Letters

6-Gbit/s Uncompressed 4K Video IP Stream Transmission
and OXC Stream Switching Trial Using JGN II
Daisuke Shirai†, Kenji Shimizu, Yasunori Sameshima,and Hirokazu Takahashi
Abstract
A trial of the transmission of an uncompressed 4K video IP (Internet protocol) stream was conductedat the JGN II Symposium in Sendai, Japan, on January 18, 2006. Video images with four times the resolution of HDTV (high-definition television) were used to evaluate the feasibility of next-generation
video production environments and relay services. In this article, we outline the trial and present itsresults.

1. BackgroundIn the field of video transmission, the move toward
high-definition and high-quality video presentation
has been accelerating in recent years as image processing technology has advanced and broadband networks and high-capacity storage devices havebecome mainstream. The term “4K video” refers to avideo image consisting of 4096 × 2160 pixels, which
is about four times the resolution of HDTV (high-definition television). This level of resolution is attracting increased attention, and it has been adopted as thetop standard in the Digital Cinema System Specification [1] of Digital Cinema Initiatives, LLC. NTT
developed the world’s first 4K video transmission
technology using the JPEG 2000 encoding method.
This technology has been well received and wasincorporated into the digital cinema specifications[2]. Application of 4K video is not restricted to digital cinema—it is expected to be used for high-quality
broadcasting services of sports matches, concerts,
and other events and in various fields including
remote education. However, when 4K video is used
for realtime applications such as live broadcasts andvideoconferencing, or for video production, whichrequires extremely high-quality picture, video encod† NTT Network Innovation Laboratories
Yokosuka-shi, 239-0847 Japan
Email: shirai.daisuke@lab.ntt.co.jp

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ing/decoding delays must be minimized. Furthermore
the video must be transmitted “as-is” in uncompressed form. Against this background, we conducted the world’s first trial of uncompressed 4K video
transmission over an actual IP (Internet protocol) network using JGN II*1 at the JGN II Symposium inSendai, Japan, held on January 18, 2006. Our objective here was to evaluate the feasibility of uncompressed 4K video IP stream transmission technology
and of next-generation video services.
2. Overview of the trial
In this trial, we used live video taken by a 4K digital video camera at Keio DMC (the Keio University
Research Institute for Digital Media and Content) in
Mita, Tokyo, and 4K digital cinema material stored
on an uncompressed 4K video server at NTT
Musashino R&D Center. Each source video in
uncompressed form was converted into IP packets
and transmitted to the symposium hall as a 6-Gbit/s
stream over JGN II and presented using a 4K liquidcrystal projector. The system configuration is shownin Fig. 1. The network had a bandwidth of 10 Gbit/s.
*1 JGN II: An ultrahigh-speed, high-performance open testbed network for research and development that began operating under theNational Institute of Information and Communications Technology (NICT) in April 2004 as an enhancement to the original JGN(Japan Gigabit Network) that operated up to March 2004 [3].

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Switches video streams by
GMPLS wavelength path switching
Keio DMC

Sendai International Center

4K IP stream

4K digital
video camera

4K gateway
OXC
Osaka

HD-SDI × 4(audio embedded)

10 GbEswitch

HD monitorTokyo1

Tokyo2

1 GbE × 2
i-Visto gateway

NTT Musashino R&D Center
4K gateway

Uncompressed 4K
video server

4K gateway
4K projector
HD-SDI × 4

4K IPstream

10 GbELR × 2

HD-SDI × 1

10 GbELR × 2JGN IISendai

HD-SDI
loop out

10 GbE
switch
10 GbELR

To hall
PA system

Audio
Audio delayde-embedding adjustment
HD-SDI × 1
i-Vistogateway

HD camera

4K IP stream
10 GbELR × 2

GEMnet

10 GbE
switchGEMnet: global enhanced multifunctional network
10GbE:
10-Gigabit Ethernet
LR:long range
PA system: public address system

Fig. 1. System configuration of the uncompressed 4K video transmission trial.

In this trial, the system switched video streams fromthe two sources by switching wavelength paths*2
using an optical cross connect on the network.
3. IP stream transmission of uncompressed 4K
video using 4K gateway
3.1 Overview of 4K gateway
The IP stream transmission of uncompressed 4K
video in this trial was performed using a newly developed 4K gateway based on the i-Visto gateway [4],[5] developed by NTT (Fig. 2). The i-Visto gateway
is a system that takes HDTV video signals input via
HD-SDI (high-definition serial digital interfaces),transforms them into IP packets in real time, andtransmits IP video streams in uncompressed form(Fig. 3). The 4K gateway has four HD-SDI processing boards and two 10-Gbit Ethernet (10-GbE) interfaces. First, the system divides one frame of 4K video
into four 2K images, inputs that frame as four synchronous HD-SDI signals, and converts each of thosefour signals into an IP-packet stream. The bit rate of*2 Wavelength path: A gigabit-class high-speed optical circuit
deployed between optical cross connects (OXCs) that can guarantee communication quality with a high degree of privacy bymonopolizing a single wavelength.

Vol. 5 No. 1 Jan. 2007

Fig. 2. 4K gateway.

each of these streams is 1.5 Gbit/s. One 10-GbE interface transmits two streams using UDP/IP (UDP: user
datagram protocol). The outputs from two Ethernet
interfaces are then aggregated by one 10-GbE switch
resulting in a stream with a total bit rate of 6 Gbit/s
output to the network.
3.2 4K video stream synchronizing function
At the time of input, the four HD-SDI signals areclock synchronized so that they can be regarded as a79

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4K camera

30 fps Transmitter
4K gateway

Receiver4K gateway
HD-SDI × 43 Gbit/s
or

10 GbE
switchHD-SDI × 4
3 Gbit/s

Uncompressed
4K video server

10 Gb E

10 GbE
switch

6 Gbit/s

4K projector

24 fpsClock adjustment
based on buffer level
Master stream
Receive buffer

Master clock
Signal output

1

Reference clock input
Signal output
2

2

1

3
4
IP stream

HD-SDI processing boards

34
Video signal (HD-SDI)

Fig. 3. Transmission system using 4K gateway.

single video signal. However, during network transmission, there is no means of performing clock level
synchronization between individual streams. Therefore, there is no other choice but to handle them as
separate independent video streams. Consequently,
the four streams must again be clock synchronized on
the receiver side so that a video display device canrecognize them as one video signal. The 4K gateway
on the receiver side converts the received IP stream
into four HD-SDI signals and then creates one mastervideo stream from them. A master video clock isregenerated from the master video stream with an
HD-SDI processing board. Each of the other three
HD-SDI interfaces inputs this master clock as the reference clock, synchronizes with it, and plays back theIP stream, resulting in four synchronized streams ofHD-SDI signals in total that can now be shown as 4K
video.
3.3 Remote clock synchronization of 4K video
In the above discussion, the clock of the video signal on the transmit side and the clock of the video signal on the receive side are independent of each other.
This means that the frequency mismatch of the video
clocks can accumulate if streaming is of long duration, leading to buffer underflows or overflows on thereceive side. This problem is commonly solved byredisplaying or skipping a video frame. In contrast,
the i-Visto gateway monitors changes in the buffer
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level on the receive side to detect the clock mismatchand dynamically changes the clock frequency on thereceive side to perform remote clock synchronization
between the transmitter and receiver. In the 4K gateway, this function is actually applied only to the master stream, but since the other three streams fall in linewith the master stream as described above, remoteclock synchronization is, in effect, applied to allstreams.
4. Video stream switching by OXC
Since the bit rate of an uncompressed 4K video
stream is 6 Gbit/s, only one stream can be transmitted
at one time on a network with a bandwidth of 10Gbit/s. An application is therefore needed that canselect and play back one of several 4K video sources
located at remote points. Such an application can beachieved by either transmit start/stop control directed
at transmit-side 4K gateways handling the video
sources to be switched or by a mechanism thatswitches the stream to be relayed at nodes on thetransmission path.
In this trial, we installed optical cross connects(OXCs) at two locations in Tokyo and one location in
Osaka and interconnected them to form the transmission path denoted as Tokyo1-Osaka-Tokyo2-Sendai
having a total length of 1500 km. We switchedstreams by switching the wavelength path of theNTT Technical Review

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Tokyo1-Osaka segment.
An OXC has a function for changing the directionof a wavelength-multiplexed optical signal in units ofwavelengths [6]. Combining this function with generalized multiprotocol label switching (GMPLS)
enables flexible wavelength-path setting in accordance with user needs while enabling transmissionpath switching without affecting the optical transmission bandwidth.
5. Experimental results
We began the trial by delivering live video taken by
a 4K camera set up at Keio DMC and holding avideoconference with Sendai International Center(Fig. 4). The video from Sendai International Center
was taken by an HD camera and transmitted to Keio
DMC via an i-Visto gateway.
Next, by manipulating the OXC at the Tokyo1 location using RSVP-TE*3 (resource reservation protocolwith traffic engineering) signaling of GMPLS, weswitched the wavelength path of the Tokyo1–Osaka
segment to deliver 4K digital cinema material fromNTT Musashino R&D Center to the hall. The 4K live
video was played back at 30 frames per second (fps)and the 4K digital cinema material was played backat 24 fps.
The 4K-gateway remote clock synchronization
function was used to perform video transmission withno frame dropping. The clock frequency on thereceive side could be changed only within the range
allowed by the HD-SDI standards, so the bufferinglevel at the beginning of transmission was enough toprevent buffer under/overflow. The frequency wasthen changed a little at a time until the amount of datain the buffer converged to a certain level and stable
operation could be observed.
In general, it has not been possible to prevent adelay of the time length of several video-frames overthe entire system due to the effects of internal buffers
in the 4K digital video camera and 4K projector.
However, the delay generated at the 4K gateways andby network transmission is very small (less than oneframe), so we were able to hold a natural conversationin the 4K videoconferencing trial. Visitors to the hallpraised the uncompressed 4K video content as beautiful and expressed admiration for the videoconferencing demonstration.
*3 RSVP-TE: Label-switching technique using MPLS employed for
QoS assurance and high-speed rerouting. It enables flexible pathsetting by conveying dynamic path information.

Vol. 5 No. 1 Jan. 2007

Fig. 4. Example of 4K videoconferencing(Sendai International Center).

6. Future developments
We intend to improve the performance and operability of GMPLS and OXCs to establish streamswitching technology on layer 3 and a 4K video editing scheme between remote points. We also intend tocreate ultrahigh-speed network services toward nextgeneration video-content production featuring theseamless editing and use of super-high-definition
video material located at multiple production points
and broadcast stations.
Part of this trial was conducted in conjunction withthe “Research and Development of Next-generation
Video Content Production and Distribution Technologies” program of the Ministry of Internal Affairs
and Communications (MIC) in cooperation with theDigital Cinema Technology Forum.
References
[1]
[2]

[3]
[4]

[5]

[6]

http://www.dcimovies.com/DCI_Digital_Cinema_System_Spec_v1.pdf
K. Shirakawa, M. Nomura, K. Ishimaru, T. Yamaguchi, and T. Fujii,“NTT Technology Supporting Digital Cinema,” NTT TechnicalReview, Vol. 4, No. 7, pp. 23-28, 2006.
http://www.jgn.nict.go.jp/e/index.html
K. Shimizu, K. Harada, A. Minami, and T. Okimoto, “Joint Experiment on Multipoint Synchronous Transmission of Uncompressed
HDTV Video by i-Visto,” NTT Technical Journal, Vol. 17, No. 3, pp.
85-88, 2005 (in Japanese).
T. Mochida, T. Kawano, T. Ogura, and K. Harada, “The i-visto Gateway XG Uncompressed HDTV Multiple Transmission Technology
for 10-Gbit/s Network,” NTT Technical Review, Vol. 3, No. 4, pp.
38-43, 2005.
Y. Sameshima, T. Ohara, and Y. Okano, “Nation-wide GMPLS/OXC
networking experiments over JGN II test bed,” Optics East, 6388-01,
SPIE, Oct. 2006.

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Daisuke Shirai

Yasunori Sameshima

Media Networking Laboratory, NTT Network
Innovation Laboratories.
He received the B.E. degree in electrical engineering and the M.E. degree in computer sciencefrom Keio University, Tokyo, in 1999 and 2001,
respectively. He joined NTT Network Innovation Laboratories in 2001. Since then, he has
been researching super-high-definition imaging
systems and their transmission technology. His
current interests are in terabit-level image transmission and robust image transmission.

Photonic Transport Network Laboratory, NTT
Network Innovation Laboratories.
He received the B.E. degree in mathematics
from Keio University, Tokyo, in 1988. He joined
NTT in 1988. Until 1999, he was engaged in
R&D of design for LSI testing. He was involvedin establishing the global IP-VPN service in NTT
Communications during 2000-2003. Since 2004,
he has been studying optical transport networking technologies, such as GMPLS. He has also
been working as a research fellow of NICTTsukuba Research Center since 2004.

Kenji Shimizu

Hirokazu Takahashi

Media Networking Laboratory, NTT Network
Innovation Laboratories.
He received the B.E. and M.E. degrees in electronics engineering from Sophia University,
Tokyo, in 1998 and 2000, respectively. He joined
NTT Network Innovation Laboratories in 2000.
He is currently studying processing system architectures and Internet systems. His research interests include high-speed protocol processing, traffic monitoring, and content delivery networktechnologies.

Media Networking Laboratory, NTT Network
Innovation Laboratories.
He received the B.E. and M.E. degrees in electrical engineering from Nagaoka University ofTechnology, Niigata, in 2000 and 2002, respectively. Since joining NTT Network Innovation
Laboratories in 2002, he has been researching
multicasting technologies for realtime applications. His current interests include reliable multicasting techniques.

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