If you're a beginner, this appendix answers common questions about producing streaming media clips for RealSystem. It also supplies Web URLs where you can find tools and helpful information about developing streaming media presentations.
RealProducer is the basic tool for creating clips. The RealProducer manual or online help guides you through the encoding process. This production guide gives you background information and tips on creating high-quality streaming media.
You start with an audio or video source file in a digitized format on your computer. You then use RealProducer's encoding wizard to select the file and set encoding options. The encoding process creates a new streaming clip, leaving the source file unchanged.
Yes. RealProducer accepts live video input from a camera and live audio input from a microphone. The camera and microphone connect to an audio/video capture card on your computer. RealProducer's encoding wizard then lets you select the live input as the source. In this case you go directly from live input to encoded clip without creating a digitized source file.
Quality starts at the source. You need high-quality video and audio input for RealProducer to create high-quality streaming clips. Chapter 4 and Chapter 5 give some tips on producing good audio and video, respectively. If you are new to media production, learn your media editing hardware and software thoroughly, paying close attention to the manufacturers' recommendations for producing high-quality media files.
In addition to audio and video, RealSystem can stream these types of clips:
To produce streaming media clips, you need audio and video production tools as well as RealProducer to handle the encoding.
You can use any hardware or software designed for capturing and editing audio and video. The digitized output must be in a format that RealProducer accepts, however. Some video editing programs save digitized video in a proprietary format that RealProducer can't read. However, they typically let you export the video to a common format (such as AVI, QuickTime, or MPEG) that RealProducer accepts.
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| You can purchase hardware and software for capturing and editing audio and video from RealStore at http://www.realstore.com. |
RealProducer accepts many common audio and video formats. These may vary by operating system, though. RealProducer on Macintosh accepts the formats widely used on the Mac, such as QuickTime, while RealProducer on Windows or Unix supports the formats widely used on those platforms. Check the RealProducer manual for your operating system for a list of accepted formats. Information is also available at:
http://www.realnetworks.com/products/producer/freevsplus.html
RealNetworks makes versions of RealProducer for Windows 95/98/NT/2000, Macintosh, and Linux. You can download the free version or purchase RealProducer Plus at:
http://www.realnetworks.com/products/index.html
Through its graphical interface, RealSlideshow lets you create streaming RealPix presentations from still images. It also lets you add a soundtrack and voice narrations for each image. You can download RealSlideshow from:
http://www.realnetworks.com/products/index.html
You can also create RealPix presentations by hand with the RealPix mark-up language, which is described in RealPix Authoring Guide, available at:
http://service.real.com/help/library/encoders.html
You create animation with Flash by Macromedia. RealSystem currently streams Flash 2. You can develop animations with Flash 3 or 4, but you must export your file in Flash 2 format. Chapter 6 provides tips for making Flash animation stream well with RealSystem. It doesn't explain how to create Flash animations, however. You can learn more about Flash at http://www.macromedia.com/software/flash/.
The Authoring Kit bundles several RealNetworks tools and manuals into one archive that you can download. This gives you one source for the basic tools and information used to create streaming media clips. The Authoring Kit is available free at:
http://www.realnetworks.com/products/authkit/
SureStream provides advanced streaming technology for RealSystem. For more on SureStream, read "Using SureStream Clips for Multiple Bandwidths".
SureStream is a technology that lets a single RealAudio or RealVideo clip stream at different bit rates. It does this by bundling into a single clip multiple streams that each run at a different bit rate. You can make a SureStream clip that streams at either 28.8 Kbps or 56 Kbps, for example. When a RealPlayer requests the clip, it automatically receives the stream that best suits its connection speed.
RealProducer lets you choose SureStream when you encode audio or video input. The number of SureStream streams you can encode in the clip depends on the type of RealProducer you use. The free RealProducer encodes two speeds per clip, while RealProducer Plus encodes up to six speeds per clip.
No. A SureStream clip has several streams encoded in a single clip. Unlike RealServer, a Web server cannot extract a specific stream to send to RealPlayer. If you plan to deliver clips with a Web server, you need to choose single-rate encoding with RealProducer.
Chapter 7 explains the basics of SMIL. Chapter 8 covers RealNetworks' extensions to SMIL. Appendix D is a quick reference you can use once you understand SMIL.
Pronounced "smile," SMIL stands for "Synchronized Multimedia Integration Language." It is an industry-standard mark-up language used to lay out and time streaming media presentations. SMIL works for RealPlayer the way HTML works for a Web browser.
When you want to stream just one clip, such as a single RealVideo clip, you don't need to use SMIL. You just link your Web page to the clip through a Ram file. For more information, see "What is a Ram File?".
When you stream multiple clips, SMIL lets you lay out and time the presentation. It also provides other features, such as letting you create hyperlinks that start a new presentation. See "Writing a SMIL File" for a rundown of basic SMIL features.
SMIL is a simple mark-up language that you can write with a word processor or text editor. Some software tools also write SMIL for you. RealSlideshow creates SMIL files automatically, for example.
You can stream clips yourself with RealServer, through a service provider that has RealServer available, or, in some cases, with a Web server.
RealServer streams the clips created by RealProducer. To run it, you need a computer on an intranet, or one that has a direct presence on the Internet. You can't run RealServer if you use an Internet Service Provider (ISP) to connect to the Internet. If you use an ISP, check to see that they have RealServer and can host your streaming presentations for you.
RealServer runs on Windows NT/2000 and many UNIX operating systems, including Linux. For a list of available platforms, visit RealNetworks' technical support Web site at http://service.real.com.
RealServer is available through RealNetworks' Web site at http://www.realnetworks.com/products/index.html. The basic RealServer is free.
A Web server can deliver many clips, including RealAudio and RealVideo. There are limits on Web server delivery, however. If you plan to use a Web server for clip delivery, read "Limitations on Web Server Playback" first.
A Ram file, also called a "metafile," is a simple text file with the extension .ram. A Ram file typically consists of one line: the URL to a streaming presentation. Your Web page does not link directly to your presentation. Instead, it links to the Ram file, which ensures that RealPlayer launches. RealPlayer then uses the URL in the Ram file to request the presentation. "Creating a Ram File Manually" explains how to write a Ram file.
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| When you stream clips with RealServer, you can eliminate the Ram file by using the Ramgen utility. For more information, see "Using Ramgen". |
Yes. The SMIL file lists the URLs for clips, the Ram file gives the URL to the SMIL file (or your streaming clip if you're not using SMIL). The Ram file is always necessary because its .ram extension launches RealPlayer.
Yes. Chapter 9 explains how to embed clips and RealPlayer controls in a Web page. RealPlayer still plays the clips, but it does so "behind the scenes" as a browser plug-in rather than by launching separately.
Web servers use the HTTP protocol to deliver Web pages and graphics. HTTP is designed to download small files quickly and efficiently. It is not suited for streaming large media clips, though. RTSP, which stands for "Real-Time Streaming Protocol," is an industry-standard protocol that overcomes the deficiencies of HTTP for streaming media. It lets RealServer and RealPlayer stream long clips and compensate for changing network conditions.
When a clip resides on RealServer, make sure the URL used to request it starts with rtsp:// rather than http://. An RTSP URL must be in a file read by RealPlayer, such as a Ram file or a SMIL file. It can't be in an HTML page hyperlink because a Web browser does not know how to make an RTSP request. For more on this, see "Using RTSP and HTTP in URLs".
Chapter 10 explains how to stream ads using SMIL. The RealServer administrator carries out most of the work for setting up ad streaming, as described in RealServer Administration Guide.
Ad streaming uses <RealAdInsert/> tags in SMIL files to designate when and where ads appear. When RealServer serves a SMIL file, it replaces the tags with URLs to ad files. These URLs come from a separate ad server, and the RealServer administrator can configure RealServer to work with virtually any ad serving system.
RealServer can stream banner ads in image formats such as GIF, JPEG, and PNG. It can display one ad per presentation, or make new ads appear at specific intervals while the presentation plays. RealServer can also stream ads in RealAudio, RealVideo, or Flash formats. These ads might appear before the requested clips, or during the clips as commercial breaks.
You need a RealServer with the optional Advertising Extension. You also need to have an ad server, or to sign up with an online ad provider like DoubleClick. The RealServer administrator configures RealServer to work with your ad serving system, determining what types of ads are streamed. You then write SMIL files with <RealAdInsert/> tags that determine where ads are placed.
No. Writing your own SMIL files gives you a more flexible way to stream ads, but RealServer can automatically include ads with requested clips or SMIL presentations. If your RealServer hosts a large number of RealAudio or RealVideo clips, for example, you can simply let RealServer lay out an ad for each clip without writing any SMIL mark-up by hand.
For complete information about broadcasting (also known as "Webcasting"), see your RealProducer manual, the RealServer Administration Guide, and Chapter 12 of this production guide.
If you connect to the Internet through an Internet Service Provider (ISP), you may be able to broadcast, provided that your ISP has RealServer available and offers broadcasting services. You'll also need a fast Internet connection to your ISP. You cannot broadcast through an ISP by running RealServer on your home machine.
Yes. Using SureStream is recommended because it allows users connecting at different speeds to receive the best possible stream. You need to ensure that the computer running RealProducer has enough power to encode all the SureStream streams at the same time, however. Check your RealProducer manual for machine recommendations, and perform a trial run first.
No, you need RealServer to broadcast. Web servers are meant to serve HTML pages and graphics to different users at different times. They are not designed to broadcast the same presentation to multiple users.
No. "Broadcasting" means to send out a stream that more than one RealPlayer user can view. The broadcast can be live, meaning the input originates from a microphone or video. It can also be prerecorded, meaning it originates from a digitized clip prepared in advance. If it's prerecorded, you don't need to use RealProducer during the broadcast. You just put the clip on RealServer and set up RealServer to broadcast the clip as a simulated live event.
Yes. You can use SMIL to include ads with the broadcast, deliver a static clip alongside the broadcast, or anything else. In the SMIL file, you simply treat the broadcast as a static clip. The only difference is that you use a special URL created by the RealServer administrator that identifies the resource as a broadcast rather than a clip.
That depends entirely on your RealServer and the network bandwidth it has available. Each RealServer can broadcast to a specific number of RealPlayers, as defined in its license agreement. For large broadcasts, several RealServers can be coordinated in a network to reach many thousands of RealPlayers.
Yes. Real Broadcast Network (RBN) offers a wide range of services for hosting broadcasts. Learn more about RBN at:
http://www.realnetworks.com/rbn/index.html
RealNetworks offers a range of technical support features and documentation at http://service.real.com.
RealNetworks technical support operates an extensive Web site at http://service.real.com. The site includes answers to frequently asked questions, a documentation library, and a searchable knowledge base. To place a service call with technical support, fill out the e-mail form at:
http://customerrelations.real.com/scripts/rnforms/contact_tech_service.asp
RealNetworks Technical Support maintains a documentation library at http://service.real.com/help/library/index.html. Most documents are available as bundled HTML archives that you can download, uncompress, and read through a Web browser. Many documents are also available in PDF format, which is suitable for printing. To read PDF, you need Adobe's Acrobat Reader, which is available at:
http://www.adobe.com/products/acrobat/readstep.html
The RealNetworks DevZone is the main information site for content authors and software developers working with RealSystem products. Find it at:
http://www.realnetworks.com/devzone