This chapter introduces you to streaming media and how Helix Producer creates streaming media. It gives you a brief look at how streaming works, the different types of streaming media that you can create with Helix Producer, and the different RealNetworks products that you use when streaming.
Streaming media is also known as RealMedia, or separately as RealAudio® or RealVideo®. Before the advent of streaming media, your audience had to wait for your media file to download from the Internet or a network server in order to experience it. With streaming media, your audience can see and hear your media almost instantly.
A streaming clip consists of small packets of information that are sent over a network connection. The user receives these information packets in a "stream" and, using a player, experiences your media piece by piece. Thus, the streaming is almost invisible to the user. The process is similar to viewing a film; each frame of a filmstrip is like each data packet. When they are pieced together by a projector, you see the film as one continuous piece.
Helix Producer creates streaming media data packets by a process called "encoding." During encoding, the source media is transformed into streaming media using "codecs" (compression/decompression algorithms). The entire process is summed up in the following steps:
While the steps involved in encoding streaming audio and video are similar for you, for Helix Producer there are some basic differences between the media types.
Encoding audio is much simpler than encoding video. A basic, streaming audio clip is created by using a audio file or live audio source as the input. Helix Producer uses various audio codecs to convert your standard audio into a format that can be streamed.
A more complex task for Helix Producer is converting standard video into streaming media. A RealVideo clip is created by converting a video file or by capturing from a video source, such as a video camera or video cassette player, to your computer via a video capture card. Helix Producer converts different attributes of the video—such as frame rate, type of motion, and size of the image—into a RealVideo clip using a video codec. Plus, if the video includes audio data, that must also be converted using the audio codecs.
Before Helix Producer can compress the input media data, it needs to know something about the audience that you will be targeting. An audience is defined by the bit rate at which they can connect. For example, a person using a 56 kbps dial-up modem to connect to your stream is a member of the 56K Modem audience. If you target only one audience, you are targeting a single bit rate.
Since compressing data loses some information, picking the correct audience is key to deciding how much of your source's data you keep. With Helix Producer's SureStream technology you can reach the widest possible audience, and provide all users with the best listening and viewing experience optimized for their bandwidth.
There are advantages to using SureStream. You can create a single RealMedia clip recorded for multiple target audiences, or you can create a clip that will automatically switch to a lower bandwidth during poor network conditions. SureStream RealMedia files can combine several different streams that take advantage of these features.
For example, you can record a video clip for 56 kbps, 112 kbps, and 256 kbps audiences, and RealOne Player will automatically use the correct stream based on the user's connection speed. All streams are contained within a single RealMedia file.
Helix Producer is a member of the RealNetworks family of software products. Three components works together to stream your media:
The following diagram illustrates how these RealNetworks products work together.
You are the person who creates the streaming media to be used with RealNetworks products. As the "content creator," you will use Helix Producer. This product is used to encode audio and video into RealMedia that Helix Universal Server can then stream.
You can also create a Synchronized Multimedia Integration Language (SMIL) file to synchronize several clips within a presentation. SMIL is an extensible mark-up language, designed to be the standard markup language for timing and controlling streaming media clips. A SMIL file coordinates the layout and playing of two or more media clips in parallel (simultaneously) or in sequence. For an in-depth look at SMIL and how to use it to create RealMedia productions, refer to the RealNetworks Production Guide.
Just as a Web server delivers pages to Web browsers over the Internet, Helix Universal Server serves streaming media clips to your audience. It enables users to stream the media clips rather than download them. By streaming the content, the user can begin to watch the clip almost immediately and doesn't have to wait for the entire file to be downloaded.
There are two different ways to deliver your content. You can deliver it on- demand or broadcast it live. On-demand means that you encode your RealMedia content before your audience needs it. Live broadcasting is when you are encoding the RealMedia at the same time your audience is playing it. For both types of delivery, you can use Helix Universal Server in conjunction with Helix Producer.
A client such as RealOne Player plays the streamed media. Helix Universal Server also supports streaming content to QuickTime and Windows Media Players.
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