Audio for Multimedia

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Audio for Multimedia

• Christian Guirreri

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Topics

• Software Recommendations
• File Formats
• General Tips
• Compression vs. Compression
• File Size and Quality in Captivate
• Bitrate and Cutoff Frequency
• Removing Breathing
• Removing Noise
• Flash Audio

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Software Recommendations

• Audio Editing
• Audacity free!
• Sony Sound Forge
• Steinberg Wavelab
• other
• Making Sweet Noise
• Sony Acid
• Apple Garage Band
• Adobe Soundbooth
• Ableton Live
• MP3 Encoders
• LAME most popular, slightly slow, best quality
• Xing, GoGo super fast, poor quality
• Fraunhofer started the MP3 bandwagon, good
  quality
• BladeEnc a bit slow, good quality
• Decoding (dont do it)
• Lots to choose from
• Audio Editors
• AWave

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File Formats

• Audio File Header and Data
• Wrapper other features licensing, streaming,
  etc
• Codec used to encode / decode a file
• WAV (RIFF) Windows (Microsoft and IBM)
• IFF (AIFF) Mac (Apple and Sun)
• Both are containers for uncompressed PCM
• Other formats
• MP3 MPEG-1, layer 3, lossy
• WMA Windows Media Audio, lossy and lossless
• AAC Advanced Audio Coding, lossy and lossless
• M4P MPEG-4, part 14, container (iTunes)
• RA RealPlayer Audio, lossy and lossless
• OGG Ogg Vorbis, lossy
• FLAC Free Lossless Audio Codec, lossless

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General Tips

• Quality recording Quality playback
• Flash doesnt know audio properties
• Always fade in and out
• Add space
• Use Mono, 16-bit, 44.1kHz
• Only use what you need
• Preload audio separately

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Compression vs. Compression

• Conversion of data in order to reduce the space
  occupied
• (i.e. WAV - MP3).
• A process that manipulates the dynamic range of
  an audio signal
• (i.e. reducing the difference in volume between
  the softest and loudest sounds to make the
  overall volume more audible)
• Normalization is different
• Compress before or after?

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File Size and Quality in Captivate

• Testing
• Bandwidth Analyzer
• Test download time in Flash
• Making files smaller
• Sampling Rates and Bitrates
• Remove Silence

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Bitrate and Cutoff Frequency
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Removing Breathing

• Volume 0
• Fade In / Out
• Noise Gate

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Timeline Audio in Flash

• Stream vs. Event
• Stream
• guarantees sync
• will start to play before the sound is completely
  downloaded
• must be reloaded every time it needs to be played
• Event
• no guarantee of sync no clue when the sound
  will end
• will not play until it has been completely
  downloaded
• does not have to be reloaded again, remains in
  memory

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Flash Audio

• Problems
• Transitions tend to be harsh clicks pops
• Timeline audio is difficult to deal with
• Audio embedded in-FLAs makes large, cumbersome
  swfs
• Flash MP3 conversion quality is not so great
• Solutions
• Use the Sound Class to control fades
• Use the Sound Class to dynamically import audio
• Import audio one at a time for dynamic preloading
• Import audio directly from audio files already
  converted for better quality