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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
Can I add audio and video to my Web site or Web-based publication?
How can I achieve optimal combinations of speed and quality? Which tools are best for creating specific types of multimedia experience? How audio and video can be presented and served?
Modalities of Audio and Video on the Internet 1. Binary file downloading and local playback
The whole file must be downloaded before playback can start File occupies disk space in client Live transmission is not possible Interactivity is not possible Impractical except for very small files
Audio Player Plug-Ins
Plug-Ins for Videos
Apple QuickTime Windows Media Player
Modalities of Audio and Video on the Internet 2. Streaming audio and video
A continuous flow of digital packets is sent to the client and played as they arrive Speed is independent of file size There is no need to store the file in the client Real time transmission is possible Interaction is possible
Streaming Media Client Server
Continuous playback of audio and video packets Sends audio or video files in a continuous stream of small packets
RealMedia Plug-In Presentation
Video alone or synchronized video and audio
RealMedia Plug-In Presentation
Audio file alone
Streaming Audio and Video
Vivo and RealSystems were the first companies to deliver real-time streaming audio and video over the World Wide Web. Streams are compressed and encoded from either a preexisting sound file or live audio, using a protocol called codec . The 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
Sound/Video Acquisition and A/D Conversion RealMedia Encoder RealMedia Server RealMedia Player
How RealMedia Works
A RealAudio Server connection is a two channel, two-way communication system: The UDP protocol is used for sound-data transmission The TCP protocol is used to interchange bandwidth and codec data as to communicate pause, fast forward, play, and rewind commands.
RealAudio Features
RealAudio is an open architecture application The Playback Engine Application Programming Interface (API) provides software developers with direct access to the functionality of the RealAudio Player It is continually evolving. Latest technology ( G2 ) delivers high quality audio and video with interactive features Very easy to create and deploy content.
The RealAudio Player
Two versions: a and a stand-alone program also be used as a browser helper application, browser plug-in.
that can The 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.
Works with any sound and video boards Free 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
WAV 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.
The 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 A 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
Audio codec and bit rate Video codec and bit rate Frame rate Frame size
Some Technical Tips
If you're serving an audience that has a variety of connection speeds, encode the content with several different codecs, one for each speed.
You should budget 3M of RAM plus 60K for each simultaneous user.
Selection of Video Rate
Fixed camera shot with low motion--The frame rate will run between 4 and 10 Fixed camera shot with some motion--The frame rate may drop toward 2 fps.
Fixed camera shot with high motion--The frame rate drops to about 1 fps.
Zooming camera with low motion--Expect a frame rate of about 2 fps.
Multiple shots, low motion--The frame rate approaches 1 fps.
Multiple shots, high motion--The frame rate drops below 1 fps.
Software for Editing Digital Audio and Video
Adobe Premiere Creative Multimedia Suite
Choosing the Best Format Type of Audio
Voice Background music Foreground music
Codec Bit Rate
6.5 Kbps codec 6.5 Kbps RealMedia 8 Kbps 12 Kbps 8 Kbps 12 Kbps
Audio Formats Type
WAV AU
Sampling Rate
8, 11, 22, 44 KHz 8, 22, 44 KHz PCM data 8, 11, 22, 44 KHz
Resolution
8/16 bit monophonic monophonic 8/16 bit monophonic
Choosing Video Bit Rates
Connection Speed 28.8 kbps 56 kbps 64 kbps 128 kpbs Target Bit Rate 19 kbps 44 kbps 56 kbps 105 kpbs
Inserting Multimedia into the Web page
Call to the external helper application A separate window opens up, with all RealPlayer controls, which can be customized by the user Embedded plug-in calls, with several options for display and playback control, set up by the developer There is a wizard for selecting the desired combination and generating HTML code
Referencing the File
A RealAudio URL has the format: pnm://server:port#/pathname pnm:// indicates the file is located on a RealAudio Server system. Server:Port# pathname name. is the address of the RealAudio Server. is the complete directory path and file Example: pnm://audio .
realaudio.com/welcome.ra
This pointer is placed into na ASCII file with the extension .ram
or .rpm
(metafile)
Referencing the File
HREF: Patient case EMBED:
Synchronized Multimedia
Synchronized HTML pages with streaming audio (guided tours, slide shows)
Synchronized Multimedia
Packing audio and PowerPoint slides into a RealMedia file (synchronized audio with slides control: great for slide shows
How RealPresenter Works
Create slide presentation using Microsoft PowerPoint Using mike and PC´s sound board, narrate the slide show, pressing the ´next slide´ key as you go PowerPoint will create a set of linked WAV files, one for each slide, with timing Click on Tools/Create RealMedia wizard to create .RA file and follow the Create .RAM metafile, upload to server
Other Streaming Solutions
Netscape´s Media Player (LiveAudio) MPEG 3 ISO CD 11172 Moving Pictures Experts Group XING´s StreamWorks MPEG-based, encoder (WAV, QT, AVI), player VXTreme, VDONet Apple QuickTime
The Microsoft Approach
Aims to establish its Active Streaming Format (ASF) as the de facto standard for streaming video. Has demonstrated a unified multimedia technology called DirectX. Has developed a streaming video product, NetShow, to challenge RealVideo for market dominance. NetShow comes with tools that convert existing video files, including AVI and QuickTime movies, to streaming files