This chapter introduces you to the steps for creating streaming or downloadable media. It describes the major features of RealProducer, and explains the procedures for encoding and delivering static clips or live broadcasts.
RealProducer encodes RealAudio and RealVideo clips and broadcasts from audio and video input. This input can be a file in a format such as WAVE, AVI, or MPEG. Or, the input may be live material that you have captured with a microphone or camera attached to an audio or video capture card on the RealProducer computer.
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For More Information: For a list of acceptable input formats, refer to "Audio and Video Input Formats". |
Before you encode a clip with RealProducer, you can use the audio or video editing program of your choice to edit a digitized input file. Using this program, you can set a video's length, for example, cropping out any unnecessary parts. Although RealProducer provides some editing functions such as cropping, it does not provide all of the advanced features found in audio and video editing programs.
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Tip: The quality of a streaming audio or video clip starts with the source file. The more you know about audio and video editing, the better you'll be able to produce a great streaming clip. For some pointers about preparing files for encoding, see Chapter 4 and Chapter 5. |
Once you have your media input ready, you can encode the input as a RealVideo or RealAudio clip. Taken together, these clip types are called RealMedia. This section explains the aspects of RealProducer you use to encode a RealMedia clip or broadcast.
On Windows, there are two ways to run RealProducer. You can use the RealProducer graphical application, or run the RealProducer command-line application. On Linux, you can use the command-line application.
The RealProducer graphical application provides an easy-to-use interface for encoding RealMedia clips and broadcasts. Using the graphical application, you can drag-and-drop input files, select your encoding options, and save the encoded output to a clip or send it to a server for broadcast. Chapter 6 explains the basic procedures for using the graphical application.
You can run the command-line application from the command prompt on Windows or Linux. It provides all of the features of the graphical application, as well as a few advanced features not available through the graphical application. See Chapter 14 for information about running the command-line application.
A job is a central aspect of encoding RealMedia with RealProducer. The job defines how to encode your clip or broadcast. It selects the media inputs, sets the encoding properties, and defines the destinations, such as whether to save the encoded stream to a clip, forward it to a server for broadcast, or both.
Whether you use the graphical application or the command-line application, you can save your job settings in a job file for later use. You can also modify a job file's settings, either through RealProducer or by hand, to create a new job quickly. The job file uses an XML-based format to define all of the job's encoding settings.
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For More Information: The section "Using Jobs" explains how to define jobs through the graphical application. See "Job File Options" for information about specifying jobs on the command line. Appendix B explains the job file syntax. |
When you set up a job, you choose one or more audiences. An audience defines several aspects of the encoding job. Most importantly, it defines the bit rate at which a clip or broadcast streams. For a downloadable clip, the audience selection affects the clip's quality and file size. Selecting an audience is therefore one of the most important decisions you make when encoding a clip. RealProducer predefines a number of audiences designed for low- bandwidth streaming to modems and smartphones, high-quality download files, and many other uses.
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For More Information: Chapter 7 describes the predefined audiences. "Choosing Audiences" explains how to select audiences through the graphical application. The section "Audience Definitions or Audience Files (-ad)" does the same for the command-line application. You can also create your own audiences, as explained in "Creating and Editing Audiences". |
Each audience is either constant bit rate (CBR) or variable bit rate (VBR). The CBR audiences are designed for streaming. When you use them, you can encode multiple audiences into a clip or broadcast. For example, a single clip can stream to 56 Kbps modems and faster broadband connections when you use CBR encoding.
The VBR audiences are designed for downloadable clips, but can also be used for streaming in some instances. When you encode a downloadable clip, you select a VBR template according to how highly you want to compress the input, or how well you want to preserve the input's quality. Unlike CBR clips that can have multiple audiences, VBR clips can include just one audience.
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For More Information: For background about CBR and VBR, refer to "Constant Bit Rate Video" and "Variable Bit Rate Video". |
RealProducer stores audience information in an XML-formatted audience file that you can edit by hand. You can also copy and modify an existing file to create your own audience definition. Appendix C explains the audience file syntax. Refer to the section "Audiences Section" for information about how to copy audience file information into a job file.
Each job defines an output, which is the encoded media data and all of its properties. To define where RealProducer sends its output, you specify one or more destinations.
A destination may be an encoded RealMedia clip, which is a file that uses the
file extension .rm or .rmvb. Or, server destinations can send the encoded
output to one or more Helix Servers for broadcast. All destinations receive the
same output data. If network problems prevent encoded data from reaching a
server destination, for example, a clip destination still records the data.
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For More Information: You can encode multiple destinations for a single output through the graphical application as described in "Selecting Inputs and Destinations". "File and Server Outputs" explains how to define destinations within a job file. |
RealProducer also lets you define multiple outputs that have different properties. From the same video input, for example, you might encode a large video clip for fast, broadband connections, and a smaller video clip for slow modem connections. Because each video has a different size, it is a separate output. Each of these outputs can have one or more destinations, whether saved as a clip or sent to a server. Encoding multiple outputs is possible when you define the outputs in a job file and run the job file through the command-line application.
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For More Information: For information about defining multiple outputs in a job file, see "File and Server Outputs". |
In addition to the audience selection, your job can define many additional encoding parameters.
Clips or broadcasts standardly encode information such as the presentation's title, author, and copyright. The section "Adding Clip Information" explains how to add clip information through the graphical application. Refer to the section "Clip Information Options" for instructions about doing this through the command-line application. You can also add clip information directly to a job file, as described in "Clip Information".
Video filters allow you to alter and improve the video input before encoding it. You can use these filters to remove artifacts such as video noise, as well as to crop and resize the video. The section "RealVideo Filters" explains the filters. See the section "Filtering Video Input" for information about applying filters through the graphical application. "Prefilter Options" explains how to specify filters on the command line, and "Prefilters" covers the filter syntax used in the job file.
After you have encoded a RealMedia clip using RealProducer, you can move the clip to Helix Server for streaming, or place it on a download server. However, you may first want to use another application to edit or modify the encoded clip.
The RealMedia Editor allows you edit an encoded RealVideo or RealAudio clip. For example, you can use this application to change the clip information, remove a scene from a video, or combine several clips into a single clip. The RealMedia Editor is included with RealProducer Plus. You can run it as a graphical application on Windows, or a command-line application on Windows or Linux. Chapter 12 explains how to run the RealMedia Editor.
Using the RealMedia Events utility, you can encode clip information into an existing RealAudio or RealVideo clip. You can also add image maps or timed URLs to the clip. This allows viewers to click a video clip to open related Web pages in their browser. Or, an audio or video clip can open Web pages automatically when the clip reaches certain positions in its timeline. See Chapter 13 for information about defining clip events.
If you need to protect media assets, you can use RealNetworks' digital rights management technology. Using Helix DRM Packager, you can encrypt the contents of a RealMedia clip, then assign rights to that clip on an individual basis using Helix DRM License Server. Digital rights management is an optional and separate part of the media encoding process.
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Note: For more about RealNetworks' DRM technology, visit http://www.realnetworks.com/products/drm/index.html. |
Once you encode a clip, it is ready for streaming or downloading. Additionally, you can use various scripting or markup languages to combine multiple clips and Web pages into a media presentation. Other guides available from RealNetworks explain scripting and markup languages you can use with clips and broadcasts encoded by RealProducer.
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For More Information: You can download RealNetworks' content creation guides in PDF or HMTL format from http://service.real.com/help/library/encoders.html. |
When your presentation is ready to stream, you may want to write a Ram file,
which is so-named because it uses the file extension .ram, as in movie.ram. Also
known as a metafile, the Ram file links your Web page to your media. Although
a Ram file is not necessary when you stream a clip or broadcast using Helix
Server, it is useful for passing simple parameters to RealPlayer. It might
instruct RealPlayer to open the clip in full-screen mode, for example, or
provide the URL to a Web page that displays as the clip plays.
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For More Information: For information about writing a Ram file, refer to the Ram file chapter in Introduction to Streaming Media. The Ram file is also covered in the presentation delivery chapter of RealNetworks Production Guide. |
You can also create a Synchronized Multimedia Integration Language (SMIL) file to integrate several clips into a single presentation. SMIL is the standard markup language for timing and controlling streaming media clips. Using a SMIL file, you can coordinate the layout and playback of multiple media clips in parallel (simultaneously) or in sequence. SMIL can also open HTML pages as a clip plays and provide interactive options, such as playing one of three different videos depending on which button the viewer clicks.
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Note: For the basics of SMIL, see Introduction to Streaming Media. For a comprehensive look at SMIL, refer to RealNetworks Production Guide. |
RealPlayer supports Javascript and VBScript methods that you can use to play clips based on viewer interaction with forms or elements displayed in a Web page. If you are familiar with Web-based scripting, refer to RealPlayer Scripting Guide for more information.
Just as a Web server delivers Web pages to browsers, Helix Server serves streaming media to RealPlayer. Using Helix Server, you can stream clips that you have encoded using RealProducer. You can also set up live broadcasts in which RealProducer encodes live content in real-time, sending it to Helix Server for distribution to RealPlayer viewers.
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For More Information: For information about Helix Server features, refer to Helix Server Administration Guide, which you can browse or download from http://service.real.com/help/library/servers.html. |
To deliver a streaming presentation, you need to have access to Helix Server. If you are not running Helix Server yourself, the Helix Server administrator can set up a method for you to deliver content. To stream a clip on-demand, you simply transfer the clip to a Helix Server content directory and add a link to the clip in a Web page.
Broadcasting a live event requires a closer coordination between RealProducer and Helix Server. The Helix Server administrator must set up certain server features to allow the broadcast stream. On RealProducer, you define certain server parameters that allow RealProducer to deliver the live stream. Chapter 10 explains the issues involved with broadcast. Refer to Chapter 11 for instructions about delivering a broadcast stream to Helix Server.
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©2004 RealNetworks, Inc.
For more information, visit RealNetworks Click here if the Table of Contents frame is not visible at the left side of your screen. |
