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Preparing Audio for the Internet Nick Kereakos - MPR
 Topics
Covered:
Static Audio
Files
Audio Streams
Automation
Static Audio Files
 What
is it?
Standard
computer data file
Data reduced for internet broadcast
Audio encoded using a bit reduced
perceptual audio coder.
What do I need?
 Digital Audio
Personal
Workstation (DAW)
Computer with an audio card.
Digital Audio Workstation software.
Ex.) Protools, Cubase, Sonic Solutions,
Peak Audio, Sonic Foundry, Cool Edit,
etc…
Digital Audio Workstation
Protools Example
Perceptual Audio Coder
 Standard
Coders include:
RealNetwork’s
RealAudio
Windows Media Player
MPEG Layer III - MP3
Apple’s QuickTime
Perceptual Audio Coding
 Principles:
 Aims
to achieve fidelity perceivable by
humans.
 This means removing sound we cannot hear.
 Reproducing sound we can hear.
Preparing Audio for the Web
Step 1 - Convert Analog source to Digital
Method’s

Use DAW:
 Prepare
& Edit Digital Audio File
 Process the file
 Encode file with Encoder of choice

Use Only Encoder:
 Record
audio source with Encoder
 Create an encoded audio file.
MPR’s Method
 Use a DAW:
 Increased flexibility
 Original Source file
 Can be use for multiple Encoders
 Ability to edit content
 Better sound quality
 Integration with Broadcasting & Automation
systems.
Digital Audio Workstation
Protools Example
DAW and Sound files:
 Sound
file formats:
.WAV
(Apple & Windows)
.AIFF (Apple)
.SND (Apple)
Sound Designer II (Apple)
Sound Files
 PCM
CD
Linear Audio File:
Quality 44.1 kHz, 16bit
Broadcasting standard audio file
Non data reduced
Cross platform
Sound Files
 Broadcasting
Systems using files:
Audiovault
Enco
- Dad Pro32
DCart
Preparing Audio for the Web
Step 2 - Prepare Soundfile for Encoding
Audio Processing & Dynamics
 Process
the sound file:
 Compression
- reduces dynamic range
 Limiting - to set brick wall upper audio limit
 EQ, to soften upper frequencies
Audio Processing & Dynamics
 MPR
uses WaveConvert:
Audio Processing & Dynamics
 Compression
- Reduces dynamic range the
Encoder needs to calculate. For lower bit rates,
this is especially important and effective.
 Limiting
- This avoids distortion for the end
user listening via the Web.
 EQ
- Softens inherent harshness of low bit rate
encoded audio.
Digital Audio Levels
Analog Meter
Digital Meter
Digital Audio Levels
Analog Meter
Digital Meter
Waveform View
Original Source

Audio Sample - 44.1 kHz 16bit Mono
Waveform View
Processed Soundfile

Audio Sample - 44.1 kHz 16bit Mono
Before and after processing
Original Source
Processed File
Preparing Audio for the Web
Step 3 - Real Audio Encoding
O=ginal urce

Audio Sample - 44.1 kHz 16bitMono
Real Audio Encoded
Coding Effects Comparison
 Original
 Wave
Source File
Convert Processed file
 Real Audio
Encoded
Web Audio Stream
 Uses
same exact principles
Audio
is sent as a continuous data stream
rather than existing as a static file.
Data is reduced for internet broadcast
Audio encoded using a bit reduced
perceptual audio coder.
Audio Processing & Dynamics
 Process
the source:
 Compression
- reduces dynamic range
 Limiting - to set brick wall upper audio limit
 EQ, to soften upper frequencies
 Use
outboard audio equipment:
 Compressor/Limiter
 EQ,
to manipulate frequencies
Audio source flow
Source
Encoder
Audio source flow
Encoder
RealServer
End User
What if there are problems?
 Monitor your stream:
 Install a PC to playback the stream.
 Wire the output of the PC’s audio card to a
silence sensor.
 When the alarm goes off, you know there is a
problem with the stream.
Monitoring the Stream will alert you
when:
The
Encoder fails
The
source is interrupted or fails
Your
Network fails
Automated Static Web Encoding
 Process:
 Source Audio
file is compiled/recorded
 Dynamics are applied to the audio file
 File is processed in Real Producer
 Web Encoded file is delivered to destination
MPR’s Design
 ENCO
- Dad Pro 32:
 Controls
SAS Router
 Records appropriate source to a PCM Linear
.WAV file.
MPR’s Design

Static Encode Box:
 Running
Windows NT 4.0
 NT script moves file from ENCO drive
 WaveConvert Pro applies dynamics to .WAV file and
creates new file
 Real Producer encodes new .WAV file
 Newly encoded file waits for delivery
MPR’s Design
 Caravan:
 Developed
by MPR Online personnel
 Script runs 24 days monitoring directory
contents
 When a new Real Audio file is delivered,
Caravan moves it to its proper location
Overall Goals
 Reduce
 Keeps
Bit Rate:
data costs down.
 Reaches more people simultaneously.
 Allows access to people on a dial up modem.
Online Resources

Real Networks:
 http://www.real.com
 Real
Producer is free
 Real Player is free
 User forums and FAQS are helpful
 http://service.real.com/help/library/guides/production/ht
mfiles/whatsnew.htm
Online Resources

Helpful articles to read:
 http://www.sospubs.co.uk/sos/may00/articles/mp3.html
 http://www.iis.fhg.de/amm/index.html
 http://www.minidisc.org/PerceptualCoding.html
 http://www.wired.com/wired/archive/7.08/codecs.html
 http://www.webdeveloper.com/multimedia/multimedia_
guide_realaudio_2.html