ISO-IEC/JTC1/SC29/WG11N1617
MPEG 97
April 1997 / Bristol
| Source: | Convenor of mpeg (iso/iec jtc1/sc29/wg11) |
| Status: | Approved by WG11 |
| Subject: | Press Release |
| Date: | 21 April 1997 |
Highlights
The Moving Pictures Experts Groups (MPEG) met for the 39th time, in Bristol, UK, from 17-21 April 1997. While the work on the object-based standard MPEG-4 got most of the attention, the promotion of the excellently performing MPEG-2 AAC to 'International Standard' was a major milestone for MPEG-2, and the work on the recently initiated multimedia description standard MPEG-7 is rapidly gaining momentum.
MPEG-2
At this meeting, part 7 of the MPEG-2 Standard, the specification of Advanced Audio Coding, was promoted to International Standard. AAC provides broadcast quality signals at 320 kbits/s for a five channel surround sound service. It provides better audio quality at 320kb/s than any other codec tested worldwide under the same conditions, even when the other codecs are working at twice the bitrate.
MPEG-4
The Committee Draft status of MPEG-4 is nearing quickly, and this means that difficult decisions between competing technologies for inclusion in the standard had to be made. Also, it became clear that MPEG-4 will have extensions that widen its scope of functionality in the area of programmability, higher bitrates video coding (possibly up to lossless for archiving purposes), and the coding of synthetic, computer-generated objects and scenes. In July, two new proposals for Video Coding will be formally tested using Subjective Evaluation procedures. The core experiments on audio scalable coding give better results than had been anticipated. Their performance means that the scalable codecs will provide a more economical service than the equivalent using simulcast techniques.
MPEG issued a Call for Proposals for technology for the management of Copyright, or more precisely 'Content-related Intellectual Property Rights', in MPEG-4.
MPEG-7
A special open MPEG-7 Seminar, with invited speakers - experts from scientific areas relevant to MPEG-7 - was well visited, giving better insights in the demands and requirements for the new standard. Topics covered were data navigation, image searching, multimedia indexing, video mail retrieval, data mining, browsing of video, and audio analysis.
MPEG-7 will define a standardized description of multimedia content, so that it can be searched for around the world. Applications are for example the WWW, and selection of an interesting TV program out of the many that users will be offered in the future.
Details
The remainder of this document gives information organized according to the different subgroups. It expands on the highlights mentioned above.
MPEG-2
AAC, or MPEG-2 Advanced Audio Coding, is a state of the art perceptual audio coding algorithm, bitstream definition, and decoder specification that provides very high quality multichannel audio at 64kb/s/channel, as shown in extensive formal tests on 5-channel audio material. It allows for 1-48 audio channels, 0 to 16 low frequency effects channels, 0 to 16 internal data streams, and multiprogramme/ multilingual/voice-over audio programmes, all in one audio stream providing sample-locked synchrony.
AAC has three profiles, called "Main", "Low Complexity", and " Scalable Sampling Rate". The Main profile is targeted for applications where memory and processing considerations are not highly constrained. The Low Complexity profile is targeted for use where both processing and memory are at a premium. The SSR profile is arranged so that decoders providing different output sampling rates can be built, with corresponding reduction in both memory and processing according to the output sampling rate.
AAC has been extensively tested in subjective tests with critical, well-trained listeners and has been shown, for a signal consisting of 5 audio channels, to provide better audio quality for both the Main and LC profiles at 320kb/s than any other codec tested worldwide under the same conditions, even when the other codecs are working at twice the bitrate.
AAC is configured for sampling rates from 8kHz up to 96kHz, and for bitrates from less than 16 kb/s/channel to more than 192kb/s/channel. A 5-channel main profile, 48 kHz sampling rate, 320 kbit/s, software decoder running on a 133MHz Pentium PC in real time has been demonstrated. Additionally, a 2 channel low complexity profile decoder requiring 5-6% of CPU usage for real time decoding on an SGI-O2 platform, or less than 20% of a P133 PC, at a sampling rate of 48kHz, has been demonstrated.
The MPEG-2 AAC standard will be part of the upcoming MPEG-4 standard.
Next to the promotion of AAC to IS, there is still another MPEG-2 activity: the 'First Working Draft' of part 10 of the MPEG-2 standard, DSM-CC Conformance Testing (ISO/IEC 13818-10) was approved.
Requirements
MPEG's Requirements Group is trying to find a way of dealing with 'Profiles' in MPEG-4. As many more degrees of freedom exist than in MPEG-2, it is much more difficult to specify the necessary performance of the decoder. Still broadcasters, a major class of users of the MPEG-4 standard, have expressed a wish that such performance guarantees be made, similar to what was specified in MPEG-2. In the existing situation, most broadcasters use MPEG-2's Main Profile at Main Level, which specifies the syntax of the bitstream but also gives bounds on the performance level needed at the decoder.
An activity was started to collect requirements for MPEG-4 applications on the DVD. MPEG wants to investigate whether the current draft of the standard provides all the tools for this potentially important application area.
Experts from the content production and management world were present to define requirements and solutions for dealing with 'Content-related Intellectual Property Rights' in MPEG4. (It is called 'content-related' to distinguish it from algorithm-related IPR). MPEG believes that providing the mechanisms to deal with these rights are crucial to the success of MPEG-4. Therefore a Call for Proposals was issued, asking for technology that allows identifying, protecting and trading of MPEG-4 encoded content.
Video
The MPEG-4 video group made a large progress in the convergence towards a Committee Draft to be released in October 1997. The Committee Draft is the first of three versions of the final standard on which there is a ballot, and forms a first fairly stable version.. Beside of this convergence work, the video group made first plans for extensions of MPEG-4, that will be standardized after the first phase of MPEG-4.
Tools for the coding of interlaced video objects have been adopted in the MPEG-4 video standard. The goal is to allow coding of arbitrarily shaped objects at high resolution and recorded with line interlace, still the most common format of video nowadays.
The resilience against transmission errors has been enhanced by means of markers of groups of video object planes, comparable to the Group-Of-Pictures (GOP's) of MPEG-1 and MPEG-2.
For the compression of the contours of arbitrarily shaped video objects, a completely new algorithm has been adopted. The new algorithm is based on arithmetic coding. Remarkable is the fact that in this decision, which was a very close call between several proposals, having the lowest implementation complexity played an important role. Following the principle of having as few different tools as possible in the standard, this has been one of the points were difficult decisions were necessary. Some people that had worked for more than a year on improving their technology had to be disappointed, and this is a hard, yet well-accepted part of the work in MPEG.
Also an algorithmic tool for the compression of video with a precision of 12 bit in every picture element has been adopted. This is useful in applications that use another part of the light spectrum than the visual part, e.g., for infra-red video, for which the material to be coded has a larger dynamic range.
In order to improve the quality at a very low bit-rates, MPEG-4 now has specified a new deblocking filter that reduces artifacts usually visible at high compression ratios.
The most important outputs of the MPEG-4 video group are version 7.0 of the Verification Model, (the reference encoder for the tests) and version 3.0 of the Working Draft: a preliminary version of the final standard.
The video group foresees for an extension of the MPEG-4, which will be standardised after 1998, the specification of the coding of stereoscopic video material, the coding of shape for MPEG-7 applications, possibly lossless compression for archiving, and fine granularity scalability.
Systems
The current Systems workplan gives priority to the specification of 2D scene description, multiplex, buffer management, synchronization and IPR identification. These are the features targeted for the October Committee Draft (CD). Specifications for 3-dimensional scene description are currently well documented and also this issue may be standardized in the first phase of MPEG-4, but only if sufficient software is made available. MPEG believes that software should be available for the standard if it is to be used by industry.
A few issues are currently planned for extensions to the MPEG-4 standard; the most important of them are definition of API's as interfaces to MPEG-4 tools and description of behavior of audiovisual objects.
Two software projects (one in Java, managed by Intel, one in C++, managed by VDOnet) were launched. They will develop and demonstrate a simple integrated Systems Layer, featuring 2D scene composition, synchronization and multiplex - all with real-time performance. The first results are due in July.
The Bristol meeting yielded an integrated picture of the MPEG-4 architecture, in which the different blocks found their place. The Systems multiplex now has a defined interface to the DMIF architecture, the various elements related to composition developed in the Audio, SNHC and Video groups have been identified, and most of them have been integrated in the BIFS format. 'BIFS' means Binary Format for Scene description: the MPEG-4 Systems format to describe audiovisual scene.
MPEG-7
Next to the successful MPEG-7 Seminar, there was another
milestone for the MPEG-7 work: a first draft of an MPEG-7
Requirements Document was issued. This document is at the moment
still for internal use, but a public document, called MPEG-7
Context and Objectives is also available. It can be obtained,
like other public MPEG documents, through the MPEG homepage.
Background information
Future MPEG meetings will be held in Stockholm, SE (July '97), Fribourg, CH (October '97), Tokyo, JP (March '98), Dublin, IE (July '98), Israel (Nov. '98) and Korea (Mar. '99).
For further information about MPEG, please contact:
Dr. Leonardo Chiariglione, (Convenor of MPEG)
CSELT
Via G. Reiss Romoli, 274
10148 Torino, ITALY
Tel.: +39 11 228 6120; Fax: +39 11 228 6299
Email: leonardo.chiariglione@cselt.it
or refer to the MPEG homepage:
http://www.cselt.it/MPEG
The MPEG homepage has links to other MPEG pages, that are maintained by some of the subgroups. It also contains links to the public documents, that also non-MPEG members can freely download.