Presentation on theme: "Lecture 6: Audio Intro to IT COSC1078 Introduction to Information Technology Lecture 6 Audio James Harland"— Presentation transcript:
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)