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2.5 Representing images and sounds

Teacher’s notes in the Notes Page

Flash activity (these are not editable)Icons:

Unit 2 Digital Media

Worksheet or support sheet available

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Curriculum linksCurriculum links

This presentation supports the following areas of knowledge in the Naace Curriculum Framework for KS3 ICT:

This presentation supports the following sectionsof the Programme of Study for KS3 Computing:

understand how instructions are stored and executed within a computer system; understand how data of various types (including text, sounds and pictures) can be represented and manipulated digitally, in the form of binary digits

Technical Understanding – Programming and control

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Learning objectives

how images are represented in binary

how metadata is used in image files

how colour depth and resolution affect file size

how sound is stored in digital form

what affects the size and quality of an audio file

what can be done with image and sound data after it has been digitized.

By the end of this presentation we will have learned:

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Representation of sound

Like colour, sound is not digital but analogue. However, to be stored by a computer it must be in a digital format.

While analogue signals can have any value, digital signals must store data using only the values 0 and 1.

How could you store analogue sound waves like the ones above using binary?

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Sampling

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File size

What factors do you think affect the size and quality of a sound file?

The higher the sample rate, the higher the sound quality will be. The file size will also be larger because more samples require more storage space.

Even at a relatively low sample size, uncompressed digital music files stored in RAW format are often very large. Compression reduces the size of the files by applying algorithms and codecs to store repeated patterns in the data.

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After digitizing

After the data has been digitized, the computer is able to:

work with the data to display a picture, play a sound or calculate new values and new data

store the data on other devices, hard drives and memory sticks and display stored data on the screen

use specialist software to edit the sound or image

share the data with others through email, WiFi or Bluetooth

copy or back up the data.

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