The Process of Encoding RealAudio

The process of encoding RealAudio begins with a source file. A source file can either be recorded on a microphone or come from another audio medium such as tape or CD. Some programs such as CD Streamer will encode your RealAudio files directly from CD avoiding any extra steps. As with all audio recording the final result is only as good as the original source file. Adding extra noise to a RealAudio file can be even worse since it takes up extra bandwidth. If possible you should try to record your original source files in a professional studio and get them as 16-bit WAV files for conversion to RealAudio. In reality, not everyone has a recording studio. Even if you are just recording at your computer using a microphone and a sound card there are things you can do to improve sound quality.

Professionals know that the best end product comes from a good source file. There are several things both professional and amateurs should know about RealAudio encoding:

• Use High-Quality Source Media - CDs and DAT tapes are very good source media. Try to avoid recording from consumer grade tapes such as Type 1 VCR tape or cheap audio tape. At Discovery we've tried to encode taped phone interviews that have turned out very poorly.
• Choose Professional Recording Equipment - Every piece in the encoding chain introduces noise. Buy good equipment. Make sure the microphone is a professional one, not the one included with your computer. Make sure the sound card is capable of 16bit recording at 44MHz or 48Mhz. Poor equipment can introduce hiss to the final product that adds to bandwidth and subtracts from clarity.
• Use Shielded Cables - Cheap cables can pick up on interference from other devices in the room such as the computer. This Radio Frequency Interference can introduce line noise. Make sure to separate your audio cables and power cables.
• Set Input Levels Correctly - The input levels on your mixing board must be set within their tolerance. If they are set outside their best signal to noise ratio this can introduce hiss into the the audio. The signal chain includes a microphone, a mixing desk, a compressor, and a sound card.

At home there are several things you can do to improve quality.

• Separate microphone cords from power cords, this reduces noise in the recording.
• Get a good microphone, not the cheap one that came with your system.
• Make sure the volume is loud enough
• Record at 16-bit 44 MHz audio
• Record in a quiet room

You should record to a WAV file or AIF or Quicktime audio on the Mac. These files can be quite large if you are recording several minutes of audio. Once you have your raw WAV file open RealProducer.

RealProducer has a wizard that will walk you through encoding. When RealProducer first starts you will be presented with three wizards, Record from File, Record from Media Device, and Live Broadcast. Since we have a WAV file we choose Record from File. If we had wanted to record from a microphone or from CD we would have chosen the second option.

The Wizard lets you browser for your source file, then include copyright and date info. The next page lets you chose between SureStream and single bandwidth delivery. SureStream encodes the file at variable rates so that a user can click on one link and get streaming audio at the appropriate bandwidth. This can only be done on files that will be served from a Real Server. If you will be serving streaming audio from a regular web server choose the single bandwidth stream. If you do this you will need to encode several different streams and let the user choose. The next screen allows you to choose the bandwidth of the single file.

Techniques for Encoding RealAudio
RealAudio
Incorporating RealAudio into the SMIL File