11

Video and Audio Over The NetVideo and Audio Over The Net

Mahdi ZandakbariMahdi Zandakbari Vesal HajiabbasVesal Hajiabbas

22

Audio/Video Transition over the NetAudio/Video Transition over the Net

StreamingStreaming– Webcasts Webcasts

– Online video/audio chanelsOnline video/audio chanels

– Video ConferenceVideo Conference

– Audio ConferenceAudio Conference VOIP (Voice Over IP)VOIP (Voice Over IP) Video Over IPVideo Over IP

33

Key Definitions:Key Definitions:

CODEC CODEC Formed from two roots compression and de-compression Formed from two roots compression and de-compression

CO + DEC = CODECCO + DEC = CODEC Actually algorithms which are required by both the media Actually algorithms which are required by both the media

server and player server and player

Encoding Encoding Refers to the process of preparing video for streamingRefers to the process of preparing video for streaming

Streaming mediaStreaming media A combination of audio and video that can be delivered to A combination of audio and video that can be delivered to

the viewer across the internetthe viewer across the internet

44

Video/Audio StreamingVideo/Audio Streaming

First found in 1995 and soon supported by RealAudio First found in 1995 and soon supported by RealAudio It enables undisrupted web broadcastsIt enables undisrupted web broadcasts You do not need to download the whole video/audio fileYou do not need to download the whole video/audio file If the streaming audio/video is broadcast live, then it If the streaming audio/video is broadcast live, then it

may be called "realtime audio/video" may be called "realtime audio/video" How?How?

– The client side stores a few seconds of the stream in a The client side stores a few seconds of the stream in a bufferbuffer before it starts sending it to the speakers before it starts sending it to the speakers

– fast forward impossiblefast forward impossible

– rewind, pause possible!rewind, pause possible!

55

MM Networking ApplicationsMM Networking Applications

Typically Typically delaydelay sensitivesensitive– end-to-end delayend-to-end delay– delay jitterdelay jitter

But But loss tolerantloss tolerant: infrequent losses cause : infrequent losses cause minor glitchesminor glitches– Video loss is more welcome than the audioVideo loss is more welcome than the audio

66

Streaming a videoconferenceStreaming a videoconference

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

77

Streaming Systems ArchitectureStreaming Systems Architecture

88

So here are what you actually need:So here are what you actually need:

EncoderEncoder– resource used at time of captureresource used at time of capture– It could be software-based or hardware-basedIt could be software-based or hardware-based

ServerServer– Platform from which the stream is dispersed to the Platform from which the stream is dispersed to the

useruser PlayerPlayer

– A decoder located on the end users computer + A A decoder located on the end users computer + A player (e.g. Windows Media Player, QuickTime, player (e.g. Windows Media Player, QuickTime, RealPlayer,…)RealPlayer,…)

99

Codec and formatCodec and format

Codec TypeCodec Type Expense in Real-timeExpense in Real-time Target BandwidthTarget Bandwidth H.261H.261 (moderate) (moderate) (wide rang)(wide rang) H.263 H.263 (moderate)(moderate) (wide rang)(wide rang) Mpeg1 Mpeg1 (high) (high) (1-1.5 mb)(1-1.5 mb) Mpeg2 Mpeg2 (high) (high) (4-15 mb)(4-15 mb) Mpeg3(mp3)Mpeg3(mp3) Mpeg4Mpeg4 (high)(high) (less than 64kb)(less than 64kb) Real Audio codecs Real Audio codecs (high)(high) (wide range)(wide range) Microsoft formatsMicrosoft formats (high)(high) (wide range)(wide range)

Notes:Notes:

1. 1. real-time codecsreal-time codecs are usually expensiveusually expensive2.New technologies offer dynamic coding and decoding (e.g. java 2.New technologies offer dynamic coding and decoding (e.g. java multimedia API, Mpeg-4 Syntactic description language MSIL,…)multimedia API, Mpeg-4 Syntactic description language MSIL,…)

1010

Streaming media standardsStreaming 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 ProtocolRTP (Real Time Transport Protocol)) RTCP (Real Time Control Protocol)RTCP (Real Time Control Protocol) MSILMSIL

XML-based markup language geared toward long-form XML-based markup language geared toward long-form multimediamultimedia

Packet format for Internet audio/video (streaming and Packet format for Internet audio/video (streaming and conferencing)conferencing)

Datatypes and codecsDatatypes and codecs MP3, GIF, JPEG, PNG, H.261, H.263, MPEG-4MP3, GIF, JPEG, PNG, H.261, H.263, MPEG-4

1111

RTSP OperationRTSP Operation

1212

Protocols mapProtocols map

1313

Commercial Real Time Video Commercial Real Time Video StreamersStreamers

MacroMedia's Streaming MacroMedia's Streaming ShockwaveShockwave

– serverless product which relies on the HTTP protocol only

– No live feeds– Uses flash files (see

WWW.CNN.COM) Progressive Network's Progressive Network's

RealVideoRealVideo– RSTP on UDP– Needs RealServer 4.0

Xing Technology's Xing Technology's StreamWorksStreamWorks– Mpeg1

VDONet'sVDONet's VDOLiveVDOLive– UDP based– Uses Wavelets for compression

VosaicVosaic– VDP based– MPEG-1 ,2 ,H.263 ,GSM

VXtremeVXtreme– uses a layered compression

scheme to divide the compressed video into multiple streams

VivoactiveVivoactive– Uses both HTTP and UDP– H.263 video compression and

G.723 audio compression Microsoft's NetShowMicrosoft's NetShow

– ASF files are created using MPEG-layer3, Microsoft MPEG-4, Vivo G.723 (audio) and H.263 (video)

– It also supports other standardIt also supports other standard

1414

Types ofTypes of

MulticastMulticast– Webcast (e.g. Webcast (e.g.

www.cnn.cowww.cnn.comm ) )

– Could be real-Could be real-time or nottime or not

UnicastUnicast– Video Video

conferenceconference

– Usually real-Usually real-timetime

1515

VOIP (Voice Over IP)VOIP (Voice Over IP)

Specially refers to a Specially refers to a technology that enables a technology that enables a voice conversation using the voice conversation using the Internet. (putting voice in IP Internet. (putting voice in IP packets.packets.

First appeared in 1995 and hit First appeared in 1995 and hit the market depending on the the market depending on the expense reductions it expense reductions it introduced.introduced.

VOIP typesVOIP types– PC 2 PCPC 2 PC– PC 2 PhonePC 2 Phone– Phone 2 PhonePhone 2 Phone

1616

VOIP Protocols And StandardsVOIP Protocols And Standards

Similar to streaming protocols Similar to streaming protocols H.323 is the most popular in all IP based H.323 is the most popular in all IP based

multimedia.multimedia. Like streaming it really depends on the network Like streaming it really depends on the network

architecturearchitecture

1717

Video Over IPVideo Over IP

Recently appeared due to respond to emerging Recently appeared due to respond to emerging video phonesvideo phones

Similar to VOIPSimilar to VOIP Few additional protocols and standardsFew additional protocols and standards