COSC1078 Introduction to
Information Technology
Lecture 8
Video
James Harland
james.harland@rmit.edu.au
Lecture 8: Video
Intro to IT
Introduction to IT
1 Introduction
2 Images
3 Audio
4 Video
5 Binary Representation
WebTest 1, 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 IT
Assignment 3, Peer and Self Assessment
Lecture 8: Video
Intro to IT
Overview
 Questions?
 WebLearn Test 1
 Assignment 1
 Video
 Questions?
Lecture 8: Video
Intro to IT
Web Test 1
 Week 5
 Quizzes (practice tests) up now
 Content will be on weeks 2-4
Images
Audio
Video
Lecture 8: Video
Intro to IT
Introduction
Who is this bloke?
Lecture 8: Video
Intro to IT
Overview
01010100001010101010100110100010101001101001010010
100011100010101010100101111001001010…
Lecture 8: Video
Intro to IT
Images and Perspective …
Frame rate is often 30 per second
COOL!
BORING!
Lecture 8: Video
Intro to IT
Time codes and all that …
Time for videos HH:MM:SS:FF
HH hours
MM minutes
SS seconds
FF frames
Often 30 frames per second (nice and neat!)
NTSC colour uses 29.97 frames per second (!!)
This means there are two timecode systems ….
Lecture 8: Video
Intro to IT
Non-drop-frame timecode
HH:MM:SS:FF
Behaves as expected
Frames Minutes
(30 fps)
Non-drop-frame
timecode
1799
1800
17981
17982
0.9994
1
9.989
9.990
00:00:59:29
00:01:00:00
00:09:59:11
00:09:59:12
18000
10
00:10:00:00
Lecture 8: Video
Intro to IT
Drop-frame timecode
HH;MM;SS;FF
Seems bizarre!
Skips time codes
00;01;00;00 00;01;00;01
00;02;00;00 00;02;00;01
00;03;00;00 00;03;00;01
….
00;09;00;00 00;09;00;01
00;00;59;29
00;01;00;02
…
00;01;59;29
00;02;00;02
…
00;09;59;29
00;10;00;00
Skips 18 codes per 10 minutes
Lecture 8: Video
Intro to IT
Drop-frame timecode
Frames Minutes
Minutes
(29.97fps) (30 fps)
Drop-frame
timecode
1799
1.0004
0.9994
00;00;59;29
Non-dropframe
timecode
00:00:59:29
1800
17981
1.001
9.999
1
9.989
00;01;00;02
00:09:59:29
00:01:00:00
00:09:59:11
17982
18000
10
10.010
9.990
10
00;10;00;00
00;10;00;18
00:09:59:12
00:10:00:00
Lecture 8: Video
Intro to IT
Video file size
Video files can be big!
How much space is need for 1 second of HDTV?
1440 x 1080 pixels
24-bit colour
30 fps
Stereo (2 audio channels)
Audio sampling 48 kHz and 16-bit depth
Lecture 8: Video
Intro to IT
Video file size
Audio: 48,000 samples/s x 1s x 16 bits/sample x 2
= 1,536,000 bits = 192,000 byes ≈ 188 KB
Video: 1440 x 1080 pixels/frame x 24 bits/pixel
= 37,324,800 bits/frame
37,324,800 bits/frame x 30 fps x 1s
= 1,119,744,000 bits
= 139,968,000 bytes
= 133 MB (!!)
This takes 133MB per second! Need to compress
Lecture 8: Video
Intro to IT
Colour Sampling
Eye more sensitive to brightness than colour
YUV model: Y luminance U,V chrominance
3 samples per pixel, so 12 samples per 4 pixels
Name YUV
Size
Saving
4:4:4 4Y, 4U, 4V
12
0%
YUV YUV YUV YUV
4:2:2 4Y, 2U, 2V
8
33%
Y
4:2:0 4Y, 2 (U or V)
6
50%
Y
Lecture 8: Video
UV
U
Intro to IT
Y
Y
Y
Y
UV
U
Y
Y
File size and Data rate
Overall file size is one thing
133MB x 60 minutes/second x 60 minutes/hour x
x 2 hours
= 957,600 MB ≈ 935 GB (!!)
Still need to be able to extract data at
133MB per second, even for only 1 second …
48x CD is about 7MB per second …
Lecture 8: Video
Intro to IT
Compressing Video Files






Lower frame size
Lower frame rate
Lower picture quality (ie data rate)
Lower colour depth (not often done …)
Lower audio quality (not much effect)
Compression methods (lossy vs lossless)
compressor/decompressor or codec
Lecture 8: Video
Intro to IT
Assignment 1
JUST
DO
IT!
 Use GIMP (or a similar tool) to perform some
manipulations on an image
 Address two issues in relation to this
 Lab classes 2 and 3 based around GIMP
 Main emphasis is on process, not result!
 Is in the Learning Hub
 SUBMIT VIA WEBLEARN
Lecture 8: Video
Intro to IT
Conclusion
 Get Assignment and WebTest done this week,
if possible
 Submit early!
 Keep reading! (book particularly)
Lecture 8: Video
Intro to IT