Intro to Sound

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Intro to Sound Videoon the Web

• WWW 131
• Week 14

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Multimedia What is it?

• The use of computers to present text, graphics,
  video, animation, and sound in an integrated way.
  
• Multimedia applications were, until the mid-90s,
  uncommon due to the expensive hardware required.
• With increases in performance and decreases in
  price, multimedia is now commonplace. Nearly all
  PCs are capable of displaying video, though the
  resolution depends on the power of the computer's
  video adapter and CPU.
• http//www.dole5aday.com

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Web Page Additions

• External Media
• The sound or video file is accessed through a
  hyperlink
• Useful when the user has a low-bandwidth
  connection because user is given the choice of
  whether or not to take the time to download a
  large multimedia file
• Internal Media
• Clips are placed into the Web page itself as
  embedded objects
• Works like an inline image and can be played
  within the Web page itself. Descriptive text can
  appear alongside an embedded video clip, but the
  user is forced to wait for the clip to be
  retrieved by the browser

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Sound Files

• To be used in a Web page, a sound must be
  converted from an analog form to a digital sound
  file.
• Background amplitude and frequency
• Amplitude is height of sound wave, loudness
• Frequency is speed at which sound wave moves
• Higher frequency--higher pitch

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Sound Wave
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Important Factors

• Sampling Rate
• The number of samples of sound taken per second
• Sampling Resolution
• The measurement precision of each sample
• Channels
• Stereo or monaural (mono) sound

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Sampling Rate

• A sound wave is a continuous function.
• To convert it to a form that can be stored in a
  sound file, your computer must record
  measurements of the sound at discrete moments in
  time.
• Each measurement is called a sample
• The number of samples taken per second is called
  the sampling rate.
• Measured in kilohertz--8KHz, 11KHz, 22KHz, 44KHz
• (A higher sampling rate means that more samples
  are taken per second--more realistic
  sound--larger file.)

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• Sampling Rates

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Sample Resolution

• The precision in measuring the sound within each
  sample
• 8-bit Smaller file, but also less quality
• 16-bit
• Twice the size of 8-bit file, but
  improved sound quality

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Sound Channels

• Monaural (mono)--smaller files
• Stereo--richer sound, but double the file
  size
• Examples
• 8 KHz, 8-bit, mono Telephone
• 22 KHz, 16-bit, stereo Radio
• 44 KHz, 16-bit, stereo CD

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Sound Editors

• Sound editors are available on the Web
• Can be used to modify the sampling rate, sample
  resolution, of channels, add special sound
  effects, remove noise, copy and paste sounds
  between files.
• CoolEdit http//www.cooledit.com/
• Shareware Music Machine http//www.hitsquad.com/sm
  m/
• Sonic Control http//www.soniccontrol.com/
• Free Music Directory http//www.angelgrrl.c
  om/directory/
• Flash http//www.macromedia.co
  m/software/flash/

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Sound File Formats

• WAV format was developed for Windows and is the
  most commonly used format on the Web. WAV files
  can be recorded in 8-bit or 16-bit sample
  resolutions, in stereo or mono, and under a wide
  range of sampling rates.
• RealAudio--a popular format on Web, designed for
  real-time playing over low-bandwidth, small
  files, but lower quality--streaming media
• MPEG, MP3--usually video, but small size for
  whole music recordings

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More Formats

• AIFF/AIFC (Audio Interchange File Format)-
  -Macintosh
• SND A Macintosh format not widely supported on
  Web
• AU (?law) One of the oldest formats, mainly
  for UNIX
• MIDI Musical Digital Interface--not used for
  general sound recording--limited to
  synthesizers--create much smaller files

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Sound Archives

• Broadcast.com http//www.broadcast.com
• Historic Sound Clips
  http//www.webcorp.com/sounds/
• MSU Voice Library http//www.lib.msu.edu/vi
  ncent/
• Sound America http//www.soundamerica.com
  
• (Check copy rights for anything you wish to use!)

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Link to Sound File

• How do you link to a file?
• Ringing Telephone (250K WAV)

Ringing Telephone
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Embed a Sound File

• Use the EMBED tag
• autostartfalse
• (width and height--size of sound control player)
• (false means sound does not play automatically)

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Internet ExplorerBackground Sound

• Internet Explorer supports a BGSOUND tag
• NOTE (In Netscape)width0 height0 autostarttrue

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Note

• Helper ApplicationWhen a link to a sound file
  is clicked, the browser looks for a program
  installed on the system designed to handle that
  type of file such as Microsoft Media Player.
• Plug-inTo use embedded objects, the browser
  must support them and it must have access to
  plug-in software. The user may have to download
  the plug-in like ActiveX controls or LiveAudio.

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Video Files

• CHALLENGINGVideo clips can be an informative
  and attractive feature to add to a Web page,BUT,
  the files can be very large.
• Background frame rates and codecsIndividual
  frames are shown in sequence to give the illusion
  of motion.
• Frame rate--The number of frames shown in each
  unit of time (fps). VCRs use 30 fps. Lower frame
  rates Smaller file sizes
• Codec--Compression/Decompression

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Video File Formats

• QuickTime--Originally for Macintosh, it has
  become a Web standard (.mov)
• AVI--Audio Video Interleave, the standard format
  for Windows. Resolution is and max of 30 fps
• MPEG--Moving Picture Experts Group allows for
  high compression and full-screen, full-motion
  video. (Special software needed.)
• RealVideo--Streaming video, but poorer quality
• ASF--Advanced Streaming Format by Microsoft
  intended to replace AVI

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Linking to Video

• Antique Telephone (200K
  AVI)
• Antique Telephone (225K
  Quicktime, MOV)

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Embedding Video

• Click the telephone image below to see an
  antique in action
• autostartfalse

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Using Multimedia

• Audio and video can add to the appeal and
  usefulness of your Web page
• Remember
• Avoid embedding large files--Use links
• Indicate the size of the media clip in your links