Πολυμεσικό Υλικό στο Internet: Συγχρονισμός, Επεξεργασία και Διακίνηση Συγχρονισμός Πολυμεσικών Εφαρμογών & Σχετικά Εργαλεία 19/11/2015 Β. Μάγκλαρης Μ. Γραμματικού Δ. Καλογεράς

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

Real-Time Protocol (RTP) 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 time based on UDP protocol

Real-Time Control Protocol (RTCP) 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

Real Time Streaming Protocol (RTSP) RTSP is 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 the IETF 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

ITU – H.323 (I) 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.931 protocol – is suited for transmitting calls across networks using a mixture of IP, PSTN, ISDN, and QSIG over ISDN

ITU – H.323 (II) Network Elements for H.323 system : – Terminals - the devices that users would normally encounter – Multipoint Control Units (MCUs) - responsible for managing multipoint conferences – 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 H.323 utilizes both ITU-defined codecs and codecs defined outside the ITU. 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

Session Initiation Protocol (SIP) SIP: a signalling communication protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP) networks SIP was originally designed by Henning Schulzrinne and Mark Handley in 1996 Text Based (like HTTP) SIP address like : host Same services with Η.323 but : – H.323 MCU as a special purpose component – SIP: server-based multi conference SDP (Session Description Protocol) a format for describing streaming media (audio, video)

Synchronized Multimedia Integration Language (SMIL) 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

A Rough History of Web Standards (ref) 2004WHATWG started 2008W3C Working Draft 2012 (2010)W3C Candidate Rec 2022W3C Rec 1996 – CSS 1W3C Rec 1998 – CSS 2W3C Rec 1999 – CSS 3Proposed 2001 – CSS 3W3C Working Draft 2005 – CSS 2.1W3C Candidate Rec HTML 1HTML 2HTML 4XHTML 1 HTML 5 CSS 1CSS 2T-less DWeb 2.0CSS3 JSECMA, DOM DOM 2AjaxDOM, APIs HTML CSS

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

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

Browser Support 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

HTML5 Video HTML5 specification introduced the element, partially replacing the element HTML5 video is intended to become the new standard way to show video on the web without plug-ins The element was proposed by Opera Software in February 2007

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

Using HTML5 Media Elements Your browser does not support the audio element. I'm sorry; your browser doesn't support HTML5 video in WebM with VP8 or MP4 with H.264.

MP4 or H.264: – codec supported by Apple and Microsoft – provides good quality video and small file sizes ogg/Theora: – 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: – uses the VP8 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 HTML5 Video - Codecs that Browsers Support

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 On 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 Adobe – Apple Controversy

html5-video-and-audio-2/ html5-video-and-audio-2/ US/docs/Web/Guide/HTML/Using_HTML5_audio_and_video US/docs/Web/Guide/HTML/Using_HTML5_audio_and_video html5-videos html5-videos References