Internet Applications Development Electronic Publications in the Age of Streaming Audio and Video: How to Do It
Renato M.E. Sabbatini, PhD Editor-in-Chief Intermedic Journal Informática Médica Center for Biomedical Informatics State University of Campinas, Brazil
Adding Audio and Video zCan I add audio and video to my Web site or Web-based publication? zHow can I achieve optimal combinations of speed and quality? zWhich tools are best for creating specific types of multimedia experience? zHow audio and video can be presented and served?
Modalities of Audio and Video on the Internet 1. Binary file downloading and local playback yThe whole file must be downloaded before playback can start yFile occupies disk space in client yLive transmission is not possible yInteractivity is not possible yImpractical except for very small files
Plug-Ins for Videos Apple QuickTime Windows Media Player
Modalities of Audio and Video on the Internet 2. Streaming audio and video yA continuous flow of digital packets is sent to the client and played as they arrive ySpeed is independent of file size yThere is no need to store the file in the client yReal time transmission is possible yInteraction is possible
Streaming Media Continuous playback of audio and video packets Sends audio or video files in a continuous stream of small packets ClientServer
RealMedia Plug-In Presentation zVideo alone or synchronized video and audio
z Audio file alone RealMedia Plug-In Presentation
Streaming Audio and Video zVivo and RealSystems were the first companies to deliver real-time streaming audio and video over the World Wide Web. zStreams are compressed and encoded from either a preexisting sound file or live audio, using a protocol called codec. zThe codecs can output files that are optimized for 14.4 to 56 Kbps modem delivery, or delivery over a higher speed line such as LAN, ISDN or T1.
How RealMedia Works RealMedia Encoder RealMedia Server RealMedia Player Sound/Video Acquisition and A/D Conversion
How RealMedia Works zA RealAudio Server connection is a two- channel, two-way communication system: yThe UDP protocol is used for sound-data transmission yThe TCP protocol is used to interchange bandwidth and codec data as to communicate pause, fast forward, play, and rewind commands.
RealAudio Features zRealAudio is an open architecture application zThe Playback Engine Application Programming Interface (API) provides software developers with direct access to the functionality of the RealAudio Player zIt is continually evolving. Latest technology (G2) delivers high quality audio and video with interactive features zVery easy to create and deploy content.
The RealAudio Player zTwo versions: a stand-alone program that can also be used as a browser helper application, and a browser plug-in. zThe stand-alone application is a fully functional program that you can use to play RealAudio files from any source, including a hard drive, a corporate intranet, or the Web. zWorks with any sound and video boards zFree downloading of standard version, there is also a commercial professional version.
Sound Quality and Compression: Example 0ne-minute monaural sound file sampled at 22 kHz zWAV file is 2.6 megabytes; RealAudio, encoded for 6.5Kbps is 42 kilobytes, for ISDN is 296 kilobytes. Compression ratios of 62:1 and 8:1, respectively. zThe low-bandwidth file has AM radio quality and is best for speech only, whereas the quality of the high- bandwith approaches CD-ROM quality, adequate for stereo music zA loss correction system minimizes the impact of lost packets. Works well with 2-5 % loss, but works with up to 8% loss.
Development Steps Digital Recording of Audio/Video Digital Editing and Preparation Conversion to Streamed Format Uploading to Server
Development Steps Digital Recording of Audio/Video Digital Editing and Preparation Conversion to Streamed Format Uploading to Server WAV AVI RA
Critical Selection Parameters zAudio codec and bit rate zVideo codec and bit rate zFrame rate zFrame size
Some Technical Tips zIf you're serving an audience that has a variety of connection speeds, encode the content with several different codecs, one for each speed. zYou should budget 3M of RAM plus 60K for each simultaneous user.
Selection of Video Rate zFixed camera shot with low motion--The frame rate will run between 4 and 10 zFixed camera shot with some motion--The frame rate may drop toward 2 fps. zFixed camera shot with high motion--The frame rate drops to about 1 fps. zZooming camera with low motion--Expect a frame rate of about 2 fps. zMultiple shots, low motion--The frame rate approaches 1 fps. zMultiple shots, high motion--The frame rate drops below 1 fps.
Software for Editing Digital Audio and Video zAdobe Premiere zCreative Multimedia Suite
Inserting Multimedia into the Web page zCall to the external helper application A separate window opens up, with all RealPlayer controls, which can be customized by the user zEmbedded plug-in calls, with several options for display and playback control, set up by the developer zThere is a wizard for selecting the desired combination and generating HTML code
Referencing the File zA RealAudio URL has the format: pnm://server:port#/pathname ypnm:// indicates the file is located on a RealAudio Server system. yServer:Port# is the address of the RealAudio Server. ypathname is the complete directory path and file name. yExample: pnm://audio. realaudio.com/welcome.ra yThis pointer is placed into na ASCII file with the extension.ram or.rpm (metafile)
Referencing the File zHREF: Patient case zEMBED: zRealPlayer Controls and Options: CONTROLS, AUTOSTART, CONSOLE, and NOLABELS
Synchronized Multimedia zSynchronized HTML pages with streaming audio (guided tours, slide shows)
Synchronized Multimedia z Packing audio and PowerPoint slides into a RealMedia file (synchronized audio with slides control: great for slide shows
How RealPresenter Works zCreate slide presentation using Microsoft PowerPoint zUsing mike and PC´s sound board, narrate the slide show, pressing the ´next slide´ key as you go zPowerPoint will create a set of linked WAV files, one for each slide, with timing zClick on Tools/Create RealMedia and follow the wizard to create.RA file zCreate.RAM metafile, upload to server
Other Streaming Solutions zNetscape´s Media Player (LiveAudio) zMPEG 3 ISO CD 11172 Moving Pictures Experts Group zXING´s StreamWorks MPEG-based, encoder (WAV, QT, AVI), player zVXTreme, VDONet zApple QuickTime
The Microsoft Approach zAims to establish its Active Streaming Format (ASF) as the de facto standard for streaming video. zHas demonstrated a unified multimedia technology called DirectX. zHas developed a streaming video product, NetShow, to challenge RealVideo for market dominance. zNetShow comes with tools that convert existing video files, including AVI and QuickTime movies, to streaming files