INTERNATIONAL
ORGANISATION FOR STANDARDISATION
ORGANISATION INTERNATIONALE DE NORMALISATION
ISO/IEC JTC1/SC29/WG11
CODING OF MOVING PICTURES AND ASSOCIATED AUDIO
ISO/IEC
JTC1/SC29/WG11 N0707
MPEG
94/
25 March 1994
|
Source:
|
Leonardo Chiariglione - Convenor |
|
Title:
|
Press Release |
| Status: | Approved at 26th meeting |
Press
Release
Summary
The
26th meeting of ISO/IEC JTC1/SC29/WG11 (MPEG) was held in Paris this week,
hosted by AFNOR, the French National Body of ISO at Conservatoire National des
Arts et M�tiers and has produced a set of results that represents an important
contribution to the establishment of interoperable digital audio-visual services
and applications on a world-wide scale.
The
results include the promotion of part 4 of ISO/IEC 11172-4 (MPEG-1 Conformance
Testing) to the status of DIS (Draft International Standard), the promotion of
ISO/IEC 11172-5 (Software for MPEG-1 coding) to CD (Committee Draft) status, the
promotion of ISO/IEC 13818-2 (MPEG-2 Video) and ISO/IEC 13818-3 (MPEG-2 Audio)
to DIS status, the official start of the so-called DSM-CC (Digital Storage Media
Command and Control) extension for wider functionalities compared to those
existing in ISO/IEC CD 13818-1 (MPEG-2 Systems), start of the 10-bit extension
of MPEG-2 Video, official start of the so-called Audio NBC (non backwards
compatible mode), assessment of the first MPEG-2 Video quality verification
tests and preparation of the second round of video quality verification tests.
Finally the activity carried out to date on the New Work Item on Very Low
Bitrate Audio-Visual Coding (so-called MPEG-4) has led to the production of a
first draft of the Requirements document that will be at the basis of the
technical development of the new standard.
The
promotion of MPEG-2 Systems to DIS status will occur at the next MPEG meeting
planned to be held on 8 to 10 June. MPEG can then confirm that all 3 parts of
MPEG-2 will reach IS (International Standard) status at its 29th meeting in
Singapore on 7 to 11 November 1994.
ISO/IEC
11172 (a.k.a.MPEG-1)
MPEG-1
is a three-part standard (Systems, Video and Audio) that was published in August
1993. A number of products
available today in the market make use of this standard.
A fourth part of the standard, on conformance testing, was raised to DIS
status at the Paris meeting. The
purpose of the conformance testing part is the specification of methodologies
for testing bitstreams and decoders for conformance with parts 1, 2 and 3. The
attainment of DIS status at the Paris meeting reassures the users that the
methodologies identified by ISO/IEC DIS 11172-4 can be used with high
reliability.
The
full software implementation of the three parts of MPEG-1 contained in part 5 of
MPEG-1 is an aid to implementors and novices providing an example encoder and
decoder for Systems, Video, and Audio. This software has also a wide domain of
applicability thanks to the ever increasing processing capability of computers
that promise to make possible software implementation of the standard under
certain conditions.
MPEG-2
The
promotion of MPEG-2 to DIS for its Video and Audio part (Systems will follow in
about 2 months) is a very important signal for a variety of technical and
business communities which are poised to
introduce this technology for a variety of applications and services.
The
completion of the work related to the video part of the standard, developed
jointly with ITU-T, has prompted the execution of a campaign of subjective tests
of the Main Profile, thought to be the one to be used in largest scale, at the
resolution of today's television. This work has been carried out in
collaboration with EBU, ITU-R and SMPTE. A variety of test materials have been
selected and used as input to a large number of software encoders with different
degrees of optimisation. The pictures produced were subjectively assessed by
over 250 observers from 3 continents.
The
results proved that MPEG-2 video has the capability to comply with the
identified requirements, up to the highest quality if an adequate bit rate is
selected. For all test material 9 Mbit/s coding provides near transparent
quality while at 6 Mbit/s the achieved quality for all test material equals or
exceeds those of conventional TV systems. At lower bit rates, such as 4 Mbit/s
high quality pictures will be obtained on most picture material.
Association with professional contribution links raises no significant problems.
A
similar set of subjective tests were carried out to validate the current
performance of the MPEG-2 multichannel audio coding standard, which is
backwards-compatible with the two-channel MPEG-1 Audio coding standard. Two
additional non backwards compatible codecs from AT&T and Dolby were also
added to provide evidence on the need to develop an unconstrained multichannel
audio coding standard.
The
tests were carried out at Telekom and BBC during the period January to March
1994 to evaluate the audio quality on a representative range of test material.
The loudspeaker arrangement, the listening conditions and the methodology were
those recommended by the ITU-R, viz. three frontal loudspeakers and two surround
loudspeakers all of the same high quality. The subjective test listeners were
all experienced listeners, from professional audio production facilities and/or
with prior experience of critical audition tests.
More than 20 listeners took part at each test site but only one listener
at a time took part in the tests and had personal control over which stimulus he/she
auditioned at any instance.
The
programme material was selected from 64 items provided
internationally for these tests. These were pre-auditioned by a selection
panel after coding and decoding to supply the necessary ten critical test items
used for the tests.
At
the low bitrates (320 and 384 kbit/s) selected for the tests (operation at 384
kbit/s means a compression ratio of 10) the average performance of most codecs
was satisfactory, but all codecs showed deviations from transparency for some of
the items.
One
conclusion drawn from the tests was that, at the current state of encoder
optimisation, some applications making use of the MPEG-2 Multichannel Audio
coding standard may need to use a higher bitrate than used for the tests in
order to reach the desired quality level. Encoder optimisation, at present in a
rather immature stage, is expected subsequently to permit reduction of these
bitrates with comparable quality.
MPEG-2
extensions
Work on a number of features was started at the meeting that will complement ththose on the current draft standard. The first is the Digital Storage Media Command and Control (DSM-CC), a protocol intended to provide support to interaction between set-top terminals and video servers, interaction with business video databases, CD-based MPEG video games, and a number of others. A comprehensive set of technical requirements aimed at providing a highly functional and interoperable environment for storage and network based MPEG applications were produced and an aggressive work schedule is being pursued designed to bring the work to Working Draft level by the end of 1994 and IS status in July 1996. A general call for contributions requesting technical proposals to satisfy portions or all of the group�s requirements was issued. These contributions will be assessed and merged during the July MPEG meeting in Grimstad, Norway.
The
second extension kicked-off in Paris is the support of 10-bit video coding, a
higher input video sample precision required by some applications. The procedure
to request the formal activation of this extension was initiated in Paris.
Non
backwards compatible audio is the third extension decided in Paris. The results
of the audio validation tests confirmed that backwards compatibility, an
important feature in the progressive introduction of digital audio-visual
services, does carry some performance penalty. Thus it was agreed that MPEG-2
will have an NBC extension. A call for proposals was issued. Submissions will be
considered at the November 1994 meeting with a workplan leading to IS status in
March 1997.
MPEG-4
MPEG-4
is the work item formally approved in July 1993 which is attracting a
considerable number of new members in the group . The standard will find
applications in cases of very low bitrate transmission channels or reduced
storage capacity. The relevant applications and operational environments are
studied by a special subgroup within MPEG.
