1. Media Types
N4 & 5 Computing Science

2. Contents National 4 National 5 Sound, graphics, video, text
Standard file formats:
text: txt, rtf
audio: wav, mp3
graphics: jpeg, bmp, gif, png
video: mp4, avi
pdf
Factors affecting file size and quality, including resolution, colour depth, sampling rate.
Calculation of file size for colour bitmap
Need for compression

3. 4/5
Media Types
Information Systems can contain the following types of media:
Sound, graphics, video & text

4. 4/5
Sound
Sound files can be very useful when developing an information system.
Sound files can hold e.g. :
recordings of
Facts / information e.g. Explanations of complex ideas
Music
Sound effects

5. Graphics Graphics are very useful for
4/5
Graphics
Graphics are very useful for
Illustrating facts / information / explanations
Making the information system more attractive

6. Video Video clips are very useful
4/5
Video
Video clips are very useful
They combine moving images and sound and can illustrate very complex ideas
They can make the information in a system readily accessible to everyone e.g.
Here is a video clip of Asimo the robot
Asimo videos can be found here:-

7. Text Information systems can - Display text on a screen5
Text
Information systems can -
Display text on a screen
Hold text files which you can choose to open

8. Text files Text files can be saved in many formats5
Text files
Text files can be saved in many formats
You need to know about txt and rtf
A .txt file has no information about the format of the document e.g.
text style, alignment, fonts, sizes
Because it lacks formatting information -
a .txt file will be smaller than a Rich Text file
will need less storage space
be quicker to transmit across a network
You can open a .txt file using any text editor or word processor

9. Rich Text Format (RTF) Rich Text Format (RTF)5
Rich Text Format (RTF)
Rich Text Format (RTF)
A file saved in .rtf has formatting information and the actual text
It includes information about styles, fonts, sizes, paragraphing and indentation
It will be larger than an equivalent .txt file

10. Questions Describe an advantage of saving a document as an RTF file
4/5
Questions
Describe an advantage of saving a document as an RTF file
A document is saved as a txt file and as an RTF file:-
Which is larger?
Why is it larger?
Which is quicker to transfer across a network?

11. The need for compression5
The need for compression
Graphic, Sound and Video files can be very large
Video files can be Gigabytes in size
They take up lots of storage space
They can take a long time to transmit across a network
So they need to be compressed

12. Factors affecting the file size and quality of graphics files5
Resolution
Colour depth

13. 5
Resolution
The resolution is the number of pixels that make up an image e.g
1280 x 1024
1600 x 1200
1920 x 1200
The higher the resolution the better the quality of the graphic & the greater the file size

14. 5
Resolution example

15. 5
Resolution

16. Number of possible colours.5
Colour Depth
The colour depth is the number of bits used to represent each pixel
The greater the colour depth:-
the more colours
the greater the file size
Colour depth
Number of possible colours. 1
2 ( black or white) 8
256 16
65,536 24
16,777,216

17. How graphics are stored
4/5
How graphics are stored

18. 5
Colour Depth

19. Questions How does the resolution affect the:-
4/5
Questions
How does the resolution affect the:-
the quality of a graphic?
the file size of a graphic?
How does the bit depth affect the:-

20. Calculating the size of a graphic - 15
Calculating the size of a graphic - 1
Use this formula to calculate the size of a graphic:
File size = number of pixels x bit depth
File size = 6 x 150 x 4 x 150 x 24
= Megabytes
Colour depth
Resolution
Dimensions 24
150 dpi
6” x 4“

21. Calculating the size of a graphic - 25
Calculating the size of a graphic - 2
Use this formula to calculate the size of a graphic:
File size = number of pixels x bit depth
File size = 3664 x 2748 x 16
= 19.2 Megabytes
Without compression graphic files can be very large
Colour depth
Resolution 16
3664 x 2748

22. Questions Calculate the file size of these graphics:- 5
Colour bit depth
Resolution
Dimensions a 24
1920 x 1200 b 8
72 dpi
4” x 3” c 16
3264 x 2448

23. 5.a) File size = 1920 x 1200 x 24 bits = 55296000 bits = 6912000 bytes
Colour bit depth
Resolution
Dimensions a 24
1920 x 1200 b 8
72 dpi
4” x 3” c 16
3264 x 2448 5
5.a) File size = 1920 x 1200 x 24 bits
= bits
= bytes
= 6750 Kilobytes
= Megabytes

24. 5.b) File size = 4 x 72 x 3 x 72 x 8 bits = 497664 bits = 62208 bytes
Colour bit depth
Resolution
Dimensions a 24
1920 x 1200 b 8
72 dpi
4” x 3” c 16
3264 x 2448 5
5.b) File size = 4 x 72 x 3 x 72 x 8 bits
= bits
= bytes
= Kilobytes

25. 5.c) File size = 3264 x 2448 x 16 bits = 127844352 bits
Colour bit depth
Resolution
Dimensions a 24
1920 x 1200 b 8
72 dpi
4” x 3” c 16
3264 x 2448 5
5.c) File size = 3264 x 2448 x 16 bits
= bits
= bytes
= Kilobytes
= 15.3 Megabytes

26. Graphic Files You need to know about the following graphic files:5
Graphic Files
You need to know about the following graphic files:
.BMP, .GIF, .JPEG, .PNG

27. 5
BitMap (BMP)
The .bmp format stores color data for each pixel in the image without any compression
.bmp files can be very large

28. Graphics Interchange Format (GIF)5
Graphics Interchange Format (GIF)
Each pixel is represented by an 8-bit colour code
Number of possible colours is 28= 256
Unsuitable for storing photographic images
Used to represent charts, cartoons, or drawings
Uses lossless compression to reduce the file size without losing any of the data about the image

29. JPEG A bit map graphics file format which uses lossy compression5
A bit map graphics file format which uses lossy compression
Makes the graphic file smaller by changing the colour of some pixels (to match neighbouring pixels) that won’t be noticed by the human eye
Often used in digital cameras when storing digital photographs
Not used for storing cartoons or drawings because some of the data is lost and this reduces the quality of the image

30. Portable Network Graphics {PNG}5
Portable Network Graphics {PNG}
PNG compresses files
Like GIF format it uses lossless compression
Compresses graphics more than the GIF format { a PNG file can be up to 25% smaller than the equivalent GIF file}
Used for graphics that will be sent across a network because they are lossless and small
Bit depth of up to 48 bits = variety of 248 colours
Graphic can have a degree of transparency

31. Questions Name 2 graphic file formats that use lossless compression5
Questions
Name 2 graphic file formats that use lossless compression
Name a graphic file format that uses lossy compression
Name a graphic file format that does not use compression
State 3 facts about the GIF format
State the graphic file format that is most suitable for a photo that will be sent across a network

32. 5
Practical Task
Find a graphic that you like and save it in a folder called Graphic files.
Open the graphic with Paint then save it a number of times using different file types to complete this table:-
File type
Resolution
File size
Number of colours
Bit Depth
Quality
JPEG
329 x 299
82.8 Kb
224 24
Excellent
GIF
256 8
16 colour bitmap 16 4
2 colour bitmap 2 1

33. Factors affecting the file size and quality of sound files5
Sampling rate (frequency):
E.g kHz
Bit depth
E.g. 8 bits, 16 bits
Time ( seconds) affects the size – but not the quality

34. Sampling Rate 5
The sampling rate is the number of samples of a sound wave measured each second
This is measured in kHz ( thousands per second) e.g kHz = 44,100 samples per second

35. Sampling rate 5
The higher the sampling rate the better the quality of the sound + the bigger the file size

36. Audio sample Bit depth (Sample depth)5
The bit depth is the number of bits used to represent each sample of the sound wave
The more bits used = the higher the quality = the larger the file size

37. Audio Files You need to know about these audio file formats: WAV , MP35
You need to know about these audio file formats:
WAV , MP3

38. WAV WAV is the standard for storing sound files on windows systems5
WAV is the standard for storing sound files on windows systems
Bit depth: 8 bits or 16 bits
Sampling rates: KHz, KHz, or 44.1KHz
Wav files can be very large
1 minute of sound can take up as much as 27Mbytes of storage

39. MP3 MP3 is a file format for compressing sound files5
MP3 is a file format for compressing sound files
It cuts out parts of the sound that human ears cannot hear
It cuts out quiet sounds when a loud sounds happens at the same time
It reduces the file size without a noticeable loss of quality

40. WAV and MP3 Comparison 5
Note the difference in file size between the .mp3 version and the WAV version

41. Factors affecting the file size and quality of video files5
Resolution of each image(frame)
Bit depth of each image
Frame rate: the number of frames per second
Time: in seconds

42. Video File Formats 5
You need to know about the following Video File Formats:
AVI , MP4

43. Audio Video Interleave format (.AVI)5
The Audio Video Interleave format was developed by Microsoft and is commonly used in Windows applications like Media Player
This format does not have built-in compression.
Maximum resolution is 320 x 240
Maximum frame rate is 30 frames per second
File size limited to 2Gb

44. Avi AVI files contain the audio and video data in one file5
AVI files contain the audio and video data in one file
This allows synchronous audio/video playback of a file
AVI is a container format, meaning it can contain video and audio compressed using many different combinations of codecs
(A codec is a program that compresses and decompresses files)

45. MPEG4 5
MPEG-4 is an(audio and video) compression method designed specially for low-bandwidth (less than 1.5MBit/sec bitrate) video/audio encoding purposes
MPEG-4 can deliver high-quality audio and video over the Internet to desktops, laptops, tablets &smartphones

46. Comparison of AVI & Mpeg45
Both AVI and MPEG are lossy formats which sacrifices quality for file size
Both AVI and MPEG can contain both audio and video data in a file container
The quality of a video file is not dependent on the type of container file format - it is dependent on the type of codec contained within the container file
H.264 video codec frequently used with the MP4 container is thought to be one of the highest-quality video standards available.

47. PDF – Portable Document Format5
PDF was developed in the early 1990s as a way to share documents
Adobe Acrobat or Foxit Reader are used to display the files
Used for documents with text and images
Allows documents to be viewed on different platforms that don’t have the same application software

48. Questions Describe the purpose of a of a codec?5
Describe the purpose of a of a codec?
Describe a container file
Describe the AVI file format
Describe the MPeg4 file format
Do AVI and MPeg4 use lossy or lossless compression?
Describe the PDF format and explain why it is useful

49. 5 File type Uses Type of compression Factors affecting file size
Text files
TXT
RTF
Graphics files
Bit map
Gif
JPEG
PNG
Audio files
WAV
MP3
Video files
AVI
MPEG-4

50. Revision
4/5
Create a mind map about Media Types