded in the line
21
sub-channel at a data rate of two bytes per line in accordance with the encoding technique set forth in EIA-608. The Federal Communication Commission (FCC) mandates that line
21
is reserved for captioning services as specified by EIA-608. The line
21
sub-channel is in turn divided into multiple sub-sub-channels. Four of these sub-sub-channels (T
1
, T
2
, T
3
and T
4
) are used to carry textual information. Another of these sub-sub-channels (XDS) is used to carry other information such as the current time and “V-chip” program rating codes. Four other of these sub-sub-channels (CC
1
, CC
2
, CC
3
and CC
4
) are used to carry closed captioning information. A television receiver can capture the closed captioning information of one such sub-sub-channel and display it as a text subtitle along with the television video to assist the hearing impaired.
VBI lines
10
through
20
, on the other hand, are available for a higher speed communication sub-channel for the communication of data. Data may be encoded in VBI lines
10
through
20
at a data rate of approximately thirty-six bytes per line in accordance with the NABTS (North American Basic Teletext Specification) teletext system standard set forth in EIA-516. The sub-channel of VBI lines
10
-
20
is therefore hereinafter referred to as the “teletext sub-channel”. Due to there being eleven of these VBI lines per field, there being sixty fields per second, there being about thirty-six. bytes of data per line, there being eight bits per byte, and an error correction mechanism being employed, the teletext sub-channel has a maximum data rate of approximately 100,000 error-corrected bits per second.
It has been desired to synchronize the display of web (HTML or XML) pages to broadcast television video so that an appropriate web page can be viewed along with a predetermined part of the television video. One approach has been to broadcast web page content over the high speed teletext sub-channel. The amount of web page content is significant so the use of the high speed teletext sub-channel has been considered appropriate. After the web page content has been received, it is stored locally in the receiver under a file name for later access. Next, when the web page content is to be displayed at a particular time in the television video, a “trigger” that contains the file name of the web page content is broadcast over the teletext sub-channel. When the trigger is received, the file name of the trigger is used to retrieve the associated file containing the web page content from local storage so that the web page can be displayed.
The reception of web pages over the teletext sub-channel can, however, be somewhat unreliable. Cable television operators or local broadcast stations may use certain of VBI lines
10
-
20
for their own purposes, thereby interfering with the communication of web page content on these VBI lines. Moreover, televisions disposed in some geographical locations may not receive VBI lines
10
-
20
in a consistent fashion. If VBI lines
10
-
20
are not reliably received, then the web page content that was broadcast over those VBI lines will not be present in local storage and cannot be displayed. In another scenario, web page content is received over VBI lines
10
-
20
but the trigger to display that web page content is not. In such a situation, the web page content is present in local storage, but the web page content is not displayed due to the failure to receive the required trigger. A solution is desired.
SUMMARY
The line
21
sub-channel (VBI line
21
) is subject to government regulation. Care is taken to insure that VBI line
21
and the closed captioning information it carries can be received reliably by televisions throughout most broadcast regions. The line
21
sub-channel can therefore be considered to be a relatively reliable communication sub-channel in comparison to the teletext sub-channel.
In accordance with some embodiments, a receiver unit monitors the one-way broadcast communication channel (for example, the teletext sub-channel afforded by VBI lines
10
-
20
) for information resources such that if an information resource (for example, web page content) is successfully received by the receiver unit, then the information resource is stor

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