Concern about violence on television is almost as old as the medium itself. However, the passage of the Telecommunications Act of 1996, which was signed into law on February 8, 1996, has made the issue one of particular concern to broadcasters. This paper will address the technical issues associated with implementation of the so-called "V-Chip" provision of this Act. Specifically, manufacturers of television receivers are required to equip TV sets with a "parental control device", the V-Chip, which would facilitate the blocking of "sexual, violent, or other indecent material" from entering the home. Broadcasters are not required by the Telecommunications Act of 1996 to transmit the signals used by the V-Chip to qualify the incoming program material, but the Federal Communications Commission (FCC) would be authorized to require ratings transmission if the broadcast industry does not voluntarily begin to do so within one year.

SYSTEM OVERVIEW

A system which would allow parents to selectively block or pass broadcast television programming would have essentially three parts:

1.) A common ratings system would have to exist which would allow programming to be categorized based on content. The ratings system used by the Motion Picture Association of America (MPAA) is a good example.

2.) The technology would have to be available to allow the ratings to be somehow embedded or otherwise added to the program at the time it is broadcast.

3.) The technology would have to be available to allow the home television receiver to extract the ratings information and automatically block or pass the program material.

Fortunately, the perfect system for inserting program-related data into the broadcast video signal is already in place. This system is well defined, using a mature technology, and has already gained wide, if not universal, acceptance. The system is the "Line 21 Data Service" also known as Closed Captioning.

FUNDAMENTALS OF CLOSED

CAPTIONING

The initial work on a closed captioning system began in the early 1970's with the Public Broadcast Service (PBS). Using a concept first proposed by the National Bureau of Standards, PBS developed and demonstrated the feasibility of a closed caption data transmission system. By November 1975, PBS was able to submit to the FCC a Petition for Rulemaking asking the commission to amend its television standards to provide for the transmission of Closed Caption information. Since then, two important pieces of Federal legislation, the Americans With Disabilities Act (ADA) and the Television Decoder Circuitry Act (TDCA), have made the PBS Closed Caption system a common part of television production and broadcast.

Closed Caption information is added to the video signal on Line 21 of the Vertical Blanking Interval (VBI). Initially, only Line 21 of the odd fields (Color Fields 1 and 3) were used for transmitting Closed Caption data. Recently, the Electronic Industries Association (EIA) has redefined and expanded the original Closed Captioning standard to use the even fields (Color Fields 2 and 4) to transmit Closed Caption data. (It should be noted that people in the caption industry routinely refer to the odd fields as "Field 1" and the even fields as "Field 2." This convention will be followed throughout this paper.)

To assure adequate caption performance wherever a usable picture can be obtained, a low instantaneous data rate of 503 kilobits/second (32H) was chosen. Data is preceded by a seven-cycle sine wave (analogous to color burst) called the "Clock Run-In" and three start bits that are always "0", "0", and "1". Two bytes of data, transmitted LSB first using seven bits, odd parity format, are possible on a given line. The rise time of the data bits is controlled (2T) and the amplitude of the data and clock run-in is 50IRE Units. Using only Line 21, Field 1, of the VBI, a delivery rate of about 3600 characters, or approximately 500 words per minute, is possible. Tests conducted by PBS determined that the typical reading rate for captioning is about 125 words per minute. (Incidentally, spoken dialogue may exceed 200 words per minute.)

Particularly with the availability of Field 2, the data delivery capacity of the Line 21 Data System far exceeds the requirements of simple program-related captioning in a single language. Therefore, the recent EIA standard known as "Recommended Practice for Line 21 Data Service" (EIA-608) defines additional data channels that may be multiplexed into the Closed Caption data stream. These channels are defined in this way:

Field 1

CC1   The Primary Synchronous Caption Service. These are captions in the primary language that must be in sync with the sound, preferably matched to a specific frame.

CC2   The Special Non-Synchronous Use Captions. This channel carries data that is intended to augment information carried in the program.

T1       First Text Service. This may be various non-program related data. 

T2       Second Text Service. Additional data, usually not program related.

Field 2

CC3    Secondary Synchronous Caption Service. Alternate program-related caption data, typically second language captions.

CC4    Special Non-Synchronous Use Captions. Similar to CC2.

T3/T4  Third and Forth Text Services. These data channels should be used only if T1 and T2 data bandwidths are not sufficient.

XDS   Extended Data Services. This data channel covers over 40 different types of information, including the program title, program type, and station ID. For this reason, it is extremely valuable for use in implementing the "parental control" system.

Most modern television receivers equipped with a Closed Caption decoder can display any of the data transmitted in Field 1. A few televisions sets that are currently available can also extract and display the Field 2 caption information, including the XDS

EXTENDED DATA SERVICE

Extended Data Service (XDS) data is transmitted by interleaving unique data packets into any pre-existing data on a space-available basis. Individual data channels are preceded by unique "Control Codes" which identify the beginning of data for that particular data channel. The EIA-608 Recommended Practice defines seven different classes of XDS data:

CURRENT---Used to describe a program currently being transmitted.
FUTURE---Used to describe a program to be transmitted later.
CHANNEL---Used to describe non-program info about the transmitting channel.
MISCELLANEOUS---Used to describe various other information
PUBLIC SERVICE---Used to transmit data of a public service nature.
RESERVED---Reserved for future definition
UNDEFINED---For use in any closed-loop system.

Several types of data are defined under each XDS class. Each data packet, defined according to Class and Type, is preceded by a unique code which allows the receiving decoder to identify it. All packets are terminated by a common "end of packet" code followed by a checksum character for data validation.

V-CHIP SUPPORT

Eleven types of data packets are defined under the Current Class of the XDS. Of these, three are of particular interest:

1.) Program Name: The Program Name packet is simply an ASCII string of up to 32 characters which carry the name of the program currently being transmitted.

2.) Program Type: This packet also consists of up to 32 ASCII characters. However, these characters are coded as keywords. (See accompanying table.) At the time of data encoding, the service provider or program producer should specify all keywords which apply to the program and should order them according to their importance.

3.) Program Rating: This packet would appear to be the critical one in supporting a "parental control" system and is covered in greater detail below. The EIA "Recommended Practice for Line 21 Data Service" has defined this packet. However, an alternate proposal will be presented.

Under the Channel Information Class, two data packets are of particular interest:

1.) Network Name: Simply an ASCII string of up to 32 characters which carry the name of the network associated with the local channel.

2.) Call Letters (Station ID): A packet of 4 or 6 ASCII characters which carry the local station call letters and (optionally) the channel number.

Any of these XDS data packets could theoretically be used by a "V-Chip" equipped television set to automatically qualify the program currently being received

PROGRAM RATING

Regarding the Program Rating packet, the EIA-608 document defines it as two informational (non-ASCII) characters for "Rating" and "Advisory" data. The individual bits are defined as follows:

The Advisory character bits would indicate the level of program Violence content (bits v0 and v1), Sexual content (bits s0 and s1), and Mature content (m0 and m1). Each two bit field can indicate four levels of content in each category. Rating character bits are defined as follows: bit a0 indicates whether or not the Advisory character is in effect.
Bits r0 through r2 are defined according to the following chart.

Please note that the EIA Program Rating packet definition is subject to change. The definition given here is accurate at the time of this writing.

An alternate proposal is currently being tested in Canada, where the V-Chip has already gained wide acceptance. In fact, the Canadian Radio-Television and Telecommunications Commission (CRTC) announced on March 14, 1996, its "Policy on Violence in Television Programming," which mandates program-rating code insertion beginning in September 1996. Initial tests were conducted beginning in December 1994 in Edmonton, sponsored by Shaw Cablesystems. Later tests were also conducted by Rogers Cablesystems in Toronto and Ottawa, and by CFCF Cable in Montreal. Two US television stations, WUTV (Buffalo, NY) and KVOS (Bellingham, WA) have also participated. Original tests employed the T2 data channel, but subsequent tests have utilized the XDS. The Canadian system would use all the bits of both characters for more detailed rating code insertion. The MPAA codes are retained along with the Violence and Sexual content fields. However, the. Mature content field is replaced by a Language field. In each category, a third bit is added to provide up to eight possible levels of content, although only six levels are likely be used.

The following table illustrates the proposed rating scheme.

Bits v0 through v2 would carry program Violence content, bits s0 through s2 Sexual content, and bits l0 through l2 Language content. Each three-bit field would contain a binary number from zero (000) through five (101) indicating the program content level in each category.

THE TELEVISION RECEIVER

V-Chip technology would allow parents to program their television sets to automatically accept/reject a particular level of violence, sexual content, or strong language as indicated by the XDS Program Rating packet. Typically, an on-screen menu display could be selected on the home receiver, and a personal access number, making violent or otherwise explicit programming accessible to the adults, could be permanently stored in the television receiver. Various levels within each category (violence, sexual content, and language) would then be entered, setting the threshold for blocking or passing an incoming program. Depending upon the level of support offered by the manufacturer of the television, other XDS data packets could be monitored by the television receiver as well. For example, programs could be rejected based upon Program Name or Program Type. Even the XDS Time of Day Packet (Miscellaneous Class) could be used to make sure the television is turned off at a certain time!

Typically, program rejection is handled in this manner: when a television signal is received in which the embedded (XDS) rating codes exceed the threshold previously set by the parents, the V-Chip would blank the screen and display a message indicating that the incoming signal has been automatically blocked. The viewer could then change channels, or could enter the pre-programmed access code to "un-block" the program for viewing. After a certain period of time has elapsed without the occurrence of either of the two acceptable actions (changing channels or entering the access code), the television receiver would turn itself off.

One final note regarding the implementation of the V-Chip: It is not likely that the V-Chip will appear in the television receiver as a chip at all! The embedded micro-controller already resident in modern television receivers would handle the XDS data recovery/comparison and implement the program blocking feature attributed to the V-Chip. Indeed, IC manufacturers Mitusibishi, Motorola, Sanyo, and Zilog already offer microcontrollers with built-in Closed Caption and On-Screen Display (OSD) functions. Implementation of V-Chip technology would simply require a software change.

XDS ENCODING

The area of primary importance to the broadcaster is actual the XDS data insertion. The effort required of the local broadcaster depends upon their level of participation. In some cases, the broadcaster may find that no XDS data has been inserted upstream at all. In other cases, several  levels of data insertion may be present. For example, the program producer may insert the rating codes at the time that the program is Closed Captioned. The Network may then insert the network name at the time of broadcast, and the local network affiliate could add their own Station ID and Time of Day. Finally, bear in mind that any XDS insertion must not interfere with the caption data resident in Field 2 (CC3 and CC4).

A typical XDS insertion application would require a personal computer (PC) with an appropriate software package, along with a compatible Closed Caption encoder. A typical system would use the ViewLevel Controller software from AutoGraph Systems of Brampton, Ontario, along with the  PDR-885 Closed Caption Encoder/Decoder from Link Electronics of Cape Girardeau, Missouri. Armed with this system, a broadcaster could enter his playlist several days in advance using the ViewLevel Controller software and assign a Program Rating code to each program. Up to seven additional XDS packets may be entered by the local broadcaster as well, including Program Name, Program Type, Station ID, Network Name, and Time of Day. The Link PDR-885 Closed Caption Encoder would receive a serial (RS-232) data feed from the ViewLevel PC and automatically handle the Field 2 data insertion, adding and/or replacing XDS data as desired without interfering with Field 2   Closed Caption data. The PDR-885's built-in Closed Caption decoder allows the new Field 2 data stream to be monitored during the encoding process.

Minimum hardware requirements for proper operation of the system are as follows:

1.) IBM-compatible computer system: ........................... type 386 or higher

2.) 4MB RAM memory: .................................... (8MB recommended)

3.) 80MB Hard Disk Drive: .........................500MB or Higher recommended

4.) 1.44MB Floppy Disk Drive: ............................ CD ROM would be nice

5.) SVGA monitor: ....................................... (640x480 resolution)

6.) Keyboard

7.) Mouse: ........................................... or other pointing device

8.) 2-RS-232 Serial Communications Ports

9.) 1-Parallel Printer Port

10.)CC Encoder: ............................... Closed Caption Encoder/Decoder

In addition, the ViewLevel software requires MS-DOS Version 6.0 or higher and Microsoft Windows Version 3.1 or 3.11. For full system automation, a PC- resident time code reader card would be required.

CONCLUSION

An easy to use and flexible automated system for Program Rating code insertion is now available. In addition to meeting the minimum requirements for V-Chip operation, local stations can reap additional benefits from XDS encoding. For example, Time of Day packet encoding can allow certain videocassette recorders (VCRs) to set their own clocks. Also, the attention of viewers who are "channel grazing" (or "surfing") may be captured when they see the current program name displayed during commercial breaks. Supporting the "V-Chip" provision of the Telecommunications Act of 1996 offers benefits to both the broadcaster and the consumer far beyond "parental control."

REFERENCES:

1. Report No. E-8302, Television Captioning for the Deaf, Phase II - Final Report, Project Director: David Sillman, Public Broadcasting Service, May 31, 1983.

2. Television Decoder Circuitry Act of 1989/90, 101st Congress, (House Resolution 4267, Senate Resolution 1974). Senate sponsors: Harkin, McCain, Inouye, and Simon.

3. Telecaption Demonstration Program, Daniel Fapp, Sears Marketing Public Relations, January, 1980

4. EIA-608, Recommended Practice for Line 21 Data Service, Electronic Industries Association, Draft of June 17, 1993.

5. Emerging Business Opportunities Through Captioning In The Nineties, Carlos W. Suarez, Cheetah Systems, Inc., NAB 1993 Broadcast Engineering Conference Proceedings.

6. Closed Captioning Extended Data Services: Broadcaster Technical Implications, Paul Kempter, Nielsen Media Research, NAB 1994 Broadcast Engineering Conference Proceedings.

7. FCC Report and Order FCC 91-119 as modified by FCC Memorandum, Opinion and Order FCC 92-157, Closed Caption Decoder Requirements, Federal Communications Commission, March 23, 1992.