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.
