# Chapter 2: Overview

Designed for powerful and flexible media delivery, Helix™ Universal Server version 9.0 streams the widest variety of media, such as audio, video, animation, images, and text, to the broadest range of media players, including RealOne Player, Windows Media Player, and Apple QuickTime Player. If you are new to Helix Universal Server, this chapter introduces you to Helix Universal Server concepts and features.

# Media Formats

Helix Universal Server can stream on-demand clips and broadcast live events in more media formats than any other media server. Depending on its license, Helix Universal Server can serve the file formats listed below. Although not exhaustive, the following list represents the major media formats available with Helix Universal Server, which can deliver additional formats through plug-ins created by third-party developers.

RealNetworks: | RealAudio (`.rm`), RealVideo (`.rm, .rmvb`), RealPix (`.rp`), RealText (`.rt`)
Macromedia: | Flash (`.swf`)
Microsoft: | Windows Media (`.asf`, `.wma`, .`wmv`)
Apple: | QuickTime (`.mov`)
Standards-Based: | MPEG-1, MPEG-2, MPEG-4, MP3
Image Formats: | GIF (`.gif`), JPEG (`.jpg`, `jpeg`), PNG (`.png`)
Other: | AU (`.au`), AIFF (`.aif`, `.ief`), WAV (`.wav`)

Helix Universal Server can deliver the same media formats on any of its supported operating systems, which include Windows and many UNIX variants such as Linux. This allows you to stream the media formats you want, using the operating system of your choice. Helix Universal Servers running on different operating systems are completely interoperable, allowing you to deliver homogeneous media services in a heterogeneous network environment.

| Tip: To determine if Helix Universal Server can stream a clip, open the clip in RealOne Player from your desktop. If RealOne Player can play the clip, Helix Universal Server typically can deliver it, as long as the clip is in a streaming format rather than a format designed for download. Note, however, that Helix Universal Server can also stream clips that RealOne Player does not play.

| For More Information: The specific versions of media formats and media players supported by Helix Universal Server are subject to change. Check http://www.realnetworks.com/resources for the latest information.

## RealMedia

Helix Universal Server streams RealAudio, RealVideo, RealText, RealPix, and SMIL (1.0 and 2.0) to RealOne Player and earlier versions of RealPlayer. It supports all past codecs and file formats, meaning that you can deliver any existing RealMedia clip with the current version of Helix Universal Server.

### SureStream RealAudio and RealVideo

Because different viewers have different streaming bandwidths available to them, RealAudio and RealVideo clips can use SureStream technology to encode multiple streams at different bandwidths in a single clip. When a RealPlayer requests a clip, Helix Universal Server delivers the stream suited for that player's connection speed. This way, each viewer receives the highest- quality stream possible. In addition, Helix Universal Server and the player can switch between streams to compensate for changing network conditions.

| For More Information: For instructions on encoding SureStream RealAudio and RealVideo clips, see Helix Producer User's Guide. See also the audio and video chapters of RealNetworks Production Guide.

### SMIL

For media streamed to RealOne Player, the content creator may use Synchronized Multimedia Integration Language (SMIL) to coordinate multiple clips into a single presentation. A SMIL file, which has the file extension `.smil`, uses XML-based markup to lay out and time any number of clips played together or in sequence. It can also open HTML pages in RealOne Player, and create special effects such as fades during clip transitions. RealPlayer G2 through RealPlayer 8 can play SMIL 1.0 files. RealOne Player supports SMIL 1.0 and 2.0.

| For More Information: See RealNetworks Production Guide for instructions about using SMIL.

### RealPix

Using RealPix, you can stream slideshows composed of still images in GIF, JPEG, or PNG formats. The RealPix markup language includes special effects, letting you fade between images, for example, or zoom in on an image detail. You can even use SMIL to coordinate your slideshow with a streaming soundtrack.

| For More Information: RealNetworks Production Guide contains a chapter on producing RealPix slideshows.

### RealText

With RealText, you can create timed text clips that can stream alone or in combination with other media such as audio or video. This makes RealText a handy means for adding text to SMIL presentations. Using RealText, you can add subtitles to a video, for example, or provide closed-captioning.

| For More Information: See the RealText chapter in RealNetworks Production Guide.

## Macromedia Flash

RealPlayer 8 and RealOne Player support Macromedia Flash version 4, 3, and 2. Earlier versions of RealPlayer support Flash version 2. Flash is well-suited for linear presentations that have a continuous audio track and animated images synchronized along a timeline. Such presentations can include demonstrations, training courses, product overviews, and movie trailers.

| For More Information: Learn more about Flash from Macromedia's Web site at http://www.macromedia.com/software/flash. See the Flash animation chapter in RealNetworks Production Guide for information about streaming Flash to RealOne Player.

## Windows Media

Helix Universal Server can stream Microsoft Windows Media audio and video to Windows Media Player versions 6.4 and later. Helix Universal Server supports the MMS protocol, as well as Microsoft's multiple bit rate (MBR) encoding technology. It can receive live streams from the Windows Media Encoder for unicasting and multicasting. Windows Media formats do not stream to RealOne Player.

| For More Information: For information about producing clips or live broadcasts in the Windows Media format, visit http://www.microsoft.com/windows/windowsmedia/defa ult.asp.

## QuickTime

Helix Universal Server can stream hinted QuickTime clips to Apple's QuickTime Player 4 and later. It can deliver QuickTime clips encoded in all major proprietary and standards-based codecs, including Sorenson, Cinepak, Qualcomm PureVoice, and Qdesign. Helix Universal Server can stream live QuickTime broadcasts from Sorenson Broadcaster, as well as simulated broadcasts from Playlist Broadcaster and the Helix Universal Server SLTA utility.

| For More Information: For QuickTime information, visit Apple's Web site http://www.apple.com/quicktime/. For more about Sorenson tools, visit http://www.sorenson.com.

| Note: If you encode a QuickTime clip with a standards-based codec, such as h.261, h.263, or MP3, you can also stream the clip to RealPlayer 8 and higher. RealNetworks media players do not play QuickTime clips encoded with proprietary codecs such as Sorenson, however.

## MPEG Audio and Video

Helix Universal Server streams the standards-based MPEG formats, including MPEG-4 and MP3, which is the audio layer of the MPEG-1 format. Helix Universal Server accepts requests for streaming MPEG content over the RTSP control protocol, and can deliver the stream to any client that supports the RTP packet format. RealOne Player plays most of the supported MPEG formats.

- MPEG-1

Helix Universal Server delivers ISO/IEC 1172 compliant video and system bit streams over RTSP/RTP. RealOne Player and QuickTime Player, for example, can play MPEG-1 streams. Helix Universal Server delivers MPEG-1 content with file extensions of `mpa`, `mpg`, `mpeg`, `mpv`, `mps`, `m2v`, `m1v`, and `mpe`.

- MPEG-2

Helix Universal Server delivers ISO/IEC 12818 compliant video and program bit streams over RTSP/RTP. ISO/IEC 12818 compliant transport bit streams are not supported. Although RealOne Player does not play the MPEG-2 format, you can use Helix Universal Server to stream MPEG-2 to any player or device that has licensed the rights to play MPEG-2.

- MPEG-4

Helix Universal Server streams hinted MPEG-4 content over RTSP/RTP. It delivers ISMA/3GPP compliant bit streams, and you can view MPEG-4 bit streams using any ISMA/3GGP compliant client that supports RTSP/RTP, such as RealOne Player, RealOne Mobile Player, and Apple QuickTime Player 6. MPEG-4 clips commonly use the file extension `mp4`.

| For More Information: There are many MPEG resources available. The official home page for the MPEG working group is http://mpeg.telecomitalialab.com/index.htm.

## RTP-Delivered Formats

Helix Universal Server includes broad support for the standards-based RTP packet format, which is used by default with QuickTime and MPEG, and optionally with RealMedia. This allows Helix Universal Server to deliver on- demand clips or live broadcasts for virtually any media type that streams over the RTSP control protocol and the RTP packet format.

| For More Information: The section "Packet Formats" explains RTP.

# Encoding Tools

Helix Universal Server delivers clips and live streams, but does not create them. The following sections explain the encoders and production tools that you can use with Helix Universal Server.

## Streaming Media Encoders

For delivering on-demand clips, the three major steps are encoding a clip with an encoding tool, streaming a clip through Helix Universal Server, and playing a clip with a media player. Many encoders also accept live input, encoding it as a stream that is sent to Helix Universal Server for live broadcast without being saved as a streaming clip first.

##### Encoding, Streaming, and Playing

For each media type, you use a specific tool (or family of tools) to encode audio and video as a streaming clip or live broadcast. Helix Producer, for example, turns files in formats such as AVI, WAV, and uncompressed QuickTime into RealAudio and RealVideo clips. It can also encode live input from a camera or microphone. Tools like Microsoft Windows Media Encoder and Sorenson Broadcaster can encode audio and video input for streaming to Windows Media Player and the QuickTime Player, respectively.

##### Universal Media Encoding and Delivery

| Tip: This manual uses the generic term encoder to refer to any software that creates live streams or prerecorded clips in a format that Helix Universal Server can deliver.

| For More Information: Helix Producer User's Guide explains how to encode RealAudio and RealVideo clips.

## Production Tools

Encoding a media clip or broadcast is the last step of a process that involves capturing, digitizing, editing, and optimizing audio or video data. A streaming media author uses various production tools to accomplish these jobs. These tools typically include video cameras, microphones, recording media such as tapes or CDs, mixing hardware, and audio and video editing software. You can use any tools you want to capture and edit audio and video input. You just need to ensure that your tools can save digitized files in formats that your encoding tools can accept.

##### Production Process for On-Demand Clips

| For More Information: RealNetworks Production Guide contains a presentation planning chapter that explains these basic steps. See also that guide's audio and video chapters for tips on capturing and editing digital media.

# Streaming Protocols

Helix Universal Server streams media to clients over internal networks and the public Internet. Although Helix Universal Server can deliver HTML pages, it's usually employed along with a separate Web server to coordinate the delivery of HTML pages and streaming media. The following sections summarize the supported communications protocols. For details, see "Protocol Layers".

## Real Time Streaming Protocol (RTSP)

RTSP is a standards-based streaming media protocol endorsed by the Internet Engineering Task Force (http://www.ietf.org/). It enables Helix Universal Server to communicate with all versions of RealPlayer starting with RealPlayer G2, as well as the QuickTime Player and any RTSP-based MPEG player. Helix Universal Server also supports the RTP packet protocol, the standards-based companion to the RTSP control protocol.

## Progressive Networks Audio (PNA)

PNA is an older, proprietary protocol used in earlier versions of RealSystem Server and RealPlayer. Helix Universal Server and RealOne Player still support PNA for backward compatibility with earlier players and servers. Starting with RealPlayer G2, all RealNetworks servers and clients use RTSP as their primary protocol.

## Microsoft Media Services (MMS)

MMS is a proprietary control protocol used by Helix Universal Server to communicate with Windows Media Player.

## HyperText Transfer Protocol (HTTP)

Although HTTP is not a streaming media protocol, Helix Universal Server uses HTTP in a number of ways. For example, it uses HTTP to deliver the Helix Administrator HTML pages that allow you to configure and run Helix Universal Server.

# On-Demand Streaming

On-demand streaming is the most common method of delivering media. Comparable to rented videos, on-demand clips are available at any time. The media is digitized, encoded in a streaming format, and stored on Helix Universal Server. Each viewer who requests an on-demand clip receives a separate data stream from Helix Universal Server. The clip starts at its normal, encoded beginning, and each viewer can fast-forward, rewind, or pause the presentation independently.

## Basic Streaming Features

After installation, Helix Universal Server requires no configuration to stream clips on-demand. You can simply place your clips in the main content directory, and link to them from a Web page. Chapter 5 explains how to write links to on-demand clips. It also explains some basic streaming features that you can use:

- "Adding a Mount Point for On-Demand Clips" explains how to store clips anywhere on a network, defining mount points that indicate the clip location.

- You can create aliases to shorten long URLs or hide clip locations as described in "Adding a Mount Point for On-Demand Clips".

- See "Browsing On-Demand Content" to learn how to list all on-demand clips residing on Helix Universal Server.

- As described in "Displaying Source Information", you can allow RealOne Player viewers to download a clip's encoding information, as well as see the markup for SMIL files.

## Features for Multiple Servers

Several features help you to administer a large network that contains multiple Helix Universal Servers delivering on-demand content. Chapter 6 discusses these features, which include the following:

- Instead of having RealOne Player reconnect to the same Helix Universal Server if clip delivery is interrupted, you can point RealOne Player to a backup server, as explained in "Implementing Redundant Servers".

- When you have a large network, you may want to replicate media assets across different Helix Universal Servers. The features described in "Content Caching" let you do this.

- In addition to multiple Helix Universal Servers, your network can contain multiple Helix Universal Proxys. The section "Using a Media Proxy" explains how you can control the content that a Helix Universal Proxy caches or splits.

## Authentication and Access Control

Keeping your media assets secure is an important function of Helix Universal Server. To allow you to verify and control connection attempts, Helix Universal Server offers the following features:

- The features described in "Controlling Connections" allow you to limit the number of simultaneous connections, or the amount of outgoing bandwidth.

- Chapter 12 explains how to associate connection rules based on IP addresses. These rules can allow or deny connections to specific protocol ports.

- Authentication, which Chapter 13 covers, verifies the identity of a user requesting streaming media. This verification can take the form of asking for a user name and password. Or, it can be entirely hidden from the viewer.

- For Internet Service Providers, Helix Universal Server works with existing user accounts and directory structures to make media files available for streaming. For each ISP account, you can allocate a minimum and maximum number of connections. Chapter 14 explains this feature.

## Monitoring and Reporting

Helix Universal Server offers several features that allow you to monitor current connections, and view past information stored in a log file:

- From the access log, which Chapter 16 explains, you can create reports that enable you to see trends, gather information, or check on the status of your Helix Universal Server.

- Custom logging, as described in Chapter 17, allows you to customize logged information based on templates that you define.

- As described in Chapter 18, Helix Administrator includes a real-time tool that displays activity on your Helix Universal Server. The monitor displays information such as who's using your Helix Universal Server, the peak use times, and which files are requested the most.

## Feature Availability

Depending on which Helix Universal Server product you use, some of the features described in this manual may not be available to you, or may be limited in some way. Consult your license file for a list of which features are enabled in your version of Helix Universal Server. If you'd like to augment your Helix Universal Server's capabilities, contact RealNetworks or your reseller.

| For More Information: For instructions on reading license files with Helix Administrator, see "License File Information".

# Live Broadcasting

As with a live television event, a user can tune into a live Internet or intranet broadcast to join the presentation in progress. Because the event streams in real-time, the viewer cannot fast-forward or rewind through the broadcast. As the following sections explain, you can deliver live streams in several different ways, based on your needs and network capabilities.

| Tip: Most of the features described previously for on-demand delivery, including URL aliases, authentication, access control, and monitoring, work for live broadcasts as well.

## Unicasting

Unicasting, which Chapter 7 covers, is the simplest method of live broadcasting. It works with most supported media formats and requires little setup. In unicasting, a media encoder delivers a live stream to Helix Universal Server, which then delivers a separate broadcast stream to each media player. Because each player receives its own stream, unicasting is limited by your number of licensed client connections, as well as your outgoing bandwidth.

##### Unicasting

## Multicasting

As explained in Chapter 8, multicasting dramatically reduces the bandwidth required for broadcasting, allowing many more viewers to participate. In a multicast, media players do not receive separate broadcast streams from Helix Universal Server. Instead, they all connect to the same stream (or streams). Multicasting requires a multicast-enabled network, however, and is primarily suited for intranets, although multicasting on the Internet is possible.

##### Multicasting

Helix Universal Server supports three kinds of multicasts:

- Back-channel multicasts maintain a low-bandwidth control channel between Helix Universal Server and RealOne Player, enabling Helix Universal Server to monitor how many players are connected. You can multicast any media format played by RealOne Player. In fact, you can make all unicasts simultaneously available as back-channel multicasts through the same broadcast hyperlink.

- Scalable multicasts do not maintain a control channel. Helix Universal Server does not monitor the number of connected players, but it can broadcast a single stream to any number of players. It can also direct players to send quality of service statistics back to it, or to a Web server, at the end of the broadcast. Helix Universal Server supports RTP-based media players that comply with scalable multicasting standards, including RealOne Player and QuickTime Player.

- Windows Media multicasts are scalable multicasts for Windows Media Player only. You can broadcast to any number of players, and direct client statistics to a Web server. Unlike with back-channel multicasts, you cannot make all Windows Media unicasts simultaneously available as multicasts.

## Splitting

Whereas unicasting and multicasting deliver broadcast streams to media players, splitting transmits a broadcast stream in any media format from one Helix Universal Server to another. As explained in Chapter 9, a Helix Universal Server acting as a transmitter delivers a live media stream to other Helix Universal Servers acting as receivers. Each receiver then broadcasts the stream to media players, either through unicasting or multicasting.

Splitting is a powerful feature that provides many ways to deliver a broadcast to any number of Helix Universal Servers connected on an intranet or through the Internet. By increasing the pool of Helix Universal Servers broadcasting an event, you can unicast to many thousands of viewers on the Internet, or multicast behind the firewalls of different facilities your organization maintains around the world.

##### Splitting

## Archiving

Live events don't exist as files, but you can use the archiving feature to write live content to a file as you broadcast. You can then stream the archive on- demand if you wish. Archiving a broadcast on Helix Universal Server works only with RealMedia and MP3 broadcasts. For more information, see "Archiving Broadcasts".

## Redundant Encoders

For important live broadcasts, Helix Universal Server can use multiple encoding sources. Should one source become unavailable, Helix Universal Server switches automatically to the next source. Encoder redundancy works with any media format, is easy to set up, and has a few global parameters that the section "Using Broadcast Redundancy" explains.

## Simulated Live Broadcasting

A broadcast event does not have to be a live stream delivered by a media encoder. Using the SLTA utility, which Chapter 10 covers, you can simulate a live broadcast using any number of prerecorded audio or video clips. This is a handy way to reach viewers in different time zones, for instance, or to stream encore presentations of live events. You might also broadcast clips that were never broadcast live. You can set up a playlist of songs, for example, and use SLTA to stream an Internet radio program. To the viewer, a simulated live broadcast appears to be a live event.

# Feature Comparison

The Helix Universal Server features described in the preceding sections work for all audio and video content, including RealMedia and MPEG, streamed to RealOne Player. Not all features are available when you stream other media formats to other media players, however. The next table summarizes the Helix Universal Server features available when you stream the following formats to the following media players:

- Windows Media (`.asf`, `.wma`, `.wmv`) to Windows Media Player

- QuickTime (`.mov`) or MPEG-4 (`.mp4`) to Apple QuickTime Player

- standards-based RTP-based formats, such as MPEG-4 (`.mp4`), to an RTP-based player

Helix Universal Server Feature Comparison for Various Media Players
Helix Universal Server Feature | Windows Media | Apple QuickTime | RTP-Based | Reference
--- | --- | --- | --- | ---
HTTP cloaking for firewalls | yes | no | no | click here
Launch utility for Web page links | yes | no | no | click here
Aliases in URLs | yes | yes | yes | click here
Viewable clip source information | no | no | no | click here
Reconnection to a redundant server | no | no | no | click here
Cached content | yes | yes | yes | click here
Proxied on-demand and live streams | yes | yes | yes | click here
Unicasting | yes | yes | yes | click here
Redundant live stream encoders | yes | yes | yes | click here
Back-channel multicasting | no | no | no | click here
Scalable multicasting | yes | yes | yes | click here click here
Splitting from transmitter to receiver | yes | yes | yes | click here
Simulated live broadcasts | yes | yes | yes | click here
Access control by IP address | yes | yes | yes | click here
User name and password validation | no | yes | no | click here
Media player ID validation | no | no | no | click here
SMIL-based ad insertion | no | no | no | click here
Access request logging | yes | yes | yes | click here
Custom logging reports | yes | yes | yes | click here
Online activity monitoring | yes | yes | yes | click here

# Helix Universal Server Components

Helix Universal Server runs on several server operating systems, including Windows and many UNIX variants. Although a few of its features are specific to Windows or UNIX, Helix Universal Servers on all operating systems are virtually identical in their setup and operation. The following sections describe the major components of Helix Universal Server.

## Plug-ins

Plug-ins provide the functionality of Helix Universal Server's individual features, and reside in a `Plugins` subdirectory of your Helix Universal Server installation directory. Helix Universal Server uses one plug-in to stream RealVideo, for instance, and another to stream QuickTime. Plug-ins also provide server features such as user authentication. Using Helix Universal Server's open architecture, third parties can create additional plug-ins, enabling you to extend Helix Universal Server's capabilities.

## Helix Administrator

Helix Administrator is a secure, HTML-based interface that lets you run Helix Universal Server through a frames-capable and Java-enabled browser located anywhere on your network. Helix Administrator divides Helix Universal Server features into functional areas, and supplies easy-to-use forms and screens that allow you to configure Helix Universal Server features, as well as monitor activity. See "Using Helix Administrator" for details.

## Configuration File

A human-readable, XML-based text file named `rmserver.cfg` stores Helix Universal Server's configuration information. When you change Helix Universal Server's configuration through Helix Administrator, this file is updated automatically. You can also edit the file manually, and maintain different files for different configurations, selecting the appropriate file when you start Helix Universal Server. Because all configuration information is stored in this single file, you can create a master file that you propagate across multiple Helix Universal Servers to set up an entire network quickly. Appendix A explains the configuration file syntax.

## License File

You need one or more license files, which Helix Universal Server reads at start- up, to enable your Helix Universal Server features. RealNetworks distributes license files by e-mail. If you have a network of Helix Universal Servers, you can distribute licenses to create a pool of client connections available to all Helix Universal Servers. For more information, see "Distributing Server Licenses".

# Working with Other Professionals

Delivering streaming media clips or broadcasts typically requires the effort of several people. As the Helix Universal Server administrator, you'll need to interact with content creators, as well as other network administrators. This guide points out cases where you need to provide Helix Universal Server information to other professionals. The following sections summarize some important aspects of working with others to deliver streaming media presentations.

## Encoding Professionals

The people who encode media, whether live broadcasts or on-demand content, need to know the address of Helix Universal Server, protocols, port numbers, and mount points to use in links, especially if you've changed the settings from the defaults. RealNetworks Production Guide, which is written for content creators, explains the formats for linking to on-demand clips. However, you'll need to give content creators the URLs to broadcasts, which vary depending on the broadcast features you use.

## Helix Universal Server Administrators

If you have multiple servers in different facilities, you'll need to communicate certain information with other Helix Universal Server administrators. When you use splitting, for instance, a Helix Universal Server transmitter in one facility needs address and other information about a Helix Universal Server receiver in another facility, and vice versa.

## Firewall Administrators

If there are users within your network who either cannot receive presentations from Helix Universal Servers on the Internet, or who receive poor-quality streams, the information in Chapter 11 will help the firewall administrator understand what changes can be made to enhance the viewing experience.

| © 2002 RealNetworks, Inc. All rights reserved. For more information, visit RealNetworks Click here if the Table of Contents frame is not visible at the left side of your screen.