This chapter introduces you to streaming media, shows you the different parts of a streaming media presentation, and gives you tips for creating quality input. Although you do not need to know this information in order to use RealProducer Pro for basic tasks, it is recommended that you have a working knowledge of these topics.
Streaming media presentations created by RealProducer Pro can contain RealAudio, RealVideo, and RealText. Prior to streaming, you had to wait for a file to download from an Internet or network server in order to experience it. When you create a streaming media presentation, users can view it almost instantly.
Streaming media allows you to send small packets of information over a network connection. The user receives the information packets and plays your media piece by piece. The process is almost invisible to the user, except for a small amount of buffering at the beginning.
RealProducer Pro G2 is an integral part of the RealNetworks RealSystem G2. RealProducer Pro creates the presentations, RealServer™ G2 sends them across the Internet, and RealPlayer™ G2 shows them to the user.
A presentation created with RealProducer Pro can be as simple or as complex as you wish. It can include audio, video, and text in a layout designed for streaming to RealPlayer G2, or it can just be a sound clip embedded in a Web page. Any of these media elements can then be synchronized together to create a rich, multi-media presentation.
This section introduces you to the different components that can make up a streaming media presentation created with RealProducer Pro.
A video clip consists of a series of individual pictures, or "frames," displayed rapidly to simulate motion. The higher the frame rate, the smoother the motion. For example, a video clip recorded at 30 frames per second (fps) makes the motion appear natural.
Using a computer, you convert the analog video frames from a video tape to digital form. Files converted on a computer have the file extension .avi and are frequently referred to as "AVI files," "AVI videos," or "AVI movies."
A frame rate of 30 fps works out to 1800 frames for a minute of video, which partly explains why video files are so large. A large file increases the download time, discouraging viewers from playing your video. Adding audio to a video clip further increases its size. For this reason, converting AVI files into a streaming RealVideo file allows your work to be seen without waiting for long downloads.
Clear and good-sounding audio in a presentation can greatly improve a user's experience. You can create RealAudio files either by converting digital WAV files or by converting just the soundtrack of an AVI video.
RealProducer Pro gives you various compression options based on the type of audio you are converting: voice, voice with background music, music only, or stereo music. As expected, the quality of the original audio will have the greatest effect on the ultimate quality of the compressed audio.
You can use RealProducer Pro to add text to a presentation by adding a caption. A caption is any typed text that enhances the audio or video and appears in the presentation at a time that you designate.
Text can be useful, for example, if you need to subtitle a foreign language program. For more information on adding text to your presentations, see "Adding a Caption".
The way in which all of the above media elements are brought together is through a layout. RealSystem G2 uses the SMIL (pronounced "smile") mark-up language to format layout. Refer to the RealSystem G2 Production Guide if you want to learn more about the SMIL language.
RealProducer Pro contains a number of SMIL layout templates that fit most common needs. For more information on creating a custom layout for your presentation, see "Creating Custom Templates".
Ultimately, the quality of the input media file and its soundtrack will have the greatest effect on the video and audio in your output streaming media files. RealProducer Pro cannot make up for limitations in the input media file. For example, if your input media file uses voice-quality sound, selecting stereo sound in the RealProducer Pro will not result in a media file with stereo quality sound. You need to recapture the input media file in stereo sound before converting it with RealProducer Pro.
To help you in situations such as this, RealProducer Pro will analyze your input media source. It notes the settings you select and flags cases where you stand a better chance of achieving your intended results by improving the quality of the input media file. When a media file is flagged, you will see a warning icon (a yellow triangle or a red dot) next to the file in the Input list. For more information, see "Using the Analyzer".
Following are some general tips for creating quality media files that work best as media sources for your streaming presentation.
In order to get high quality output, your video source should meet these requirements:
Other video compressor drivers may be required if your media clip uses compressed video. However, if you captured an AVI file on the same machine as RealProducer Pro, there is typically no problem.
Follow these tips in order to get the best quality from your audio source. Generally, the better your recorded WAV file sounds, the better the generated media presentation will be.