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Lecture 6: Audio Intro to IT COSC1078 Introduction to Information Technology Lecture 6 Audio James Harland [email protected]
Lecture 6: Audio Intro to IT
COSC1078 Introduction to Information Technology
Lecture 6
AudioJames Harland
Lecture6: Audio Intro to IT
Introduction
James Harland• Email: [email protected]• 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-
12.30What is the view like from
my office?
Lecture 6: Audio Intro to IT
Overview Questions?
Assignment 1
Audio
Questions?
Lecture 6: Audio Intro to IT
Introduction to IT1 Introduction 2 Images3 Audio4 Video WebLearnTest 1 5 Binary Representation Assignment 16 Data Storage7 Machine Processing8 Operating Systems WebLearn Test 19 Processes Assignment 210 Internet11 Internet Security WebLearn Test 312 Future of IT Assignment 3, Peer and Self Assessment
Lecture 6: Audio SE Fundamentals
Questions?
How did you spend 6-8 hours on this course last week? This week?
Lecture 6: Audio 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%
Lecture 6: Audio 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)
Lecture 6: Audio 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
Lecture 6: Audio Intro to IT
Overview 01010100001010101010100110100010101001101001010010100011100010101010100101111001001010…
Lecture 6: Audio Intro to IT
Digitising Sound
Sampling: how often discrete readings are taken (from a continuous signal)
Quantisation: howmany different values each element can have
Lecture 6: Audio Intro to IT
Audio vs Images
One of the biggest differences between images and audio is ….
TIME
Lecture 6: Audio Intro to IT
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
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 MBSo an 800MB CD can hold about 80 minutes of music….
Lecture 6: Audio Intro to IT
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 60 s x 192,000 samples/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
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 60 s x 11,025 samples/s x 8 bits/sample = 476,280,000 bits = 59,535,000 bytes≈ 56 MBSo adding 3 extra ‘voice over’ tracks only adds about 168 MB to an 8 GB DVD …
Lecture 6: Audio Intro to IT
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
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 tobe heard Based on `psychoacoustic models’ Emerged in early 1990’s
(Moving Picture Experts Group)
Lecture 6: Audio Intro to IT
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 localdevice
Lecture 6: Audio Intro to IT
Conclusion Go to laboratory classes (and tutorials) this
week!
Do online quizzes later this week
Keep reading! (book particularly)
