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Published byAshley Little Modified over 9 years ago
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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.
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Where does this topic fit? Internet concepts –Applications –Technology –Implications Internet skills –Application development –Content creation (audio)
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All data types are compressible Image Text Numeric Audio Video
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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.
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1. click to playclick to play 2. click to playclick to play Which sounds best? Worst?
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Audio file File size (Kbytes) Bit rate (Kbits/s) Play low qualityPlay low quality (.mp3)16 Play originalPlay original (.wav)676688
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1. playplay 2. playplay 3. playplay 4. playplay 5. playplay Which sounds best? Worst?
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No.Data rateFile typeFile size 1320 kbps.mp3112 kB 2Original.wav233 kB 364 kbps.mp326 kB 416 kbps.mp310 kB 5128 kbps.mp347 kB
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Record and edit at high quality
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Export > Save as MP3 > click Options Compress for distribution
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Variable bit rate
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Bit rateQuality 8 kbpstelephone 16 kbpsshortwave radio 32 kbpsAM radio 64 kbpsFM radio 96 kbpsnear CD 128 kbpsCD Quality rules of thumb
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Lossy compression Information is lost– the original cannot be recovered
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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.
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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
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Image Text Numeric Audio Video Which data type(s) is/are suited to lossless compression? Lossy compression? Why?
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