Long before TV was as ubiquitous as it is today, someone boldly said that "someday all TV will be pay TV." Needless to say, that statement, regardless of who made it, prompted a great deal of debate, though that scenario is becoming more and more true as time passes. If that same individual had raved about how TV would one day become interactive, he or she might have been committed. But now, after years of promises and rhetoric, we finally seem to be nearing the age of digital interactive television. Many devices in the home, as well as the networks that carry the information, are becoming digital. Why? Because the broadband digital multimedia-enabled home will be much richer in terms of interactivity and the visual quality of entertainment content.
Broadband digital home entertainment can be delivered in a variety of ways, including via digital cable, satellite, telephone, multichannel multipoint distribution service and high-speed Internet lines. Most challenges inherent in interactive television and networking multimedia apply to all delivery methods, though clearly some-such as reducing packet size and compensating for latency-are more applicable to the lower-bandwidth delivery methods.
In the case of digital multimedia, and especially where interactive television is concerned, many networks and protocols may be involved in the transmission of information. This requires complex communications software on the client system to accommodate those standards, potentially increasing the size of the client software required to decode the various network protocols. It also makes it difficult for manufacturers to predict how the different standards will react to latency, packet loss and many other factors.
One example of a system mixing several protocols might be an asynchronous transfer mode network that delivers MPEG packets inside of ATM cells. The MPEG packets contain audio, video and private data. The private data may include Internet Protocol (IP) packets intended for use by an application. Some of that information may be encrypted, requiring additional handling before it becomes useful to an application. Some of the IP data may be sent out to a local-area network for use by one or more client devices.
The client device-let's say a digital set-top box, for example-needs to be a very capable communications device to supply dependable services. The software decrypting those disparate protocols and languages needs to be extremely sophisticated, while maintaining a small footprint requiring little processing power-a daunting set of requirements for any programmer.
Telephone wiring coming into the home supplies information to a modem that carries multiple signals simultaneously. One signal, or virtual circuit (VC), transports video in the form of digitally compressed MPEG files. As a subset of the MPEG transport stream, compressed data may also be transported in some frames in the form of private data in the data stream. That data might be directed at updating an electronic program guide in real-time, or supporting other applications that offer different services to the subscriber.
Other VCs may be used to transport IP packets destined for an Ethernet-connected PC or IP-enabled device. That allows an in-home PC to also access the Internet or other external network using a broadband connection as a subset of the bandwidth provided to the home for all of the converged services. This complex communications environment places great strains on traditional communications software.Managing change
Experience with the Web has shown us that new protocols as well as algorithms for processing content may be introduced after a device is designed and initially deployed. Set-top boxes are most often offered by a network provider as part of the subscribed service, and must be able to adapt and be remotely upgraded if they are to survive and possess a reasonable life cycle in an environment of rapidly changing technologies.
Modern desktop systems have the processing power to handle complex networking and multimedia applications. The difficulty, and the holy grail, lies in delivering networked multimedia to television sets. Delivering this content to televisions allows massive market penetration. Devices for this market will need to be significantly lower in cost than today's desktop computers to really achieve large volumes. Consequently, the processing power will be less, and the memory footprint of the devices will be much less than in desktop systems. In this low-cost, low-power environment, the software will need to be smaller and faster in order to supply a satisfying experience to the consumer.
The Web has demonstrated the possibilities of multimedia as well as the major hurdles. Multiple streaming-media formats compete to deliver multimedia to the user. Web users see the possibilities of information and entertainment content on demand. Virtually everyone has experienced undependable delivery that produces irregular playback of movie clips and audio as a result of Web bottlenecks. It has been pounded into everyone's head at this point, but broadband Internet access is key.
The level of service required in order to meet the expectations of the mass market viewing multimedia on a TV set will have to exceed what's available on the Web today. Unreliable playback will result not only in a channel change, but potentially in the permanent loss of a viewer as well. For those reasons, the primary entertainment device-the television-cannot be delivered in an uncontrolled network environment like the Web.
Information to a new-generation set-top box does not typically terminate at the set-top. It is also generally transmitted to and from any number of devices on the premises, including digital televisions, digital recording devices, camcorders, printers, digital cameras, wireless keyboards, remote controls, residential gateways, security systems, intelligent consumer devices, desktop computers and handheld computers. Those systems will be connected by different transmission mediums that introduce new protocols. Among the connectivity options are Ethernet, Bluetooth, IEEE 1394, IEEE 802.11 and Universal Serial Bus.
Applications need to be portable across network topologies. They also need to be protocol-independent. In order to accomplish this, the communications foundation must offer a single, consistent interface to the application.
Client devices of today and tomorrow must be able to efficiently handle high data speeds reliably. Information will be coming into the home at speeds supplied only to powerful mainframe computers just a few years ago. The task of handling the high-speed, multiple-protocol data will be addressed by lower-cost, lower-performance processors in a dedicated massmarket client device.
Traditional approaches used to address the needs of multiprotocol environments have employed independent tasks for each protocol, communicating by means of interprocess communications techniques. As the environment becomes more complex, this approach can break down because of the need for more context switches, more memory and greater CPU power.
What you'll get
A successful modern solution with sophisticated framework characteristics will accomplish the following:
- Combine protocol-handling software components in a single task;
- Dynamically add or remove components;
- Minimize the need to copy data for use by protocol handlers;
- Supply a well-defined and documented framework interface;
- Reduce overhead required to conform to the framework;
- Offer the ability to test the software within an emulation environment;
- Reduce the need for interprocess communications;
- Supply an easy-to-use, well-documented API for application programmers;
- Be reliable.
An example of such a framework is Microware's SoftStax product, which was developed to meet the needs of the increasingly complex digital television environment. The SoftStax framework allows protocol "drivers" to be dynamically stacked within one task or process, which reduces context switches. The design of SoftStax also allows protocol drivers to be downloaded and used without the need to recompile applications to take advantage of the new protocol.
In the case of the digital set-top box, the desirable characteristics of the software foundation are relatively simple to landscape. Typically, size is first. Since set-top boxes are meant to be relatively low-cost devices compared with today's home computer, minimizing the memory required to perform all designated functions is important. Similarly, adequate performance is critical. As was mentioned previously, a small, very efficient software foundation requires a less costly CPU. The related benefit here is lower power consumption as well as less heat. A well-designed platform will take advantage of those characteristics.
A second and equally important consideration for the set-top is to provide diverse network adaptability. Today's digital subscriber line networks can operate using the ATM foundation protocols and provide service from less than one megabit/second to as high as 52 Mbits/s. While the connection-oriented ATM foundation is likely the most reliable and efficient means of delivering streamed media to the home, competing router-based protocols that use IP are also pervasive for a variety of reasons. To be widely deployable and successful, today's set-tops must be network-agnostic. A full suite of ATM- and IP-based protocols must be available to support deployment applications.
A third and often-ignored piece of the software foundation is support for a wide variety of peripheral interfaced devices. As set-tops take their place in homes in the coming years, the range of features, functions and services offered that will take specific advantage of these peripheral interfaces is countless.
Personal video recorders, DVDs, handheld music players, security cameras, digital still and video cameras, printers, telephony devices (voice and video), and fixed and mobile networked devices are just some of the more common ones.
Others will come. The transition toward what is often called the "home gateway" will come with it. What will it look like? A home gateway is likely to take on many forms. The rapidly emerging broadband market is fueling the move toward quality networked multimedia, though many questions remain. Will it be wired or wireless? Satellite, especially for rural customers, is one extremely viable choice. Will it be a box by the TV or on a shelf in a closet? Will it be upgradable?
The answers to those questions will most likely come in the very near future. As with any emerging technology, nothing is certain, but it's most likely that in a very short time, networked digital multimedia content will be piped into living rooms across the world for the first time.