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Compaq ProLiant 1600 White Paper

Video streaming technology
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July 1998
Compaq Computer
Corporation
ECG Emerging Markets
and Advanced
Technology
C
O N T E N T S
V
T
.............. 3
IDEO
ECHNOLOGY
The Human Eye ....................... 3
Analog Video............................ 4
Analog Composite Video.............. 4
Analog Component Video ............ 4
Digital Video ............................. 5
Digital Video Formats .................. 5
Network Delivery Challenges ....... 6
The Bandwidth Problem............ 6
Scaling ........................................ 7
Compressing—Codecs ................ 8
Video Codec Standards............ 9
H.261 .......................................... 9
H.263 .......................................... 9
JPEG and MJPEG....................... 9
MPEG ....................................... 10
V
-S
.............. 12
IDEO
TREAMING
Isochronous Video...................13
Video Streaming System .........14
Network Considerations...........15
LANs/Intranets .......................... 17
Public Internet ........................... 18
Public Broadband Networks ....... 20
V
S
.................. 22
IDEO
ERVERS
Application Software................22
Video Server Hardware............23
High Capacity Disk Storage ....... 24
High Sustainable Throughput ..... 24
High Performance Network ........ 24
Multiple CPUs ........................... 24
Expandable System Memory ..... 24
High Availability ......................... 24
Rack-mount for Easy Access..... 25
Attractive Cost per Stream......... 25
Example: Compaq ProLiant .....25
A
......................... 27
CRONYMS
R
....................... 28
ESOURCES
ECG068/0798
W
HITE
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Video Streaming Technology
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If a picture is worth a thousand words, then a video is worth a thousand pictures. The
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sights and sounds of video teach us, entertain us, and bring our fantasies to life. While
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text, graphics, and animation provide for interesting content, people naturally gravitate
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to the richer and more realistic experience of video. That is because video—with audio—
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adds the ultimate level of realism to human communication that people have come to
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expect from decades of watching moving pictures in the real-world media of TV and
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movies.
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As all such real-world media continues to migrate toward "everything digital", video too
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is becoming digital. Video delivery has evolved from the analog videotape format of the
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1980s to a digital format delivered via CD-ROM, DVD-ROM and computer networks. As
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a series of digital numbers, digital video has the advantage of not degrading from
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generation to generation, and, because it can reside on a computer disk, it is easy to
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store, search, and retrieve. It can also be edited and easily integrated with other media
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such as text, graphics, images, sound, music, as well as transmitted without any loss in
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quality. And now it is possible to deliver digital video over computer networks including
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corporate Intranets and public Internets directly to desktop computers.
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What makes this network delivery possible is the emergence of new technology called
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"video-streaming". Video streaming takes advantage of new video and audio
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compression algorithms as well as new real-time network protocols that have been
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developed specifically for streaming multimedia. With video streaming, files can play as
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they are downloaded to the client, thus eliminating the necessity to completely download
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the file before playing, as has been the case in the past. This has the advantages of
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playing sooner, not occupying as much disk space, minimizing copyright concerns, and
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reducing the bandwidth requirements of the video.
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This white paper discusses the salient characteristics of this new video-streaming
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technology. How the properties of human vision shape the requirements of the
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underlying video technology. How the high bit rate and high capacity storage needs of
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video drives the demand for high video compression and high bandwidth networks. How
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the real-time nature of video demands the utmost in I/O performance for high levels of
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sustained throughput. How the characteristics of video streaming shapes the
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requirements of video server hardware. And finally, how Compaq video streaming
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servers meet these demanding requirements through high performance I/O architectures
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and the adherence to industry standards.
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Please direct comments regarding this communication to the ECG Emerging Markets and Advanced Technology Group at:
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EMAT@compaq.com
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1
P
APER

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Summary of Contents for Compaq ProLiant 1600

  • Page 1 How the characteristics of video streaming shapes the Attractive Cost per Stream..25 requirements of video server hardware. And finally, how Compaq video streaming Example: Compaq ProLiant ..25 servers meet these demanding requirements through high performance I/O architectures ......
  • Page 2 INFORMATION), EVEN IF COMPAQ HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. The limited warranties for Compaq products are exclusively set forth in the documentation accompanying such products. Nothing herein should be construed as constituting a further or additional warranty.
  • Page 3 HITE APER (cont.) Video Technology The Human Eye An understanding of video technology starts with an understanding of the properties of the human eye. This is because the electronic eye of the video camera tries to mimic what the human eye sees.
  • Page 4 HITE APER (cont.) Analog Video Analog Composite Video Analog video represents video information in frames consisting of fluctuating analog voltage values. In early analog video systems individual video signals— brightness, sync, and color— were all combined into one signal known as "composite" video. This composite signal can be transmitted over a single wire.
  • Page 5 HITE APER (cont.) Digital Video A major disadvantage of analog video is that it tends to degrade from one generation to the next when stored or reproduced. Another is that it often contains imperfections in the form of "artifacts" such as "snow" in the picture due to noise and interference effects. In contrast to analog video, digital video represents the video information as a series of digital numbers that can be stored and transmitted error free without degrading from one generation to the next.
  • Page 6 HITE APER (cont.) The '4' in the above descriptions indicates that luma is sampled at 4 times the basic 3.375 MHz frequency and the '1' and '2' indicates that the chroma is sub-sampled at 1 or 2 times the basic frequency.
  • Page 7 HITE APER (cont.) 2. Compressing the video using lossy compression techniques. This is generally needed for almost all networks because of the high bandwidth requirements of uncompressed video. 3. Streaming the video using data packets over the network. Small video files may be downloaded and played, but there is a tendency to stream larger video content for faster viewing.
  • Page 8: Codec Types

    HITE APER (cont.) deliver very many streams for most network delivery. To achieve further reduction in data rate, video compression is needed. Compressing—Codecs Different algorithms and techniques known as "codecs" have been developed for compressing video signals. Video compression techniques take advantage of the fact that most information remains the same from frame to frame.
  • Page 9 HITE APER (cont.) Video Codec Standards H.261 The H.261 video-only codec standard was created by the ITU in 1990 for global video phone and video conferencing applications over ISDN. It was designed for low bit rates assuming limited motion as is typical with videophone applications. It was also assumed that ISDN would be deployed worldwide.
  • Page 10 HITE APER (cont.) MJPEG stands for "motion JPEG" and is simply a sequence of JPEG compressed still images to represent a moving picture. Video capture boards sometimes use MJPEG since it is an easily editable format, unlike MPEG, described next. A disadvantage of MJPEG is that it does not handle audio.
  • Page 11 HITE APER (cont.) Depending on the amount of motion in the video, P-frames may not come fast enough to give the perception of smooth motion. To compensate for this, B-frames are therefore inserted in between the I and P-frames. B-frames are "bi-directional" in that they use information in the previous I or P-frame as well as in the future I or P-frame.
  • Page 12 HITE APER (cont.) standard for DVD-ROM which, at 7x the capacity of the CD, is ultimately expected to replace CD-ROM and VHS tapes for long-play quality video. DVD-ROM can hold at least 130 minutes of MPEG-2 video with Dolby AC-3 surround-sound stereo audio. (DVD-ROM supports Dolby AC-3 audio rather than the MPEG-2 audio).
  • Page 13 HITE APER (cont.) network. The disadvantage is that the user may have to wait for a long time for the download to occur, plus have a large amount of disk storage space available to store the video file. There are also copyright concerns since a copy of the video is made to the user’s hard drive.
  • Page 14 HITE APER (cont.) Internet since individual packets may take different paths and arrive at different times at the destination. In some cases, packet errors or lost packets may also result in re-transmission causing disruption of the video. On Intranets such as shared Ethernet video packets may also have to contend with other data traffic such as file transfers, database access, access to shared modem and fax, etc.
  • Page 15: Network Considerations

    HITE APER (cont.) Step 1. Capture: As this diagram shows, the first step in the process of creating streaming video is to "capture" the video from an analog source such as a camcorder or VHS tape, digitize it and store it to disk. This is usually accomplished with an add-in analog video capture card and the appropriate capture software.
  • Page 16 HITE APER (cont.) Quality of Service (QoS)—As mentioned earlier, video streaming works best when there is continuous availability of sufficiently high bandwidth in the communications channel. This is especially important for time-critical applications such as video and audio. Variable video/audio packet delays can cause picture jitter and annoying audio starts and stops.
  • Page 17 HITE APER (cont.) Broadcasting, on the other hand, is a special case of multicasting that delivers a single stream simultaneously to all network clients. This is the method used for example, for live broadcasts of executive presentations or new product announcements to all corporate employees worldwide. All users on the network can view the broadcast at the appointed time.
  • Page 18 HITE APER (cont.) The Ethernet switching hub only routes video packets that are addressed to the specific client devices on the appropriate output ports. This keeps video traffic flowing smoothly to the desktops that need it, and insulates the corporate backbone network from high bandwidth video. This establishment of dedicated "subnets"...
  • Page 19 HITE APER (cont.) A standard HTTP web server sometimes acts as a "metaserver" that delivers the necessary URLs and information about the video content to the client for access. The video server often uses a different protocol called "Universal DataGram Protocol", or UDP, to provide the client with VCR- like controls and to provide a more "synchronous"...
  • Page 20 HITE APER (cont.) RTSP RTSP stands for "Real-Time Streaming Protocol." It is a higher-level client/server protocol for controlling the efficient delivery and quality of service of a multimedia stream along with controls such as stop, pause, rewind, fast-forward, etc. It also contains provisions for security as well as for usage measurement and rights management so that streaming content providers can control and charge for the usage of their streaming content.
  • Page 21 HITE APER (cont.) ECG068/0798...
  • Page 22 HITE APER (cont.) Video Servers Application Software The goal of a video server is to match end users to video content, store and retrieve video data as efficiently as possible, transmit it across the network continuously without interruption, and finally, to respond to user interactive VCR-like control. To accomplish this, specialized video server application software runs on a dedicated video server hardware platform that is optimally configured for real-time video delivery.
  • Page 23 HITE APER (cont.) Video server application software that runs under the Microsoft Windows NT Operating System is available from a number of vendors including: Microsoft: NetShow and NetShow Theater Oracle: Oracle Video Server Starlight Networks: StarWorks, StarCast RealNetWorks: RealServer Video Server Hardware One of the primary tasks of a video server is to read video data from disk storage, packetize it, and to put it on the network as quickly as possible.
  • Page 24 HITE APER (cont.) High Capacity Disk Storage As a rule of thumb, MPEG-2 compressed video data takes about 1 GigaByte of storage per hour of video content. A dozen two-hour movies would therefore require about 24GB of disk storage. Therefore, an important characteristic of video servers is their ability to accommodate the highest capacity disk drives such as 9.1 or 18.1 GB.
  • Page 25 Example: Compaq ProLiant The Compaq ProLiant family of servers includes a number of models that make excellent video server platforms. A good example is the Compaq ProLiant 5500. This server features: Multiple high performance processors.
  • Page 26 Dual In-line Memory Modules (DIMMs) the Compaq ProLiant 5500 provides breakthrough cost per stream for video streaming applications. Other members of the Compaq ProLiant family that also feature the Highly Parallel System Architecture and other key features needed in video server configurations include the ProLiant 3000 and the ProLiant 1600.
  • Page 27 HITE APER (cont.) Acronyms ADSL—Asymmetrical Digital Subscriber Loop ASF—Advanced Streaming Format ATM—Asynchronous Transfer Mode AVI—Audio-Video Interleave CD-ROM—Compact Disk-Read-Only Memory CIF—Common Intermediate Format CODEC—enCODer/DECoder DVD-ROM—Digital Video Disk-Read-Only Memory FDDI—Fiber Distributed Data Loop GOP—Group of Pictures (in MPEG standard) HBR—High Bit Rate HDTV—High-Definition Television HTML—HyperText Markup Language HTTP—HyperText Transfer Protocol...
  • Page 28 HITE APER (cont.) Resources For more information on Compaq Computer Corporation, products, and solutions, visit http://www.compaq.com/ For information on video server solutions from Compaq visit http://www.compaq.com/solutions/enterprise/index.html For information on standards and specifications affecting video streaming technology visit one of the following: http://www.ipmulticast.com...

This manual is also suitable for:

Proliant 3000Proliant 5500