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                                  Tutorial Web 2.0




                                                                             Slide 1: Digital Broadcasting Assessment is at the end of this booklet Bas
                                  From: jkim21
                                                                             Networking & Unicast Streaming – LAB Surveying the status of machine
                                  Views: 615 Comments: 1
                                                                             The machines are currently setup for streaming and currently have all IP
                                  Tutorial Web 2.0
                                                                             addresses, subnets and each computer is named. These machines also hav
                                                                             network cards installed. The main University network uses NIC (network
                                                                             interface card) card 1 and our internal network uses NIC card 2. Networki
                                                              See all        Streaming on Windows 2003 Server/clients What is needed to network
                                                                             computers to create a local area network and what do you have to do? On
                            scale a couple of network cards, a network switch (or hub) and CAT 5 net
                            cabling with 2 or more computers required. When all hardware is correctl
                            installed you are ready to begin setting them up. E6 Networking Laborato
ore plicks from this user   PC‟s in E6 are installed with three operating systems. For the purposes of
                            laboratory all students will mainly be using the Windows 2003 server boo
                            option. Starting the servers PC‟s. 1. Boot the Pc 2. Choose the Windows 2
                            Server boot option 3. On log in screen enter User = Administrator Passwo
                            serves Check the current IP address on the PC - IPCONFIG Start > Run >
                            in command or cmd to start the command prompt. A black command scre
                            boot up resembling a DOS screen. 1
                            Slide 2: In this window type “ipconfig” and press enter. Firstly, you are to
                            current IP address, the subnet and the gateway of the Local Area Connecti
                            no IP configuration information is displayed it means all NIC cards are cu
                            disabled. Testing the Network The network is currently setup and to test f
                            communication you are going to deploy the use of “ping”. Ping verifies
                            connections to a remote computer or computers. This command is availab
                            if the TCP/IP protocol has been installed. To ping a specific computer use
                            following command Ping other pc by entering ping followed by the I.P. ad
                            of the corresponding machine. E.g ping 111.111.111.100 and press enter.
                            message similar to below (but with replacement IP address) will be as the
                            following diagram shows. Ping sends out 32 bytes of information. It has a
                            (time to live of 128) which means it can travel through 128 switches/hub o
                            routers before it will be destroyed. This ensures that they do not live forev
                            the machines should be able to ping each other and respond with a messag
                            says “Request Timed out” it means no signal has been returned. 2
                            Slide 3: Class Layout of PC‟s in Lab Follow the diagram below to ensure
                            know whose machine you are pinging. They will also know they can ping
                            too. Naming a Computer All computers need to have names. The NetBEU
                            protocol demands all computers are named e.g Computer 1, Computer 2 o
                            names like TIM, PETER & HEATHER are just as acceptable. It is also ea
                            find computers if you know the name of them. Calling a computer
                            111.111.111.111 is hardly an easy number to remember. The machines in
                            lab are named e6-XX To change the PC name. Right click the My Compu
                            from the desktop and click properties to enter the computers system prope
                            section. Click the Network Identification tab from the top. The full compu
                            name and the workgroup is on display. To change them click the Propertie
                            below the Network ID. (Network ID is a quick way to gain access to settin
                            network protocols). Properties of the Network ID 3
                            Slide 4: Name the computer whatever you wish, however, the workgroup
                            be called workgroup. Then hit the ok button and exit this box. For change
                            effective a reboot is necessary. Setting up a local area network (LAN) The
                            machines are networked by standard CAT 6 network cable (1000mbps) an
                            network switch (also 1000mbps). The job of the switch is to link the PC‟s
                            together. None of the PC‟s in this lab are connected to the main University
                            network so we can have full control whilst studying Internet Streaming an
                            effect any other area of the network. Networking the Computers To succe
start a network each machine must be running a network language (a proto
Setting up the Networking Protocols Right click the Network neighbourho
the desktop and choose properties 4
Slide 5: Right click the local area connection icon and click properties. Th
image on the PC‟s in F11 will have 2 local area connection links present b
is greyed out. These machines have 2 NIC cards installed. (nic = network
interface card). For this testing only one card is used because the greyed o
is configured for usage on the main University network. Installing Protoco
After selecting the properties of the network connection a box will be aski
network protocols to be installed or turned on. (identical to the picture on
page). 5
Slide 6: Then highlight the Internet Protocol option (TCP/IP) and click
properties. How to Set up a Network using the Internet Protocol (TCP/IP)
Properties Set the IP address, subnet mask and ignore the gateway and the
The gateway is the computers connection to the outside world. DNS is Do
name server. Example - The server, which allows the machine to be on th
student domain like yourselves. Click – Use the following IP address opti
button Enter a 32 Bit IP address in the boxes. For this test ensure the
experiment‟s IP address begins with 111.111.111 _ _ _ . The last digit wil
to 12 6
Slide 7: depending on the number given to you in class. The use the Subn
255.255.255.0 To communicate successfully in our Lab each machine doe
need to be on the same subnet but it is good practice to ensure machines in
same area have the same subnet. You could say it is like organising them
sections. Testing the Streams Start Internet explorer and type the URL of
stream in the address bar. Currently there is no Internet connection on thes
machines. To view your stream type either
mms://name_of_your_server/name_of_publishing_point/pinball.wmv or
mms://ft9-161/pubone/pinball.wmv or
mms://111.111.111.161/pubone/pinball.wmv in the URL bar. You can tes
from any machine on the network in the lab. Useful Definitions OVERVI
NetBEUI (courtesy of Microsoft help guide) NetBIOS Extended User Inte
(NetBEUI) is suited for use in small workgroups or LANs. You can instal
NetBIOS gateway and the NetBEUI client protocol on all remote access s
running Windows 2000 and most Windows networking clients. Previous
Windows NT remote access clients, LAN Manager remote access clients,
DOS remote access clients, and Windows for Workgroups remote access
may use NetBEUI. NetBEUI is not routable, and the only configuration re
for the protocol is a computer name. TCP/IP Transmission Control
Protocol/Internet Protocol (TCP/IP) is the most popular protocol, and the
for the Internet. Its routing capabilities provide maximum flexibility in an
enterprise-wide network. On a TCP/IP network, you must provide IP addr
to clients. Clients may also require a naming service or a method for name
resolution. This section explains IP addressing and name resolution for Ne
and Dial-up Connections on TCP/IP networks. It also describes the FTP a
Telnet tools that are provided by Windows 2000 TCP/IP. 7
Slide 8: Compression – Encoding for the web Compression in its most ba
form looks for redundant data. Most sentences are made up from words th
repeated frequently. At the transmission end data is compressed. Any data
repeated can therefore be remember once and then pointed at again to recr
the same message at the receiver end. A vector calculation will enable the
sentence to be recreated. Vector calculations also take up very little memo
actual data. Data compression is compression that works on generally ran
content like computer files and it does not have to know details of what th
contents are. One of the most popular compression algorithms over the pa
decade is .zip from PKzip. Apples use .Sit from Aladdin systems. Have yo
wondered why a compressed image or piece of data will not recompress a
a smaller size? Well uncompressed information in numerical format looks
contains lots of patterns of numbers. Compressed data under the same test
very random. So if data is compressed efficiently in the first place the enc
file looks very random and thus is nearly impossible for a compression sc
to understand it and therefore becomes near by impossible to compress m
more. Using programmes like Winzip on a piece of uncompressed video y
would probably achieve at least a 2:1 compression ratio. Where as on a jp
would achieve very little. There are two main types of compression; lossy
lossless. A lossless codec preserves all of the information contained withi
original file. TIFF and PNG are lossless. Lossless codec‟s do not always
compress the file smaller than the original. Lossy basically means data is l
and cannot be retrieved. Only a best effort of reproducing the original file
possible such as with a JPEG compression. Lossy codec‟s generally allow
specify a wanted data rate. Media Cleaner offers this service across all the
Windows and QuickTime compression setting. All compression for video
audio across the web is lossy. Interlaced and Progressive TV Pictures
Televisions create their image by drawing (scanning) lines of light on the
face, left to right, top to bottom, to produce a picture over the entire screen
resultant images that make up the motion picture are comprised of alterna
interlaced fields: that is, one field consists of all the odd lines (1,3,5 etc. th
625), and the other consists of all the even lines (2,4,6 etc. through 624). T
result is that only half of the video's display is drawn every 50th of a seco
simulation of this is shown on the left. Field 1 is scanned, and then Field 2
scanned. Traditional talk quotes PAL television as having 25 frames per s
each being comprised of two interlaced fields. That is incorrect and should
erased from your mind. The PAL interlaced system shows 50 unique imag
(fields) per second, and each field is an independent snapshot in time. So
don't want to think of interlaced televisions in terms of 8
Slide 9: frames but rather in terms of fields, interlaced fields, and 50 of th
second. As long as nothing in the picture changes (such as when showing
image), the alternating fields will actually complement each other and for
complete picture. The display will flicker and scan lines will be visible (b
inherent of an interlaced system), but that's life in an interlaced world. We
spend the evening looking at a still picture on the TV though. The momen
something moves, we get interlacing artefacts.
http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-
5progressive-10-2000.html Progressive Scan Progressive displays, such a
performance CRT/LCD/DLP/LCOS projectors and the new HDTV-ready
can show progressive scanned images as opposed to interlaced. We learne
above that an interlaced display shows 50 fields per second. But with
progressive, each scan of the CRT face is a complete picture including all
lines, top to bottom, now called a frame, and we are showing 50 of those p
second. The benefits of a progressive display are no flicker, scan lines are
less visible (permitting closer seating to the display), and they have none o
artefacts we described for the interlaced display (as long as they are fed a
progressive signal). But sources which are truly progressive in nature are
come by right now. Movies on DVD are decoded by the player as interlac
fields. All of the film's original frames are there, but they are just divided
"halves". What we're going to talk about next is how we take the interlace
content of DVD and recreate the full film frames so we can display them 9
Slide 10: progressively. The term commonly used to restore the progressi
image is deinterlacing, though we think it is more correct to call it re-
interleaving, which is a subset of deinterlacing. The magnitude of the chan
you will see also depends on what you were watching before. If you switc
a regular interlaced TV to a progressive-scanned 576p picture, you should
much smoother, more film-like picture, with much less obvious scan line
structure, and more apparent vertical resolution. The difference should, in
be pretty obvious. But if, like most new high-end TVs, your TV has a buil
deinterlacer (often called a “line doubler”), then the television has been
converting your interlaced signal to 576p already, so the smoothness and l
line structure are already there. So what can a progressive DVD player off
Better deinterlacing, to start with. In other words, the deinterlacer in the D
player is likely better than the one in your TV (the DVD player's deinterla
also performs the deinterlacing in the digital domain right off the disc, rath
than sending an analogue video signal to the TV, which has to convert it b
digital for deinterlacing). Computer monitors use a progressive scan. Ther
compression for the web has to include deinterlacing if the original signal
from a Pal or NTSC video source. This not only improves the viewable im
but reduces the bit rate too. But upon my quick test the file started I used w
originally 35MB and 3 seconds in duration and was reduced to 249KB
deinterlaced and 251KB interlaced (140:1 ratio approx to original). The
difference in data rates per second is not significant but the deinterlaced
(progressive file) was displayed much clearer on screen and would be far
for the media player to reassemble at the client end. This is a fundamental
to compression and it is called the Shannon limit. Claude Shannon invente
information theory in 1948. He created mathematical solutions to calculat
much information could physically be transferred over a telephone or tele
wire. As random data cannot be compressed anymore its limit will be the
size will be the same even after the compress algorithm has been run. Wh
with highly redundant data the Shannon limit can be tiny. For example a f
consists of 10 billion “010101010” can be compressed to simply a 0 and a
Most compression applications have a value that controls some kind of tra
between speed and compression efficiency. In compressing for the web yo
to think of more things whilst compressing video such as compression tim
compression efficiency, decoding it and then the careful balance to leave t
signal to be acceptable by the audience. The decoding time for modern co
such as Real Networks Helix and WM9 is very CPU intensive thus only u
for fast modern computers. MPEG 4 also demands a powerful machine to
decode the signal. The compression time is also a negative exponential. B
mean it describes the compression time increases more and more when yo
to compress a file more. A 10% increase in compression may take 100% 1
Slide 11: more time to successfully do it. Therefore you are trying to reac
Shannon‟s limit. Decisions to make about streaming video. Target bit rate
knowing the connection speeds Balancing audio vs. video bit rate Image s
Frame rate I - frames To compensate for congested networks the target bit
always set lower than the ideal bit rate. (eg. 50kbps modems can only ach
53kbps). Many encoding technicians will target a bit rate of 36 – 42 kbps.
two channel ISDN live with a max bandwidth of 128k you target 80 – 100
Broadband connections can generally be set closer to full capacity eg 512k
full. A T-1 runs at 1.5mbps but if it shares it with several users. T-3 lives
44mbs. Audio vs Video bit rate Obviously video requires much more bit-r
than the audio signal. Although, it can be common to find audio being sac
for better video. Compression experts and user experience have shown tha
better audio quality provides a better overall impression of the video. Tho
with a 56k modem you must choose a bit rate of 5-8 kps to leave enough r
for the video. Ultimately your target audience will decide factors in how y
deliver your audio. You have to choose the sampling rate and where you w
stereo audio or mono. Most codec‟s dictate these parameters based on the
rate you have chosen. Reducing Bit Rate Scaling your frame size is an exc
method of lowering bit rate. It scale you frame size it is advisable to scale
factor of 4. 720 x 576 to 180 x 144 ( a division of 4) This is because the co
work by encoding blocks of 4 or 16 and you get a better quality picture by
so. As to encode it only has to remove 3 out of 4 pixels and you could say
makes life easier with symmetrical encryption. A usual size is 160 x 120 w
using a dedicated capture device. This frame size is adequate for a 56k mo
If you are streaming to 56k and you have 11
Slide 12: captured at DV rates, it‟s recommended to resize to 4 reduction
144). Large frame sizes are generally expected at broadband rates. 240 x 1
320 x 240. Occasionally if distribution is only via LAN or a high speed
connection you can encode at 640 x 480 this is classed as full screen. Fram
Rate Frame rate is another important factor to reduce bit rate. At 56k rate
will find encoding takes place at 15 fps in USA and 12.5 in UK. 10 is arou
minimum. Over the next few years you will see the fps go up to full frame
recommend 15fps using low speed connections. Keyframes Keyframes ar
up of what they refer to as l-frames similar to MPEG. The video codec‟s u
these keyframes as anchor frames. The keyframe requires more bits to enc
than other frames. The other frames are called difference frames. They are
from a prediction from its previous frame. Similar to the P-frame in MPEG
the information needed to encode and decode a keyframe comes from a si
source frame called the intraframe or l-frame (keyframe). Keyframes are u
for random access in a movie but using less of them does help to reduce d
rate. Media cleaner Pro has an option to reduce the scale quality. This opti
applies very complex filtering to the image prior to scaling it, thereby redu
or eliminating aliasing or jagged edges. It is usual to use the accurate func
here but it will take longer to render. So it depends if you are short of time
interlacing Due to TV being captured with 2 fields, each field containing h
lines. Removing a field will immediately half the bitrate. Putting these tw
together can cause jagged edges as the fields are separated in two. You ca
choose to blur these lines together by selecting the blend option. This will
to smooth out high motion sequences particularly as when you stream you
reduce the fps gives better compression. You can also select one field or t
other. Usually it does not matter which field you choose unless you have s
details. Field Dominance Change This is a property which defines whethe
odd fields or the even fields come first in the interlaced pattern. Occasiona
single lines become separated from objects because of the compression an
causes jagged moving edges that should not be doing that. You can use th
cure this problem but the majority of time it can be ignored. Inverse Telec
Slide 13: Many pieces of software such as MCP (Media Cleaner Pro ) hav
Inverse telecine. It‟s on the de-interlace menu. If original video came from
at 24 fps and converted to 25 or 30 so at some point unnecessary informat
was created so you can remove it. It‟s a process called 3-2 pulldown. Filte
for Signals Just as a one-dimensional filter can be applied to an audio sign
improve it, 2D filters can be applied to images to improve the final compr
Low pass filters can be used to help reduce the bit-rate. Applying it to an e
will spread that edge out over several pixels. As the codec codes the differ
and not identical areas it reduces the bitrate. Blurring applies a low pass fi
across the entire image giving a softer focus, making more colours the sam
making it easier for the codec to work. Adaptive noise reduction only app
blue (filter) to flat areas so edges are not affected. It‟s usual to apply the la
unless you‟re looking for a softer focus. In this instance when you have ar
uniform colour. Football matches could have this applied because the gree
needs to be uniform and its flat so very little encoding could take place.
Differences Frames The frames in between the keyframes are called differ
frames (sometimes called delta frames, these are the P frame sin MPEG‟s
code the difference between themselves and the previous frame. So, if the
identical to last frame nothing will be coded. These difference frames atte
code only motion in the video. Noise and transitions make changes in betw
frames. Note, If you are shooting for the web and you wish to keep the qu
reasonably high, it is advisable to use no transitions. Apple The early pion
media streaming and using movies on the web were Apple. They started p
video on the Internet using their QuickTime 2 format. Streaming at this st
was not possible. They would place short clips on their websites for
downloading and viewing using Apples Movie player, or a plug in web br
Apple upgraded to Quicktime 2.5 by adding a fast start feature allowing th
movie to being playing before it was fully downloaded. This became know
progressive download. This is still used today, offering higher quality mov
slower connections. Movie trailers and product demo‟s are encoded as
progressive downloads. Cinepak was traditionally the codec of choice for
platform delivery of Quicktime but it‟s an older technology intended for C
Rom delivery of media. 13
Slide 14: With advent of web video, apple teamed up with several compan
offer the very best in compression. These included Sorenson Qualcomms
Voice and Qdesign‟s music codec. True streaming was introduced with
QuickTime 4, however this also introduced the need for a QuickTime stre
server, which permitted real time delivery of content. Sorenson The Soren
video codec is the choice for streaming or downloading QuickTime movie
because it is designed to package large amounts of information into very l
rates. When choosing frame rates a good idea is to choose a frame rate wh
evenly divided into the source frame rate: Eg – 12.5 fps. as it allows the c
keep one frame every two frames in 25 fps movie. Keyframes Sorenson h
default setting of 1 keyframe every 10 seconds. If you find video deteriora
too much between keyframes, try placing them closer together. If you nee
reduce bit-rate spread them out. Preprocessing audio and video content fo
actually allows you to control what information you feed to the codec‟s.
Compressing the I frame (you can it spatial compression) is a major metho
reducing the data rate. The I frame is twice as big a the difference frames.
difference frames (delta) are made up from these frames. The more the I i
compressed the less data in the P frames. But at the expense of quality. Ge
proper parameters Knowing your target audience, including platforms and
connection speeds, in an integral step for achieving quality video and audi
Setting reasonable frame sizes and frame rates will reduce the amount of d
codec must compress, offering higher quality content for every it that cou
Cropping Cropping, you‟ll want to crop the image if there is tearing or bla
bands around any of the frame edges. These pixels occur during capture a
to unnecessary pixels that can waste precious bandwidth. If you crop ensu
crop the frame to the same aspect ratio of a tv 43. But I can really recomm
you crop to ensure a 4x4 or 16x16, otherwise multiples of 4. This 14
Slide 15: is because the codec‟s divide images into multiples of 4. Then th
codec will not try to resize your image to fit its inherent constraints. Intell
Scaling of Image Size In order to improve quality and achieve higher fram
rates, especially at laser connection speeds, you may want to scale your vi
even more. Real Video Codec‟s. Real system was designed especially for
web and is the earliest contender in this arena back when we used 14k mo
Real Introduced Real Audio. Their audio codec‟s were well developed and
highly specialised for many different connections. They then started devel
video streaming codec‟s. However, each time a new video codec was intro
it required a new player to be downloaded. The latest version is called G2
Real version 8. Real offer 3 basic options Realtime for streaming WWW M
setting (for progressive download) Surestream for dynamic scaling of you
streams. Real WWW Movie only offers 3 settings - small, middle and hig
generally presents a higher overall bit rate for stream than the Realtime th
because it „tricks‟ the user into thinking the quality is so much better for th
same encoding bit rate. If you are using a standard web server you need to
choose the straight Real video codec. If you are using a media server use t
codec. G2 has been developed to include SVT (Scalable Video Technolog
The server can drop frames dynamically in order to keep up with the strea
This does works not like surestream, which clocks down the connection. R
has a proprietary intelligence built in to the encoder, which uses mathema
algorithms to insert keyframe for you. You can have manual control but it
efficient and to increase quality you will increase BR. Real system also al
you to prioritise audio or video when network connectors become congest
This option is only available when running from a Real server system. If y
choose audio quality over video in a „During congestion‟ option you shou
expect dropped frames and frozen video. When the roles are reversed it w
audio tracks during congestion. Sure Stream Scalability It dynamically sca
content that your serving based on the connection speed of your client. Yo
encode multiple streams in one file. When you select the encoding rates e
ISDN, Dual ISDN, T1 the real server will provide the highest possible bit
within the file boxed on the actual connection. 15
Slide 16: Real also gives you the option of a max fps where it will automa
drop so many fps if the client cannot provide a continuous playback
performance. Microsoft‟s Windows Media Codec‟s WM technologies inc
several streaming media components based around the Win 2000 server O
are capable of encoding a 640x480 video at 30fps over a 1mps stream. Th
components are grouped in Media Encoder. To create .wmv file use windo
media services to serve the .wmv stream and WMplayer allows you to wa
Windows media resource but helps producers in creation, distribution and
playback of .wmv files. Windows Media Encoder 7.1 includes de-interlac
inverse telecine to improve the compressed picture quality. As explained e
in lecture. Osprey 500 card is developed and optimised to exclusively sup
WM format. It is the first digital captive card to include tight integration w
WM Encoder. The reduction is 655 is reduced because the A to D convert
lossless. This particular card does the DV decoding on its card rather than
CPU like a normal IEEE1394. This particular card has a maximum file siz
17 terra bytes. It is state of the art, so it can directly capture large amounts
data. With WM technologies, Microsoft introduced Microsoft media serve
MMS is its server protocol. MMS protocol has both a data delivery mecha
which ensures that packets reach the client and a control mechanism to ha
clients requests eg stop/play URLS;s point to media clips or a windows m
server usually being MMS:// MMS has in itself two protocols which acts a
subject to explicitly request the stream to use UDP or TCP. Mmst and Mm
protocols are now encompassed inside MMS. HTTP protocol can stream f
normal web server but it is the slowest of the protocols. Unlike RTSP and
it cannot 100% support a constant bit rate. It just serves the stream as fast
can. With Real server, real networks introduced as its primary server proto
the real time streaming protocol. RTSP RTSP is an open standards based
protocol for streaming. To use this protocol URL‟s point to media clips on
Real server, they begin with RTSP://. WM architecture encompasses man
delivery mechanisms, but the familiar. AST format (Active Streaming For
targeted at the streaming market. 16
Slide 17: They adopted this format when they entered the web video mark
MPEG 4 codec was still in development and so their MBEG 4 is not a true
MPEG4 they renamed it Windows Media Video codec. The latest version
but you require an updated media player, which is freely available. This a
allows you to set the amount of keyframes, which WM encoder refers to a
frames. You can control the compression by finding a happy medium betw
smoothness or crispness. If motion is important you edge the slider toward
lower end of the scale and it will smooth and blur the image slightly. If im
data such as text or edges is more important you set a higher setting for
crispness. Microsoft‟s current technology for dynamic scaling is called
intellistream. It works like Real Surestream. You are limited to just two di
bit rates of video and the audio rate must be saved on both. Assessment H
Part one of the assessment asks you to choose the Big, medium and small
settings to create streaming files for Real, QuickTime and Microsoft. You
not alter any settings for part1 just choose boxes and render the files. Only
be chosen at a time (unlike my picture). How to do the encoding part of th
assessment Set up the file with the following parameters, this allows a fair
be conducted. Frame Size 320 x 240 17
Slide 18: Frame Rate of 15fps Data Rate split between audio and video V
300kbit Audio – 80kbit This gives you the ability to see what the processi
filters actually, visually do. Analyse your observations and base your conc
of these pre-processing filters on the observation and the theory.
REQUIREMENTS In a group of four, utilising two computers you are to
a live stream suitable for streaming a live radio station. Using 2 computers
will encode the audio into a window media audio file and a Microsoft Me
Server to stream the live file. Live Audio streaming Insert a CD into the C
player and using media player play the CD. Set the sound card audio reco
properties to wave out. The enables the sound from the CD player to be se
inside the PC and so windows media encoder can listen for it. To navigate
sound card properties double click the volume control (the speaker like ic
the bottom right hand corner of the windows desktop. Tehn click
options>properties then hit the recording button and select wave out mix.
Slide 19: Wave out will then be available for you to select like shown belo
Without this selected the signal cannot be received by windows media enc
Encoding the audio using Windows Media Encoder For the purposes of th
you will be using Windows Media encoder ver 9. This software is availab
from
http://www.microsoft.com/windows/windowsmedia/9series/encoder/defau
19
Slide 20: Setup windows media encoder to broadcast your live audio strea
Follow the wizard. De-select the video check box and ensure the audio ch
is select. (see diagram above). Set the file to broadcast on port 7070. This
any port expect but for today we shall use this particular port. Information
ports A port can be thought of as a hole, which your bit stream of data is s
through to the network. A PC can have thousands of ports, each service th
Slide 21: uses the NIC (network interface card) e.g Email, Internet etc use
separate port. The Internet uses port 80 where as FTP information uses po
These can be monitored by running a firewall on your PC. E.g Sygate Per
Firewall can monitor incoming and outgoing packeted information. Unica
Streaming Unicast is a one to one client server relationship. It‟s a little lik
you turn on a VCR. A unique stream is sent from the server. No other clie
access to this stream either. But I wouldn‟t hold me to this if discussing it
security terms. Each stream can be terminated by the server or the client. T
communication channel between the client and the server stays open as pa
travel from the server to the client. This maximises the ability to compens
lost data and deliver a better experience to the end user. Uses can also pau
forward and rewind the incoming stream. This is not the case if the file is
streamed from a web server but only from a real media server. Multicast
Streaming Multicast streaming is like watching TV. A Media server gener
one single stream that allows multiple player-clients to connect to it. User
watch the content from the time they join the broadcast. The client conten
the stream but not the server. Thus, because the clients do not connect to t
server feedback cannot be sent. This means replacement packets cannot be
if they are lost. This does save bandwidth as 1000 connections to a 500k s
means no more to the server than 1 connection. To support multicasting
networks must be equipped with routers and switchers supporting multica
protocols. Many Internet service providers do not have hardware to suppo
packets delivery via multicast protocols. As the 21
Slide 22: Internet was designed the hardware and software on to delivery
images, text and applications but not real time data such as video and audi
recent years ISp‟s have been upgrading their networks to increase bandwi
it will take 5-10 years before all ISP‟s can fully multicast. Corporations te
be the main users of multicasting. ISP‟s to the home will be the slowest un
streaming media users rises heavily it will not happen too quickly. When t
modem has been buried and unicast streaming loads become too much thr
high volume usage will the ISP‟s sort this out. Prehaps then we will see th
TV channels go too video streaming as well as traditional transmission.
Multicasting also uses class D IP addresses in the range 224.0.0.0 – 239.0
Protocols Media delivery protocols used for streaming range from UDP,
Multicast UDP and TCP which allows a choice of delivery based upon RT
time protocol). Real, Windows and QuickTime all use UDP initially as th
preferred mode of delivery. If UDP is blocked by a firewall (firewalls bloc
from coming in from specific ports) it rolls over to use TCP. The Microso
MMS protocol can also automatically rollover to http streaming (not 100%
reliable though). The UDP stream is classed as connectionless. TCP is not
connectionless 22
Slide 23: because it constantly generates authentication and verification si
that adds to data on networks. It also allows for things like FF, RW and PL
of unicast in demand media streams. Both MMS and RTSP uses TCP to c
the requests for interaction over the streaming media even if they are steam
via UDP or HTTP. When a client calls the server, a TCP request asks for a
connection. When the server confirms the content it first attempts to send
packets over the UDP port. If the network congestion or a firewall blocks
data the player attempts to get the server to use the TCP port. It will then u
HTTP port. (HTTP = 8080). However, you can configure your streams to
through any port. Using Real you use the following code
Rtsp://real_server_name:8080/file.rm?cloakport “554, 7070, 8080” 554 =
port 8080=Http port 7070 = PNM port (Progressive Networks Media) So,
have discussed the job of the server but what about the media player? The
must be able to understand the real time streaming protocol. Decode the m
and perform error correction (as necessary) and then play it. This is a very
complex process that self adjusts to network loads and delays several time
second all the while trying to appear as if the audio and video is playing w
interruption. It contains a buffer which stores the steamed packets in RAM
time is invaluable in allowing the packets to be resent. If the player is
extensively buffering it generally means network congestion and the playe
cannot display the missing packets quickly enough to be real time. Anothe
delay is bottlenecking. This happens when the user attempts to view a stre
big for their connection. In networking, the term protocol refers to a set of
that govern communications. Protocols are to computers what language is
humans. Since this article is in English, to understand it you must be able
English. Similarly, for two devices on a network to successfully communi
they must both understand the same protocols. What's a playlist? Many di
audio and multimedia players for your computer support playlists. A playl
offers you better organization and management of the various music files
your computer by controlling what files are played and in what order, muc
a music playlist used by radio stations. Playlists are commonly used by am
and professional computer DJs at parties and dances to allow a continuous
of music, queuing programmed and requested songs. More advanced prog
playlist feature can support fading and mixing between tracks, sorting by
or genre, and effectively give you the ability to turn your computer into a
modern jukebox. 23
Slide 24: Within a playlist file (which can be viewed as a text document)
local (hard-drive) and/or remote (Internet) location of each file within that
playlist. As the audio player moves through each file on the playlist, it sou
that file from the specified location, either on your hard-drive or the Intern
URL). Playlist formats: • • • • • .pls [WinAmp MPEG PlayList File] - The
extension for a playlist created in Winamp that can contain MPEG audio f
.m3u [MPEG URL file] - This extension is used to stream and MP3 file o
.asx [Active Streaming File - Windows Media] .wvx/.wax [Windows Med
metafiles] - When a browser downloads a file with one of these extension
a Web site, it opens Windows MediaPlayer. Windows Media Player then
and plays the content specifiedin the file. .m2a [MPEG Archive Enhanced
Playlist File] A playlist can be written in two formats. SMIL and ASX. SM
has now taken over from ASX. Creating a SMIL File You can create a SM
(extension .smil) with any text editor or word processor that can save outp
plain text. If you are familiar with HTML mark-up, you will pick up SMIL
quickly. In its simplest form, a SMIL file lists multiple clips played in seq
<asx version= 3.0> <entry> <ref href ="http://mediaserver/folder/one.wm
<audio src=" http://mediaserver/folder/two.wmv "/> <audio src="
http://mediaserver/folder/three.wmv "/> </entry> </asx> <smil> <body> <
src="rtsp://realserver.example.com/one.rm"/> <audio
src="rtsp://realserver.example.com/two.rm"/> <audio
src="rtsp://realserver.example.com/three.rm"/> </body> </smil> Legal A
of Content Distribution In its early stages the internet was saw as a global
system designed to deliver data or documents. The exploitation of the web
so fast 24
Slide 25: governments had no legal infrastructure in place. An example f t
the ongoing process in the USA to establish Internet Tax Laws. The most
famous being battle belongs to the music industry. Record label bosses fai
envision the potential of the internet as a major distributor. 1999 saw the s
legislation task forces to search the globe to eliminate the free distribution
media in violation of copyright laws. It was essential to write and pass law
online copyright laws. In November 1999 at the first MP3 conference in N
York record companies witness the distribution of CD in MP3 format. Th
suddenly realised their revenue was under threat and sent their lawyers to
to stop companies from illegal distribution. Companies like MP3.com and
Napster had to then comply with US copyright laws and pay fines or face
shutdown. The law currently states any means of distribution of media mu
authorised by the owner. A financial statement is needed between the own
the distributor, the sharing of media without consent and with no exchang
fees was viewed as a clear violati0on of copyright laws (only after the law
updated!). www.publaw.com Unicast v IP Multicast. There are two key
streaming delivery techniques: unicast and multicast. Unicast refers to
networking in which computers establish two-way, point-topoint connecti
Most networks operate in this fashion....users request a file, and a server s
the file to those clients only. When streaming multimedia over a network,
advantage to unicast is that the client computer can communicate with the
computer supplying the multimedia stream. The disadvantage of unicast is
each client that connects to the server receives a separate stream, which ra
uses up network bandwidth. Multicast refers to the networking technique
which one computer sends a single copy of the data over the network and
computers receive that data. Unlike a broadcast, routers can control where
multicast travels on the network. When streaming multimedia over the net
the advantage to multicasting is that only a single copy of the data is sent
the network, which preserves network bandwidth. The disadvantage to
multicasting is that it is connectionless; clients have no control over the st
they receive. To use IP multicast on a network, the network routers must s
the IP Multicast protocol. Most routers now handle multicast The Video
Streaming Server is responsible for delivering compressed video to each
individual request for a particular video stream. This is usually handled by
of the commercial streaming media software packages such as RealNetwo
RealSystem™ or Microsoft® Windows Media™ Technologies. The band
connection to the Video Streaming Server must accommodate the total
bandwidth of all the requests for a video stream, unlike the Encoding Stati
which must only accommodate one copy of each. As a result, the Video
Streaming Server usually has a direct connection to a very 25
Slide 26: high bandwidth line. For example, if there were 100 requests for
video stream compressed at 28.8 Kbps, the server would require at least a
Mbps connection. The Encoding Station and the Video Streaming Server
one single system. However, unless hardware encoding is used, this would
typically be for a situations requiring limited performance (e.g. a single in
stream and a small number of viewer requests). Even so, it would still req
fairly high-performance system. It is much more common to have two sep
systems. The Web Server for video streaming is in no way different from
Web Servers. The web site merely contains a URL link to the Video Strea
Server - one for every available video stream. Typically this is an icon on
web page which gets selected. A Video Player application is required to d
the specific video stream received by the system requesting the stream ov
Internet (or corporate Intranet). The most popular current video streaming
applications are RealNetworks® RealSystem™ and Microsoft® Windows
Media™ Technologies. Both of these require downloading a correspondin
Video Player application such as RealPlayer® or Windows Media™ Play
both of these are free. There are other video streaming applications that ar
implemented in such a way as to include the player in the stream and no
download is required. Internet Protocols. There are several internet protoc
available for streaming data, TCP, UDP, RTP, RTSP, MMS & HTTP.
Generally, each configures the data into packets, with each packet having
'header' that identifies its contents. The protocol used is usually determine
the need to have reliable or unreliable communications. TCP is a reliable
protocol designed for transmitting alphanumeric data; it can stop and corr
itself when data is lost. This protocol is used to guarantee sequenced, erro
transmission, but its very nature can cause delays and reduced throughput
can be especially annoying when streaming audio and video. User Datagra
Protocol (UDP) within the IP stack, is by contrast, an unreliable protocol i
which data is lost in preference to maintaining the flow. Real-Time Protoc
(RTP) was developed by the Internet Engineering Task Force (IETF) to h
streaming audio and video and uses IP Multicast. RTP is a derivative of U
which a time-stamp and sequence number is added to the packet header. T
extra information allows the receiving client to reorder out of sequence pa
discard duplicates and synchronise audio and video after an initial bufferin
period. Real-Time Control Protocol (RTCP) is used to control RTP. With
RealServer™, RealNetworks introduced as its primary server protocol the
RealTime Streaming Protocol (RTSP); an open, standards-based protocol
Slide 27: for multimedia streaming. To use this prot0col, URLs that point
                                                                     media clips on a RealServer™ begin with rtsp:// With Windows Media™
                                                                     Technologies, Microsoft introduced Microsoft Media™ Server (MMS) as
                                                                     primary server protocol. MMS protocol has both a data delivery mechanis
                                                                     ensure that packets reach the client and a control mechanism to handle cli
                                                                     requests such as Stop/Play. MMS includes both Microsoft Media Server
                                                                     protocol/UDP (MMSU) and Microsoft Media Server protocol/TCP (MMS
                                                                     subsets to explicitly request the stream to use UDP or TCP respectively. M
                                                                     Stream Broadcast Distribution (MSBD) protocol was used to transfer stre
                                                                     from the Windows Media™ Encoder to the Windows Media™ Server or
                                                                     between servers. However, Windows Media™ Encoder 7 no longer suppo
                                                                     MSBD and uses HTTP instead. URLs that point to media clips on a Wind
                                                                     Media™ Server usually begin with mms:// Hyper Text Transport Protocol
                                                                     (HTTP) is the slowest of the protocols and is used by Internet Web Server
                                                                     HTTP is transparent to some older firewalls and can bypass security in su
                                                                     cases. Unlike RTSP and MMS that can serve the stream at a steady bitrate
                                                                     HTTP would just serve the stream as fast as it could, hence it is better to h
                                                                     separate web and streaming servers. 27

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