Networking - RealPlayer
Contents
1. 53 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual Firewalls and Security Security is one of the biggest concerns for people connected to the Internet whether at a business or at home Businesses however have specific concerns and specific ways of dealing with those concerns For this reason certain precautions have become common on networks When you log on to a computer at work you almost always have to type in a username and password to gain access to the full network This is one type of security Password security is mainly designed to control access to your machine at its present location Firewalls a different type of security are designed to protect your computer and network from outside influences Figure 6 9 Firewall RealServer n e e e hr a a a a l w s Firewalls are a complex topic but there is one specific aspect that is of interest to RealPlayer customers In general a firewall is a gatekeeper on the network All outside traffic passes through the firewall when communicating with the Internet and other off site computers Most of this traffic is one way the firewall will allow you to send commands out such as requesting a Web page but it won t allow two way communication that would give outside machines and programs control over internal machines and programs Damage to the network and theft of information is curtailed by using this method Howev2. 39 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual Internet unique address and all the bits pieces of information have an address to which they will eventually be delivered For those that know about multicast that is discussed in Multicast on page 53 For those that don t be patient we ll get there A piece of information can be very small such as a simple yes answer or very large such as your favorite song If everyone on a network were given exclusive use of the wire until the whole message was sent or received it wouldn t work very well Can you imagine trying to get your e mail and having to wait while someone else listened to Beethoven s Fifth symphony To avoid this problem messages are broken into lots of little pieces of information that are called packets On most common networks each packet is the same size and is addressed as described above This process may sound like extra work but it keeps the flow of information smooth and constant with fewer bottlenecks It is easier for a number of same sized cars to merge onto the freeway from the same ramp than it is for a bunch of cars and an 18 wheel trailer to merge on from the same ramp In the latter scenario a large number of cars will have to wait as the trailer passes and then wait again while the trailer waits for room on the highway so it can finish its merge Handling the flow of information are a number o
3. af WHAT IS STREAMING MEDIA AND HOW 7 DOES IT WORK fs RealPlayer 8 Plus and RealSystem G2 with Flash are a huge leap ahead for streaming technology on the Internet RealSystem G2 is the collective name for the newest generation of RealNetworks collection of servers and tools that create and serve content to your RealPlayer Of course most of the bits and pieces of RealSystem G2 are hidden from you when you watch or listen to clips What follows is an explanation of how streaming media works and how RealSystem G2 and RealPlayer fit into the scheme of it all a little techy but in an easy to understand way we want you to be as excited by what s going on as we are Networking To understand how RealPlayer works you first need to understand networking In its most simple form networking is one computer exchanging information with 401 another machine This isn t much 22 different from mailing a letter 103 425 101 The first computeraddresses a piece of information to 101 another computer and then sends it across the wire the 1401 cable that connects computers to one another The second computer checks the addresses of all of the messages coming by and reads only the messages addressed to it Of course when you have many computers and a great deal of information this process gets more complex The eSsentials described above however are the same no amp matter the size of the network Every computer has a
4. RealPlayer sends the Normal and Maximum bandwidth settings from the Connections tab of your Preferences to the RealServer serving the clip 2 The RealServer automatically selects the streams encoded at a bitrate closest to your Normal setting without exceeding it If your actual connection is faster than Normal the server will upshift to a higher bitrate if it is available This ability to upshift is a RealSystem G2 feature called SureStream Prior to RealSystem G2 whatever bitrate you connected to initially was what you were stuck with for the entire clip even if your connection got faster or slower Because streams in the new RealSystem G2 can be encoded for several different bitrates within the same file RealServer is able to intelligently pick the best possible stream for your current connection SureStream also monitors your connection for you If it senses too much congestion it will downshift certain streams Content providers can choose which streams they feel are more important to your experience for example voice quality over animation If SureStream senses that your connection is better than expected it will upshift to a higher bandwidth on all or some of the streams to bring you a higher quality presentation Upshifts and downshifts will happen automatically Figure 6 7 Multiple Streams SureStream becomes especially important RealText 5 Kbps when you are viewing some of the newer d Animation p 12 Kbps presen
5. is for RealPlayer Each stream carries specific types of information When you watch a video the visual part what you watch comes to you in one stream while the sound comes in another RealPlayer synchronizes these two separate streams so that the right words come out of a newscaster s mouth when they should or so that music crescendos appropriately when the action requires it 44 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work Figure 6 4 Bandwidth Additionally streams can be optimized for different bandwidths Bandwidth is essentially the amount of information that can pass through a particular point of the wire in a specific amount of time The higher the bandwidth the greater the amount of information that can come through see Figure 6 4 Bandwidth The speed of your modem if that is what you use to 56 Kbps 28 8 Kbps connect to the Internet determines the bandwidth of the stream that you can receive A 28 8kbps modem can receive approximately 28 8 thousand bits per second A 56K modem is capable of receiving approximately 56 thousand bits per second almost double the capability of a 28 8 modem remember a bit is a single binary number Of course these capabilities assume that your phone connections are perfect which few are In other words your actual mileage may vary You may incorrectly hear people refer to these speeds as the BAUD rate However BAUD i
6. Codecs read digital information and process it into analog information for your player so you can listen to it CD players use codecs that convert the digital information on a CD into sound waves that you hear on your speakers or headphones Your RealPlayer decodes each specific type of file video text etc with a specific codec or plug in Additional Information You can see what plug ins and add ins you have by looking on the Upgrade tab of your Preferences see Upgrade Preferences on page 63 When you first install RealPlayer you will have several plug ins RealAudio RealVideo RealPix RealText and RealG2 with Flash Each of these different 48 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work types of media is encoded separately and sent in separate streams that your RealPlayer can decode synchronize and play From time to time we will update one or more of these plug ins or even add new plug ins to enhance your RealPlayer Tip The latest plug ins are always available via AutoUpdate Just select Check for Update from your Help menu Also if you attempt to play a clip that requires an updated plug in you will be notified and offered the opportunity to upgrade How does streaming occur Ok we now have streams of data being encoded and decoded by the plug ins and RealPlayer turning all of that information into rich presentations but where do these streams come fro
7. RealPlayer offers everything from music to entertainment to sports to news And because the menu talks to RealNetworks we make sure that the connections are always the right ones If the site moves we keep track of it so you don t have to do it yourself Of special interest should be your Real com Guide selections The Real com Guide is a collection of RealNetworks web pages with links to programming all over the Internet covering live and pre recorded streaming media of specific topics 56
8. as several built in features to help you as well as access to web pages that do some of the sifting for you Channels and Live Stations Your best tools are part of RealPlayer Radio Tuner and My Channels and Real com Take 5 Each have a number of pre loaded links to clips both live and recorded Additionally the Radio Tuner has the ability to search for Live Stations by content type see Radio Tuner on page 22 Media Access bar Radio Tuner connects you to the latest up to date list of radio and TV content on the Web Search offers you the opportunity to type in words or phrases of interest and looks for streaming media related to those subjects see Figure 3 10 Real com Media bar on page 15 Search will return a results page similar to those you see when you search for Web pages You must be connected to the Internet for Search to function Guide will take you directly to the Real com Guide the most comprehensive media hub for free Internet audio and video software and programming Find programming featured on the Internet and play it with one click Choose from 55 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual a comprehensive listing of downloadable music personal calendars and access to premiere programming More than 2 500 radio and television stations 8 000 Web sites and 500 daily live events are offered Web Sites Sub Menu The Web Sites sub menu under Favorites on your
9. ealServer which sends the actual stream and stays in contact with RealServer so you can fast forward or rewind or otherwise navigate through the clip In the case of Channels and Live Stations RealPlayer speaks directly to the RealServer without the need for the earlier pointer file RealServers are similar to Web servers but rather than serving pages to browsers they serve streams to RealPlayers RealServers work in concert with Web servers to bring multi media to networked environments such as the Internet Note Why networked environments rather than Web or Internet Because RealServers are also being used on company networks to make company wide addresses training and other information easily available to employees RealServers are available for download at http www realnetworks com RealPlayer and RealServers can communicate with each other so that RealServers can pick the appropriate streams to send you If a RealServer attempted to send a stream that was encoded at a high bitrate for example T1 a really fast connection and you only had a 28 8K modem you would not have a very good experience 50 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work SureStream So how do you get the appropriate stream for your RealPlayer when you try to play a clip RealPlayer as mentioned above can talk to the RealServer that is sending the stream In a more exact view of the process 1
10. ee How does streaming occur on page 49 so your RealPlayer can play it for you Additional Information This holds true for live broadcasts as well As with live television the performance or event is viewed by the cameras and or microphones and is converted as it happens to a form that can be sent to you a few seconds later Encoding The process of getting a file ready to be streamed is called encoding Encoding takes a file and breaks it up into readable packets so it can be sent and read on the fly remember Figure 6 1 Sending a book page by page on page 43 Every clip or every stream in a clip is encoded for a specific bitrate see also SureStream on page 51 The higher the resolution the more information a stream has the higher the bandwidth the larger the hose it needs to get the information through to you at a useable speed Additional Information Encoding is performed by special tools such as RealProducer by RealNetworks available at http www realnetworks comRealPlayer is able to read these files and encode new files when it is recording When you are playing a clip you can see at what bandwidth a stream has been encoded by looking at your Status bar see Figure 3 11 Status bar on page 15 The number shown is the stream bandwidth you are receiving at that moment For a single audio stream this is straight forward if you are receiving a 20Kbps kilobits per second audio stream that s what will show up o
11. er RealPlayer requires a two way connection to function properly Without two way communication you cannot fast forward through a clip or let a RealServer know that your system can accept a higher bandwidth stream RealPlayer can work through a firewall without exposing your network to any security risk but you may need to change your Proxy Preferences see Proxy Preferences on page 69 Proxy services in concert with your Transport Preferences allow RealPlayer to contact the Internet through a two way connection while still providing 54 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work protection to the rest of the system Proxy services act as an intermediary making requests on behalf of people on the inside of the firewall For example a web proxy knows how to get requests on behalf of a web browser Many proxy servers firewalls require that every program running inside a firewall have special configuration options RealPlayer can work using proxy but it must be configured to do so see Proxy Preferences on page 69 Additional Information For a much more in depth discussion about firewalls or to solve problems when trying to use RealPlayer from work see our web page http service real com firewall Content How to find it With over eight million servers each hosting thousands of web pages the Internet is overwhelmingly huge Finding content can seem daunting but RealPlayer h
12. f specialized traffic cops routers brouters bridges servers gateways etc However there are only two that you need concern yourself with servers and routers Servers are computers that store information e g videos e mail and ina company setting programs e g word processors These computers serve the information and programs to other computers on the network to which they re connected Every network has at least one server and sometimes several servers Routers scan the flow of information read the address on each packet of information and sends each packet along the appropriate route thus their name to get to its final destination The Internet is not a single specific entity You can t point to one thing and say That s the Internet The Internet is an interconnected collection of networks that speak to each other just as a network is an interconnected collection of servers and computers Sometimes this connection is physical 40 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work such as a wire or fiber optic connection but sometimes the connection is via satellite or microwave This might sound familiar When you pick up your phone to call someone the signal sometimes travels by wire to the person you are speaking to but it is often sent via microwave tower or satellites depending on how far away and where you are calling Some very quick history Yes Yo
13. f the newest language sets on the Web While HTML Hyper Text Mark up Language controls how Web pages present text and pictures on your computer screen SMIL controls how complex media presentations should be streamed to and laid out within your RealPlayer Figure 6 8 SMIL presentation RealPix RealText RealVideo By complex we mean a presentation that includes more than one clip being received by RealPlayer which is then synchronized with each clip being presented in a separate space For instance you could watch a music video RealVideo see the lyrics RealText hear the music RealAudio and browse stills from the concert RealPix all presented to you at the same time see Figure 6 8 SMIL presentation 52 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work In fact the Tutorials that introduce the new RealPlayer to you are SMIL presentations that include RealAudio RealPix and RealText Each element of the presentation is created and encoded see Encoding on page 47 separately and then the lay out is described to your RealPlayer using SMIL so it can present them together Additional Information To learn more about SMIL go to http www w3c org AudioVideo Multicast Multicast is the organic chemistry of streaming If you had the joy of taking organic chemistry or almost any higher level science class the first thing you are told is Forget everything you ve been taug
14. ht before because it s wrong Well we won t be quite that cruel here but multicasting is a unique process in the network environment In networking every packet of information is uniquely addressed to a specific computer Usually this makes a great deal of sense as each computer is more often doing something different than any other computer connected to the Internet at any one time But what about when 25 000 people all tune in to see the same concert or sports event Suddenly these people are watching exactly the same thing but each person has to have their own individual stream This can really slow down the Internet and diminish your experience Multicast takes an innovative approach to this problem What if you created one stream or a limited number of streams and told every player connected to the event to read the same stream by dipping into it Rather than 25 000 replications of each stream there are only a few replications which keeps congestion low and your connection more reliable and responsive Multicast is automatically selected by RealPlayer if it is available for a broadcast Additional Information Multicast requires special hardware on the Internet that must be provided by Internet Service Providers ISPs and other hosting services and isn t always available Also Multicast may not be selected if your Transport Preferences are set to use only one specific transport see Transport Preferences on page 66
15. m and how does your RealPlayer find them Remember the Internet is a simply a bunch of connected servers Servers serve information to other computers this is a loose definition but accurate for the moment A clip is any number of streams that make up a presentation As we discussed earlier a clip can be made up of more than one stream such as a video stream and a sound stream Clips themselves can be a single entity or several clips in a row This is why we say clip or in the case of multiple presentations multi clip So what happens when you click on a link in a web page to hear a clip or multi clip Figure 6 6 How RealPlayer connects to a RealServer Web Browser E gt fe RealPlayer RealServer 49 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual Step 1 All Web pages are stored on special servers called web servers When you click on a link in a Web page to listen to a clip whether live or pre recorded the web server sends your browser a small pointer file that is associated with that link Step 2 Your browser recognizes that the file isn t just another page so it checks to see what program can read it When it recognizes that it is a RealPlayer file it starts up RealPlayer and passes the file off to the your program Steps 3 and 4 The file is very small and contains only the name and location of the clip on a RealServer Your RealPlayer contacts the R
16. n your 47 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual Codecs Status bar What if you are receiving multiple streams The answer is Stream bandwidth is additive For example if you are watching a Macromedia Flash animation encoded at 12Kbps that also has an audio stream encoded at 10Kbps the bandwidth will appear on the Status bar as 22Kbps see Figure 6 7 Multiple Streams on page 51 The pipeline or bandwidth available from your modem has a set limit you can t make your modem work faster than it is capable of working Content providers usually encode their streams to handle a variety of bandwidths The higher the bandwidth the more information the better your experience RealPlayer uses buffering RealPlayer Plus can also use PerfectPlay see PerfectPlay on page 37 to overcome minor slowdowns on the Internet But to watch a stream encoded as a 56K stream using a 28 8K modem you would have to buffer a large amount of information Buffering means waiting and using a good deal of memory If something is encoded you must decode it in order to read it To decode information on your computer you use a codec Codec like modem is a word created by combining two actions of a process Modem modulator demodulator Codec coder decoder Modems convert digital information from your computer into analog information sound waves that can be sent over traditional phone lines
17. ns Large animations and video have a unique problem Both large animations and video are essentially a whole bunch of still pictures that need to be seen at a very quick rate to give the illusion of movement Until recently the best way to ensure that video and large animations worked well over the Internet was to download the whole file and run it from your machine at home If you downloaded the file yourself the download time was obvious you had to wait a long time till the file had finished saving Sometimes though you would just be waiting a very long time for the movie or large animation to begin During that time it was being downloaded to a temporary file on your hardrive before it started to play Enter Streaming Streaming takes files whether they are sound video animation or other media types breaks them up into smaller pieces and sends them to their destination This is very similar to how computers send information across a network or the Internet in general You may be scratching your head now asking But you just told me that information is sent to my computer in little pieces anyway What s the difference A good question Figure 6 1 Sending a book page by page Figure 6 2 Receiving a book page by page A A 43 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual The answer is what makes your RealPlayer so exciting RealPlayer is able to read the file stream as i
18. ommon practice for all internetwork communication Where do streams come from Streams have to be created by someone for you to watch them with your RealPlayer This means that an original performance or broadcast was recorded and then turned into a stream But how exactly does this happen Looking at Figure 6 5 Creating an audio stream you can see the four steps necessary for creating any kind of content Figure 6 5 Creating an audio stream 1 Capture Audio 2 Digitize and Optimize Audio E Sound Editing Station 3 Encode RealAudio M 4 Deliver RealAudio Clips Encoder eeoede ere RealAudio Encoder RealAudio RealPlayer Step 1 The performance is captured Captured simply means recorded or created in some way so that it can be changed later into a stream With some content e g animation there is no performance only the artist s drawings which are created The idea however is the same The originals are captured on the computer so they can be changed at a later time into a stream 46 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work Step 2 The captured performance is edited so that the presentation you receive is what the content provider wanted to show you Step 3 The edited performance is encoded see Encoding below into a stream Essentially this means that the file is prepared to be streamed Step 4 The encoded file is placed on a RealServer s
19. ore of the secure DARPA sub system Universities began adding additional servers and connections the Internet was born For many years the Internet was not much more than a massive e mail exchange and bulletin board system posted messages people could respond to in kind 41 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual This is now In 1990 CERN European Laboratory for Particle Physics with the help of Tim Berners Lee and the ideas of Ted Nelson began prototyping a standardization for information sharing that became known as the World Wide Web Additional Information You may recognize that the www in most common Internet addresses is in fact World Wide Web To this day Berners Lee still shapes and directs how the Web develops through the W3C World Wide Web Consortium http www w3c org While the Internet is made up of physical entities the WWW is more an agreed upon collection of standards or rules about how to address packets and how to create Web pages with Hypertext Mark up Language HTML Before these standards everyone had different formatting codes much as different word processors create files that other processors may or may not be able to read HTML gave everyone a way to share information easily Information began to flow at an increased rate Additional Information You may have noticed that every Internet address begins with http HTTP Hyper Text Tran
20. s actually how frequently the base sound usually called a carrier wave changes per second Information is interpreted by how that sound changes Originally a single change say from a high tone to a low tone was a single bit of information Because of improvements in compression many more than just a single bit of information can be transmitted per change in the carrier frequency The important point is that the higher the bandwidth you can receive the higher the quality the sound or video will be Additional Information BAUD is named for French inventor Jean Maurice Emille Baudot 1845 1903 Among his other accomplishments Baudot patented in 1874 the telegraph code that eventually supplanted Morse code Morse code fell out of general use by 1920 Baudot s new code was a 5 unit combination of on off signals of equal duration as opposed to Morse s long short dash dot The code consisted of 32 five unit characters 45 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual covering each letter of the alphabet punctuation and additional machine controls The modern version uses 7 or 8 on off signals or bits that have 128 characters and is otherwise known as ASCII code now Not content with simply improving transmission speed and accuracy in 1894 Baudot invented a distribution system for simultaneous multiplex transmission of several telegraph messages on the same circuit which is now c
21. sfer Protocol is another kind of standard or protocol HTTP tells your browser and computer that HTML has been sent to it so it can read the incoming information HTTP gives the server and your computer a common dictionary so that the information coming in makes sense In the case of your RealPlayer you may notice that the addresses start PNM Progressive Networks Media or RTSP Real Time Streaming Protocol which your RealPlayer recognizes and speaks PNM is an older protocol but many clips are still around in that form Any newer RealSystem G2 content will have RTSP before the address of the clip Edit a Favorite to see its address URL These protocols become important if you are using your RealPlayer at work because of firewalls see Firewalls and Security on page 54 42 RealPlayer 8 Plus User Manual CHAPTER 6 What is Streaming Media and How does it Work Streaming Equally as important cheaper faster hardware became available in the mid 80 s and early 90 s to the public at large The Internet exploded from a text based system to one that contained pictures sounds videos and animations Why Simple text words and letters requires very little information to reproduce It is easy to send around whole pages of information in relatively few packets quickly even at slower connection speeds Sound files can be small but it depends on their quality and length The same is true for pictures and small animatio
22. t is coming in and begin playing it long before the rest of the file arrives Imagine reading a novel as someone hands you page after page rather than waiting for them to finish the whole book and handing you the entire novel at once Of course if the file was simply read and played for you as it came in you would have a good number of interruptions think about how often you have to wait for a Web page to display on your screen Now consider that Web pages are much smaller than most media files audio video animation etc RealPlayer combines another technology with streaming to make playback smooth buffering During buffering a whole bunch of packets are collected before being played Figure 6 3 Buffering Imagine a cup being filled from above in fits and starts A small hole in the bottom Incoming ofthe cup allows a constant stream of Packets water to drain from the cup As long as there is enough water backed up in the cup the stream will continue to flow out Buffered 2 a steady rate see Figure 6 3 Buffering Reserves As RealPlayer begins to play the file it continues to collect packets in reserve This means that even if there are minor Constant delays in getting the information packets ar li to your computer your experience of the music will be continuous rather than having it stutter along erratically So what is a stream Above we explain what streaming does but not exactly what it is At least not what it
23. tations that RealPlayer is capable of Voice over playing When playing a SMIL presentation 8 Kbps see SMIL below each of the different streams for each of the components of the N _ presentation has a bitrate associated with Presentation it The total of all of those bitrates is the e lowest connection speed you need to have to play the clip without excessive buffering 2a ps For instance a presentation that had an 8Kbps voice over a 12Kbps Macromedia 51 CHAPTER 6 What is Streaming Media and How does it Work RealPlayer 8 Plus User Manual SMIL Flash animation component and a SKbps RealText component would need at least a 25Kbps connection 8 12 5 25 to play without buffering constantly Each stream flows into the same river and adds to the whole presentation that your RealPlayer plays see Figure 6 7 Multiple Streams Of course RealPlayer buffers for you automatically to help you play higher bitrate streams So even over slower connections you can experience superior quality media The price you pay to watch higher bitrates over slower connections is the time it takes to buffer which is still much shorter than it would be to wait for the whole file to download Now the fun begins RealPlayer can play multiple clips presented simultaneously as a single presentation This is done using SMIL pronounced smile Synchronized Multimedia Integration Language you see why we stick with acronyms SMIL is one o
24. u can skip this but didn t you always wonder Unlike the phone system no one set out to create the Internet as we know it today In fact it didn t even begin life as the Internet but rather as ARPANET Advanced Research Projects Agency Network in 1969 Note To be wholly honest no one set out to create the American phone system as it is today either It was a number of smaller private companies that eventually merged into one giant company before it became several smaller companies again That was then ARPANET s original purpose was to help universities the American military and the U S Defense Department contractors maintain internal communication even during natural disasters and wars and exchange information easily ARPANET began life with four servers a far cry from the eight million or more servers that comprise the Internet today In 1973 ARPANET became DARPANET Defense Advanced Research Projects Agency Network DARPA pioneered the research of how to best exchange information across this internetwork Their research led to the development of TCP IP Transmission Control Protocol Internet Protocol that for the purpose of this discussion is currently the standard way all those packets of information your computer sends out are addressed so they get to the right place all together and in the correct order Universities were quick to exploit this amazing infrastructure of communication Around the c
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