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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. 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

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  1. Preparing Audio for the Internet -Nick Kereakos - MPR • Topics Covered: • Static Audio Files • Audio Streams • Automation

  2. Static Audio Files • What is it? • Standard computer data file • Data reduced for internet broadcast • Audio encoded using a bit reduced perceptual audio coder.

  3. 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…

  4. Digital Audio Workstation Protools Example

  5. Perceptual Audio Coder • Standard Coders include: • RealNetwork’s RealAudio • Windows Media Player • MPEG Layer III - MP3 • Apple’s QuickTime

  6. Perceptual Audio Coding • Principles: • Aims to achieve fidelity perceivable by humans. • This means removing sound we cannot hear. • Reproducing sound we can hear.

  7. Preparing Audio for the Web Step 1 - Convert Analog source to Digital

  8. 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.

  9. 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.

  10. Digital Audio Workstation Protools Example

  11. DAW and Sound files: • Sound file formats: • .WAV (Apple & Windows) • .AIFF (Apple) • .SND (Apple) • Sound Designer II (Apple)

  12. Sound Files • PCM Linear Audio File: • CD Quality 44.1 kHz, 16bit • Broadcasting standard audio file • Non data reduced • Cross platform

  13. Sound Files • Broadcasting Systems using files: • Audiovault • Enco - Dad Pro32 • DCart

  14. Preparing Audio for the Web Step 2 - Prepare Soundfile for Encoding

  15. Audio Processing & Dynamics • Process the sound file: • Compression - reduces dynamic range • Limiting - to set brick wall upper audio limit • EQ, to soften upper frequencies

  16. Audio Processing & Dynamics • MPR uses WaveConvert:

  17. 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.

  18. Digital Audio Levels Analog Meter Digital Meter

  19. Digital Audio Levels Analog Meter Digital Meter

  20. Waveform View Original Source • Audio Sample - 44.1 kHz 16bit Mono

  21. Waveform View Processed Soundfile • Audio Sample - 44.1 kHz 16bit Mono

  22. Before and after processing Original Source Processed File

  23. Preparing Audio for the Web Step 3 - Real Audio Encoding

  24. O=ginal urce • Audio Sample - 44.1 kHz 16bitMono

  25. Real Audio Encoded

  26. Coding Effects Comparison • Original Source File • Wave Convert Processed file • Real Audio Encoded

  27. 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.

  28. 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

  29. Audio source flow Compressor/Limiter Source Encoder

  30. Audio source flow Encoder RealServer End User

  31. 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.

  32. Monitoring the Stream will alert you when: • The Encoder fails • The source is interrupted or fails • Your Network fails

  33. 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

  34. MPR’s Design • ENCO - Dad Pro 32: • Controls SAS Router • Records appropriate source to a PCM Linear .WAV file.

  35. 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

  36. 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

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

  38. 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

  39. 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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