Lecture 6: Audio Intro to IT COSC1078 Introduction to Information Technology Lecture 6 Audio James Harland

Lecture6: AudioIntro to IT Introduction James Harland URL: Phone: Office: (Building 14, level 10, room 1) Consultation: Mon , Thu What is the view like from my office?

Lecture 6: AudioIntro to IT Overview  Questions?  Assignment 1  Audio  Questions?

Lecture 6: AudioIntro to IT Introduction to IT 1 Introduction 2 Images 3 Audio 4 Video WebLearnTest 1 5 Binary Representation Assignment 1 6 Data Storage 7 Machine Processing 8 Operating Systems WebLearn Test 1 9 Processes Assignment 2 10 Internet 11 Internet Security WebLearn Test 3 12 Future of ITAssignment 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: AudioIntro to IT Assessment Process  Submit all assignments via Blackboard in the Learning Hub  Assignment 1due 11.59pm Sunday 1 st April  Assignment 2due 11.59pm Sunday 6 th May  Assignment 3 due 11.59pm Sunday 27 th May  Late assignments attract a penalty of 10% per day late, up to a maximum of 50%

Lecture 6: AudioIntro 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: AudioIntro 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’  me your group and its name so that I can set up a blog on the Learning Hub

Lecture 6: AudioIntro to IT Overview …

Lecture 6: AudioIntro to IT Digitising Sound Sampling: how often discrete readings are taken (from a continuous signal) Quantisation: how many different values each element can have

Lecture 6: AudioIntro to IT Audio vs Images One of the biggest differences between images and audio is …. TIME

Lecture 6: AudioIntro 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: AudioIntro 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 MB So an 800MB CD can hold about 80 minutes of music….

Lecture 6: AudioIntro 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: AudioIntro 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 MB So adding 3 extra ‘voice over’ tracks only adds about 168 MB to an 8 GB DVD …

Lecture 6: AudioIntro 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: AudioIntro 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 to be heard  Based on `psychoacoustic models’  Emerged in early 1990’s (Moving Picture Experts Group)

Lecture 6: AudioIntro 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 local device

Lecture 6: AudioIntro to IT Conclusion  Go to laboratory classes (and tutorials) this week!  Do online quizzes later this week  Keep reading! (book particularly)