RealSystem uses several file types, each identified by a specific file extension. A brief overview of the files and their file extensions is listed below.
RealAudio clip (.ra) | Audio encoded to RealAudio format. This type of file is delivered by RealServer and is played on a RealPlayer. |
RealVideo clip (.rm) | Audio and video encoded to RealVideo format. This file can contain multiple streams, including audio, video, image maps, and events. This type of file is delivered by RealServer and is played on a RealPlayer. |
RealAudio or RealVideo metafile (.ram) | Connects a Web page to one or more RealAudio or RealVideo clips. This metafile is located on your Web server and is linked to from your Web page. A metafile contains the URL(s) for one or more clips stored on your RealServer. |
RealPlayer Plug-in metafile (.rpm) | Like a RealAudio or RealVideo metafile (above), but used with RealPlayer Plug-in for Netscape Navigator and Internet Explorer 3.0 or later. |
RealFlash clip (.swf) | Animation in RealFlash format. |
RealAudio and RealVideo are highly compressed files that are formatted to deliver the best possible sound and video over a limited-bandwidth connection.
Because there is no single best format for delivering audio and video, several formats are available. You can use RealPublisher and RealEncoder to provide formats that are optimized for different types of content and connection. You can choose to provide a clip in one or more formats based on the type of content and the available bandwidth. For example, you would use a different format to deliver speech over a 14.4 Kbps modem than you would to deliver a music video over an ISDN connection.
RealFlash is a highly compressed file that is formatted to deliver the best possible animation over a limited bandwidth connection. RealServer provides the only streaming solution available for RealFlash synchronized with audio. Combining RealFlash with RealAudio for fully synchronized low-bandwidth animation-and-audio allows content providers to provide long-form animated presentations over their Internet or corporate intranet.
RealVideo allows users to interact with video content using clickable image maps.
An image map is an active area that overlays the RealVideo display. When clicked by the user, this "hot spot" sends a URL to the user's Web browser. The Web browser goes to the new Web page without interrupting the RealPlayer.
Image maps are fully customizable; actions can be connected to rectangular, circular or polygonal content regions and can be varied over time intervals that you define when you encode the clip.
Media files need to be encoded into RealPlayer format using one or more of the many codecs available with any installation of RealPublisher or RealEncoder.
Encoding a RealAudio or RealVideo clip is a one-way process; you cannot convert a RealAudio or RealVideo file back into the original source format. When you encode a RealAudio or RealVideo clip, the original file is not modified. If you want to be able to encode media in more than one format, it is important that you archive (save) the original source.
It is possible to modify various attributes of RealAudio and RealVideo clips without reencoding them. For example, you can override the title, author, and copyright of an encoded clip. For more information, see Configuring Your Web Site or review the RealAudio and RealVideo Content Creation Guide.
RealAudio and RealVideo clips include text strings for the title, author, and copyright. This text is displayed by RealPlayer when a clip is played. Although the player usually labels the text as title, author, and copyright, the text you supply when you encode the clip is displayed. After encoding, you can override encoded values using the metafile or RMEdit and RMTools.
The source for a RealAudio or RealVideo clip can be prerecorded file or live input. The encoded RealAudio or RealVideo clip can be stored as a file for later use, broadcast live over a network, or simultaneously stored as a file and broadcast live. If simultaneously encoding and broadcasting, you can save (or "archive") the live broadcast in the encoded format.
All versions of RealEncoder and RealPublisher can encode a live input source. For details about encoding, refer to the RealAudio and RealVideo Content Creation Guide.