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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?.

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preparing audio for the internet nick kereakos mpr
Preparing Audio for the Internet -Nick Kereakos - MPR
  • Topics Covered:
    • Static Audio Files
    • Audio Streams
    • Automation
static audio files
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
What do I need?
  • Digital Audio Workstation (DAW)
    • Personal Computer with an audio card.
    • Digital Audio Workstation software.

Ex.) Protools, Cubase, Sonic Solutions, Peak Audio, Sonic Foundry, Cool Edit, etc…

perceptual audio coder
Perceptual Audio Coder
  • Standard Coders include:
    • RealNetwork’s RealAudio
    • Windows Media Player
    • MPEG Layer III - MP3
    • Apple’s QuickTime
perceptual audio coding
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
Preparing Audio for the Web

Step 1 - Convert Analog source to Digital

method s
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
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.
daw and sound files
DAW and Sound files:
  • Sound file formats:
    • .WAV (Apple & Windows)
    • .AIFF (Apple)
    • .SND (Apple)
    • Sound Designer II (Apple)
sound files
Sound Files
  • PCM Linear Audio File:
    • CD Quality 44.1 kHz, 16bit
    • Broadcasting standard audio file
    • Non data reduced
    • Cross platform
sound files1
Sound Files
  • Broadcasting Systems using files:
    • Audiovault
    • Enco - Dad Pro32
    • DCart
preparing audio for the web1
Preparing Audio for the Web

Step 2 - Prepare Soundfile for Encoding

audio processing dynamics
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 dynamics1
Audio Processing & Dynamics
  • MPR uses WaveConvert:
audio processing dynamics2
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
Digital Audio Levels

Analog Meter

Digital Meter

digital audio levels1
Digital Audio Levels

Analog Meter

Digital Meter

waveform view
Waveform View

Original Source

  • Audio Sample - 44.1 kHz 16bit Mono
waveform view1
Waveform View

Processed Soundfile

  • Audio Sample - 44.1 kHz 16bit Mono
before and after processing
Before and after processing

Original Source

Processed File

preparing audio for the web2
Preparing Audio for the Web

Step 3 - Real Audio Encoding

slide27

O=ginal urce

  • Audio Sample - 44.1 kHz 16bitMono
coding effects comparison
Coding Effects Comparison
  • Original Source File
  • Wave Convert Processed file
  • Real Audio Encoded
web audio stream
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 dynamics3
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
Audio source flow

Compressor/Limiter

Source

Encoder

audio source flow1
Audio source flow

Encoder

RealServer

End User

what if there are problems
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
Monitoring the Stream will alert you when:
  • The Encoder fails
  • The source is interrupted or fails
  • Your Network fails
automated static web encoding
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
MPR’s Design
  • ENCO - Dad Pro 32:
    • Controls SAS Router
    • Records appropriate source to a PCM Linear .WAV file.
mpr s design1
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 design2
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
Overall Goals
  • Reduce Bit Rate:
    • Keeps data costs down.
    • Reaches more people simultaneously.
    • Allows access to people on a dial up modem.
online resources
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/htmfiles/whatsnew.htm
online resources1
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
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