Audio compression Skills: Audacity compression IT concepts: quality-file size trade off,...

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Transcript of Audio compression Skills: Audacity compression IT concepts: quality-file size trade off,...

  • Slide 1
  • Audio compression Skills: Audacity compression IT concepts: quality-file size trade off, capture-edit-compress, lossy versus lossless compression This work is licensed under a Creative Commons Attribution-Noncommercial- Share Alike 3.0 License.
  • Slide 2
  • Where does this topic fit? Internet concepts Applications Technology Implications Internet skills Application development Content creation (audio)
  • Slide 3
  • All data types are compressible Image Text Numeric Audio Video
  • Slide 4
  • Bit DepthSample Rate1 minute3 minutes 1644,10010.1 Mb30.3 Mb 1648,00011.0 Mb33 Mb 2496,00033.0 Mb99 Mb MP3 File128 k/bit rate0.94 Mb2.82 Mb Examples of files sizes for stereo recordings MP 3 is a compressed format.
  • Slide 5
  • 1. click to playclick to play 2. click to playclick to play Which sounds best? Worst?
  • Slide 6
  • Audio file File size (Kbytes) Bit rate (Kbits/s) Play low qualityPlay low quality (.mp3)16 Play originalPlay original (.wav)676688
  • Slide 7
  • 1. playplay 2. playplay 3. playplay 4. playplay 5. playplay Which sounds best? Worst?
  • Slide 8
  • No.Data rateFile typeFile size 1320 kbps.mp3112 kB 2Original.wav233 kB 364 kbps.mp326 kB 416 kbps.mp310 kB 5128 kbps.mp347 kB
  • Slide 9
  • Record and edit at high quality
  • Slide 10
  • Export > Save as MP3 > click Options Compress for distribution
  • Slide 11
  • Variable bit rate
  • Slide 12
  • Bit rateQuality 8 kbpstelephone 16 kbpsshortwave radio 32 kbpsAM radio 64 kbpsFM radio 96 kbpsnear CD 128 kbpsCD Quality rules of thumb
  • Slide 13
  • Lossy compression Information is lost the original cannot be recovered
  • Slide 14
  • Audio compression Skills: Audacity compression IT concepts: quality-file size trade off, capture-edit-compress, lossy versus lossless compression This work is licensed under a Creative Commons Attribution-Noncommercial- Share Alike 3.0 License.
  • Slide 15
  • How many bytes in a three minute, CD quality song? How many bytes in a three minute telephone quality conversation? What is the final step in audio, image and video processing? A few questions
  • Slide 16
  • Image Text Numeric Audio Video Which data type(s) is/are suited to lossless compression? Lossy compression? Why?