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Compaq ProLiant 1600, White Paper, Page: 7 / 28

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Compaq ProLiant 1600 White Paper Download Page 7

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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.

Scaling

While converting from the RGB color space to a subsampled YCrCb color space helps reduce file
size, it is only a 1/3 to 1/2 reduction which is not nearly enough.  Techniques to lower this further
involve scaling one or more of the three factors mentioned above: frame rate, color depth, and
frame resolution.  For example, scaling the frame resolution results in different size windows for
showing the video on the screen.

Further scaling of all three parameters can dramatically reduce the video rate as can be seen in
the following diagram.

Even though the above scaling represents over a 10:1 reduction in data rate at the expense of size
and video quality, it is still not enough for most network delivery.  For example, a 10BaseT
Ethernet network supports data rates of 10 MegaBits/sec.  This is not enough bandwidth to
deliver even one video stream at the above scaled data rate.  Further scaling can be done.  For
example, the video can be scaled to a "thumbnail" size video at a few frames per second with 8-bit
color—but this is poor in quality and still does not accomplish the data rate reduction necessary to

1/4 Screen

1/8 Screen

Full Screen

Frame Rate: 30 fps (Full Motion)
Resolution: 640x480 (Full Screen)
Color Depth: 24-bit (True Color)

Data Rate = (640 X 480 pixels)*
(3 bytes/pixel)*(30 fps)/(1024000
bytes/megabyte)*8 bits/byte
= 

216 Megabits per second

Frame Rate: 15 fps
Resolution: 320x240 (Quarter Screen)
Color Depth: 16-bit

Data Rate = (320 X 240 pixels)*
(2 bytes/pixel)*(15 fps)/(1024000
bytes/megabyte)*8 bits per byte
= 

18 Megabits per second

x 1/2
x 1/4
x 2/3

Summary of Contents for ProLiant 1600

Page 1: ...bers digital video has the advantage of not degrading from generation to generation and because it can reside on a computer disk it is easy to store search and retrieve It can also be edited and easily integrated with other media such as text graphics images sound music as well as transmitted without any loss in quality And now it is possible to deliver digital video over computer networks includi...

Page 2: ...guration or configurations tested or described may or may not be the only available solution This test is not a determination of product quality or correctness nor does it ensure compliance with any federal state or local requirements Compaq Deskpro Compaq Insight Manager ProLiant Netelligent and SmartStart are registered with the United States Patent and Trademark Office Microsoft Windows Windows...

Page 3: ...y peripheral vision which is not directed at the center of the retina is not as color sensitive For color sensing there are three types of cones capable of detecting visible light wavelengths It has been determined that a minimum of three color components e g Red Green and Blue corresponding to the three types of cones when properly filtered can simulate the human sensation of color Since color do...

Page 4: ...ach called S Video is used in Hi 8 and Super VHS video cameras The RGB system separates the signal into three components Red Green and Blue and is used in color CRT displays Another approach to component video is to use Luminance Y Hue U and Saturation V as the three components Hue describes the color s shade or tone and saturation the purity or colorfulness of the color This approach dates back t...

Page 5: ...sometimes on a disk in the camcorder itself Digital video from these sources may go directly to the hard drive of a PC by using an appropriate interface card The quality of digital video may be judged based on three main factors 1 Frame Rate The number of still pictures displayed per second to give the viewer perception of motion The National Television Standards Committee NTSC standard for full m...

Page 6: ...te of 216 MegaBits per second Mbps This far exceeds the highest data rate achievable through most networks or across the bus of older PCs Until recently the only practical ways to get video on a PC were to play video from a CD ROM or to download a very large file across the network for playback at the user s desktop Neither of these approaches is acceptable for delivery of content across a network...

Page 7: ...ly reduce the video rate as can be seen in the following diagram Even though the above scaling represents over a 10 1 reduction in data rate at the expense of size and video quality it is still not enough for most network delivery For example a 10BaseT Ethernet network supports data rates of 10 MegaBits sec This is not enough bandwidth to deliver even one video stream at the above scaled data rate...

Page 8: ... This compression is achieved through the use of a codec an encoder decoder pair depicted as follows Codecs vary depending on their purpose for example wide bandwidth vs narrow bandwidth or CD ROM vs network streaming Encoders generally accept file types such as Audio Video Interleave AVI and convert them into proprietary streaming formats for storage or transmission to the decoder Multiple files ...

Page 9: ...of the MPEG 1 standard described below H 263 H 263 was developed by the ITU in 1994 as an enhancement to H 261 for even lower bit rate applications It is intended to support videophone applications using the newer generation of PSTN modems at 28 8 Kbps and above It benefits from the experience gained on the MPEG 1 standard It supports five picture formats H 263 Resolutions Format Resolution Sub QC...

Page 10: ...a rates of T1 lines MPEG 1 uses Interframe compression to eliminate redundant information between frames and Intraframe compression within an individual frame using a lossy compression technique similar to JPEG image compression Three types of frames result from the compression algorithm I frames P frames and B frames These are illustrated in the following diagram I frames do not reference other p...

Page 11: ...orward fast reverse and random access into the bitstream However as mentioned above these access points are only at the I frame boundaries The CD ROM quality audio is stereo 2 channel 16 bit sampled audio at 44KHz The main MPEG 1 resolution of 360 x 242 is called Standard or Source Input Format SIF and unlike the Common Intermediate Format CIF defined earlier differs for NTSC and PAL systems The c...

Page 12: ...minals video email wireless mobile video devices and interactive home shopping It was originally designed to support data rates of 64Kbps or less but recently has been enhanced to support a wide range of bit rates from 8 Kbps to 35 Mbps This enables it to support both consumer and professional video with a variety of resolutions corresponding to the H 263 video conferencing standard discussed earl...

Page 13: ...te copy does not have to reside on the user s hard drive Another advantage is that video content may be integrated and streamed along with other media and the video can play inside standard Web browsers The following diagrams contrast the download and play model with the new streaming model Delivering video by the download play method involves transmitting the complete file e g in AVI format to th...

Page 14: ...equence numbers in the video data packets so they can be properly assembled and played out of the receiving buffer Over IP based networks such as the Internet a new protocol called Real Time Protocol RTP has been developed to accomplish this Video Streaming System A complete video streaming system involves all of the basic elements of creating delivering and ultimately playing the video content Th...

Page 15: ...nection The video server consists of a hardware platform that has been optimally configured for the delivery of real time video plus video server software that runs under an operating system such as Microsoft Windows NT that acts as a traffic cop for the delivery of video streams Video server software is generally licensed by the number of streams If more streams are requested than the server is l...

Page 16: ...sion of video over a network is the ability to support multicasting broadcasting and unicasting of video streams Multicasting lies between broadcasting and unicasting Unicasting delivers streams 1 to 1 to each client and is sometimes referred to as Video on Demand VoD since any user can request any stream at any time Multicasting by contrast delivers streams simultaneously 1 to many clients where ...

Page 17: ...a If a data collision occurs all contending nodes back off and re transmit after a random delay This enables shared Ethernet to support a large amount of bursty data traffic corresponding to multiple shared applications and devices such as modem communications sending and receiving faxes printing accessing corporate databases such as phone directories and group calendars internal and external e ma...

Page 18: ...ckbone The next generation of Fast Ethernet Gigabit Ethernet is in development ATM Asynchronous Transfer Mode uses hardware switching to provide not only high speed 25Mbps to 2 5Gbps but it also a guaranteed Quality of Service QoS and multicasting through a circuit switched connection It uses fixed 53 byte packets and was designed from the outset for multimedia data transmission such as video soun...

Page 19: ...media data streams such as video It supports multicasting authentication encryption and a larger address space Since it can t be rolled out everywhere at once it is intended to be backward compatible with IPv4 MBONE The Multicast Backbone is an experimental overlay network on the Internet to gain experience with multicasting that will be supported in IPv6 There are approximately 1700 networks in 2...

Page 20: ...itize specific packet streams It does this by requesting the dynamic allocation of bandwidth from the network much like PC applications dynamically allocate memory for applications Public Broadband Networks Telecommunications deregulation has enabled local and long distance carriers to compete with each other as well as with cable TV operators for long distance services as well as value added serv...

Page 21: ...WHITE PAPER cont 21 ECG068 0798 ...

Page 22: ... to multiple clients sending the same video to several clients simultaneously or sending different videos to individual clients at the same time q Transmitting video over the network reading buffering formatting packetizing and sending data over the network using the specified network protocols q Storing video data providing fault tolerant support q Detecting abnormal client termination e g power ...

Page 23: ...gh capacity high performance disk drives for storing and delivering real time video content q High performance network cards such as 10 100BaseT ATM for high bandwidth network connections q Fast system and I O busses such as PCI and Wide Ultra SCSI q Tuned device drivers for network cards and disk access q Multiple high performance CPUs that can be dedicated to uninterrupted video delivery q Large...

Page 24: ...ys with controllers that support content striping For example wide Ultra SCSI 3 disk controllers provide a sustainable throughput of 40 MB sec twice that of Fast Wide SCSI 2 For some applications the availability of high rotation speed disks e g 10 000 rpm is also desirable for maximum performance High Performance Network High quality broadcast video can be delivered at bit rates ranging from 3 Mb...

Page 25: ...f concurrent streams they can deliver the cost per stream is often an important measure of video server efficiency This parameter can be a misleading comparison however if it fails to take into account the above important hardware characteristics which also have a cost impact Nevertheless the best cost per stream is more likely to come from the ranks of high volume industry standard architectures ...

Page 26: ...oLiant 5500 can be expanded from 128 MB up to 3 GB for handling high workloads of multiple concurrent video streams q High availability options To maximize availability with minimum downtime the ProLiant 5500 supports hot pluggable redundant components such as power supplies disk drives fans and network interface cards q Large number of expansion slots There are 5 PCI and 3 shared EISA expansion s...

Page 27: ...phic Experts Group LBR Low Bit Rate MBONE Multicasting BackBONE Mbps Megabits per second MJPEG Motion JPEG MPEG Motion Picture Experts Group NIC Network Interface Card NTSC National Television Standards Committee U S TV standard NVOD Near Video on Demand PAL Phase Alternation Line European TV standard PCI Peripheral Component Interconnect PSTN Public Switched Telephone Network QoS Quality of Servi...

Page 28: ...oks q Video and Media Servers Technology and Applications Focal Press Karl Paulsen 1998 q Publishing Digital Video Academic Press Jan Ozer 1997 q A Technical Introduction to Digital Video Charles A Poynton John Wiley Sons 1996 q Digital Video An Introduction to MPEG 2 Haskell et al Chapman Hall 1997 q Video Dialtone Technology Daniel Minoli McGraw Hill 1995 q The Digital VideoMaker s Guide Kathryn...

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