IPTV Workshop FDB104

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FDB104 IPTV workshop

FDB104 IPTV workshop

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  • 1. Workshop 1 IPTV James HarrisFDB09104 Page 1
  • 2. What is IPTV?IPTV describes a system where TV is delivered over the internet.These systems can take many forms from traditional broadcaststyle channels that are multicast to entire networks of computersthrough to on demand services where content can be viewed atany time, for example youtube.IP NetworksWhen we talk about the internet we are just describing a group ofcomputers that are connected together using the Internet Protocol.This gives us an extremely flexible way of transferring databetween computers, but it is not without its limitations.BandwidthOne of the limiting factors of any network is bandwidth, this ishow much data can be transferred across the network in a givenamount of time and is usually expressed in kilobits per second ormegabits per second. This becomes slightly more complicated fora home broadband connection as the system used (ADSL –Asynchronous Digital Subscriber Line) has a different bandwidthin each direction.According to YouTube*, the average connection speed is around 4megabits per second downstream (from the ISP to to the user).Upstream data is not available but for ADSL would usually belimited to 512 kilobits per second upstream.*This data is aggregated from YouTube video servers. All ISP andgeographical speed numbers are averages across many types of Internetconnectivity. Data retrieved 2/3/2011.FDB09104 Page 2
  • 3. Video compressionIn order to use the internet to send video, we must usecompression. Normally video would require vast amounts ofbandwidth (the magic number for standard definition is 270megabits per second) thankfully video compression can reduce therequired bandwidth to a useful rate for IPTV.The more compression is applied the lower the bandwidthrequired to send the video, but also the more noticeable thecompression becomes. The video will tend to look more and more“blocky”, these artefacts are due to the way the compression isachieved.So when we compress video for IPTV we have to think about howmuch compression to apply. Too little and we wont be able tosend our video over the internet, too much and the videocompression artefacts will become objectionable to the viewer.Clients and serversNetworks are traditionally made up of two main classes ofcomputers, these are clients and servers. Servers are computersthat provide a service or services to other computers in a networkwhile clients receive services from servers.In the context of IPTV a client will be the computer the viewer isusing to access the video and the server is the computer that issending the video. Most IPTV services use a client-serverarchitecture.It is also possible to have a system known as peer-to-peer whereFDB09104 Page 3
  • 4. all computers are considered to be peers, neither clients norservers. Data (video) can then be exchanged between computerswithout relying on a server. Most peer-to-peer networks dohowever use a server to track peers, making an initial connectionfor each peer.StreamingThere are principally two ways the video can reach the viewer,either the video can be streamed where it is viewed as it is beingtransferred or it can be progressively downloaded and viewed afterthe download is complete.Progressive downloading can be a huge advantage for viewerswith a slow internet connection as the rate at which the video isdownloaded does not affect the quality of the video.Streaming on the other hand provides for near real-time viewingas long as the internet connection can support the bandwidthrequirement of the video being viewed.The webWe need a common way of exchanging data between computersso we have HTML, or the Hyper Text Mark-up Language. This isa way of describing pages of text and images so that informationcan easily be shared.HTML contains a number of tags that describe the formatting ofthe page and allow other content to be embedded. Because the tagsare just text inside the < and > symbols we can edit web pageswith a simple text editor such as notepadFDB09104 Page 4
  • 5. A basic HTML file (a web page) might look like this:<html><body><h1>This is my Main Page</h1><p>This is some text.</p><p><a href="page1.htm">This is a link to Page 1</a></p><p><a href="page2.htm">This is a link to Page 2</a></p></body></html>When displayed in a web browser it would look like this: This is my Main PageThis is some text.This is a link to Page 1This is a link to Page 2The tags are interpreted by the browser which makes the necessarychanges to the formatting of the text as well as adding specialfeatures (in this case we have added 2 hyperlinks to other pages).Embedding Youtube videoYoutube video is easy to embed into a web page:Firstly you will need to find a youtube video you want to embed, Ichose a video about embedding videos:http://www.youtube.com/watch?v=ZnehCBoYLbcFDB09104 Page 5
  • 6. Once you have found the video you want, look below the videoand you should see a button marked embed, clicking this buttonopens up some embedding options:Include related videos – At the end of a video, users are given theoption to watch other related videos, this may take them awayfrom the rest of your site if left ticked.Privacy enhanced mode – Reduces the amount of informationstored in cookies on the computer viewing the video.Use HTTPS – If the site you are embedding the video into is on asecure server, then you should use this setting to maintain thesecurity of the site.Use old embed code – Switches from iframes embed code, back tothe old object based embed code for compatibility reasons.Choose a resolution for the video, then simply copy the text fromthe embed text box and paste it into your html file. The resolutionchosen will affect how long the viewer has to wait for the video toload (dependant on their internet connection speed).FDB09104 Page 6
  • 7. For the video I chose the embed code was:<iframe title="YouTube video player" width="640" height="510"src="http://www.youtube.com/embed/ZnehCBoYLbc?rel=0"frameborder="0" allowfullscreen></iframe>The old object based code for the same video:<object width="425" height="344"><param name="movie"value="http://www.youtube.com/v/ZnehCBoYLbc&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><paramname="allowscriptaccess" value="always"></param><embedsrc="http://www.youtube.com/v/ZnehCBoYLbc&hl=en_US&fs=1&"type="application/x-shockwave-flash" allowscriptaccess="always"allowfullscreen="true" width="425" height="344"></embed></object>Please note, anyone who uploads a video to youtube may select anoption to disallow embedding.For more information on HTML the site:http://www.w3schools.com provides a good referenceFDB09104 Page 7
  • 8. Now lets compare each system: System Advantages DisadvantagesMulticast Server requirements are Uses bandwidth to each relatively low consumer regardless of whether or not it is Bandwidth usage is being watched consistent regardless of have many viewers Each ISP must choose to watch reconfigure their network to support Content can be changed multicast data in real time eg one programme substituted for another or a news flash can be shownOn demand eg youtube Any viewer can watch Very heavy server any programme at any requirements, each time viewer directly adds to server load Content can be packaged up into Unpredictable server channels if desired requirements depending on how many viewers On demand services use the service at any can usually have live given time programmes added, for example streaming of newsPeer-to-peer Extremely low server Generally not real time. requirements Content is downloaded for later viewing Viewer content can easily be addedFDB09104 Page 8