1. 網路視訊會議系統的設計與經驗
莊 志 洋
民友科技股份有限公司

2. Agenda H.323 and related protocols Ready for right products
Design Considerations
Experiences and Suggestions

3. What is H.323? A multimedia communication protocol suite
Includes voice, video, and data conferencing
For use over packet-switched networks
* H.323 is “ITU-T Recommendation H.323: Packet-based multimedia communications systems”

4. Elements of an H.323 System Terminals Multipoint Control Units (MCUs)
Gateways
Gatekeeper
Border Elements

5. H.323 Network Elements PSN CSN H.323 Terminal H.323 MCU
H.323 Gatekeeper
H.323 Gateway
H.323 Terminal
H.323 Terminal
PSN
CSN
GSTN
GQOS LAN
N-ISDN
B-ISDN
V.70 Terminal
H.324 Terminal
Speech Terminal
H.322 Terminal
H.320 Terminal
H.321 Terminal

6. Terminals
                                                              

7. MCUs For managing multipoint conferences Contains
Multipoint Controller (MC) - manages the call signaling
Multipoint Processors (MPs) - handle media mixing, switching, or other media processing

8. Gateways Interface H.323 to other networks, Composed of MGC handles
including the PSTN, H.320 systems, other H.323 networks (proxy), etc.
Composed of
a “Media Gateway Controller” (MGC)
a “Media Gateway” (MG)
MGC handles
call signaling , non-media-related functions
MG handles the media

9. Gatekeeper Admission control Address resolution
e.g.,Phone number to IP address

10. Border Elements
Exchange addressing information and participate in call authorization between administrative domains
Often co-located with a Gatekeeper,

11. Packet-switched Network
An H.323 Stack
H.323 Application
RAS
H.245
RTP /
RTCP
H.225.0
Call Signaling
Packet-switched Network

12. H.323 basic protocols Gatekeeper Annex G Gatekeeper Q.931/H.245 RAS
Signalling (Q.931)
Endpoint
Endpoint
H.245
RTP/RTCP
Gatekeeper Routed Signaling
Direct Routed Signaling
Source: Lior Moscovici

13. H.323 related standards RTP/RTCP : Streaming T.120 - Data conferencing
Audio Codecs: G.711, G.722, G.723.1, G.728, G.729, GSM
Video Codecs: H.261, H.263, H.264

14. Past to Present Or was it? H.323 v.1 was published in 1996
was designed for LANs
Or was it?
Version 1 (1996) was designed with the Local Area Network in mind. H.323 has its roots in the video conferencing area, borrowing much of the multimedia conferencing aspects from other H.32x-series Recommendations, such as H H.323 was intended to allow people on a LAN to conduct an audio, video, and data conference (with the help of T.120). Or was it?
Local Area Network

15. Past to Present
But, it was used in WANs, large private VoIP networks, and the Internet
It worked very well
Early comers to the H.323 market, such as VocalTec, recognized H.323’s potential for Internet Telephony.

16. Past to Present H.323 proved that
RTP is able to carry real-time audio and video over IP networks that span the globe
Indeed, H.323 was much more than a LAN protocol
RTP, as probably everyone in the IP Telephony space knows, is the same media transport protocol used by both H.323 and SIP devices. The early designers of H.323 recognized the potential of embracing, not only the packet network, but also the IETF protocols have helped make the Internet what is is today. For this and other reasons, H.323 is well-suited for multimedia conferencing over IP networks, including the Internet.

17. Past To Present
Recognizing the fact that H.323 was much more than a LAN protocol, the name was changed in H.323 Version 2 (1998)
Enhancements were made, including:
Security
Performance
Supplementary Services
Scalability
The name of H.323 was changed to “Packet-based multimedia communications systems”.

18. Strength in Numbers Partial Listing Accord Networks Aethra
AG Communications
Agilent
Anatel
Aspect
Atlantic
Avaya
Axent
Brooktrout Technology
CUseeMe
Callserve
Catapult
CheckPoint
China Netcom
China Telecom
China Unicom
Cirilium
Cisco Systems
Clarent
Comverse
Data Connection
Delta Information Systems
Dialogic
Dialpad
E-Tech Canada Ltd.
Elemedia
Equivalence
e-tel
eZenia!
FVC
Genuity
HearMe
Huawei
Hughes Software Systems
iBasis
IBM
Inalp Networks
Inari Inc.
Innovaphone
Intel
ISPhone
ITXC
Ji-Tong Communications
Komodo Technology
Lotus
Lucent
Macchina
Madge Networks
Microsoft
Motorola
MultiTech Systems
Natural MicroSystems
NetSpeak WebPhone
Netergy Networks
Network Associates
NexTone
Nuera Communications
Nx Networks
OKI
Packetizer
Pagoo
PictureTel
Polycom
RADCom
RADVision
Ridgeway Systems
Siemens
Smith Micro
Sorenson Vision
Swyx
Symbol Technologies
Telxon
TINY
Teles
Trillium
Unylogix
VCON
VegaStream
VIVE Technologies
VTEL
VocalTec
WowRing
Zydacron
Partial Listing

19. The Market Today
Today, the biggest market for H.323 applications is Voice over IP. Why?
Lack of right video terminals to address:
Low bit-rate Internet connections make video and data intensive applications less appealing
It’s a young industry– and with all such industries, it takes time to mature good products
Companies can provide VoIP services today at a low cost and provide new competition to the incumbent carriers

20. Video Communication Era
Future, expect to see video and data communication to become more pervasive
Broadband connectivity is making it possible
Video and data are logically the next services customers expect to find in conference rooms, at home and on their computer screens

21. Why current H.323 products is not good?
Unstable Video Quality
Good over dedicated lines or in demo room
Deteriorates significantly over Internet
Difficult to install
Not easy to use
Too expensive
Business model

22. Design Considerations

23. Networking environment
Backbone band-width oversupply
Last-mile bandwidth getting better
> 384K bps at < NT$2,000/m
xDSL, ADSL, VDSL
Cable
WLAN / WiMax 3G

24. IP Network Issues Lack of IP addresses Use of NAT Firewall
Dynamic IP
Virtual IP
Use of NAT
Adds difficulties to address resolution
Firewall
Blocks media packets
Make plug & play less possible

25. Codec Issues Standard algorithms Implementations: Hardware vs Software
Computation speed
Bit rate vs picture quality
Hardware vs Software
DSP
No longer a dominating issue

26. Performance bottlenecks
Not at computation unit (DSP or CPU)
Systems:
Buffers
Internal bus
Memory speed
Graphics display

27. Right prices for right users
Corporate users
Large conference room ~NT$1.0M
Small conference room NT$50k – NT$100k
Desk top with PC ~NT$3K
Soho users < NT$50k
Home users < NT$10k
Personal users < NT$6k

28. Common Requirements 接近電視的影音品質 維護容易又穩定 容易安裝，網路設定比PC簡單 不必學就會用 不必守在機器旁
慣用的撥接方式 (phone, PC, PDA, etc)
不必守在機器旁
各式來電通知機制 (ring, , mobile, etc)

29. Common requirements 固定IP、浮動IP、虛擬IP的用戶都可接通 網路擁塞 – Lack of QoS in Net
智慧型影音流量調控
Use better end-point QoS
對話安全
影音加密

30. 貼近企業文化的設計 讓傳真變彩色 PC上的資料可隨時取得 反映手寫習慣的電子白板 輕鬆地作現場演示 遠距簡報洽商業務 異地同仁如處同地辦公
連接網路的芳鄰
反映手寫習慣的電子白板
輕鬆地作現場演示
遠端PC程式執行能力
遠距簡報洽商業務
異地同仁如處同地辦公
遠距同步操作PC

31. 貼近企業文化的設計 多點同步會議功能 各個角度都看得到 保留珍貴的會議時況 內建MCU 遙控攝影機: 轉向,聚焦 多攝影機設計
多頻道數位錄影 – 影音圖文同步錄影

32. Suggested HW architecture
P4 for corporate and soho users
SOC = DSP + RSIC
for home and personal/mobile users
Camera
VGA resolution at 30 fps
High-end webcam is good enough
Display
VGA monitor vs TV
Speaker and Microphone
Headphone is uncomfortable
Conference phone is a good choice
Full duplex and echo cancellation

33. Suggested SW Architecture
Embedded Linux
Spport P4 & RISC platforms
Complete TCP/IP stack
Embedded Windows and GUI
Small but rich
Interoperable vs compatible
Standard H.323
Optimized implementation

34. Data Conference Work with PC / MS Windows RDP Network Neighbor – Samba
Graphical terminal
Network Neighbor – Samba
Network file system
Multi-point screen sync
T.120
H.323 whiteboard standard

35. More than Data Conference
Distance Collaboration
Run programs
Co-design
Life demonstrations
Scratch paper – notepad
etc

36. Results
嵌入式設計、多點視訊會議、影音加密、代碼撥號、來電通知、遠端影音調控、PC網路芳鄰、遠距簡報、電子白板與即時圖文通訊、線上文字交談、彩色傳真、Fax over IP Gateway、影音留言、會議錄影
More than a H.323 system
At an affordable price

39. Product Varieties Stand-alone Embedded in LCD monitor/HDTV
Embedded in xDSL
Built-in PDA/PPC/PMP/DSC
Must have in mobile phone

40. Remarks Internet is ready for video communication
H.323 is a valid protocol, SIP simplifies call setup
Multimedia communication with Voice, video, text, graphics, 3D,
Design issues are on the system integration, HW and SW
Embedded in various products