@We have progressed
with our research on Hybridcast®,
which makes possible new services that meet the needs of viewers
by combining broadcasting and communications.
‘ Hybridcast platform
@Hybridcast makes broadcasting more advanced, flexible and
extensible by taking advantage of the complementary characteristics
of broadcasting and communications. The NHK three-year administrative
plan beginning in FY2012 sets a priority target of developing
new services suited to the era of integrated broadcasting
and communications (Figure 1). In line with this plan, we
aim to make Hybridcast a reality within two years.
Figure 1. Hybridcast overview
@At the STRL Open House, we introduced prototype television
and set-top-box (STB) receivers developed by television manufacturers
and a STB with highly accurate synchronization technology
to present multi-view or stereo 3D television. Various services
for prototype mobile devices that communicate with TVs were
also introduced. These efforts demonstrated that it will be
possible to provide such Hybridcast services very soon (Figure
2). We also exhibited a screen display control technology
that can reliably give priority to emergency information from
broadcasts such as earthquake early warnings.
Figure 2. Hybridcast prototype receivers exhibited
at the STRL Open House
@We widely promoted the possibilities of these services, domestically
and internationally by exhibiting Hybridcast and making presentations
at CEATEC2011, IMC2011, IBC2011, and others. In particular,
our Hybridcast presentation won the Best Paper Award at NAB2011(1).
@We continued work on prototype test receivers in cooperation
with television manufacturers toward the early launch of Hybridcast.
@We published technical descriptions summarizing the overall
architecture, service models, and technical requirements of
Hybridcast at the time of the Open House. After that, we continued
to study the detailed specifications. Since these specifications
are for a browser-based system, NHK is participating in W3C,
which is a community standardizing web-related technologies
including HTML5. In particular, NHK proposed a set of requirements
for services combining broadcasting with communications which
should be satisfied by a browser in a TV and HTML5 language.
We are also participating in the HTML5 working group at the
IPTV Forum, which is developing technical specifications for
combining broadcasting and communications in Japan.
@In the future, we will complete these specifications by testing
prototype receivers equipped with HTML5 browsers developed
by television manufacturers and conduct field trials using
these receivers. Part of this research was conducted in cooperation
with Sony Corporation and NTT Corporation.
‘ Security for receivers combining
broadcasting and communications functions
@We are researching and developing security technology for
Hybridcast, to provide services that link broadcasting and
communications safely and securely. In FY2011, we developed
control schemes for presenting communications applications
on television screens and for accessing broadcast resources
and receiver functions.
@Hybridcast enables new services that cannot be realized with
broadcasting alone and that are to be implemented through
use of communications applications; a problem is that there
is a possibility that important information about the broadcast
content could be obscured by these applications. Thus, it
is important to have a mechanism that ensures that priority
information is conveyed while also considering the needs of
viewers. Accordingly, we developed a screen display control
scheme(2) for when broadcast content and communication
applications are combined on the screen. It sends a presentation
policy reflecting the broadcaster's intentions to the receiver
so that important information such as Earthquake Early Warnings
can be given higher display priority (Figure 3). Tests of
Hybridcast prototype receivers confirmed that this scheme
is effective and that receivers so equipped can quickly and
appropriately control the display of applications according
to the broadcast information such as Earthquake Early Warnings.
@Hybridcast assumes that receivers will provide a specialized
application programming interface (API) that will allow communications
applications to use receiver functions and broadcast resources.
The API will allow applications to easily reference and control
receiver functions and broadcast resources such as channel
tuning, program specific information and service information
(PSI/SI). However, allowing all communications applications
to use these APIs unconditionally presents security risks,
so we have developed a scheme for API access control to be
used in Hybridcast receivers, to protect viewer information
and broadcast content according to application authentication
and the viewerfs intentions.
Figure 3. Screen presentation control
‘ Multiplexing schemes for
@Hybridcast realizes varied and versatile services by combining
video, audio, and data components on various delivery channels,
such as broadcast and communication networks. Components can
be reliably delivered with a fixed delay on broadcast channels,
but there is a delay variation on communication networks and
a portion of components sent may be lost. This means the multiplexing
technology must reliably transport these components on the
various delivery channels with the appropriate timing.
@To achieve this, we are developing an advanced multiplexing
scheme based on MPEG-2 Transport Stream (TS), which combines
components on the current digital broadcast system with components
on Internet Protocol (IP) based communication networks. We
are also developing an IP-based multiplexing scheme for when
broadcasting and communications become based on IP in the
@With the MPEG-2 TS based multiplexing scheme, both components
from broadcast channel and communication networks are synchronized
with the system-clock delivered on the broadcast channel.
However, when a broadcast station (Station B in Figure 4)
receiving a TV program from the original broadcast station
(Station A in Figure 4) and retransmits it, the system-clocks
on the both stations are not the same. In this case, because
of the difference in the system clocks, a receiver receiving
the components from Station B cannot synchronize components
in the same way as a receiver receiving the components from
Station A does. To deal with this problem, we developed a
system that calculates and corrects the difference between
the system clocks. Our system enables every receiver to synchronize
any set of components.
Figure 4. Synchronization using time adjustment data
@In the future, when broadcasting and communications are based
on IP, much more flexible and integrated services will be
possible. However, in the case of IP, neither transmission
delay nor delivery quality is fixed, so reliability cannot
be maintained by simply transmitting MPEG-2 TS in IP packets.
Because of this, MPEG-2 TS has been extended many times in
various ways. As a result of the extensions, MPEG-2 TS has
become too complicated.
@Recognizing the necessity of an IP-friendly media transport
mechanism, we have developed the Advanced Transport Scheme
(ATS), which is an IP-based multiplexing scheme on heterogeneous
networks(3). We proposed it to MPEG as a candidate
technology for the next-generation MPEG Media Transport (MMT)
and are actively promoting standardization of the scheme.
MMT will be a system technology that will enable media transport
over heterogeneous networks and will be a system part of the
new MPEG multimedia standard, MPEG-H.
‘ Future directions
@Going forward, we will contribute to standardization of technologies
that integrate broadcasting and communications in Japan, based
on specifications proposed by NHK and through discussions
with other broadcasters and manufacturers. We will work toward
early field trials at events such as the London Olympics.
@We will also pursue standardization of our new multiplexing
scheme, using IP for both broadcasting and communications,
Hybridcast® and its logotype
are registered trademarks of the NHK Engineering Service Inc.
(1) A. Baba, K. Matsumura, S. Mitsuya, M. Takechi, Y. Kanatsugu,
H. Hamada and H. Katoh: gAdvanced Hybrid Broadcast and Broadband
System for Enhanced Broadcasting Services,h NAB Broadcast
Engineering Conference, pp. 343-350 (2011)
(2) K. Otsuki, H. Ohmata, A. Fujii, K. Majima and T. Inoue:
gA Presentation Control Method of Applications in Hybridcast,h
ITE Annual Convention, 11-11 (2011) (in Japanese)
(3) S. Aoki, K. Aoki, H. Hamada, Y. Kanatsugu, M. Yamamoto
and K. Aizawa: gA New Transport Scheme for Hybrid Delivery
of Content over Broadcast and Broadband,h IEEE International
Symposium on Broadband Multimedia Systems and Broadcasting,