4.Flash????????

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• 1.??????
• 2.??????
• 3. ??????
• 4.Flash????????
• 5.????
• 6.??????????
• 7.???????

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Lesson 5-Sound
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Overview

• ???? Introduction to sound.
• ?????????Multimedia system sound.
• ?????Digital audio.
• MIDI ??MIDI audio.
• ?????????Audio file formats.
• ????????????Adding sound to multimedia project

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????? Introduction to Sound

• ??????Vibrations in the air create waves of
  pressure that are perceived as sound.
• ????????????Sound waves vary in sound pressure
  level (amplitude) and in frequency or pitch.
• ?????????????????Acoustics is the branch of
  physics that studies sound.
• ?????????DB???Sound pressure levels (loudness or
  volume) are measured in decibels (dB).

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??????? Multimedia System Sound

• ??????????????????????????????,????????????????
• ??????
• ??????????????
• ???????????????

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?????

• ??????????????????????????,????????????????????
  ,????????????,?????????,???????,?????????????????
  
• ????????,??????????????????????????(???)???,??????
  ?(Fourier Transform)???,??????????????????????????
  ??????20?2????????????????????,??????????????

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??

• ????????????????
• ?????????,??,??
• ????
• ??????(???)??(??)??(??)
• ??????????? MIDI????????????
• ??????WAV MIDI CDA MP3?

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??????? Multimedia System Sound

• ???? System sounds are assigned to various system
  events such as startup and warnings, among
  others.
• Windows ????????????In Windows, available system
  sounds include start.wav, chimes.wav, and
  chord.wav.
• ??????????????????MIDI???Multimedia sound is
  either digitally recorded audio or MIDI (Musical
  Instrumental Digital Interface) music.

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???? Digital Audio

• ?????????????Digital audio data is the actual
  representation of sound, stored in the form of
  samples.
• ???????????????????????,?????????????????????

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• ?????
• ????????????????????
• ??????????
• ????
• ????
• ????

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???? Digital Audio

• ???????????????,???????,??KHZ/S samples represent
  the amplitude (or loudness) of sound at a
  discrete point in time.
• ????????????????????,?????????????????,?BIT????
• ???????????????,???????Quality of digital
  recording depends on the sampling rate, (or
  frequency) that is, the number of samples taken
  per second.

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Digital Audio

• ??????????????The value of each sample is rounded
  off to the nearest integer (quantization).
• ?????????????????

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Digital Audio

• ??????Crucial aspects of preparing digital audio
  files are
• ?????????????????????????????
• ?????????
• Balancing the need for sound quality against
  available RAM and hard disk resource.
• Setting appropriate recording levels to get a
  high-quality and clean recording.

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Digital Audio

• 1????????
• ???????????
• ????(??)????????/8?????
• ??
• 44.110316/826010.584MB
• 2??????????,?????
• ??????????????????????Compression techniques
  reduce space but reliability suffers.

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????????????????

• ??????????????????????????????????A sound files
  format is a recognized methodology for organizing
  data bits of digitized sound into a data file.
• ??????????MP3, WMA, OGG, MP3pro, AAC, VQF, ASF??
• WAV??????????????????,????????,??????????,?Windows
  ?????????????WAV??????????,????????????????,??44.1
  kHz?????,16?????,??WAV????CD????,?WAV?????????????
  ??????.

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????????????????

• ??????????APE, FLAC,WavPack,LPAC,WMALossless,Apple
  Lossless,La,OptimFOG,Shoten?
• ?????,???????AIFF or AIFC ??On the Macintosh,
  digitized sounds may be stored as data files,
  resources, or applications such as AIFF or AIFC.
• PC?????????WAV??In Windows, digitized sounds are
  usually stored as WAV files.
• ??Microsoft sound system??sound
  Finder????AIF?WAV??

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MIDI ????? MIDI Versus Digital Audio

• MIDI?????80???????????????????????????????????????
  ????????????????????????????
• ??MIDI ?????????????,?????????MIDI is device
  dependent while digitized audio is device
  independent.
• MIDI ?????????MIDI files are much smaller than
  digitized audio.
• MIDI ???????MIDI????????????????,MIDI files sound
  better than digital audio files when played on a
  high-quality MIDI device.

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MIDI Audio

• ??MIDI ????,?????????????Since they are small,
  MIDI files embedded in web pages load and play
  promptly.
• MIDI ????????????, MIDI ?????????Length of a MIDI
  file can be changed without affecting the pitch
  of the music or degrading audio quality.
• ??MIDI ?????????,?????????????????Working with
  MIDI requires knowledge of music theory.

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???????MIDI???????
MIDI ?? ??
MIDI ??/ ?? ??
?? ???
??? ??
????
???
?????
MIDI??
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MIDI ?? MIDI Audio

• MIDI ?????????????????MIDI is a shorthand
  representation of music stored in numeric form.
• MIDI ?????????It is not digitized sound.
• ??MIDI ?????????,??????????????? A
  sequencer software and sound synthesizer is
  required in order to create MIDI scores.
• MIDI ?????,???????????????????MIDI is device
  dependent.

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MIDI??

• FM????MIDI????????????,????????????????,?????????
  ???????????????????????????????????????ISA????????
  FM??,?????????????????MIDI?????????????????,????
  ????????????YAMAHA OPL????,???????
• ????????????WAVE TABLE,??????????????????????
  ?????????????(?????????)????,?????????????,??MIDI?
  ???????????????,???????????????,????????????????
  ???????????,?????????FM??????????????44.1KHz?16Bit
  ?????,??????????????,?????????????

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Digital Audio

• 1???????Once a recording had been completed, it
  almost always needs to be edited.
• ????????????????????????????Basic sound editing
  operations include trimming, splicing and
  assembly, volume adjustments and working on
  multiple tracks.

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Digital Audio

• ?????????????????????????????Additional available
  sound editing operations include format
  conversion, resampling or downsampling, fade-ins
  and fade-outs, equalization, time stretching,
  digital signal processing, and reversing sounds.

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Audio File Formats

• CD-ROM/XA ???????CD,????????????????CD-ROM/XA
  (Extended Architecture) format enabled several
  recording sessions to be placed on a single CD-R
  (recordable) disc.
• CD???????????????????.cda?Linear Pulse Code
  Modulation is used for Red Book Audio data files
  on consumer-grade music CDs.

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Audio File Formats

• ???????????????RAM??????.ra .ram,??????????
• Adobe???Flash??????????????????,??MP3??????
• ?????Quicktime??????????????????????????.mov

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?????

• ?????????????????
• ???????????PCM????????????????????????????,??????
  ???,???????,????????????????????
• ??????????????DPCM???????????????,?????????????
• ??????????????ADPCM??DPCM ?????,????????,????????
  ???????,?????????????
• ???????????????????

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MIDI Versus Digital Audio

• MIDI????????
• ???????
• ??MIDI??????

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??????????Adding Sound to Multimedia Project

• ??????????????????????File formats compatible
  with multimedia authoring software being used
  along with delivery mediums, must be determined.
• ????????????Sound playback capabilities offered
  by end users system must be studied.

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Adding Sound to Multimedia Project

• ???????????????????????????????The type of
  sound, whether background music, special sound
  effects, or spoken dialog, must be decided.
• ?????MIDI ????????????????????????Digital audio
  or MIDI data should be selected on the basis of
  the location and time of use.

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????????Professional Sound

• ??????????CD????Red Book (or ISO 10149) standard
  is a standard for digitally encoding high-quality
  stereo.
• ??????,??????????????For this standard, the
  digital audio sample size is 16 bits and sampling
  rate is 44.1 KHz.
• ??????????????????????????The amount of digital
  sound information required for high-quality sound
  takes up a great deal of disk storage space.

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????

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Summary

• ???????MIDI ??MIDI is a shorthand representation
  of music stored in numeric form.
• ?????????????????Digital audio provides
  consistent playback quality.
• ??????????????MIDI files are much smaller than
  digitized audio.
• ???????????????????????MIDI files sound better
  than digital audio files when played on
  high-quality MIDI device.