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Computer Networking From LANs to WANs: Hardware, Software, and Security Chapter 14 Multimedia Networking Objectives • Explain the basic properties of GIF, JPG, and PNG image files • Discuss the various sound file formats, such as WAV, MID, and MP3 • Describe MPEG, Voice-over-IP, and multicasting Computer Networking From LANs to WANs: Hardware, Software, and Security 2 Image Files • Web browser image types – Graphics Interchange Format (GIF) – Joint Photographic Experts Group (JPEG) – Portable Network Graphics (PNG) • Image file types and their properties – Affect Web page application development and performance Computer Networking From LANs to WANs: Hardware, Software, and Security 3 GIF images • 256 colors possible (maximum) – Eight bits needed to store pixel color – Not photographic quality – Suitable for buttons, banner ads, or other Web page graphics • Lossless compression – Uses LZW (Lempel-Ziv-Welch) algorithm • No original image data lost during compression Computer Networking From LANs to WANs: Hardware, Software, and Security 4 GIF Images (cont’d.) • Animation and transparency support built-in – Animation images stored in a single GIF image file – Appropriate time delays inserted between each stored image display • Transparency – Accomplished by assigning one of the 256 color values to be the transparent color Computer Networking From LANs to WANs: Hardware, Software, and Security 5 JPG Images • 24-bit color (16,777,216 colors possible) – Provides high quality photographic-quality color • Lossy compression – Using the DCT (Discrete Cosine Transform) algorithm on 8-by-8 blocks of pixels – Superior to lossless GIF compression • No animation or transparency features available Computer Networking From LANs to WANs: Hardware, Software, and Security 6 Table 14-1 Comparing EARTH.JPG and EARTH.GIF files Figure 14-1 Sample image and the effect of compression on text Computer Networking From LANs to WANs: Hardware, Software, and Security 7 PNG Images • PNG-8: – Supports 8-bit color palette (256 colors), 1-bit transparency – Better compression than equivalent GIF image • PNG-24 – Supports 24-bit color palette (16 M colors) – Similar to JPG image except lossless compression method used • Animation – Provided by the Multiple-image Network Graphic (MNG) image format Computer Networking From LANs to WANs: Hardware, Software, and Security 8 PNG Images (cont’d.) • Pixel transparency – Value between 0 (full transparency) and 255 (no transparency – Called alpha channels – More realistic blending of images with backgrounds Computer Networking From LANs to WANs: Hardware, Software, and Security 9 Sound Files • Three types of sound files are popular on the Web – WAV files – MID – MP3 Computer Networking From LANs to WANs: Hardware, Software, and Security 10 WAV Files • Standard Windows audio file format Figure 14-2(b) Windows Vista Sound Recorder ready to record Figure 14-2(a) Windows XP Sound Recorder displaying a portion of BLAST.WAV Computer Networking From LANs to WANs: Hardware, Software, and Security 11 WAV Files (cont’d.) Figure 14-4 Changing the sampling properties Figure 14-3 BLAST.WAV properties Computer Networking From LANs to WANs: Hardware, Software, and Security 12 MID Files • File extension – Used on Musical Instrument Digital Interface (MIDI) files • Contains information (MIDI sequencer commands) – What notes to play, how to play them • 128 pitched instruments can generate 24 notes in 16 channels – PC sound card uses MIDI information to reproduce notes • Produces very complex sounds – With small amount of data Computer Networking From LANs to WANs: Hardware, Software, and Security 13 MP3 Files • MPEG Audio Layer 3 files • Moving Picture Experts Group (MPEG) audio, video – Encoding methods for creating high quality, low-bit rate multimedia files – Three audio layers • Use perceptual audio coding and psychoacoustic compression for encoding audio, compressing data Table 14-2 MPEG audio layer differences Computer Networking From LANs to WANs: Hardware, Software, and Security 14 MP3 Files (cont’d.) • Benefit: smaller file size, identical sound quality • Used to burn audio CD-ROM • Downloadable into a portable MP3 player Table 14-3 Comparing WAV and MP3 file sizes Computer Networking From LANs to WANs: Hardware, Software, and Security 15 The Digital Conversation Figure 14-5 Analog and Digital conversions Computer Networking From LANs to WANs: Hardware, Software, and Security 16 Transmitting Data over a Network • Network overhead – 26 bytes of Ethernet framing – 24 bytes of IP header – 24 bytes of TCP header Figure 14-6 Network overhead in an Ethernet frame Computer Networking From LANs to WANs: Hardware, Software, and Security 17 Transmitting Data over a Network (cont’d.) • Network overhead (cont’d.) – Affects bandwidth requirements – 74 bytes of overhead • 5.28% of a 1400 data byte message • 92.5% of a 80-byte data message Computer Networking From LANs to WANs: Hardware, Software, and Security 18 Transmitting Data over a Network (cont’d.) Table 14-4 Transmitting 8000 bytes (64,000 bits) of data using multiple packets Computer Networking From LANs to WANs: Hardware, Software, and Security 19 Voice-over-IP • Method for sending voice and fax data – Uses the IP protocol • Interfaces with the public switched telephone network (PSTN) – Attempts to provide same service quality • Several different IP protocols used – Real-Time Transfer Protocol (RTP) – Real-Time Control Protocol (RTCP) – Resource Reservation Protocol (RSVP) Computer Networking From LANs to WANs: Hardware, Software, and Security 20 Figure 14-7 VoIP architecture Computer Networking From LANs to WANs: Hardware, Software, and Security 21 Voice-over-IP (cont’d.) • H.323 standard – Specifies voice processing, gateway/terminal operation • Factors impacting conversations – – – – End-to-end delay Jitter Packet loss Out-of-order arrivals Computer Networking From LANs to WANs: Hardware, Software, and Security 22 Voice-over-IP (cont’d.) • Standards exist for rating VoIP conversation quality • Lacks security – Can extract entire conversation from packet capture Table 14-5 Voice Quality Test Scores Table 14-5 Voice Quality Test Scores Computer Networking From LANs to WANs: Hardware, Software, and Security 23 Voice-over-IP (cont’d.) • VoIP services becoming more common – Residential, business communities • VoIP service providers – Offer all traditional phone company features • Many VoIP network devices on the market today Figure 14-10(a) Linksys PAP2 indicator lights Computer Networking From LANs to WANs: Hardware, Software, and Security 24 Video • Great bandwidth required • User can easily spot problems with video stream • Real-time video requirements – Powerful processor, fast network connection • Protocols used to manage information stream – RTP, RTCP, RSVP • Video cameras now affordable for PCs Computer Networking From LANs to WANs: Hardware, Software, and Security 25 MPEG Files • Defines set of digital video parameters – Bit rate, resolution, compression techniques • Video compression: lossy – Uses Discrete Cosine Transform • Three frame types: – I (Intra): stand-alone video frame – P (Predicted): generated using most recent I or P frame – B (Bidirectional): generated based on past, future frames Computer Networking From LANs to WANs: Hardware, Software, and Security 26 Multicasting • Eliminates large portion of duplicated information – Server sends one copy of video data to a multicasting-enabled switch – Switch forwards single copy to other multicastingenabled switches • They replicate video data, forward copies to each client • IP multicasting – Uses Internet Group Management Protocol (IGMP) • MBone – Experimental multicasting backbone • Supports multicasting over the Internet Computer Networking From LANs to WANs: Hardware, Software, and Security 27 Figure 14-14 Unicasting versus multicasting Computer Networking From LANs to WANs: Hardware, Software, and Security 28 Games • Network computer games growing in popularity • One machine runs game in server mode – Multiple game client machines connect to it • Factors developers consider for real-time environments – Available bandwidth, communication delay, processing speed • Packet problems affect game play – Dead reckoning • Combats effect of packet loss on player position Computer Networking From LANs to WANs: Hardware, Software, and Security 29 Troubleshooting Techniques • Bandwidth issues – Streaming music and video are high bandwidth applications • CODEC issues – Video file must be played with the same CODEC used to create the video file • Quality of Service – Affects users ability to use audio, video, VoIP phone services • May be necessary to prioritize network traffic Computer Networking From LANs to WANs: Hardware, Software, and Security 30 Summary • Web browsers accept – GIF, JPG (or JPEG) or PNG images • Audio file types – Wave, MIDI, MP3 • Streaming media describes any media type (audio, video, animations ,etc.) that may be streamed • Voice-over-IP (VoIP) – Method for sending voice and fax data using IP Computer Networking From LANs to WANs: Hardware, Software, and Security 31