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Broadband Week for July 12, 1999
Quality Streamed Video, Ads At Sub-Megabit Rates Loom
By FRED DAWSON July 12, 1999
Advances in software across a wide range of vendor initiatives suggest that barriers to delivering quality video, along with interactive multimedia advertising, at sub-megabit bit rates will soon fall.
On one front, the MPEG-4 initiative (the fourth generation of the Moving Picture Expert Group standard) has picked up steam, and it is now closing in on completion of version two, with some developers signaling that they'll have MPEG-4 tool kits on the market before the year is out.
Elsewhere, innovations such as tight coupling of video-streaming client software with set-top operating systems and on-the-fly shaping of bit streams to fit moment-by-moment changes in end-user access rates contribute to prospects for far better performance in the hundreds of kilobits-per-second range than is possible today.
"We've already demonstrated that we can achieve TV quality with video delivered in the sub-megabit range in the right context," said Martin Dunsmir, general manager for emerging technologies at RealNetworks Inc. "We've progressed a long way in the past six months."
The "right context" when it comes to getting such low-rate, high-quality video to TV sets involves many things. Those include support for efficient media distribution across the backbone networks and tight integration of decoding and other streaming-processing components within the small amount of computer processing capacity resident in set-top boxes, Dunsmir noted.
But, he added, in the case of cable distribution, such as AT&T Broadband & Internet Services' Headend in the Sky operation, the backbone support is already there and the set-top capacity is in the pipeline.
"You might actually see HITS sending MPEG-2 video at 600 kilobits per second," Dunsmir said.
And, he added, similar quality levels could be achieved at these bit rates over broadband-enabled IP (Internet protocol) backbones and distribution systems, such as what Excite@@Home plans to launch in conjunction with technology supplied by RN in December, and what Enron Communications Inc. and its Internet-service provider partners are preparing.
"We're not yet at the end of the rainbow where streaming movies and other media on-demand are transparently available for viewing on TVs and PCs [personal computers], but we're at the first step," Dunsmir said.
Two recent deals coupling RN's client player software with set-top operating systems are part of that first step.
Both WebTV Networks - a unit of Microsoft Corp., which has battled RN over supremacy in multimedia streaming - and Liberate Technologies (formerly Network Computer Inc.) will incorporate RN's "G2" system into their operating systems, making it possible for set-tops to access any G2-based streaming content on the Web.
Set-tops using Liberate's OS - such as the next-generation boxes Philips Consumer Electronics Co. is making for cable, as well as for satellite and DSL (digital subscriber line) applications - will have Web-access capabilities built in.
That stems from work Liberate has done to provide for graphics rendering and transcoding from IP to NTSC (National Television Systems Committee) at the set-top, Liberate vice president of marketing Charlie Tritschler said.
"What we've focused on is squeezing the [processing] footprint to handle basic functions, where what would have taken 12 to 14 megabytes, we can now do in 1.2 megabytes," Tritschler added.
But getting to the footprint required to accommodate the G2 player, even with tight integration into its software stack, requires CPU (central processing unit) power beyond that of the current generation of digital set-tops that Liberate has OS deals to run on. They include General Instrument Corp.'s "DCT-2000," Scientific-Atlanta Inc.'s "Explorer 2000" and Pioneer Digital Technologies' "Voyager."
However, one year from now - when DSL-enabled set-tops, as well as more advanced cable and satellite set-tops, are available at retail - the CPU will be widely available for supporting direct access to Web-streamed multimedia from the TV.
For example, along with agreeing to include RN's "RealAudio G2" format in current WebTV boxes, Microsoft and RN have come to terms on an agreement that calls for developing a new RealPlayer G2 client for the Windows CE platform.
This will affect not only WebTV's move into the digital set-top environment - where a separate computer unit will no longer be required to deliver its services to TVs - but it will also apply to other Windows CE set-top applications.
Efforts to accommodate ever-better multimedia at lower streaming rates will get a powerful boost from the commercialization of MPEG-4, version two of which is expected to be finalized by year's end, according to Eric Petajan, a member of the technical staff at Lucent Technologies who represents the company in the MPEG-4 process.
"I suspect that some developers are already making tool kits that will simplify the use of MPEG-4 so that people can begin working with it to develop applications even before version 2 is finalized," Petajan said.
MPEG-4 is designed to accommodate low-bandwidth environments by separating the sequence-manipulation mechanisms associated with user interaction with content from the content itself.
This way, the graphic components to be used in rendering sequences can be stored in bursts to the end-user terminal, leaving only a small amount of information in the form of instructions as to how graphic components are to be composed and sequenced to be streamed in real time.
"You can scan over and replay content already downloaded to the terminal, allowing the level of resolution in the display to be determined by the capabilities of the CPU, rather than by available bandwidth," Petajan said.
In this fashion, a multimedia game or CD-ROM-type content played over a 28-kbps link can be displayed at graphic-quality levels and frame rates comparable with high-definition television, he added.
While it uses some of the same compression techniques that are applied in MPEG-2 and MPEG-1, MPEG-4 is not technically backward-compatible with those formats.
Instead, it is designed to ride over a tiny bandwidth slice within an MPEG-2 stream, allowing end-user terminals that have the CPU to handle the MPEG-4 processing to take advantage of the interactive multimedia components the new tier brings to MPEG-2.
"In the near term, using MPEG-4 to deliver interactive applications, such as enhanced advertising, within broadcast-TV applications makes a lot of sense," Petajan said. "You can deliver such advertising without breaking up any of the MPEG-2 infrastructure. And those customers who don't have the processing power to access the MPEG-4 component won't know the difference."
MPEG-4 also gives content developers a standardized tool environment for doing things they now have to do by bringing together a lot of disparate elements themselves, such as 3-D rendering and synchronizing various multimedia components with each other no matter which interactive choices the user makes.
The protocol also includes the use of wavelet compression technology and something called "2-D mesh" on top of the underlying discrete cosine transform that is common to MPEG-1 and MPEG-2 to allow developers to easily add zoom-in capabilities with their graphics, Petajan added.
One key to the flexibility of the new standard is the establishment of reference models that become object segments within the graphics space, which can be manipulated piecemeal as if they were being streamed together in real time.
For example, Petajan, in a recent demonstration, showed how the facial reference points he has developed for the MPEG-4 group can be made to move together in a graphic replication of someone speaking in real time. Only the instructions that affect how each reference point is rendered are sent as the person speaks.
Such capabilities have implications for online chat and community interactions, virtual call centers and other e-commerce applications, where a real person's likeness would come to life much as if a real video conference were under way, while using only the bandwidth required to transmit the audio and the instructions.
In other uses of the technology, sports events could be transmitted at low bandwidths, leaving the playing field or court with background crowd as a stored graphic-background template that would change in terms of overall scene orientation on commands delivered in real time. The actual images and action of the sports figures would be streamed in real time.
Another factor contributing to the streaming of high-quality media at low bit rates will be capabilities such as those under development at Imedia Corp., known in cable for the "CherryPicker" technology that gives operators flexibility in combining digital-TV channels from various sources at the headend.
Imedia is working on a means of applying its bit-rate-shaping technology to the IP environment, where stored files would stream at whatever speeds the last-mile connection of the end-user allows at any given moment in time.
"What our technology does well is support transcoding from one bit rate to another," Imedia cofounder and vice president of marketing Adam Tom said. "This will enable Web multicasting of media that adapts to the channel rate available to the end-user."
The capability would reside at the edge of the network, overcoming one of the key barriers to the effective use of multicasting.
Today, everything must be streamed at a set minimum rate that underplays the playback potential of users on higher-bandwidth links, Tom noted. Even using RN's G2, which supports multiple streaming rates, the content developer must choose set rates in advance. This means that even at the high end, the lowest common denominator rules.
"Today, you either multicast at minimum rates, or you don't use multicast at all," Imedia senior vice president for sales and marketing Stephen King said. "We're exploring the development of product with other parties that will go a long way toward overcoming this problem."
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