2.3 Video on Demand Scenarios

Interactivity in video distribution is increasing and new ideas for services are emerging. With VOD services, viewers can choose programs at any time they want. VOD may play a key role in driving the transition from analog TV to digital TV, as it converts the iTV receiver into a personal video rental store front. As significant demand is expected for these services, leading vendors have aggressive plans to deploy VOD services across the vast majority of platforms in all major metropolitan areas.

With typical selections of hundreds of movies, a key challenge is to allow viewers to navigate and select movies. This challenge is addressed by VOD guides, whose role is similar to the role of EPGs. The movie selection process can often be abstracted into a four step process:

1. Search : The viewer selects for display a movie search page, containing a form for specifying attributes of the desired movie. A common approach is to use a keyword matching method, using several predefined key words such as drama, comedy , rated-R, etc. Keywords could be entered without a keyboard using a variety of remote control techniques. The keywords may be refined iteratively until the viewer is happy with the list of selected movies.

2. Preview : The viewer selects a candidate movie and would like to view a description and a trailer. To increase the likelihood of selection, the preview could be customized based on the keywords presented by the viewer during the earlier search step.

3. Selection : The viewer has the option of selecting the previewed movie or going back to the search screen. If the previewed movie is selected for purchase, a VOD session is invoked, possibly following a transaction confirmation screen, and the process proceeds to step 4. Viewers should be given an option to cancel a purchase within the first few minutes of the program. Such cancellation backtracks to the search screen, causing the search results and keyword selections to be restored.

4. Viewing : The viewer is presented with a fully functional VOD session. The receiver enables controlling the video presentation through a return channel (e.g., using the Real-Time Streaming Protocol (RTSP) communication protocol [RTSP]). The video is transmitted to the receiver over the high-bandwidth forward channel (e.g., using Real-Time Protocol (RTP) or MPEG-2 transports).

VOD guides could be implemented by either pushing the guide using a broadcast, or pulling the guide from the Internet through an ISP. Although the latter may introduce delayed responses, it can achieve more manageable and cost-effective interactivity, pushing many service providers to deliver guides over the Internet. Migrating delivery of guides to push technologies that utilize local interactivity implies migrating the responsibility of the guide to be transmitted to the owner of a dedicated virtual channel. The video and data streams feeding the video trailer could be encapsulated in a dedicated elementary stream that differs from the elementary stream used to transport the HTML and image content. The (low-bit-rate) trailers are typically transmitted in a group of transport streams carrying the VOD EPG, which is separate from the transport carrying the actual video program(s).

2.3.1 VOD Search Applications

The viewer selects the VOD service and the list of all available movies is presented, each associated with a title, its rating, an icon of the content originator, and some short text describing its content. The Graphical User Interface (GUI) of the application provides a search panel, enabling the viewer to enter keywords. Once the search condition is entered, the list of movies is filtered to contain only those movies that match the key words specified by the viewer. The set of keywords can be iteratively refined until the viewer is happy with the list of remaining movies.

At any time during the search process, the viewer can browse up and down the list. The application should highlight a single movie selection at a time. On selection of the highlighted movie, the search application should automatically tune to the virtual channel carrying the trailer of the selected movie, effectively terminating itself and launching the trailer.

Once a movie is selected from the search results, the receiver automatically launches the trailer of the selected movie. The viewer is presented with a trailer application GUI that is launched automatically upon tuning to a trailer virtual channel. The GUI layout could be divided into three sections: title at the top, trailer to the left, and preview to the right. The title is a horizontal section across the top of the screen. The trailer section is further divided into two horizontal parts : the video display area and the selection buttons . The preview section is further divided into three horizontal parts: a movie poster, summary text, and preview images.

In its simplest form, the trailer application is resident at the receiver and only the data it uses is broadcast; a more complicated scenario permits the broadcast of the application's code as well. The trailer video is broadcast using a low bit rate, to allow multiple trailer videos . Each trailer is in a different virtual channel, to be broadcast in a single physical channel of a fixed bandwidth. The images and text data should be transmitted using a broadcast data carousel model that repeatedly retransmits utilizing low bandwidth as well.

The VOD concept essentially utilizes the TV as a virtual video rental store front. The combination of a search engine with a trailer application is much more effective than a traditional video store front. With a simple click of the remote control, viewers have the freedom to select from a large catalog of movies, can view trailers, and enjoy real-time VCR-like features, all in their private home.