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  • Old MPEG files could be compressed to a ratio of 10:1 On the Web now most MPEG files are either MPEG-2 or MPEG-3 Quicktime can handle MPEG-2 files, for MP3 you’ll have better luck with a helper app like WinAmp or MacAmp
  • MP3 developed for Win platform--more PC tools than Mac tools. Rio works with PCs, not Macs To use Mpecker, first you digitize the sounds, then you use Mpecker to encode them
  • Audio clips need to be "normalized" - that is, the loudest part of the clip's waveform should go to the top of the available dynamic range. There are two ways to normalize a clip: The first and easiest is to monitor the input level with your recording software as you create the clip. Make sure the loudest part of the clip pushes the input meter almost to the top of the gauge without quite reaching maximum volume. The second method is to record the clip first, then use a sound-editing program - such as SoundEdit 16, SoundForge or CoolEdit - to apply a "normalizing" filter over the recording. For clips recorded at a loud enough level, the filter won't make much difference. However, for clips recorded too softly, the filter can help dramatically.
  • Transcript

    • 1. Adding Audio to Your Web Site Adventures in Information February 17, 1999 presented byEileen Flick, ISD
    • 2. What it takes:
      • Computer (Pentium or PowerMac recommended) with a sound card
      • Plenty of hard drive space for uncompressed sound
      • Source (CD, video tape, voice, etc)
      • Input device (microphone, CD player, etc)
      • connectors (1/8” stereo to RCA cord) for external devices
      • Recording/editing software
    • 3. Embedded vs anchored sounds
      • <embed> tag features:
        • Launch sounds automatically
        • Embed the player in the flow of a page
        • When you leave a page, sound stops and file isn’t saved
        • Supported by version 3+ of Netscape & IE
      • Ex: <embed src=“audio/song.mid” controls=“console” height=60 width=145 autostart=“true”></embed>
      • <A> tag features:
        • Sounds downloaded to local drive, nothing plays until entire file is downloaded
        • Player launched separately, easy to save files, supported by all browsers
      • Ex: <A HREF=“audio/song.mid”>play the song</A>
      • <META> tag sound:
        • Automatic launch, user has no control
        • Client pull, goes in <HEAD> tag area -
      • EX: <META http-equiv=“refresh” content=“1”;url=audio/song.mid”> - page will refresh and sound will play after one second
        • Supported by Netscape and later versions of IE - use with caution
      • <BGSOUND> supported only by IE - avoid this one!
    • 4. Things to Keep in Mind
      • While adding sound to web pages is fun, remember not all computers are created equal so:
      • Use embedded sound (automatic play) judiciously - this can be a real pain on slow connections
        • This includes sound files using the <EMBED>, <BGSOUND> and <META> tags
      • Keep it small: best to keep non-streaming clips under 20 seconds
      • Watch your formats! If necessary, provide multiple options (ex: WAV and AIFF) so all can listen
    • 5. When digitizing
      • Check the sample rate
        • 44.1 recommended - higher the setting, the better the quality
      • Check compression
        • If the sound file will be going on the Web as a Real Audio file, sound must be digitized with NO compression.
        • For other file formats, 3:1 compression produces best balance of quality and small file size.
    • 6. Software (commercial tools)
      • SoundEdit (Mac)
        • Component of Macormedia Director Studio, also available as stand-alone app
        • Saves files in a variety of formats
        • Downside: expensive, memory-intensive
        • Upside: available in computer user rooms at USC
      • SoundForge (PC)
        • Win 95+
        • Pro-level editing, saves in a variety of formats
        • Downside: expensive
        • Not available at USC
    • 7. Other software
      • Kaboom (PC or Mac)
        • Records and saves sound files in a variety of formats
        • 2 minute recording limit
        • Limited compression settings
      • GoldWave (PC)
        • Nice shareware app (under $50) offers extensive editing capabilities
        • Simple interface
    • 8. Sampling Rates & Bit Depth
      • Sampling Rate
        • Higher the rate, better the quality, larger the file
          • 44.1KHz - CD quality, music
          • 22.0 KHz - good for voice, lower quality music
          • 11 KHZ and below - okay for voice, grainy sound
      • Bit Depth
        • Higher the bit, better the quality
        • 16-bit best for high-quality source (like a CD)
        • 8-bit okay for voice, produces grainy sound
      • Samples
        • 20 seconds @ 44/16 = 1.7MB
        • 20 seconds @ 22/8 = 512K
        • 20 seconds @ 11/8 = 288K
    • 9. Compression
      • Best to compress after digitizing
      • More compression produces smaller files
      • Higher compression can reduce quality
      • Ranges from 1:1 (none) to 12:1
      • Samples
        • 18 seconds @ 22KHz , 16-bit, 1:1 = 805K
        • 18 seconds @22KHz , 8-bit, 3:1 = 131K
        • 18 seconds @ 22KHz , 8-bit, 6:1 = 68K
      • Note: If you want to encode your sound file for Real Audio, you must use no compression
    • 10. Sound formats
      • Web-compatible formats:
        • .WAV - PC standard, good quality, large files, supports variable sampling rates and bit depths
        • .AIFF - Mac standard, good quality, large files, supports variable sampling rates and bit depths
        • .AU - UNIX standard, small files, okay quality, not as popular as it once was
        • MIDI - usually produced using instruments connected to your computer, very small files, requires special plug-in or helper app (though Quicktime 3 can handle it)
        • .MOV - Quicktime 3 now cross-platform, handles both audio and video, excellent quality, good compression, now streams
        • MPEG - audio and video, MPG-1 earliest, poorest quality. MP-3 produces CD-quality, small files
        • RM - Real audio/video, streams sound and video, produces very small files, quality varies depending on encoding settings
    • 11. MP3 - What it’s all about
      • MPEG Layer 3, known as MP3, is a digital audio format for quick-downloading files that sound almost as good as CDs. Compresses at 12:1; a five-minute CD song takes about 50 megabytes of storage space, an MP3 file of the same time length, occupies only about 4~5MB.
      • 20 second 44KHz 16 -bit 1:1 = 1.7MB || Same file encoded to MP3 = 333K
      • What you need to listen to MP3:
        • Player like WinAmp (PC) or MacAmp (Mac)
        • Portable player, like the Rio from Diamond Multimedia
      • What you need to create MP3:
        • Digitized sound & an encoder to copy sound from a source (like a CD)
        • Various shareware tools can do this:
          • MusicMatch Jukebox (PC) - can record sounds (ripper) & encode them
          • MPecker (Mac) - encodes already digitized sound
      • MP3 on the Web:
    • 12. Streaming vs Non-Streaming
      • Streaming (Real Audio, Shockwave Flash, Liquid Audio)
        • Starts playing immediately
        • Files delivered from servers make longer clips possible
        • Requires special players or plug-ins, Real Audio needs the Real Server (available at USC)
      • Non-streaming (WAV, AIFF, AU, etc)
        • Downloads to your computer, then plays
        • Files can be large and slow
        • Uses standard helpers or plug-ins
    • 13. Real Audio
      • Streaming technology
      • Can be delivered live (as in a webcast) or offline
      • What you’ll need:
        • Lots of hard drive space
        • Pentium PC or Power Mac, faster the better
        • Real Producer for encoding
      • Things to remember when encoding:
        • Choosing a low connection speed (14.4 voice) produces smallest file
        • Choosing a high connection speed (ISDN+) produces highest quality
        • Quality will never be any better than the source file, so make sure the original is as good as possible
    • 14. Using the Real Media Server at USC
      • Important facts:
        • Files must be loaded on CWIS
        • Users must have signed & submitted the Real Media agreement
      • For more information:
        • http://www. usc . edu / uscweb /authoring/ RealMedia
    • 15. Audio Samples
      • Real audio webcasts:
        • http://www. usc . edu / webcast /
        • http://www. npr .org
      • Quicktime 3:
        • quicktime /samples/showcase/index.html
      • Shockwave:
        • http://www. shockrave .com/t/home_more.html
      • Internet Underground Music Archive (IUMA):
      • MP3 files:
        • Make Some Noise tutorial: http://builder. cnet .com/Authoring/Audio/index.html