Preparing Audio for the Internet -Nick Kereakos - MPR Topics Covered:Topics Covered:

Static Audio FilesStatic Audio Files Audio StreamsAudio Streams AutomationAutomation

Static Audio Files

What is it?What is it? Standard computer data fileStandard computer data file Data reduced for internet broadcastData reduced for internet broadcast Audio encoded using a bit reduced Audio encoded using a bit reduced

perceptual audio coder.perceptual audio coder.

What do I need?

Digital Audio Workstation (DAW)Digital Audio Workstation (DAW) Personal Computer with an audio card.Personal Computer with an audio card. Digital Audio Workstation software.Digital Audio Workstation software.

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

Digital Audio WorkstationProtools Example

Perceptual Audio Coder

Standard Coders include:Standard Coders include: RealNetwork’s RealAudioRealNetwork’s RealAudio Windows Media PlayerWindows Media Player MPEG Layer III - MP3MPEG Layer III - MP3 Apple’s QuickTimeApple’s QuickTime

Perceptual Audio Coding

Principles:Principles: Aims to achieve fidelity perceivable by Aims to achieve fidelity perceivable by

humans.humans. This means removing sound we cannot hear.This means removing sound we cannot hear. Reproducing sound we can hear.Reproducing sound we can hear.

Preparing Audio for the Web

Step 1 - Convert Analog source to DigitalStep 1 - Convert Analog source to Digital

Method’s

Use DAW:Use DAW: Prepare & Edit Digital Audio FilePrepare & Edit Digital Audio File Process the fileProcess the file Encode file with Encoder of choiceEncode file with Encoder of choice

Use Only Encoder:Use Only Encoder: Record audio source with EncoderRecord audio source with Encoder Create an encoded audio file.Create an encoded audio file.

MPR’s Method

Use a DAW:Use a DAW: Increased flexibilityIncreased flexibility Original Source fileOriginal Source file Can be use for multiple EncodersCan be use for multiple Encoders Ability to edit contentAbility to edit content Better sound qualityBetter sound quality Integration with Broadcasting & Automation Integration with Broadcasting & Automation

systems.systems.

Digital Audio WorkstationProtools Example

DAW and Sound files:

Sound file formats:Sound file formats: .WAV (Apple & Windows).WAV (Apple & Windows) .AIFF (Apple).AIFF (Apple) .SND (Apple).SND (Apple) Sound Designer II (Apple)Sound Designer II (Apple)

Sound Files

PCM Linear Audio File:PCM Linear Audio File: CD Quality 44.1 kHz, 16bitCD Quality 44.1 kHz, 16bit Broadcasting standard audio fileBroadcasting standard audio file Non data reducedNon data reduced Cross platformCross platform

Sound Files

Broadcasting Systems using files:Broadcasting Systems using files: AudiovaultAudiovault Enco - Dad Pro32Enco - Dad Pro32 DCartDCart

Preparing Audio for the Web

Step 2 - Prepare Soundfile for EncodingStep 2 - Prepare Soundfile for Encoding

Audio Processing & Dynamics

Process the sound file:Process the sound file: Compression - reduces dynamic rangeCompression - reduces dynamic range Limiting - to set brick wall upper audio limitLimiting - to set brick wall upper audio limit EQ, to soften upper frequenciesEQ, to soften upper frequencies

Audio Processing & Dynamics

MPR uses WaveConvert:MPR uses WaveConvert:

Audio Processing & Dynamics

Compression - Reduces dynamic range the Compression - Reduces dynamic range the Encoder needs to calculate. For lower bit rates, Encoder needs to calculate. For lower bit rates, this is especially important and effective.this is especially important and effective.

Limiting - This avoids distortion for the end Limiting - This avoids distortion for the end user listening via the Web.user listening via the Web.

EQ - Softens inherent harshness of low bit rate EQ - Softens inherent harshness of low bit rate encoded audio.encoded audio.

Digital Audio Levels

Analog Meter

Digital Meter

Digital Audio Levels

Analog Meter

Digital Meter

Waveform View

Audio Sample - 44.1 kHz 16bit MonoAudio Sample - 44.1 kHz 16bit Mono

Original Source

Waveform View

Audio Sample - 44.1 kHz 16bit MonoAudio Sample - 44.1 kHz 16bit Mono

Processed Soundfile

Before and after processing

Original Source

Processed File

Preparing Audio for the Web

Step 3 - Real Audio EncodingStep 3 - Real Audio Encoding

Audio Sample - 44.1 kHz 16bitMonoAudio Sample - 44.1 kHz 16bitMono

O=ginal urce

Real Audio Encoded

Coding Effects Comparison Original Source FileOriginal Source File

Wave Convert Processed file Wave Convert Processed file

Real Audio Encoded Real Audio Encoded

Web Audio Stream

Uses same exact principlesUses same exact principles Audio is sent as a continuous data stream Audio is sent as a continuous data stream

rather than existing as a static file.rather than existing as a static file. Data is reduced for internet broadcastData is reduced for internet broadcast Audio encoded using a bit reduced Audio encoded using a bit reduced

perceptual audio coder.perceptual audio coder.

Audio Processing & Dynamics

Process the Process the sourcesource:: Compression - reduces dynamic rangeCompression - reduces dynamic range Limiting - to set brick wall upper audio limitLimiting - to set brick wall upper audio limit EQ, to soften upper frequenciesEQ, to soften upper frequencies

Use outboard audio equipment:Use outboard audio equipment: Compressor/LimiterCompressor/Limiter EQ, to manipulate frequenciesEQ, to manipulate frequencies

Audio source flow

Source

Encoder

Audio source flow

End User

Encoder RealServer

What if there are problems?

Monitor your stream:Monitor your stream: Install a PC to playback the stream.Install a PC to playback the stream. Wire the output of the PC’s audio card to a Wire the output of the PC’s audio card to a

silence sensor.silence sensor. When the alarm goes off, you know there is a When the alarm goes off, you know there is a

problem with the stream.problem with the stream.

Monitoring the Stream will alert you when:

The Encoder failsThe Encoder fails

The source is interrupted or failsThe source is interrupted or fails

Your Network failsYour Network fails

Automated Static Web Encoding

Process:Process: Source Audio file is compiled/recordedSource Audio file is compiled/recorded Dynamics are applied to the audio fileDynamics are applied to the audio file File is processed in Real ProducerFile is processed in Real Producer Web Encoded file is delivered to destinationWeb Encoded file is delivered to destination

MPR’s Design

ENCO - Dad Pro 32:ENCO - Dad Pro 32: Controls SAS RouterControls SAS Router Records appropriate source to a PCM Records appropriate source to a PCM

Linear .WAV file.Linear .WAV file.

MPR’s Design Static Encode Box:Static Encode Box:

Running Windows NT 4.0Running Windows NT 4.0 NT script moves file from ENCO driveNT script moves file from ENCO drive WaveConvert Pro applies dynamics to .WAV file and WaveConvert Pro applies dynamics to .WAV file and

creates new filecreates new file Real Producer encodes new .WAV fileReal Producer encodes new .WAV file Newly encoded file waits for deliveryNewly encoded file waits for delivery

MPR’s Design

Caravan:Caravan: Developed by MPR Online personnelDeveloped by MPR Online personnel Script runs 24 days monitoring directory Script runs 24 days monitoring directory

contentscontents When a new Real Audio file is delivered, When a new Real Audio file is delivered,

Caravan moves it to its proper locationCaravan moves it to its proper location

Overall Goals

Reduce Bit Rate:Reduce Bit Rate: Keeps data costs down.Keeps data costs down. Reaches more people simultaneously.Reaches more people simultaneously. Allows access to people on a dial up modem.Allows access to people on a dial up modem.

Online Resources Real Networks:Real Networks:

http://www.real.comhttp://www.real.com Real Producer is freeReal Producer is free Real Player is freeReal Player is free User forums and FAQS are helpfulUser forums and FAQS are helpful

http://service.real.com/help/library/guides/production/http://service.real.com/help/library/guides/production/htmfiles/whatsnew.htmhtmfiles/whatsnew.htm

Online Resources Helpful articles to read:Helpful articles to read:

http://www.sospubs.co.uk/sos/may00/articles/mp3.htmlhttp://www.sospubs.co.uk/sos/may00/articles/mp3.html

http://www.iis.fhg.de/amm/index.htmlhttp://www.iis.fhg.de/amm/index.html

http://www.minidisc.org/PerceptualCoding.htmlhttp://www.minidisc.org/PerceptualCoding.html

http://www.wired.com/wired/archive/7.08/codecs.htmlhttp://www.wired.com/wired/archive/7.08/codecs.html

http://www.webdeveloper.com/multimedia/http://www.webdeveloper.com/multimedia/multimedia_guide_realaudio_2.htmlmultimedia_guide_realaudio_2.html