Differences between Unicast, Broadcast, and Multicast, Facilitating Live Video Streaming - Case Study Example

Video streaming technologies Overview of video streaming Facilitating live video streaming of sports event Live video streaming is very popular today. This allows one to watch the video when it is still being downloaded. Thus, viewers are able to get videos in real time unlike in the past when the video had to be pre-recorded before being transmitted. Live video streaming involves conversion of signals into compressed signals that are then transferred by use of special web servers. Live event streaming technology has various advantages. It facilitates communication and allows broadcasters to grow their business and expand their audiences. Event streaming technology allows broadcasters to transmit events such as world cup in real time to selected audience. The technology allows one to broadcast from a web cam or to broadcast major sporting events such as world cup. The cost of event streaming depends on duration of the event and the number of viewers. Event streaming allows one to deliver crystal clear video and audio content to selected audience in real time. the broadcast can also be transmitted to everyone. Five major video coding standards for video streaming applications, targeting for full HD resolution with DVD quality A successful video coding standard ought to meet various requirements. First, the standard ought to be interoperable. This implies that the standard ought to assure that decoders and encoders from varied manufacturers work together seamlessly. Second, the standard needs to be innovative. This implies that a new standard ought to have a better performance than a previous standard. Third, the standard ought to allow competition between manufacturers on the basis of technical merit. This implies that only reference decoder and bit stream syntax ought to be standardized. The standard should also be independent from transmission and storage media. This implies that it ought to be flexible enough to be utilized for a range of applications. The standard should also be forward compatible in that it ought to decode bit streams from the previous standard. Finally, a successful standard ought to be backward compatible. This implies that previous generation decoders ought to be able to partially decode new bit streams. One of the major video coding standards for video streaming applications is JPEG. This was the first widespread image compression standard. It allowed compression of digital images. It is currently utilized for digital still cameras and web pages. Its compression quality is dependent on the content of the image. This standard is not optimized for video although it has been used for coding video with motion JPEG. Motion JPEG consists of independently coding frames in a digital video sequence by use of JPEG. This is commonly applied in network viedeo surveillance. The arctecture of JPEG standard is illustrated below. Another major video coding standards for video streaming applications is the H.323. this is a standard which provides a basis for audio, video and data communication across IP-based network. It defines how multimedia data streams ought to be assembled into IP packets. However, it does not provide guaranteed quality of service (QoS). It allows interoperability of multimedia applications and products from different vendors with fixed standard for compression and decompression of video and audio data streams. It also allows users to communicate without being concerned with compatibility. Gateways can be used to interoperate between H.323 and other standards. The architecture of H.323 is illustrated below. The standard is sufficiently open and hence allows interworking with other communication protocols such as SIP. It can also be adapted to any kind of codecs. Another standard is MPEG which is the most widely spread collection of standards that is used for compression and transmission of video data. It includes MPEG1, MPEG2, MPEG3, MPEG4, MPEG7 and MPEG21. The MPEG codecs employ lossy data compression. This entails division of sounds or pictures into small blocks. These are transformed into frequent space and the vector is quantized. The data that results is entropy encoded. The MPEG standard has three different frames: intra-frames, predicted frames and bi-directional-interpolated frames. MPEG video is made of several groups of o7f pictures which have sets of video frames that rely on inter-frame compression. H.26X is another major video coding standards for video streaming applications. It is composed of H.261, H.263, and H.263+ video conference codecs. It is suitable for lower rates of transmission in low debit networks. The H.261 utilizes bit rates of px64 kbits/s where p ranges from 1 to 30. This codec requires less computational effort for real time encoding as compared to MPEG. Thus it trades picture quality against motion. The H.261 exploits temporal redundancy and prediction, and spartial irrelevancy. H.263 is a H.261 extension that allows use in application such as multimedia/videophone terminals by use of public switched telephone network (PSTN). The H.261 only has CIF (common intermediate format) and quarter CIF while H.263 has an additional sub quarter CIF. Whereas H.261 is limited in motion accuracy to integer pixel accuracy, H.263 has half pixe;l accuracy. Thus H.263 has a higher entropic compression than H.261. The H.263+ has PB-frame mode, advanced prediction mode, unrestricted motion vector and syntax based arithmetic coding. It also has 13 new optional modes. H.264/MPEG4 is another major video coding standards for video streaming applications. It evolved from H.263+. Only central decoder is standardized. This allows a high degree of freedom to optimize implementation specific to appropriate application. The architecture and the core building blocks for this standard are shown below. The H.264 provides a definition for an adaptive in loop deblocking filter. This allows reduction image blocking effect. The bit-rate requirement for streaming one full HD resolution stereoscopic 3D video with DVD quality The appropriate bit rate that is required is 12Mb/s since it is the constant bit rate that is estimated to deliver 3D Challenges of transmitting multimedia information over the internet and how to overcome them There are two main challenges that arise during transmission of multimedia information over the internet. The first challenge is fairness and the second one is the useless packet transmissions. The challenge of fairness arises because the data application uses TCP which cuts back the transmission rate when the router discards packets due to congestion. However, most multimedia applications use UDP which does not cut back transmission rates. As a consequence, multimedia information gets more bandwidth than the congestion responsive TCP flows. In recent years various packet queuing and discarding algorithms have been devised to address the fairness problems. These algorithms include WFQ, CSFQ and FRED. Analysis of these algorithms has indicated that they can effectively and fairly distribute link bandwidth among competing data and multimedia flows. Some of latest products have incorporated these algorithms. Unlike fairness issue, the issue of useless packet transmission (UPT) is not well understood. The basis of UPT is that for effective and meaningful communication to take place in packetized audio and video, the packet loss rate ought to be maintained under a specified threshold. If this threshold is exceeded, the received video and audio are useless. This implies that even if fairness is attained in a router and the packet loss is beyond the expected threshold, then the audio and video transmitted is useless. As such UPT reduces the bandwidth available to competing TCP flows and as increases file download times. The prolonged file download times increase power consumption and hence have direct impact on mobile computing. the impact of UPT is expected to become significant in future due increasing popularity of voice and video applications; increasing utilization of fair packet queuing algorithms and rapid proliferation of battery powered mobile devices. A UPT avoidance algorithm has been proposed to overcome this challenge. IP Multicast Differences between unicast, broadcast and multicast Unicast involves sending packets from host to host. It involves communication from a single host to another single host. It utilizes a single devise to transmit a message that is destined for one receiver. On the other hand, broad cast is where a single device transmits a message to all other devices in a specified address range. The broadcast may reach all host found on the subnet, all subnets or all hosts on all subnets. The host portion of broadcast packets has their addresses set to ones. Broadcast over the net is limited since modern routers block IP broadcast traffic and restrict it to the local subnet. Unlike the two, multicast is a special protocol for use with IP. It allows one device to communicate with a specified set of host that is not defined by any standard IP address and mask combination. As such, multicast allows communication that is similar to a conference call. Thus anyone from anywhere can participate in the conference once he joins it. The speakers message is broadcasted everywhere but only to those in the conference call itself. Multicast communication uses a special set of addresses. Benefits of adopting IP multicast for video streaming applications IP multicast has the advantage of allowing a host to transmit packets to a group that is made up of a subset of the hosts on the network. Moreover, it has the advantage of conserving bandwidth and hence reduces traffic by simultaneously delivering a single stream of information to many recipients. It also minimizes he burden on both receiving and sending hosts and as such reduces overall network traffic. Since communication is between a single sender and many recipients there is enhanced efficiency, optimized performance and allows multipoint applications. Video on demand Video on demand (VOD) allows users to select and watch video content on demand. IPTV technology is utilized in bringing video on demand to personal computers and televisions. In true video on demand the user has complete control over the session presentation. The user has full function VCR capabilities. This includes forward and reverse play, random and freeze positioning. Only a single channel is required for a true video on demand since multiple channels become redundant. A video on demand system allows multiple users to access it simultaneously with various viewing preferences. A typical video on demand has a local database and server connected to user homes through network. The user home has both network interface and a display. The user interacts with the system through a computer keyboard or a handheld RCD. The video on demand system has programming/information archive that is connected through a high speed network to many regional distribution sites. This increases reliability and availability of data transmitted and the information delivery is tailored to the taste of the user. This also allows easier management of data and for the system to be constructed in a regional piecewise fashion. Voice on demand sessions are usually long lived and require data transfer that is continuous. Video on demand communication requires interconnectivity that is of a high degree between information servers and users. How IP multicast can be used for video on demand applications Multicast is an excellent technique for server bandwidth demand reduction. However, its inherent limitations limit the deployment of multicast in provision of true voice on demand. IP multicast can be used for video on demand applications through patching. This involves organization of the communication bandwidth of the server into logical sets of channels each of which is capable of video transmission at the play back rate. The remaining bandwidth of the server is utilized to control messages. A waiting queue is maintained by video server and all arriving requests are appended to this queue and are dispatched in the next occasion. When the channel becomes free, a next occasion arrives and requests that have been appended are dispatched. The batch is assigned to the free channel is by specifying the desired video fragment and inserting the clients in the batch into the corresponding client list. As the multicast is activated, the specified video is multicast on that channel to the clients in the list. Patching allows immediate servicing of requests and allows dynamic expansion of multicast to service new client requests. References Wang, H., Kondi, L., Luthra, A., and Ci, S. 2009. 4G Wireless Video Communications. New York: John Wiley and Sons Bing, B. 2010. 3D and HD Broadband Video Networking. London: Artech House Elbakri, W. 2011. Video Streaming. London: LAP Lambert Academic Publishing Setton, E., and Girod, B. 2010. Peer-To-Peer Video Streaming. London: Springer Minoli, D. 2008. IP Multicast with Applications to IPTV and Mobile DVB-H. London: Wiley-Interscience Fall, K., and Stevens, R. 2011. TCP/IP Illustrated, Volume 1: The Protocols, 2nd Ed. London: Addison-Wesley Read More