MPEG-4 is spilt in two. SGS is now the Chair...........................
techweb.com
September 22, 1997, Issue: 972
Section: News
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MPEG-4 to split into basic, advanced versions
By Peter Clarke
Bristol, England - MPEG-4, the multimedia specification being built atop MPEG-2 to allow the transmission of multiple video, audio and graphics data streams for composition at the receiver, is to be split in two.
Advanced functions that cannot be settled and tested adequately within the Moving Picture Experts Group's existing timetable will go into a second spin of MPEG-4, a committee hammering out the spec decided at a meeting recently in Stockholm. That follow-on version will be finalized in November 1999, a year after the more basic, first version.
The new timetable calls for freezing version 1 as a "Committee Draft" in October or November, with a further year for standardization under the auspices of the International Standards Organization (ISO). MPEG-4 version 2, a superset of version 1, is then set to become a standard a year later.
"The reason [for the split] is to do with expediency," said Paul Fellows, chairman of the implementation subgroup within MPEG and external projects manager at SGS-Thomson Microelectronics Ltd. here. "We wanted to take the technology that was mature enough and get it standardized. But there were some longer-term goals which could not be included." They mainly involve three-dimensional graphics and sound, he said.
An engineer working in a collaborative European MPEG-4 project called Momusys said, "Some companies were pushing hard for certain features to be included in version 1 because they want to begin broadcasts. For example, they wanted support for interlaced images," said Sylvie Jeannin, an engineer at the DSP group at a Philips research laboratory in Limeil, France.
"MPEG standards must come out on time," she said. "The MPEG-4 convenor wants to deliver something on time. So that's one reason for the split."
To help companies progress with prototyping and writing software, version 2 will be backward-compatible with version 1. Thus, material coded for version 1 decoders could be played on version 2 decoders.
Though MPEG-4 bit streams are intended to be shown on conventional terminals with 2-D screens, the bit streams will include 3-D information so that alternative views can constructed at the receiver terminal.
The second version of MPEG-4 will add scalable transmission of objects with arbitrary shape, support for semitransparent video objects and tools for additional efficiency improvements. In contrast, version 1 will support transmission of regularly shaped objects. Also, an object's presence in a scene is binary-either opaque or completely transparent (invisible)
'3-D' audio
Version 2 will have extensions for synthetic, or "3-D," audio that adds spatial information to make it sound as if audio sources come from an identifiable location. It will also take into account the acoustic properties of different materials and the spatial manipulation of audio sources. Thus, sound that appears to move through a three-dimensional space will also be altered depending on whether it issues from outdoors, a church hall, a small office and so on.
"With the ability to send multiple objects and sound samples, when you put them together it would be attractive to place these objects in 3-D space," said Fellows, who also heads a European collaborative project called Emphasis that is working in this area.
The committee has developed a reference model for an MPEG-4 systems decoder that models timing and buffering aspects. Nevertheless, building systems presents many challenges, not least in determining the best kind of hardware support.
"With MPEG-2 you know the processor load," Fellows said. "With MPEG-4 you don't know what size or shape or how many objects there are. The computational load will be very much more variable. It might be less than MPEG-2 or it might be much more.
"My personal feeling is that some systems will be software only, running on a high-end general-purpose processor, and these will provide an application constrained within that level of performance. Others will achieve higher performance with hardware acceleration."
SGS-Thomson is developing Chameleon, a 64-bit microprocessor, specifically to support MPEG-4 multimedia applications.
At the Stockholm meeting, MPEG got seven responses to its call for proposals for the identification and protection of content in MPEG-4. Together with the respondents MPEG is working on including methods for identifying owners and rights holders of MPEG-4 encoded content, considered crucial to marketplace success.
The next MPEG-4 meeting is scheduled for October in Fribourg, Switzerland, where version 1 is expected to be completed and frozen before standardization by ISO.
Copyright (c) 1997 CMP Media Inc. |
