Preparing for the widespread distribution of interactive applications delivered to the set-top box, Philips Consumer Electronics Co., Liberate Technologies, Texas Instruments Inc. and Wave Systems Corp. are supporting the emerging MPEG-4 digital-video-compression standard.
The companies banded together at the National Association of Broadcasters'annual convention last week to demonstrate an asymmetrical-digital-subscriber-line set-top box running a streaming video-on-demand application based on Philips'MPEG-4 technology.
A Philips server connected to a TI-based central-office unit served up the content via Internet-protocol multicast. The set-top, a Philips prototype, uses a TI programmable digital-signal processor, an ADSL-modem chip set and Liberate's middleware platform.
"Many new emerging services specifically target broadband Internet," said Pieter Noordam, general manager of the Internet and personal-TV group at Philips Digital Networks, in a press release. "Because of their entertainment focus, it makes sense to bring these services straight to the television set in the living room via a broadband Internet set-top box."
MPEG-4, developed by the Moving Picture Expert Group, is one way to make that happen. An evolution of the ubiquitous MPEG-2 standard, MPEG-4 is a compression technology originally designed for very low-bit-rate coding, but it has grown to address interactive digital audio-visual content.
While both MPEG-1 and MPEG-2 work with "frame-based" video and audio, MPEG-4 specifies a description of audio/visual scenes in the form of "AV objects." Those objects can be natural or computer-rendered, aural or visual, two- or three-dimensional, and they can incorporate interactivity. For example, objects can be hyperlinked or they can trigger other multimedia events.
One way of delivering MPEG-4 content is to embed it inside an MPEG-2 stream. Philips'MPEG-4 single-channel encoder station encodes video at up to 30 frames per second and supports MPEG-4 audio/ video output at bit rates ranging from 22 kilobits per second to 1 megabit per second.
It processes real-time video encoding at up to 25 fps at quarter common intermediate format and 12 fps at CIF.
Other features include MPEG-4 audio encoding at 64 kbps (mono), upgrades to multiple channel encoding and standard Web-browser plug-in support. Philips senior manager of media relations Jennifer Massaro called MPEG-4 "the best technology for streaming video optimized for the Internet."
With MPEG-4 eating up less bandwidth than MPEG-2, its advantages extend into the software that runs a set-top. "For the first time, we are endorsing MPEG-4 as one of the standards we're moving into," Liberate senior vice president of corporate development David Limp said.
Citing the merging of Internet streaming content with traditional TV video, Limp called MPEG-4 "a catalyst to help with that convergence."
Also a big believer in MPEG-4 is TI European product-marketing manager Remi El-Ouazzone. TI is providing an ADSL network-interface card for the Philips ADSL set-top box.
While MPEG-2 delivers content at a rate of 4 mbps to 5 mbps, MPEG-4 allows CD-quality audio, for example, to be streamed at 1.5 mbps, El-Ouazzone said.
Limp added that MPEG-4 "is much more flexible in its scalability than MPEG-2." The ramifications of this are significant in terms of streaming content over lower-bandwidth networks and accommodating the variable-bit-rate programming that many Internet-streaming content producers are creating.
In a cable-network environment, Limp said, MPEG-4 can deliver multiple channels within the 6-megahertz slot. For example, programming can be enhanced by inserting quarter-screen video content and graphic elements such as charts. Or a producer may package complementary virtual shopping or e-mail channels in the same channel that carries primary programming.
For DSL applications-where last-mile limitations challenge providers to drive more bits across copper wires-MPEG-4 "is always a more efficient compression" scheme, Limp added.
Regardless of connection methods, Philips is enlisting several partners to add more and more functionality to its line of set-tops. "We see the set-top box in the future as the gateway into the home," Massaro said.
Based on recent deals, Philips is positioning itself as a wide provider of set-tops. It now sells a TiVo Inc. personal-video-recorder set-top and a Microsoft Corp. WebTV Networks box. It has forged an agreement with MediaOne Group Inc. to supply advanced digital set-tops, and is working with America Online Inc. to develop an "AOL TV" receiver.
A vision of a set-top that meshes the TV and Internet experience also includes streaming video from the Internet, downloading music files and enabling the next generation of content.
Reinforcing the emerging residential-gateway concept, El-Ouazzone pointed out that TI's DSP architecture in the Philips set-top is programmable, meaning operators can add services through software downloads. In the case of the ADSL set-top, voice-over-DSL services are a possible add-on.
The DSP architecture-which diverges from a typical application-specific integrated-circuit architecture-serves as the "data pump" for the ADSL-modem card, allowing for real-time processing. Unused MIPs (millions of instructions per second) of the DSPs can be allocated to perform other tasks, such as voice compression, on top of processing MPEG-4 data streams.
El-Ouazzone added that spare DSP MIPs in a residential-gateway box could also be used to process a short-distance wireless-data stream.
For the time being, though, MPEG-4 is not yet raising a lot of eyebrows in the cable industry.
"We're definitely interested in finding efficient ways to deliver interactive services to the box," MediaOne director of digital video Jim Alexander said. But he added that while Philips has demonstrated its MPEG-4 technology to MediaOne, he still sees an out-of-band signaling scheme for interactive content, relying on the Data Over Cable Service Interface Specification.
As MediaOne begins to implement its advanced digital services, Alexander added, he'll look at technologies to deliver high-end interactivity.