INTERNET-DRAFT C. Finseth Firwood Consulting G. Thomas LGERCA, Inc. 28 March 2000 Guide to TV Broadcast URLs draft-finseth-guide-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This document expires 28 September 2000. Status of this Memo This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. Abstract This document provides a recommended methods for identifying resources within TV broadcast streams. These methods use the "tv:" and "lid:" URL/URI schemes. These schemes are defined in [1] and Finseth, Thomas [Page 1] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 [2]. Environment The environment is television. In this environment, you have a receiver that picks up one or more signals and deals with them. (We'll use the term "receiver" to denote the box or module that does the work.) There are a few points to keep in mind. First, the receiver may have only one source of signal, or it may have many. Typically, inputs can come from: - over-the-air antenna (NTSC, ATSC, DVB, potentially other formats) - cable feed (potentially a variety of formats) - satellite feed (again, a variety of formats) in any combination. Second, the receiver may (and usually will) have some sort of video out and/or an imaging device (picture tube/LCD/whatever). The receiver may be able to display images from multiple sources (e.g., picture-in-picture). In some special cases such as a portable stock-ticker type device, the receiver may not be able to decode the "normal" audio/video image. Third, the receiver may be stand alone, or it may be connected to some form of "back channel." The back channel may be proprietary or general-purpose (e.g., a network connection). The channel may be in the form of a phone line, DSL, cable modem, general LAN connection, etc. Assumptions Please keep these general notes in mind when reading the examples: - RFC 2396 documents the terms URI, URN, and URL. We use that document as a base. This document will use the string "URI" to refer to all three. - Consider each example as representing the class of similar cases. In particular, if your favorite example isn't on the list, ask yourself if it has the same URI requirements as another that is on the list. - You can assume that the receiver will know how to deal with already standard URIs such as http:, ftp:, mailto:, file:, etc. (Note that Finseth, Thomas [Page 2] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 this statement is "know how to" and not "be able to:" not all receivers will have the capability to use them.) - All uses of trademarks in these descriptions are for illustrative purposes only. There is no intent to assert that the trademark holders actually do or do not intend to carry out any of the suggested activities. - The term "EPG" means "electronic program guide." - This document will use the term "channel" to refer to what some protocols refer to as a "virtual channel." A channel refers to content addressible by a number. Application List This section presents a list of ways in which URIs can be used in a television context. The examples were contributed by a variety of people. The requirements are to... 1. Be able to refer to the audio/video image. 2. Be able to include queries into the receiver in a technology- independent manner (ie not relying on specific ATSC, DVB, etc SI fields). 3. Provide for technology-specific tuning, such as: * Tune to channel 100 on the EchoStar system. * Tune to ATSC channel 7.2. * Tune to NTSC channel 4. 4. Provide for network-specific tuning, such as: * Tune to the local ABC affiliate. * Tune to the HBO East feed. 5. Be able to uniquely address authored streaming content (video and/or audio) in a globally unique, network-independent, and transmitter-independent manner. 6. Be able to name discrete data content (as opposed to streaming video and audio) being broadcast by a network, and *not* available via the Internet with any known scheme (ie HTTP or FTP), and provide Finseth, Thomas [Page 3] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 a globally unique reference to it. 7. Be able to name standard web content that is *also* being made available and delivered via some tv data broadcast to local cache. http://www.wsj.com/headlines.html [ Note: this item is included for completeness. In fact, we support for this is already part of the http: standard and we don't have to do anything. ] 8. Be able to reference an application, both for inter-process communcations purposes and to provide a default Base URI for contained URIs. 9. Be the target of a trigger encoded into the line 21 of the VBI (which is must carry for broadcasters) of a TV show that loads up a "jump page" of enhanced tv content that supplements the television program. In general, be the target of any trigger. 10. It is the year 2002. Fox is broadcasting a World Cup game from South Korea in both analog and digital formats, with the broadcast reaching North America, Europe, Africa, Asia, Latin America, Australia, etc., through a wide variety of local affiliates and re- broadcast operators. Fox wishes to put a hyperlink to the broadcast on its web site, so that users of Internet-connected TV receivers all over the world with the right software (perhaps native, perhaps downloaded) can click on the hyperlink and have their receivers tune to the broadcast (or set a reminder for the broadcast, if the game is not currently on). 11. In the same situation as (10) above, the broadcast is data- enhanced, with a data carousel module or an encapsulated IP datagram containing a file which gives up-to-the-second statistics on goals scored, fouls committed, corner kicks taken, shots at goal, shots on goal, etc. Fox wants to put a URI on their web site which references this file, allowing applications on Internet-connected TV receivers all over the world to get to the file and display it in nifty ways. 12. In the same broadcast situation as (10) and (11) above, Fox wants to put hyperlinks to the program and/or data in other data files being broadcast on the same Fox channel and in other Fox channels, so that receivers can set reminders for the upcoming game and/or data file. 13. Paramount Productions wants to put on its web site a generic hyperlink to Star Trek episodes and/or movies. A user of an Internet-connected TV receiver with the right software can click on Finseth, Thomas [Page 4] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 this hyperlink, and the receiver will give the user a mini-EPG showing the Star Trek episodes and/or movies which the receiver can receive now or in the near future. The user can then select a current show for viewing or a future show to set a reminder. This link will identify _a_n_y Star Trek-related information: episodes from the Original Series, the Next Generation, Deep Space 9, etc., as well as movies, specials, or any other similar material. 14. In the same situation as in (13) above, the producer wants to put on its web site a hyperlink to the Star Trek: Deep Space Nine series, and have the mini-EPG show only the current and upcoming episodes of this series. 15. In the same situation as in (14) above, the producer wants to put on its web site a hyperlink to each of the episodes which have been filmed of the Star Trek: Deep Space Nine series. By clicking on one of these hyperlinks, the user can see a mini-EPG showing the current and upcoming showings of this specific episode. 16. A local broadcast station is having a promotion in connection with their weekly broadcasts of Star Trek: Deep Space Nine. It wants to put a hyperlink on its web site which viewers in its local viewing area can click on to tune to, or set a reminder for, its broadcast of this week's episode. 17. A large network, e.g., Fox, wants to put on its website a generic invitation to watch a particlular one of its channels, with a hyperlink which viewers anywhere in the world where the network broadcasts can click on in order to tune to that channel. 18. A local affiliate of the network mentioned in (17) above wants to put a hyperlink on its web site which viewers in its viewing area can click on to tune to a particular one of its channels. (It may be broadcasting multiple virtual channels in the same physical broadcast band, in the case of a digital broadcast). 19. It is common these days for multiple cable channels to be owned by the same parent corporation. In the future this may be increasingly true for terrestrial broadcast as well. In such a situation, consider the case where the parent corporation wants its multiple channels to be able to advertise each other, with hyperlinks allowing the user of a receiver with the right software to click on such an advertisement appearing in one channel and have the receiver automatically switch to the advertised channel, or set a reminder to an upcoming show in the advertised channel. 20. In the same situation as in (19) above, suppose a single application can operate with the data of any of multiple different Finseth, Thomas [Page 5] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 data services broadcast on different channels, for example a ticker application which can display many different categories of ticker information. The provider of these multiple different data services provides along with each service an index which the viewer can use to select the data service(s) of interest. The application uses the URI associated with each service in the index to tune to the service(s) selected by the viewer. 21. The NFL wishes to help people watch the superbowl. It distributes e-mail (to people who have signed up for such a service) containing a URI which they can click on to have their receiver look up when the SuperBowl is on. Some of the e-mail is sent via the Internet and some is sent via an "e-mail" channel and received on a TV receiver. 22. Some global brand (Coca Cola for the sake of argument, with the normal trademark note), wishes to place a URI (maybe as a datagram) in to be broadcast with the program and displayed as a pop-up, linking to one or more of: a) A web-cast infomercial on their site. b) Infomercial broadcast separately, for example the previous night, and locally stored on the receiver's memory. c) Infomercial broadcast on a separate advertising channel. d) Infomercial available on a VOD (or NVOD) channel. 23. A sponsor wishes to identify data describing their logo (perhaps animated) for inclusion in the program guide. 24. A content creator (such as an advertising agency or production studio) needs to be able to assemble and test a commercial, program or other material including all URI references, then be able to distribute a final tape (whatever) for airing over a variety of transports (ATSC, DVB, etc.). The point here is that when the URIs are locked down, the distribution format(s) is(are) not known. 25. With the advent of powerful computers and software such as Adobe AfterEffects, just about anyone can become a content creator. Thus, the naming mechanism must scale to the tens of millions of authors: it must be globally unique. 26. In the case where a receiver can obtain the same material from two different sources (e.g., over-the-air and cable), the URI scheme must provide mechanisms to: Finseth, Thomas [Page 6] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 a) allow the receiver to determine that, in fact, the same material is being received from both sources (and it can thus use either), or b) even though the material may appear to be the same, it really is not and so substitution is not permissible. In other words, the URI must not force solutions in this area. Rather, it must provide the content creators and/or broadcasters the tools to make the correct distinctions. 27. Some broadcasters may elect to transmit some material in advance of usage (as opposed to in "real time"). The URI mechanism should allow receivers that have such "pre-cached" material to make use of it while other receivers use the "real time" version from the _same_ reference in the running application . (The pre-cached version may be pre-rendered for speed or may be transmitted at a higher resolution.) 28. The URI mechanism should facilitate the recording of a program with all video, audio, and data streams and subsequent playback. 29. Given (28) the source space of URIs should be large enough that URIs need not be reused. (Since you can't tell when a live data stream is going to be mixed with the playback of a previously recorded one.) In summary, URIs reference things transmitted down the broadcast stream(s). The things that they can reference are one or more instances of: a) the tuner output b) a transmission multiplex c) a (virtual) channel d) an event e) an application f) data used by an application General Notes A full summary of the requirements that such a scheme must meet is given in [3]. This document will not repeat that discussion. Finseth, Thomas [Page 7] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 URIs used in TV broadcasts have these key properties: 1. More than one resource may be identified by the same URI. Hence, a list of matching resources would be returned. 2. A given resource may be identified by more than one URI. Hence, the same resource may be returned by more than one request. 3. While URIs can reference resources that are only available at particular times, the URIs themselves do not explicitly encode any time-related information: any such information is carried by other mechanisms. For example, a URI may reference an "event" (e.g., a TV program) and that event does carry a time context. Guide to Resources Naming This section identifies each type of resource available within a TV broadcast stream and identifies the preferred Note that the portion identifies the entity that made the assignment. The first two resources identify levels of transmission multiplex "bundling." 1. The "current TV image." The preferred form is the "tv:" scheme. Example using HTML are: ... which places the "live" image as a background and:
Upper left
Lower leftLower right
which does a "picture-in-picture" type display with the image in the upper-right corner. 2. A transmission multiplex. The preferred method is to use the "lid:" scheme. For example, the ABC network feed. These might be named: Finseth, Thomas [Page 8] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 lid://abc.com/ or: lid://abc.com/feed or: lid://feed.abc.com/ 3. A particular virtual channel. The preferred method is the "tv:" scheme. This resource identifies a particular virtual channel. Virtual channels might be named: tv:abc.com or: tv:chan.abc.com or: tv:hbo.com or: tv:west.hbo.com tv:chan.kstp.com The first two indicate typical cases of a network feed. The next two indicate naming generic and specified feeds. The last one could be attached to the same channel as either of the first two (as KSTP is the ABC affiliate in the Minneapolis/St. Paul area.) Note that there is no need for the numeric form (Channel 5). If the local affiliate were to embed a URI in web content, the context would just be: ...tune to Channel 5 now... This same form would work on web content found in the Internet (assuming that the device had a tuner and was able to receive KSTP's signal), in content found in the TV broadcast stream, or any other content. Since virtual channel numbers in a TV are re-used, an application can not usefully _e_v_e_r use the virtual channel number alone. Instead, it must refer to the context to determine how to name the desired resource. Given such a lookup, the alphabetic form of the name is no more effort to use than the numeric form. Note that the national network can use the form: ...tune to ABC now... and cause tuning to the local affiliate (assuming there is one) from anywhere. Finseth, Thomas [Page 9] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 While there may be some exceptions, TV broadcast URIs are intended mainly for internal use by the system and not for presentation to viewers. The following example illustrates why. HBO (and many other networks) have multiple feeds: in the U.S., they have both an East and West coast feed, with the West coast feed ordinarily carrying the same content as the East coast feed, but with a three hour delay (live events are carried at the same time on both). Local providers (e.g., cable systems) on the East coast ordinarily carry the East coast feed and call it "HBO". Local providers on the West coast ordinarily carry the West coast feed and also call it "HBO". Nationwide providers (e.g., satellite systems) may carry both feeds but must use different names (often "HBO" for the East coast feed and "HBOW" or "HBOP" for the West coast feed). Note that cable and satellite systems offer identical content on the West coast feed, but present that content under two user-visible names, said name depending upon the transmission path. The recomended scheme avoids problem by separating the URI naming from the user-visible naming. The provider can use the same URI whenever the content is the same. Note that the same content is just that: it's the same string of bits, even if shifted in time. For example, a promotional spot might need a background GIF resource named: lid://hbo.com/promotions/ad1453/background.gif It can (and should) use the same name whenever the resource appears in the transmission. The provider can use its normal scheduling mechanisms to handle staging of the varoius feeds. In some special cases (e.g., channels hidden from most viewers), a "lid:" URI can also be used to designate a channel. The next block of resources identify various combinations of event material. 4. A collection of event material. The preferred method is to use the "lid:" scheme in either of two ways. The first way is to assign a meaningful name. For example, the set of Gilligan's Island episodes in the schedule. This resource might be defined by attaching a URI like this: lid://gilligans-island.com/ Finseth, Thomas [Page 10] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 to each episode in the schedule. A typical use of this form of URI might be on the Gillian's Island web page. It might have a reference to: ...and click here to see a when and where it is on in your city... The second way is to use the SMPTE-assigned UPID [4] written in "lid:" form. For example, if the "Gilligan's Island" series was assigned the UPID root 1234567890, the following reference may also be used: lid://isan.smpte.org/1234567890 The latter form does not require that explicit mapping information be carried but does require that the material's UPID be transmitted. The choice of form (meaningful name vs. UPID) will be affected by marketing as well as bandwidth and memory concerns. 5. A particular episode of a event series. The preferred method is to use the "lid:" scheme, again in either of two ways. The first way is to assign a meaningful name. For example, the "Trouble with Tribbles" episode of the original Star Trek. This resource might be defined by a URI of one of these forms: lid://trouble-with-tribbles.startrek.com/ lid://startrek.com/trouble-with-tribbles lid://startrek.com/2nd-season/trouble-with-tribbles This specification does not identify which form is preferred: just as with "normal" web URIs, the preferred form is selected by the organization named in the portion. The second way is to use the SMPTE-assigned UPID [4] written in "lid:" form. For example, if the "Star Trek" series was assigned the UPID root 4567890123 and the "Trouble With Tribbles" episode was assigned the episode id 34, the following reference may also be used: lid://isan.smpte.org/4567890123/34 The latter form does not require that explicit mapping information be carried but does require that the material's UPID be transmitted. The reference can be limited to a specific version of the episode by adding the version identifier and checksum fields: Finseth, Thomas [Page 11] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 lid://isan.smpte.org/4567890123/34/456/8 In many cases, material with a the specific episode URI would also have a generic series URI: lid://trouble-with-tribbles.startrek.com/ lid://startrek.com/ 6. A particular showing of a event. The preferred method is to use the "lid:" scheme. For example, the "Trouble with Tribbles" episode of the original Star Trek that ran on Nov 16, 1998 at 10:00pm on virtual channel 5 in Minneapolis/St. Paul. This resource might be identified by a URI of the form: lid://kstp.com/trouble-with-tribbles/startrek.com The URI would be placed _o_n_l_y on the showing for the specified virtual channel and at the specified time. The naming of this example assumes that the local station is the source of the reason for the reference. For example, there is a promotion in conjunction with a local Star Trek convention. A more typical name might be: lid://kstp.com/promotion/star-trek/19981116 The point is, the organization creating the reference can use whatever name best suits their purpose. Note that it is common for local broadcasters to change the time of a broadcast, both "in advance" (e.g., always starting "E.R." 5 minutes late) or "on the fly" as local conditions change (e.g., to accomodate a live event running long). As such, URIs should never contain specific show times. Rather, they should identify the material and the receiver would process the reference through its EPG to determine actual show times. This usage requires the "meaningful name" form because the UPID is not allowed to vary with showings. The UPID form could be used in the case where a special version had been made for this showing only, which is unlikely. 7. Event material that appears someplace in the time/virtual channel/provider continuum. The preferred method is to use the "lid:" scheme in either of the two forms. Finseth, Thomas [Page 12] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 For example, the January 1999 Super Bowl. This event might carry the URI: lid://super-bowl-Jan-1999.com/ or even just, lid://super-bowl.com/ Given that only one is likely to show up in the schedule at a time. As with the nationwide network example, the reference can be embedded as: ...and click here to schedule your TV to tune to the Super Bowl!... Again, this reference is only useful if the viewer can actually receive the Super Bowl broadcast and it is in the available event guide. It also assumes that references to events in the future can integrate to a scheduling system (this situation is common in satellite and cable set-top boxes). 7. A particular once-only event. The preferred method is to use the "lid:" scheme in either of the two forms. All of the previous examples referred to events that were in some sense repeating or part of a series. The same forms and concepts apply to once-only events. The organization responsible assigns the URI and it is attached to the appearances. The last two points identify "data"-oriented resources. 8. A particular application. The preferred method is to use the "lid:" scheme. URIs can be attached to the applications themselves. These URIs can be used in two ways. First, they identify applications to each other for inter-process communications. Second, the default Base URI for the application is established by the act of naming the application itself. Example names might be: lid://coke.com/commercial45/application lid://abc.com/promo5.html Finseth, Thomas [Page 13] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 9. A particular data item referenced by an application. The preferred method is to use the "lid:" scheme. Examples are image files (JPEGs, GIFs), sounds, data streams, etc. For example, lid://coke.com/commercial45/application/background.gif Referencing Other Data This document covers how a receiver learns about URIs received _o_n_l_y over a TV broadcast stream. Receivers may use other URI schemes as they see fit. For example: - The "http:", "ftp:", and similar schemes can be used to access content from the Internet (given such a connection). - The "file:" scheme may be used to access local information. - Other TV broadcast-related schemes may coexist with this scheme (e.g., "dvb:" and "davic:"). However, their use should be avoided by well-formed applications. Security Considerations specification does not address security. It assumes that security and access control are handled by policies and procedures implemented in the systems themselves. While this specification appears to provide a level of security by virtue of the fact that the only resources accessible by an application are those named in the broadcast stream, such is not the case. Absent other policies and procedures, an ill-behaved application can access resources by using device-specific mechanisms. References [1] "Uniform Resource Identifiers for Television Broadcasts", Mark Vickers, Dan Zigmond, 02/21/2000. (10914bytes), http://ietf.org/internet-drafts/draft-zigmond-tv-url-04.txt [2] "The Local Identifier (lid:) URI Scheme", C. Finseth, Dean Blackketter, Dan Zigmond, Gomer Thomas, Michael Dolan, 02/24/2000. (12122 bytes), http://ietf.org/internet-drafts/draft-blackketter-lid-00.txt [3] ten Kate, Warner; Thomas, Gomer; Finseth, Craig, "TV Broadcast URI Finseth, Thomas [Page 14] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 Schemes Requirements", 11 March 1999. http://www.w3.org/TV/TVWeb/TVWeb-URI-Requirements-19990311 [4] "Referencing ISAN Identifiers with the Local Identifier (lid:) URI Scheme", C. Finseth. 03/28/2000. http://ietf.org/internet-drafts/draft-finseth-isanlid-00.txt [RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. Author's Addresses Craig A. Finseth Firwood Consulting 1343 Lafond St Paul MN 55104 Phone: +1 651-644-4027 Email: craig@firwood.net Gomer Thomas LGERCA, Inc. 40 Washington Road Princeton Junction, NJ 08550 Email: gomer@lgerca.com Full Copyright Statement Copyright (C) The Internet Society (2000). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implmentation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an Finseth, Thomas [Page 15] INTERNET-DRAFT Guide to TV Broadcast URLs 28 March 2000 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." This document expires 28 September 2000 Finseth, Thomas [Page 16]