Multimedia Over Today's Internet TCP/UDP/IP:"best-effort service" no guarantees on delay,loss But you said multimedia apps requires QoS and level of performance to be effective! 2 Today's Internet multimedia applications use application-level techniques to mitigate (as best possible)effects of delay,loss 7:Multimedia Networking 7-11
7: Multimedia Networking 7-11 Multimedia Over Today’s Internet TCP/UDP/IP: “best-effort service” no guarantees on delay, loss Today’s Internet multimedia applications use application-level techniques to mitigate (as best possible) effects of delay, loss But you said multimedia apps requires QoS and level of performance to be effective! ? ? ? ? ? ? ? ? ? ? ?
How should the Internet evolve to better support multimedia? Integrated services philosophy: Differentiated services Fundamental changes in philosophy: Internet so that apps can Fewer changes to Internet reserve end-to-end infrastructure,yet provide bandwidth 1st and 2nd class service. Requires new,complex software in hosts routers Laissez-faire ▣no major changes ▣more bandwidth when needed content distribution, application-layer multicast What's your opinion? o application layer 7:Multimedia Networking 7-12
7: Multimedia Networking 7-12 How should the Internet evolve to better support multimedia? Integrated services philosophy: Fundamental changes in Internet so that apps can reserve end-to-end bandwidth Requires new, complex software in hosts & routers Laissez-faire no major changes more bandwidth when needed content distribution, application-layer multicast application layer Differentiated services philosophy: Fewer changes to Internet infrastructure, yet provide 1st and 2nd class service. What’s your opinion?
A few words about audio compression ▣Analog signal sampled▣Example:8,000 at constant rate samples/sec,256 o telephone:8,000 quantized values-> samples/sec 64,000bps CD music:44,100 ▣Receiver converts it samples/sec back to analog signal: Each sample quantized, o some quality reduction i.e.,rounded oe.g.,28=256 possible Example rates quantized values ▣CD:1.411Mbps ▣Each quantized value □MP3:96,128,160kbps represented by bits Internet telephony: o8 bits for 256 values 5.3-13kbps 7:Multimedia Networking 7-13
7: Multimedia Networking 7-13 A few words about audio compression Analog signal sampled at constant rate telephone: 8,000 samples/sec CD music: 44,100 samples/sec Each sample quantized, i.e., rounded e.g., 28=256 possible quantized values Each quantized value represented by bits 8 bits for 256 values Example: 8,000 samples/sec, 256 quantized values -> 64,000 bps Receiver converts it back to analog signal: some quality reduction Example rates CD: 1.411 Mbps MP3: 96, 128, 160 kbps Internet telephony: 5.3 - 13 kbps
A few words about video compression ▣Video is seguence of Examples: images displayed at ▣MPEG1(CD-ROM)1.5 constant rate Mbps o e.g.24 images/sec ▣MPEG2(DVD)3-6Mbps Digital image is array of MPEG4 (often used in pixels Internet,1 Mbps) Each pixel represented Research: by bits Layered (scalable)video Redundancy o adapt layers to available o spatial bandwidth o temporal 7:Multimedia Networking 7-14
7: Multimedia Networking 7-14 A few words about video compression Video is sequence of images displayed at constant rate e.g. 24 images/sec Digital image is array of pixels Each pixel represented by bits Redundancy spatial temporal Examples: MPEG 1 (CD-ROM) 1.5 Mbps MPEG2 (DVD) 3-6 Mbps MPEG4 (often used in Internet, < 1 Mbps) Research: Layered (scalable) video adapt layers to available bandwidth
Chapter 7 outline ▣7.1 Multimedia 7.6 Beyond Best Networking Applications Effort 7.2 Streaming stored 7.7 Scheduling and audio and video Policing Mechanisms 7.3 Real-time Multimedia: 7.8 Integrated Internet Phone study Services and 7.4 Protocols for Real- Differentiated Time Interactive Services Applications ▣7.9RSVP RTP,RTCP,SIP 7.5 Distributing Multimedia:content distribution networks 7:Multimedia Networking 7-15
7: Multimedia Networking 7-15 Chapter 7 outline 7.1 Multimedia Networking Applications 7.2 Streaming stored audio and video 7.3 Real-time Multimedia: Internet Phone study 7.4 Protocols for RealTime Interactive Applications RTP,RTCP,SIP 7.5 Distributing Multimedia: content distribution networks 7.6 Beyond Best Effort 7.7 Scheduling and Policing Mechanisms 7.8 Integrated Services and Differentiated Services 7.9 RSVP