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Real-Time Multimedia Material on the Internet: Synchronization, Editing, and Distribution

This article explores the synchronization, editing, and distribution of multimedia material on the internet, covering real-time protocols such as RTP, RTCP, and RTSP, as well as standards like H.323, SIP, and SMIL.

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Real-Time Multimedia Material on the Internet: Synchronization, Editing, and Distribution

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  1. Πολυμεσικό Υλικό στο Internet: Συγχρονισμός, Επεξεργασία και ΔιακίνησηΣυγχρονισμός Πολυμεσικών Εφαρμογών & Σχετικά Εργαλεία10/11/2016 Β. Μάγκλαρης <maglaris@netmode.ntua.gr> Μ. Γραμματικού <mary@netmode.ntua.gr> Δ. Καλογεράς <dkalo@noc.ntua.ge> www.netmode.ntua.gr

  2. Outline • Real-Time Protocols (RTP, RTCP, RTSP) • ITU – H.323 • Session Initiation Protocol (SIP) • Synchronized Multimedia Integration Language (SMIL) • A Rough History of Web Standards • HTML5 Features

  3. Real-Time Protocol (RTP) http://en.wikipedia.org/wiki/Real-time_Transport_Protocol http://tools.ietf.org/html/rfc1889 • RTP: first published in 1996 by IETF • RTP: Defines a standardized packet format for delivering audio and video over IP Networks • Real-Time Protocol (RTP) • a framing protocol for real-time applications • there is no QoS in real timebased on UDP protocol

  4. Real-Time Control Protocol (RTCP)http://en.wikipedia.org/wiki/RTP_Control_Protocolhttps://tools.ietf.org/html/rfc3611 • RTCP: RTCP protocol monitors transmission statistics and Quality of Service (QoS) and aids synchronization of multiple streams • RTCP reports are sent in a multicast session • To avoid network congestion, the protocol must include session bandwidth management • RTCP bandwidth usage should generally not exceed 5% of total session bandwidth • 25% of the RTCP bandwidth should be reserved to media sources at all times

  5. Real Time Streaming Protocol (RTSP)http://en.wikipedia.org/wiki/Real_Time_Streaming_Protocol http://www.ietf.org/rfc/rfc2326.txt • RTSPis a network control protocol designed for use in entertainment and communications systems to control streaming media servers • It was developed by RealNetworks, Netscape and Columbia University, with the first draft submitted to IETF in 1996 • It was standardized by the Multiparty Multimedia Session Control Working Group (MMUSIC WG) of theIETF and published as RFC 2326 in 1998 • RTSP: • An application-level protocol for control over the delivery of data with real-time properties • Controls streaming media servers • It is used for establishing and controlling media sessions between end points • RTSP servers use the Real-time Transport Protocol (RTP) in conjunction with Real-time Control Protocol (RTCP) for media stream delivery

  6. ITU – H.323 (I)http://www.h323forum.org, http://en.wikipedia.org/wiki/H.323 www.rfc-editor.org/info/rfc4123 • H.323 is a system specification that describes the use of several ITU-T and IETF protocols • First version of H.323 was published by the ITU in November 1996 • Defines the protocols to provide audio-visual communication sessions in any IP (Internet) infrastructure • Point-to-point • Multi-point (Multi-Conference Unit - MCU) • H.323 addresses call signalling and control, multimedia transport and control, and bandwidth control for point-to-point and multi-point conferences • H.323 call signalling • is based on the ITU-T Recommendation Q.931protocol • is suited for transmitting calls across networks using a mixture of IP, PSTN, ISDN, and QSIG over ISDN

  7. ITU – H.323 (II)http://www.h323forum.org, http://en.wikipedia.org/wiki/H.323 www.rfc-editor.org/info/rfc4123 • Network Elements for H.323 system : • Terminals - the devices that users would normally encounter • Multipoint Control Units (MCUs) - responsible for managing multipoint conferences (additionally, H.323 MCU can mix or switch videos) • Gateways - devices that enable communication between H.323 networks and other networks, such as PSTN or ISDN networks • Gatekeepers – provides a number of services such as : endpoint registration, address resolution, admission control, user authentication • Codecs that are widely implemented by H.323 equipment include: • Audio codecs: G.711, G.729 (including G.729a), G.723.1, G.726, G.722, G.728, Speex, AAC-LD • Text codecs: T.140 • Video codecs: H.261, H.263, H.264

  8. A complete, sophisticated protocol stack inside the H.323 Terminal

  9. Session Initiation Protocol (SIP)http://en.wikipedia.org/wiki/Session_Initiation_Protocol https://www.ietf.org/rfc/rfc3261.txt • SIP: a signalling communication protocol, widely usedfor controlling multimedia communication sessions such as voice and videocalls over Internet Protocol (IP) networks • SIP was originally designed by Henning Schulzrinne and Mark Handley in 1996 • Text Based (like HTTP) • SIP address like : user @ host • Same services with Η.323 but : • H.323 MCU as a special purpose component • SIP: server-based multi conference • SIP works in conjunction with several protocols like SDP (Session Description Protocol) • SDP: a format for describing streaming media (audio, video) and making media identification and negotiations for media types

  10. Synchronized Multimedia Integration Language (SMIL)http://en.wikipedia.org/wiki/Synchronized_Multimedia_Integration_Language http://www.ietf.org/rfc/rfc4536.txt • SMIL version 1 : introduced 1999 • It is written in XML and has similarities to HTML • SMIL: a World Wide Web Consortium (W3C) recommended Extensible Markup Language (XML) to describe multimedia presentations • Defines markup for : • timing • layout • animations • visual transitions • media embedding • Presenting media items (text, images, video, audio, links) to other SMIL presentations, and files from multiple web servers

  11. A Rough History of Web Standards (ref) HTML CSS

  12. HTML5: more than HTML • HTML5 Spec • CSS3 (Cascading Style Sheet) Spec • JavaScript to tie it all together

  13. What’s new to HTML5 • Simplified and Loose Syntax • New Elements and Attributes • Embedded Media (audio, video) • Canvas • Drag and Drop • Geo-Location API

  14. Browser Support http://www.w3.org/TR/html5/ • HTML5 is not yet an official standard - browsers have not full HTML5 support • But all major browsers (Safari, Chrome, Firefox, Opera, Internet Explorer) continue to add new HTML5 features to their latest versions

  15. HTML5 Video http://en.wikipedia.org/wiki/HTML5_video http://www.w3.org/TR/html5/embedded-content-0.html#the-video-element • HTML5 specification introduced the <video> element, partially replacing the <object> element • HTML5 video is intended to become the new standard way to show video on the web without plug-ins • The <video> element was proposed by Opera Software in February 2007

  16. HTML5 Video Benefits • End users have full control over the multimedia • HTML5 video and audio are keyboard-enabled by default, which is a great accessibility benefit • End users do not need to install a plug-in to play them • Browser already has everything it needs to play movies/sound • Video and audio content on the page can be manipulated • Two new elements that can be styled, moved, manipulated, stacked and rotated • You can build your own controls using HTML, CSS and JavaScript • No new skills or development environment needed • Simple interaction with the rest of the page • Multimedia API gives you full control over the video, and you can make the video react both to changes in the video itself and to the page around it

  17. Using HTML5 Media Elements https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_HTML5_audio_and_video https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats <audio src="/test/audio.ogg"> <p>Your browser does not support the audio element.</p> </audio> <video> <source src="somevideo.webm" type="video/webm"> <source src="somevideo.mp4" type="video/mp4"> I'm sorry; your browser doesn't support HTML5 video in WebM with VP8 or MP4 with H.264. <!-- You can embed a Flash player here, to play your mp4 video in older browsers --> </video>

  18. HTML5 Video - Codecs that Browsers Support http://en.wikipedia.org/wiki/HTML5_video • MP4 or H.264: • codec supported by Apple and Microsoft • provides good quality video and small file sizes • Ogg/Theora (an open video codec): • free open standard for video encoding • it generates high quality videos with comparatively larger file sizes • hard to find tools to convert to ogg/Theora • WebM(an open media file format designed for the web): • uses the VP8 or VP9 video codec, owned by Google • high video quality, longer to encode than in H.264 • very difficult to encode, especially compared to the many free & commercial tools available for H.264

  19. Adobe – Apple Controversy http://en.wikipedia.org/wiki/Apple_and_Adobe_Flash_controversyhttps://www.apple.com/hotnews/thoughts-on-flash/ https://en.wikipedia.org/wiki/Comparison_of_HTML5_and_Flash • As of April 2010, in the wake of Apple iPad launch, a number of high-profile sites have started to serve H.264 HTML5 video instead of Flash for user-agents identifying as iPad • In November 8, 2011, Adobe announced that it was ceasing development of the Flash Player "plug-in" for browsers on mobile devices, in an effort to shift its focus on using the ActionScript programming language and Adobe AIR to develop fully functional native apps for mobile

  20. References • https://dev.opera.com/articles/introduction-html5-video/ • https://dev.opera.com/blog/everything-you-need-to-know-about-html5-video-and-audio-2/ • https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_HTML5_audio_and_video • http://html5video.org/wiki/HTML5_Player_Comparison • http://www.w3.org/2010/05/video/mediaevents.html • http://www.html5rocks.com/en/tutorials/video/basics/ • http://blog.teamtreehouse.com/building-custom-controls-for-html5-videos

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