1. Media Types
Information Systems can contain the following types of media:
Sound, graphics, video & text

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

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

4. 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
You can even link to a video clip on the internet

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

6. Text files Text files can be saved in many formats
You need to know about these: txt , rtf
A .txt filehas none of the information about the formatting of the document such
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 and
be quicker to transmit across a network.
You can open a .txt file using any text editing or word processing program.

7. Rich Text Format (RTF) Rich Text Format (RTF)
A file saved in .rtf has all the formatting information which a .txt file lacks as well as the actual text.
It includes all the information about styles, fonts, sizes, paragraphing and indentation
It will be larger than an equivalent .txt file

8. The need for compression
Graphic, Sound and Video files can be very large indeed. 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:

9. Factors affecting the file size and quality of graphics files
Resolution
Colour depth

10. 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 quality of the graphic + the greater the file size.

11. Resolution

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

13. Colour Depth

14. Calculating the size of a graphic
Use this formula to calculate the size of a graphic:
File size = colour bit depth x resolution x dimensions of graphic
File size =
Colour bit depth
Resolution
Dimensions 24
1920 x 1200
6” x 6“
= Megabytes
= without compression graphic files can be very large

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

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

17. Graphics Interchange Format (GIF)
GIF is based on an 8-bit colour code giving a maximum of 28, 256, colours.
A maximum of 256 colours means that GIFs are unsuitable for storing photographic images and is used to represent charts, cartoons, or drawings.
The GIF file format uses lossless compression to reduce the file size without losing any of the data about the image.

18. JPEG is a bit map graphics file format which uses lossy compression.
This makes the graphic file smaller by cutting out parts of the graphic, usually colour tones, that won’t be noticed by the human eye.
is often used in digital cameras when storing digital photographs.
is not used for storing cartoons or drawings because some of the data is lost and this reduces the quality of the image

19. Portable Network Graphics {PNG}
PNG compresses files
Like GIF format it uses lossless compression
It can compress graphics even more than the GIF format { a PNG file can be up to 25% smaller than the equivalent GIF file}
Because they are lossless and smaller = very useful for sending across a network.
it can have a bit depth of up to 48 bits = range of 248 colours.

20. Factors affecting the file size and quality of sound files
Sampling rate:
E.g kHz
Bit depth
E.g. 8 bits, 16 bits
Time ( seconds)

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

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

23. Audio sample Bit depth
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.

24. Calculating the size of an audio file
Use this formula to calculate the size of an audio file:
File size = sampling frequency x bit depth x time x number of channels
File size =
sampling frequency
bit depth per sample
Time ( seconds)
number of channels (mono, stereo, quad)
44.1 16 60 2
= megabytes
= without compression audio files can be very large.

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

26. WAV WAV is the standard for storing sound files on windows systems and
can be sampled at a bit depth of either 8 bits or 16 bits
uses one of the following sampling rates: KHz, KHz, or 44.1KHz.
Wav files can be very large. One minute of sound can take up as much as 27Mbytes of storage.

27. MP3 MP3 is a file format for for compressing sound files.
It cuts out parts of the sound that human ears cannot hear.
It reduces the file size without a noticeable loss of quality

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

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

30. Use this formula to calculate the size of a video file
File size = resolution x frame rate x bit depth X time
File size =
Resolution
Frame rate per second
Bit depth
Time in seconds
720 x X X X
= 1291 Gigabytes = 1.26 terabytes
= without compression video files can be very large indeed

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

32. Audio Video Interleave format (.AVI)
AVIThe 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.

33. Avi
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 audio compressed using many different combinations of codecs.

34. MPEG4
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

35. Comparison of AVI & Mpeg4
Both AVI and MPEG are lossy formats which sacrifices quality for file size.2.
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 as it is dependent on the type of codec contained within the container file format.
H.264 video codec frequently used with the MP4 container is thought to be one of the highest-quality video standards available.