Recommendation H.261
(03/93)
1
Recommendation H.261
Recommendation H.261
(03/93)
VIDEO CODEC FOR AUDIOVISUAL SERVICES AT p X 64 kbit/s
(Geneva, 1990; revised at Helsinki, 1993)
The CCITT,
considering
(a)
that there is significant customer demand for videophone, videoconference and other audiovisual services;
(b)
that circuits to meet this demand can be provided by digital transmission using the B, H0 rates or their multiples up
to the primary rate or H11/H12 rates;
(c)
that ISDNs are likely to be available in some countries that provide a switched transmission service at the B, H0 or
H11/H12 rate;
(d)
that the existence of different digital hierarchies and different television standards in different parts of the world
complicates the problems of specifying coding and transmission standards for international connections;
(e)
that a number of audiovisual services are likely to appear using basic and primary rate ISDN accesses and that some
means of intercommunication among these terminals should be possible;
(f)
that the video codec provides an essential element of the infrastructure for audiovisual services which allows such
intercommunication in the framework of Recommendation H.200;
(g)
that Recommendation H.120 for videoconferencing using primary digital group transmission was the first in an
evolving series of Recommendations,
appreciating
that advances have been made in research and development of video coding and bit rate reduction techniques which lead to
the use of lower bit rates down to 64 kbit/s so that this may be considered as the second in the evolving series of
Recommendations,
and noting
that it is the basic objective of the CCITT to recommend unique solutions for international connections,
recommends
that in addition to those codecs complying to Recommendation H.120, codecs having signal processing and transmission
coding characteristics described below should be used for international audiovisual services.
NOTES
1
Codecs of this type are also suitable for some television services where full broadcast quality is not required.
2
Equipment for transcoding from and to codecs according to Recommendation H.120 is under study.
1
Scope
This Recommendation describes the video coding and decoding methods for the moving picture component of audiovisual
services at the rates of p
× 64 kbit/s, where p is in the range 1 to 30.
2
Brief specification
An outline block diagram of the codec is given in Figure 1.
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