This appendix answers often-asked questions about producing streaming media clips for RealSystem. It also provides URLs for Web sites where you can find tools and helpful information about developing streaming media presentations.
RealProducer is the basic tool you use to create clips. Both the RealProducer User's Guide and the product's online help guide you through the encoding process. This production guide provides 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 3 and Chapter 4 include tips on producing good audio and video, respectively. If you are new to media production, learn your 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 the following 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 or 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 cannot read. However, these programs typically let you export the video to a common format that RealProducer accepts, such as AVI, QuickTime, or MPEG.
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You can purchase hardware and software for capturing and editing audio or 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 Macintosh, such as QuickTime, whereas RealProducer on Windows or UNIX supports the formats widely used on those operating systems. Check the RealProducer manual for your operating system for a list of accepted formats. Information is also available at the following Web page:
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 RealNetworks' Web site:
http://www.realnetworks.com/products/index.html
Using RealSlideshow's graphical interface, you can create streaming RealPix presentations from still images. You can even add a soundtrack, or record a narration for each image. You can download RealSlideshow from this Web address:
http://www.realnetworks.com/products/index.html
You can also create RealPix presentations by hand with the RealPix markup language, which is described in RealPix Authoring Guide, available at this Web page:
http://service.real.com/help/library/encoders.html
You create animation with Macromedia Flash. You can develop animations with Flash 2, 3, or 4. Chapter 5 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 from Macromedia's Web site:
http://www.macromedia.com/software/flash/
The RealSystem 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 you need 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 information about SureStream, read "SureStream RealAudio and RealVideo".
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, each of which runs at a different bit rate. You can make a SureStream clip that streams at either 28.8 Kbps or 56 Kbps, for example. When users request the clip, they automatically receive the stream that best matches their RealPlayer connection speed.
Using RealProducer, you can choose to use 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. RealProducer Basic encodes two speeds per clip, whereas RealProducer Plus encodes up to eight 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 from a Web server, you need to set RealProducer to use single-rate encoding.
Chapter 6 explains the basics of SMIL. Chapter 7 covers the RealNetworks extensions to SMIL. Appendix D is a quick reference you can use once you are comfortable with SMIL.
Pronounced "smile," SMIL stands for "Synchronized Multimedia Integration Language." It is an industry-standard markup language used to lay out and time streaming media presentations. SMIL works for RealPlayer the way HTML works for a Web browser.
Not always. 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 gives you the means to lay out the presentation and time its clips. It also provides other features, such as letting you create hyperlinks that start a new presentation. For a rundown of basic SMIL features, see "Understanding SMIL".
SMIL is a simple markup language that you can write with a word processor or text editor. Some software tools (RealSlideshow, for example) create SMIL files automatically.
You can stream clips yourself with RealServer, through a service provider that has RealServer available, or, in some cases, from a Web server.
Not necessarily. RealServer streams the clips created by RealProducer. To run RealServer, you need a computer connected to an intranet or one that has a direct presence on the Internet. You cannot run RealServer if you use an Internet service provider (ISP) to connect to the Internet. If you use an ISP, check whether they have RealServer and whether they can host your streaming presentations for you.
RealServer runs on Windows NT/2000 and many UNIX platforms, including Linux. For a list of available platforms, visit RealNetworks' technical support Web site at http://service.real.com.
RealServer is available on the RealNetworks Web site at http://www.realnetworks.com/products/index.html. RealServer Basic is free.
Sometimes. A Web server can deliver many types of clips, including RealAudio and RealVideo. There are limits to 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 that typically consists of just one linethe 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 supplies RealPlayer with the URL to the SMIL file (or to your streaming clip, if you're not using SMIL). The Ram file is always necessary because its .ram extension launches RealPlayer.
Yes. Chapter 8 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 HTTP 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 "RealTime Streaming Protocol," is an industry-standard protocol that overcomes the deficiencies of HTTP for streaming media. RTSP enables RealServer and RealPlayer to stream long clips and compensate for changing network conditions.
When a clip resides on RealServer, make sure that 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 cannot be in an HTML hyperlink, because a Web browser does not know how to make an RTSP request. For more on this, see "RTSP and HTTP".
Chapter 9 explains how to stream ads using SMIL. The RealServer administrator performs 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 in presentations. 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 it can make new ads appear at specific intervals during the presentation. RealServer can also stream ads in RealAudio, RealVideo, and Flash formats. You can have ads either precede the requested clips or appear as commercial breaks during the clips.
You need RealServer with the optional advertising extension installed. You also need either to have an ad server, or to sign up with an online ad provider such as DoubleClick. The RealServer administrator configures RealServer to work with your ad-serving system, determining what types of ads are to be streamed. You then write SMIL files with <RealAdInsert/>
tags that specify where ads are to be 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.
For complete information about broadcasting streaming media, see RealProducer User's Guide, RealServer Administration Guide, and Chapter 11 of this production guide.
Possibly. If you connect to the Internet through an ISP, you may be able to broadcast streaming media, provided that your ISP has RealServer available and offers broadcasting services. To do this, you will need a fast Internet connection to your ISP. You cannot broadcast through an ISP by running RealServer on your home computer.
Yes. Using SureStream is recommended because it ensures that users connecting at different speeds will each receive the best possible stream. You need to make sure, however, that the computer running RealProducer has enough power to encode all the SureStream streams at the same time. Check RealProducer's manual or online help for system requirements, and perform a trial run before streaming the actual broadcast.
No. You need RealServer to broadcast streaming presentations. Web servers are designed to serve HTML pages and graphics to different users at different times. They are not designed to broadcast the same presentation to multiple users simultaneously.
No. "Broadcasting" means to send out a stream that more than one RealPlayer user can view at the same time. The broadcast can be live, meaning that the input originates from a microphone or video camera. Or it can be prerecorded, meaning that 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 then set up RealServer to broadcast the clip as a simulated live event.
Yes. You can use SMIL to include ads with the broadcast, or deliver static clips alongside the broadcast. 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, you can use a network of RealServers to reach 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.
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 the following Web page:
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 with a Web browser. Many documents are also available in PDF format, which is suitable for printing. To read PDF files, you need Adobe's Acrobat Reader, which is available from Adobe's Web site:
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. You can find it at the following Web address:
http://www.realnetworks.com/devzone