1 Video and Audio Over The Net Mahdi ZandakbariVesal Hajiabbas

2 Audio/Video Transition over the Net Streaming Streaming –Webcasts –Online video/audio chanels –Video Conference –Audio Conference VOIP (Voice Over IP) VOIP (Voice Over IP) Video Over IP Video Over IP

3 Key Definitions: CODEC CODEC Formed from two roots compression and de-compression CO + DEC = CODEC Formed from two roots compression and de-compression CO + DEC = CODEC Actually algorithms which are required by both the media server and player Actually algorithms which are required by both the media server and player Encoding Encoding Refers to the process of preparing video for streaming Refers to the process of preparing video for streaming Streaming media Streaming media A combination of audio and video that can be delivered to the viewer across the internet A combination of audio and video that can be delivered to the viewer across the internet

4 Video/Audio Streaming First found in 1995 and soon supported by RealAudio First found in 1995 and soon supported by RealAudio It enables undisrupted web broadcasts It enables undisrupted web broadcasts You do not need to download the whole video/audio file You do not need to download the whole video/audio file If the streaming audio/video is broadcast live, then it may be called "realtime audio/video" If the streaming audio/video is broadcast live, then it may be called "realtime audio/video" How? How? –The client side stores a few seconds of the stream in a buffer before it starts sending it to the speakers –fast forward impossible –rewind, pause possible!

5 MM Networking Applications Typically delay sensitive Typically delay sensitive –end-to-end delay –delay jitter But loss tolerant: infrequent losses cause minor glitches But loss tolerant: infrequent losses cause minor glitches –Video loss is more welcome than the audio

6 Streaming a videoconference Streaming a videoconference makes it possible for any number of people to view a conference – either live or recorded for on- demand access. Streaming a videoconference makes it possible for any number of people to view a conference – either live or recorded for on- demand access.

7 Streaming Systems Architecture

8 So here are what you actually need: Encoder Encoder – resource used at time of capture –It could be software-based or hardware-based Server Server –Platform from which the stream is dispersed to the user Player Player –A decoder located on the end users computer + A player (e.g. Windows Media Player, QuickTime, RealPlayer,…)

9 Codec and format Codec TypeExpense in Real-timeTarget Bandwidth H.261(moderate) (wide rang) H.261(moderate) (wide rang) H.263 (moderate)(wide rang) H.263 (moderate)(wide rang) Mpeg1 (high) (1-1.5 mb) Mpeg1 (high) (1-1.5 mb) Mpeg2 (high) (4-15 mb) Mpeg2 (high) (4-15 mb) Mpeg3(mp3) Mpeg3(mp3) Mpeg4(high)(less than 64kb) Mpeg4(high)(less than 64kb) Real Audio codecs (high)(wide range) Real Audio codecs (high)(wide range) Microsoft formats(high)(wide range) Microsoft formats(high)(wide range) Notes: 1. real-time codecs usually expensive 1. real-time codecs are usually expensive 2.New technologies offer dynamic coding and decoding (e.g. java multimedia API, Mpeg-4 Syntactic description language MSIL,…)

10 Streaming media standards All Usually based on UDP (User Datagram Protocol) All Usually based on UDP (User Datagram Protocol) The TCP/IP protocol can not do the best here. The TCP/IP protocol can not do the best here. RTSP (Real Time Streaming Protocol) RTSP (Real Time Streaming Protocol) RTP (Real Time Transport Protocol ) RTP (Real Time Transport Protocol ) RTCP (Real Time Control Protocol) RTCP (Real Time Control Protocol) MSIL MSIL XML-based markup language geared toward long-form multimedia XML-based markup language geared toward long-form multimedia Packet format for Internet audio/video (streaming and conferencing) Packet format for Internet audio/video (streaming and conferencing) Datatypes and codecs Datatypes and codecs MP3, GIF, JPEG, PNG, H.261, H.263, MPEG-4 MP3, GIF, JPEG, PNG, H.261, H.263, MPEG-4

11 RTSP Operation

12 Protocols map

13 Commercial Real Time Video Streamers MacroMedia's Streaming Shockwave MacroMedia's Streaming Shockwave – –serverless product which relies on the HTTP protocol only – –No live feeds – –Uses flash files (see Progressive Network's RealVideo Progressive Network's RealVideo Progressive Network's RealVideo Progressive Network's RealVideo – –RSTP on UDP – –Needs RealServer 4.0 Xing Technology's StreamWorks Xing Technology's StreamWorks Xing Technology's StreamWorks Xing Technology's StreamWorks – –Mpeg1 VDONet's VDOLive VDONet's VDOLive VDONet's VDOLive VDONet's VDOLive – –UDP based – –Uses Wavelets for compression Vosaic Vosaic Vosaic –VDP based –MPEG-1,2,H.263,GSM VXtreme VXtreme VXtreme –uses a layered compression scheme to divide the compressed video into multiple streams Vivoactive Vivoactive Vivoactive –Uses both HTTP and UDP –H.263 video compression and G.723 audio compression Microsoft's NetShow Microsoft's NetShow Microsoft's NetShow Microsoft's NetShow –ASF files are created using MPEG-layer3, Microsoft MPEG-4, Vivo G.723 (audio) and H.263 (video) –It also supports other standard

14 Types of Multicast Multicast –Webcast (e.g. m ) m m –Could be real- time or not Unicast Unicast –Video conference –Usually real- time

15 VOIP (Voice Over IP) Specially refers to a technology that enables a voice conversation using the Internet. (putting voice in IP packets. Specially refers to a technology that enables a voice conversation using the Internet. (putting voice in IP packets. First appeared in 1995 and hit the market depending on the expense reductions it introduced. First appeared in 1995 and hit the market depending on the expense reductions it introduced. VOIP types VOIP types –PC 2 PC –PC 2 Phone –Phone 2 Phone

16 VOIP Protocols And Standards Similar to streaming protocols Similar to streaming protocols H.323 is the most popular in all IP based multimedia. H.323 is the most popular in all IP based multimedia. Like streaming it really depends on the network architecture Like streaming it really depends on the network architecture

17 Video Over IP Recently appeared due to respond to emerging video phones Recently appeared due to respond to emerging video phones Similar to VOIP Similar to VOIP Few additional protocols and standards Few additional protocols and standards