streaming audio

12
Streaming Audio & Video Technologies A Brief Introduction Dr. Bill Schmidt SC Budget & Control Board - Office of Information Resources 300 Gervais Street Columbia, SC 29201 USA (803) 737-9520 [email protected] This document is available online in the Acrobat 3.0 ® format at: http://www.state.sc.us/wcst/germany/acro/ The free Acrobat 3.0 reader needed to view this document can be downloaded from: http://www.adobe.com/prodindex/acrobat/readstep.html __________________________________________________________________________________________________ Additional material relating to streaming technologies, including links to several SCB&CB/OIR streaming prototypes and to streaming clips already “in production,” can be found at: http://www.state.sc.us/wcst/germany/ . For the reader’s convenience, each of the last 5 pages of this document contains an image of the initial Web page (along with explanatory text) of a different Web-based audio- or video-synchronized “slide show.” Each “show” was developed as a prototype by SCB&CB/OIR, and is available for viewing through the Internet. All “shows” use RealNetworks’ RealAudio /RealVideo streaming technology, and are viewable using a 28.8KB link. The shows are: An audio-synchronized show presenting the 4 homes managed by the Historic Columbia Foundation (Columbia, SC) A video-only synchronized show containing the same material as the HCF show described immediately above An audio-only show presenting 4 Gullah stories and their English translations A video-synchronized show describing how proteins are made (protein synthesis) A video show demonstrating how to perform the Heimlich Maneuver on an infant. The single Web page of this tutorial contains still images and text which supplement the contents of the video

Upload: ronny72

Post on 16-Apr-2017

240 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Streaming Audio

Streaming Audio & Video Technologies

A Brief Introduction

Dr. Bill Schmidt

SC Budget & Control Board - Office of Information Resources300 Gervais Street

Columbia, SC 29201 USA

(803) [email protected]

This document is available online in the Acrobat 3.0 ® format at: http://www.state.sc.us/wcst/germany/acro/

The free Acrobat 3.0 reader needed to view this document can be downloaded from: http://www.adobe.com/prodindex/acrobat/readstep.html

__________________________________________________________________________________________________

• Additional material relating to streaming technologies, including links to several SCB&CB/OIR streaming

prototypes and to streaming clips already “in production,” can be found at:http://www.state.sc.us/wcst/germany/.

• For the reader’s convenience, each of the last 5 pages of this document contains an image of the initial

Web page (along with explanatory text) of a different Web-based audio- or video-synchronized “slideshow.” Each “show” was developed as a prototype by SCB&CB/OIR, and is available for viewingthrough the Internet. All “shows” use RealNetworks’ RealAudio/RealVideo streaming technology, andare viewable using a 28.8KB link. The shows are:

• An audio-synchronized show presenting the 4 homes managed by the Historic Columbia Foundation(Columbia, SC)

• A video-only synchronized show containing the same material as the HCF show described immediately above

• An audio-only show presenting 4 Gullah stories and their English translations

• A video-synchronized show describing how proteins are made (protein synthesis)

• A video show demonstrating how to perform the Heimlich Maneuver on an infant. The single Web page ofthis tutorial contains still images and text which supplement the contents of the video

Page 2: Streaming Audio

Overview

With the development of Internet-friendly "streaming" audio and video file formats, it has become possible forcommunities, businesses, organizations, government entities, and even individuals to reach out through theInternet to interested viewers throughout the world in a way, and with information, not previously possible.

The term "streaming" refers to the audio/video files’ very important ability to play as they are being received by aclient computer, so that the user does not have to wait for minutes or hours for a file to download.(Additionally, streaming files are highly compressed so that they require just a small fraction of the storage space which is required byan audio/video file in a non-streaming format; for example, a 1-hour 160x120-pixel RealVideo color video encoded for a 28.8KBlink requires a mere 10.4MB !!)

Of nearly equal importance to the immediate playback feature noted above . . . is the ability within RealNetworks’RealAudio/RealVideo streaming technology to synchronize the playback of these audio/video files with the displayof Web pages within a browser, with different Web pages being displayed within the browser window at author-specified times during the audio/video playback.

Thus, it is possible to create audio-/video-synchronized Web-based "slide shows" which Internet users can viewat their convenience, in exactly the same manner as they might play a tape in a VCR. Fast-forward/fast-reversecapability, identical to that found in a VCR, permits the viewer to move rapidly from place to place within the show,thus permitting the viewer to visit (or revisit) only those portions of the show desired. RealAudio-/RealVideo-synchronized shows can be viewed by users accessing the Internet even through slow links such as those of a28.8K modem ! ! !

Among the many uses for such shows are:

• promote tourism and related industries, including attracting new residents

• attract new business/industry

• distribute educational and "general interest" material

• provide Web-based training/instruction

• advertise products

• enable political and business leaders to personalize reports to the public

While numerous streaming audio/video technologies have been developed within the last several years, many are nowbeing discontinued or consolidated into other streaming products (see Online Reviews, below). By contrast,RealAudio & RealVideo from RealNetworks have consistently been named as the "best" overall streaming audio/videosolutions by the various trade magazines in which streaming technology products have been evaluated, and have becomethe de facto standard for streaming audio/video on the Internet. While we have reviewed the technical literature onmost of the different streaming technologies and created prototypes with several of them, OIR has chosen to focus itsefforts on RealAudio/RealVideo due to their quality and widespread acceptance.

Currently, several state agencies are developing/preparing to develop RealAudio/RealVideo clips for their Web sites with OIR’s assistance.

Page 3: Streaming Audio

Online Reviews

Important Note

As this overview is being written, the overcrowded field of streaming video products/technologies is rapidly consolidating:Microsoft has purchased VXtreme; RealNetworks has purchased Vivo; VDONet has ceased new product development; and Xingseems to have withdrawn from the market completely.

• AS EXISTING streaming audio/video technologies have been refined and new ones developed, there has been adramatic increase in interest in all aspects of digital audio/video technology, and a corresponding increase in thenumber of articles on this subject appearing in the literature.

This hyperactivity is best summed up by the introduction to a massive article on this subject titled, "The CompleteVideo Desktop," which appeared in the October 7, 1997 issue of PC Magazine and which began: Video isn’t justfor the pros anymore. We’ll show you the best products to help make your video projects come to life using yourPC . .

This article, which is online at: http://www.zdnet.com/pcmag/issues/1617/pcmg0023.htm , reviewed the 8 majorstreaming video solutions, 6 videoconferencing solutions, 6 video editing programs, and 9 video capture boards(including Firewire and MPEG encoders). Those interested in these products and their underlying technologies willfind a wealth of information in this article.

• The Complete Video Desktop (PC Magazine - October 7, 1997)

• Streaming Video: A Welcome Reception• Desktop Videoconferencing• Video Editing• Video Capture (includes MPEG encoders & Firewire)

• AN EXCELLENT, if somewhat dated, description of streaming audio and video technology, as well as adiscussion of the special considerations placed upon streaming audio/video by the Internet, can be found in thearticle, "Audio...Video...LIVE From the Web !", which appeared in the March 26, 1996 issue of PC Magazine.This article reviewed the 5 major streaming audio, and the 2 major streaming video products which were availableat that time; many more such products have become available since this article was published. The majority of thearticle is online at: http://www.zdnet.com/pcmag/issues/1506/pcmg0038.htm .

• Audio...Video...Live from the Web (PC Magazine - March 26, 1996)

• Sound Blasts the Web• RealAudio (RealAudio 2.0 [When Sound is the Key] )• Voxware• Internet Wave• TrueSpeech• StreamWorks (not available online)

• Web TV Tunes In• StreamWorks• VDOLive

Page 4: Streaming Audio

Authoring Considerations

• Audio

In general, one creates an audio file on the computer from an audio source such as a microphone or a cassetterecorder, then converts that file to the RealAudio format. This can be done with totally free software, although itis strongly recommended that one purchase a robust, but inexpensive, sound recording/editing program (such asSyntrillium Software’s Cool Edit 96 [$50.00]), and a "good" noise-dampening microphone.

The computer on which the audio files are created/edited/converted must have a 16-bit sound board. Such boardscan be purchased for under $50.00 if your computer does not already have one.

• Video

In general, one creates a video file on the computer from a video source such as a camcorder or a VCR, thenconverts that file to the RealVideo format.

Creation of a video file in this manner requires that the computer have a video capture board ($150 - $1,000) and avideo editing program. Frequently, video capture boards come "bundled" with a video editing program. Anexcellent review of capture boards and video editors appears in the October 7, 1997 issue of PC Magazine, and isonline at the URL given for this article in the Online Reviews section, above.

Additionally, the computer on which the video is digitized must be reasonably powerful. Minimum requirementsare commonly: 64 MB of RAM, a high speed SCSI or AV hard drive which is dedicated to video capture, and a166MHz Pentium processor. Check the minimum system requirements specified by your video capture board.

Page 5: Streaming Audio

RealAudio-Synchronized Web-based "Slide Show"

* * * Prototype * * *

Below is the screen of a Web browser displaying the start of a 4 minute streaming audio-synchronized Web-based presentationof the 4 historic homes managed by the Historic Columbia Foundation of Columbia, SC. The audio controls are displayed at thetop of the screen (along with thumbnails of the houses and a banner), the Web pages are displayed at the bottom.

The loading of the Web pages is synchronized with audio playback. As the presentation begins, the audio welcomes theviewer, and the introductory screen is displayed (shown below); as each home is discussed, the Web page appropriate to thehome is displayed at the bottom; the Woodrow Wilson Boyhood Home, the Hampton-Preston Mansion, the Robert Mills House,and the Mann-Simons Cottage are presented, in that order. Note that the viewer can fast-forward/fast-reverse through theaudio and associated “slide show” using the VCR-like slider in the player controls which are located at the upper left.

This presentation uses the RealNetworks streaming audio solution, RealAudio, and requires the free RealPlayer 5.0 for viewing(available at: http://www5.real.com/products/player/realplayer_download.html). RealAudio has become the de facto standardfor streaming audio over the Web.

Web pages in “slide show” presentations such as this cannot contain audio files, but otherwise can contain any items that Webpages can contain (e.g., text/images/animations/Java/VRML/etc.).

This presentation is available at: http://www.state.sc.us/97fair/raudio/rm/sync/hctour/ao/

Page 6: Streaming Audio

RealVideo-Synchronized Web-based "Slide Show"

* * * Prototype * * *

Below is the screen of a Web browser displaying the start of a 6 ½ minute streaming video-synchronized Web-basedpresentation of the 4 historic homes managed by the Historic Columbia Foundation of Columbia, SC. The video is displayedat the left of the screen, the Web pages are displayed at the right.

The loading of the Web pages is synchronized with video playback. As the presentation begins, the video welcomes theviewer, and the introductory screen is displayed (shown below); as each home is discussed in the video, the Web pageappropriate to the home is displayed at the right; the Woodrow Wilson Boyhood Home, the Hampton-Preston Mansion, theRobert Mills House, and the Mann-Simons Cottage are presented, in that order. Note that the viewer can fast-forward/fast-reverse through the video and associated “slide show” using the VCR-like slider in the player controls which are located under thevideo.

This presentation uses the RealNetworks streaming video solution, RealVideo, and requires the free RealPlayer 5.0 for viewing(available at: http://www5.real.com/products/player/realplayer_download.html). RealVideo has become the de facto standardfor streaming video over the Web.

Web pages in “slide show” presentations such as this cannot contain audio files, but otherwise can contain any items that Webpages can contain (e.g., text/images/animations/Java/VRML/etc.).

This presentation is available at: http://www.state.sc.us/97fair/raudio/rm/sync/hctour/

Page 7: Streaming Audio

RealAudio-Synchronized Web-based "Slide Show"

Below is the screen of a Web browser displaying the 1st Gullah story in a 3 ½ minute streaming audio-synchronized Web-basedpresentation of 4 Gullah stories contained in Ron & Natalie Daise’s De Gullah Storybook. No audio controls are available tothe user; a bar displaying the audio playback status is located at the bottom left of the page.

Audio playback is synchronized with the display of each of the Web pages. As the introductory Web page is displayed, theaudio welcomes the viewer; as each story is displayed, the viewer hears the story in Gullah, followed by its English translation.A navigation bar at the left of the screen permits the viewer to move between stories, or exit the presentation entirely.

This presentation uses the RealNetworks streaming audio solution, RealAudio, and requires the free RealPlayer 5.0 for viewing(available at: http://www5.real.com/products/player/realplayer_download.html). RealAudio has become the de facto standardfor streaming audio over the Web.

Web pages in “slide show” presentations such as this cannot contain audio files other than the presentation’s RealAudio file, butotherwise can contain any items that other Web pages can contain (e.g., text/images/animations/Java/VRML/etc.).

This presentation is available at: http://www.state.sc.us/97fair/raudio/storybook/

Page 8: Streaming Audio

RealVideo-Synchronized Web-based "Slide Show"

* * * Prototype * * *

Below is the screen of a Web browser displaying the start of a 5 ½ minute streaming video-synchronized Web-basedpresentation which describes how proteins are made. The video is displayed at the left of the screen, the Web pages aredisplayed at the right.

The loading of the Web pages is synchronized with video playback. As the presentation begins, the video gives an overviewof the show, and the introductory screen is displayed (shown below). After the introductory screen, a total of 8 Web pages aredisplayed, each showing a different phase of the synthesis process which is synchronized with what is being said in the video atthat time; the show ends with a 21 second animation (QuickTime) which graphically depicts the process. Note that the viewercan fast-forward/fast-reverse through the video and associated “slide show” using the VCR-like slider in the player controlswhich are located under the video.

This presentation uses the RealNetworks streaming video solution, RealVideo, and requires the free RealPlayer 5.0 for viewing(available at: http://www5.real.com/products/player/realplayer_download.html). RealVideo has become the de facto standardfor streaming video over the Web.

Web pages in “slide show” presentations such as this cannot contain audio files, but otherwise can contain any items that Webpages can contain (e.g., text/images/animations/Java/VRML/etc.).

This presentation is available at: http://www.state.sc.us/97fair/raudio/rm/sync/protein/

Page 9: Streaming Audio

RealVideo Web-based Tutorial

* * * Prototype * * *

Below is the screen of a Web browser displaying the start of a 30 second streaming video Web-based tutorial whichdemonstrates how to perform the Heimlich Maneuver on a choking infant. The video is displayed at the right of the screen,the still images and text which accompany the video are displayed at the left.

As the presentation begins, the Web page loads, with the still images and text being displayed at the left, and the RealPlayercontrols being displayed at the right. When ready, the viewer begins the video playback by clicking on the RealPlayer’s startbutton (the arrow facing right on the controls). Note that the viewer can fast-forward/fast-reverse through the video using theVCR-like slider in the player controls which are located under the video; the viewer can also replay the tutorial as often as desiredby clicking on the player’s start button.

This tutorial uses the RealNetworks streaming video solution, RealVideo, and requires the free RealPlayer 5.0 for viewing(available at: http://www5.real.com/products/player/realplayer_download.html). RealVideo has become the de facto standardfor streaming video over the Web.

Web pages in presentations such as this cannot contain audio files, but otherwise can contain any items that Web pages canordinarily contain (e.g., text/images/animations/Java/VRML/etc.).

This presentation is available at: http://www.state.sc.us/wcst/rla/heimlich/heim-images.htm

Page 10: Streaming Audio
Page 11: Streaming Audio

RealAudio and RealVideo Content Creation Guide

12

Delivering a RealAudio or RealVideo Clip

The following figure shows the components of RealAudio and RealAudio andRealVideo System used to deliver a typical RealAudio or RealVideo clip. Thenumbers in the figure match the numbered steps following the figure.

WebServer

RealServer

WebBrowser

RealPlayer

ServerClient

3

6 6

4

2

1

3

1

5

RealAudio and RealVideo Delivery System

Page 12: Streaming Audio

Installing RealEncoder and RealPublisher on Windows Platform

13

1. The Web browser displays a Web page that contains a link to a metafile.

2. The user clicks the link. The Web browser requests the metafile from theWeb Server.

3. The Web server delivers a metafile to the Web browser.

4. The Web browser looks up the MIME type of metafile. Based on theMIME type, the Web browser starts RealPlayer as a helper application andpasses it the metafile.

5. RealPlayer reads the first URL from the metafile and requests it fromRealServer streaming media server.

6. RealServer begins streaming the requested RealAudio or RealVideo clip toRealPlayer.

Note: No messages pass between the RealServer and the Web server. The Webbrowser provides the URL of RealAudio or RealVideo clip to RealPlayer.RealPlayer does not require a Web browser to function; users can enter the URLof a .ra, .rm or .ram file directly into RealPlayer, or use the Preset or Scanbuttons on RealPlayer Plus.