Misplaced Pages

#401598

28-601: In May 2010 the largest deployments DVB-MHP are in Italy ( DVB-T ), Korea ( DVB-S ), Belgium ( DVB-C ) and Poland ( DVB-S ) with trials or small deployments in Germany, Spain, Austria, Colombia , Uruguay and Australia. MHP service was also offered in Finland by Finnish Broadcasting Corporation ( Yleisradio ), but the service was shut down at the end of 2007 after technical failure. The shutdown wasn't ever officially announced. Ultimately

56-435: A backchannel for educational purposes can function as a formal class activity or even an independent discussion without instructor participation and awareness. Aside from the normal discussion, a backchannel can also be used for note taking, asking questions, offering suggestions on different topics, and sharing resources with other students and faculty members. There are many different media networks out there that can be used as

84-544: A backchannel. Including Twitter, Facebook, Yammer and Instant Messaging. Joichi Ito 's HeckleBot includes an LED text panel displaying phrases sent from the chat room to catch the attention of the speaker or audience. The USC Interactive Media Division has experimented with "Google Jockeys" to feed visual information and search results between the speakers and the backchannel, projected on multiple screens surrounding their seminars. Software like SubEthaEdit allows for more formal backchannel: collaborative notetaking. In 2007

112-526: A chance to fact-check the presentation. First growing in popularity at technology conferences, backchannel is increasingly a factor in education where WiFi connections and laptop computers allow participants to use ordinary chat like IRC or AIM to actively communicate during presentation. More recent research include works where the backchannel is brought publicly visible, such as the ClassCommons, backchan.nl and Fragmented Social Mirror. Twitter

140-672: A large number of slower digital streams, each of which digitally modulates a set of closely spaced adjacent sub-carrier frequencies. In the case of DVB-T, there are two choices for the number of carriers known as 2K-mode or 8K-mode. These are actually 1,705 or 6,817 sub-carriers that are approximately 4 kHz or 1 kHz apart. DVB-T offers three different modulation schemes ( QPSK , 16QAM , 64QAM ). DVB-T has been adopted or proposed for digital television broadcasting by many countries ( see map ), using mainly VHF 7 MHz and UHF 8 MHz channels whereas Taiwan, Colombia, Panama and Trinidad and Tobago use 6 MHz channels. Examples include

168-573: A talk occurred on March 26, 2002, at the PC Forum conference, when Qwest CEO Joe Nacchio famously lamented the difficulties of raising capital. Journalists Dan Gillmor and Doc Searls posted accounts, from the audience, in real-time, to their weblogs . Buzz Bruggeman, a reader of Gillmor's, emailed information about a recent sizable transaction that had made Nacchio very wealthy; both Gillmor and Searls updated their weblogs with that information. Forum host Esther Dyson wrote that "around that point,

196-467: Is a COFDM transmission technique which includes the use of a Guard Interval. It allows the receiver to cope with strong multipath situations. Within a geographical area, DVB-T also allows single-frequency network (SFN) operation, where two or more transmitters carrying the same data operate on the same frequency. In such cases the signals from each transmitter in the SFN needs to be accurately time-aligned, which

224-459: Is a wireless technology utilizing the DVB infrastructure. It provides a VHF/UHF Wireless Return Channel back to the broadcaster for Interactive Terrestrial TV. It provides a data-rate of several kbit/s per user, for voting, polls, email, teleshopping, etc. If return channel is present it should provide IP with TLS support. DVB-T DVB-T , short for Digital Video Broadcasting – Terrestrial ,

252-444: Is also the format widely used worldwide (including North America) for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point. It is also used in the US by Amateur television operators. Rather than carrying one data carrier on a single radio frequency (RF) channel, COFDM works by splitting the digital data stream into

280-441: Is also widely used today by audiences to create backchannels during broadcasting of content or at conferences. For example, television drama, other forms of entertainment and magazine programs. This practice is often also called live tweeting . Many conferences nowadays also have a hashtag that can be used by the participants to share notes and experiences; furthermore such hashtags can be user generated. Victor Yngve first used

308-460: Is done by sync information in the stream and timing at each transmitter referenced to GPS . The length of the Guard Interval can be chosen. It is a trade-off between data rate and SFN capability. The longer the guard interval the larger is the potential SFN area without creating intersymbol interference (ISI). It is possible to operate SFNs which do not fulfill the guard interval condition if

SECTION 10

#1732876881402

336-671: Is largely based on MHP. Currently, Belgium's largest cable provider Telenet is rolling out their DVB-MHP system, called DigiBox. Norway's upcoming terrestrial digital TV network NTV will also use the DVB-MHP standard. In late 2008 the Info+ channel in Greece (part of the ERT Digital platform) started broadcasting DVB-MHP info, however since standards have not been set as of February 2009 for digital television in Greece, most TV sets and DVB-T receivers sold in

364-584: Is part of the terminal software, allows the user the access to all MHP applications and other DVB services (like TV and radio). Sometimes Navigator can be also a Java program itself but that is not a requirement. The MHP is just a part of a family of specifications, which all base on the Globally Executable MHP (GEM)-Standard, which was defined to allow the worldwide adoption of MHP. MHP applications come in two flavours. The first type are DVB-HTML applications. These are not very popular, partly because

392-573: Is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in February 1998. This system transmits compressed digital audio , digital video and other data in an MPEG transport stream , using coded orthogonal frequency-division multiplexing (COFDM or OFDM) modulation. It

420-407: Is the use of networked computers to maintain a real-time online conversation alongside the primary group activity or live spoken remarks. The term was coined from the linguistics term to describe listeners' behaviours during verbal communication. The term "backchannel" generally refers to online conversation about the conference topic or speaker. Occasionally backchannel provides audience members

448-716: The D-book in the UK, the Italian DGTVi, the ETSI E-Book and the Nordic countries and Ireland NorDig. DVB-T has been further developed into newer standards such as DVB-H (Handheld), which was a commercial failure and is no longer in operation, and DVB-T2 , which was initially finalised in August 2011. DVB-T as a digital transmission delivers data in a series of discrete blocks at the symbol rate. DVB-T

476-774: The UK's Freeview . The DVB-T Standard is published as EN 300 744, Framing structure, channel coding and modulation for digital terrestrial television . This is available from the ETSI website, as is ETSI TS 101 154, Specification for the use of Video and Audio Coding in Broadcasting Applications based on the MPEG-2 Transport Stream , which gives details of the DVB use of source coding methods for MPEG-2 and, more recently, H.264/MPEG-4 AVC as well as audio encoding systems. Many countries that have adopted DVB-T have published standards for their implementation. These include

504-466: The audience turned hostile". Many commentators later attributed the audience's hostility to the information people shared while surfing and communicating on their laptops during Nacchio's remarks. Research has demonstrated that backchannels help participants to feel as contributing members, not passive followers and make them feel more social. However, the research is mixed on the nature of this discussions, and especially regarding social interaction on

532-593: The backchannels: some cases report vast interaction where as others highlight that interaction on the platform was considered low. There are indicators that these tools however engage different members of the audience to provide their input. Since its inception in 1998 at Argonne National Laboratory , the Internet2 initiative known as the Access Grid (a large-format presentation, video conferencing and interactive environment) has used backchannel communications to permit

560-521: The broadcasters didn't want to upset their customers further if they had bought new expensive STBs which weren't capable of playing MHP apps, and 3) there were only a few MHP set-top boxes in the market—because Finland is such a small market, big manufacturers weren't interested in developing new MHP boxes just for Finland. MHP-capable STBs are no longer available in Finland. The U.S. cable industry has specified its own middleware system referred as OCAP , which

588-419: The case of an MHP receiver) to start and stop an application. The MHP set-top boxes may provide a backchannel for applications that wish to communicate with the outside world, for example a voting or shopping application. Typical upstream backchannels are phone line or broadband Internet connection ( ADSL , or 56k in Italy, using a modem included in the set-top box). DVB-RCT (Return Channel Terrestrial)

SECTION 20

#1732876881402

616-520: The country do not feature DVB-MHP. The MHP specifies an extensive application execution environment for digital interactive TV, independent of the underlying, vendor-specific, hardware and software. This execution environment is based on the use of a Java virtual machine and the definition of generic APIs that provide access to the interactive digital TV terminal 's typical resources and facilities. The interoperable MHP applications are running on top of these APIs. A so-called Navigator-application, which

644-582: The most popular flavour is DVB-J ( DVB-Java ) applications. These are written in Java using the MHP API set and consist of a set of class files that are broadcast with a service. DVB-Java applications are known as " Xlets ". These are a concept similar to applets for Web pages that has been introduced by Sun in the JavaTV specification. Like applets, the xlet interface allows an external source (the application manager in

672-415: The node operators to pass URLs for display at another site, troubleshoot problems and even discuss what's for lunch at their location. The Access Grid backchannel has evolved from the use of a MOO to XMPP . In 2009 Purdue University developed a tool called Hotseat that enabled students to comment on the course lectures in near real-time using social networking tools such as Facebook and Twitter. Using

700-629: The phrase " back channel " in 1970 in a linguistic meaning, in the following passage: "In fact, both the person who has the turn and his partner are simultaneously engaged in both speaking and listening. This is because of the existence of what I call the back channel, over which the person who has the turn receives short messages such as 'yes' and 'uh-huh' without relinquishing the turn." Such systems were widely imagined and tested in late 1990s and early 2000s. These cases include researcher's installations on conferences and classroom settings. The first famous instance of backchannel communications influencing

728-556: The reason for the shutdown was that MHP never gained "critical mass". The main reasons for its lack of success in Finland were: 1) 50% of the Finnish households use the terrestrial network, where broadcasting of MHP applications can be really expensive, 2) TV broadcasters never told TV viewers about the MHP services—because the digitalization of the TV networks got extremely negative publicity in Finnish media,

756-526: The self-interference is properly planned and monitored. With reference to the figure, a short description of the signal processing blocks follows. The receiving STB adopts techniques which are dual to those ones used in the transmission. DVB-T/T2 is switched off in Switzerland and the Flemish part of Belgium. The EU plans to switch off DVB-T/T2 in its member states by 2030. Backchannel Backchannel

784-427: The specification for DVB-HTML was only completed with MHP 1.1 , and partly because many broadcasters, box manufacturers and content developers find it too complex and difficult to implement. DVB-HTML applications are a set of HTML pages that are broadcast as part of a service. The spec is based around a modularized version of XHTML 1.1, and also includes CSS 2.0, DOM 2.0, and ECMAScript . The second, and by far

#401598