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COSC1078 Introduction to Information Technology Lecture 6 Audio

James Harland james.harland@rmit.edu.au. COSC1078 Introduction to Information Technology Lecture 6 Audio. Introduction. James Harland Email: james.harland@rmit.edu.au URL: www.cs.rmit.edu.au/~jah Phone: 9925 2045 Office: 14.10.1 (Building 14, level 10, room 1)

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COSC1078 Introduction to Information Technology Lecture 6 Audio

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  1. Intro to IT James Harland james.harland@rmit.edu.au COSC1078 Introduction to Information TechnologyLecture 6Audio
  2. Intro to IT Introduction James Harland Email:james.harland@rmit.edu.au URL:www.cs.rmit.edu.au/~jah Phone:9925 2045 Office:14.10.1 (Building 14, level 10, room 1) Consultation:Mon 4.30-5.30, Thu 11.30-12.30 What is the view like from my office?
  3. Intro to IT Overview Questions? Assignment 1 Audio Questions?
  4. Intro to IT Introduction to IT 1 Introduction 2Images 3Audio 4Video WebLearnTest 1 5 Binary Representation Assignment 1 6 Data Storage 7Machine Processing 8 Operating Systems WebLearn Test 1 9 Processes Assignment 2 10 Internet 11Internet Security WebLearn Test 3 12Future of IT Assignment 3, Peer and Self Assessment
  5. Questions? How did you spend 6-8 hours on this course last week? This week? Lecture 6: Audio SE Fundamentals
  6. Intro to IT Assessment Process Submit all assignments via Blackboard in the Learning Hub Assignment 1 due 11.59pm Sunday 1st April Assignment 2 due 11.59pm Sunday 6th May Assignment 3 due 11.59pm Sunday 27th May Late assignments attract a penalty of 10% per day late, up to a maximum of 50%
  7. Intro to IT Assignment Assignment will be in three parts Overall task is to produce a video Groups of up to 3 Assessed by final video and group blog Part 1: images and audio (end of week 5) Part2: hardware (end of week 9) Part 3: reflection, research (end of week 12)
  8. Intro to IT Assignment 1 Use GIMP (or a similar tool) to perform some manipulations on an image Use Audacity to perform some manipulations on sound Use a movie making tool to produce something like (and much better than!) ‘Lord of the Controllers 1 & 2’ Email me your group and its name so that I can set up a blog on the Learning Hub
  9. Overview 01010100001010101010100110100010101001101001010010100011100010101010100101111001001010… Lecture 6: Audio Intro to IT
  10. Digitising Sound Sampling: how often discrete readings are taken (from a continuous signal) Quantisation: how many different values each element can have Lecture 6: Audio Intro to IT
  11. Audio vs Images One of the biggest differences between images and audio is …. TIME Lecture 6: Audio Intro to IT
  12. Audio and Time Adds a dimension to file size (sampling, quantisation, channels, time, …) Streaming rate can be too slow Playback needs to be continuous Time to listen to audio is fixed How long does it take to view an image? How long does it take to listen to an entire CD? Lecture 6: Audio Intro to IT
  13. Audio file sizes How much space is needed for 1 minute on a CD? Two channels (stereo) 16 bits per channel (bit depth) (65,536 quanta) Sampling rate of 44,100 Hz 60 s x 44,100 samples/s x 16 bits/sample x 2 = 84,672,000 bits = 10,584,000 bytes ≈ 10 MB So an 800MB CD can hold about 80 minutes of music…. Lecture 6: Audio Intro to IT
  14. Audio file sizes How much space is needed for 90 minutes on a DVD? Surround sound is 5.1 channels 16 bits per channel (bit depth) (65,536 quanta) Sampling rate of 192,000 Hz 90 min x 60s x 192,000samples/s x 16 bits/sample x 5.1 = 84,602,880,000 bits = 10,575,360,000 bytes ≈ 9.8 GB Lecture 6: Audio Intro to IT
  15. Audio file sizes How much space is needed for 90 minutes of a human voice on a DVD? Mono (ie one channel) would be fine 8 bits per channel (bit depth) (256 quanta) Sampling rate of 11,025 Hz 90 min x 60s x 11,025samples/s x 8 bits/sample = 476,280,000 bits = 59,535,000 bytes ≈ 56 MB So adding 3 extra ‘voice over’ tracks only adds about 168 MB to an 8 GB DVD … Lecture 6: Audio Intro to IT
  16. Audio file sizes To reduce file size: Reduce sampling rate Reduce bit depth 8 bits will work for speech, but not music Reduce channels (ie just mono) Halves file size – could work for games (Reduce duration? Unlikely ) Use compression techniques Be aware of lossy vs lossless compression Lecture 6: Audio Intro to IT
  17. MP3 MPEG-1 Audio Layer 3 Lossy compression (ie loses some information) (so don’t use this for `master’ copies when editing) Reduces size by factor of 11 compared to CD Reduces accuracy of sounds which are unlikely to be heard Based on `psychoacoustic models’ Emerged in early 1990’s (Moving Picture Experts Group) Lecture 6: Audio Intro to IT
  18. MIDI Musical Instrument Digital Interface Purely digital music created by a processor Often used as a keyboard attached to a computer Note information from a digital source Small size (60s in 2KB) Easily edited Sound depends on local device Lecture 6: Audio Intro to IT
  19. Intro to IT Conclusion Go to laboratory classes (and tutorials) this week! Do online quizzes later this week Keep reading! (book particularly)
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