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# Crossing the Boundary

Crossing the Boundary. Sound. Revision. What is a pixel? What is resolution? What are the 3 primary colours used in colour representation? What is the Hexadecimal representation of the following 24 bit colour 10001010 11111111 00000011 Télécharger la présentation ## Crossing the Boundary

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1. Revision • What is a pixel? • What is resolution? • What are the 3 primary colours used in colour representation? • What is the Hexadecimal representation of the following 24 bit colour 10001010 11111111 00000011 • Name 2 advantages of Vector Graphics over Bitmap Images

2. WHAT IS SOUND?WHAT ARE THE TWO COMPONENT PARTS OF SOUND?DISCUSS

3. WHAT IS THE IMPACT OF RECORDING IN STEREO?WHAT ARE THE NEW RECORDING STANDARDS?

4. Sound is a continuous set of data points formed by a wave. Computers sample this sound at discrete points to store a digital approximation The discrete approximations (in red) can be used to recreate the original sound (grey). However, due to limitations in the number of samples we take we are often unable to truly represent a sound wave, though we can get close enough for the human ear not to notice the difference. KEY PHRASE?

5. GETTING THE SOUND IN AND OUT AGAIN What can you do with the sound once it is stored on the computer Give an example of common DAC that you have all used

6. Original Sound, continuous sound wave High sample rate, digital looks like original ½ high sample rate digital loses sharpness 1/3 high sample rate, loss of peaks

7. When recording MP3s you'll normally use a sampling rate of 32,000 (samples per second) 44,100 (samples per second) Explore and be prepared to discuss why this Sample Rate is the most common 48,000Hz (samples per second)

8. SAMPLING RESOLUTION Sampling resolution - the number of bits assigned to each sample As you saw earlier, different sounds can have different volumes. The sampling resolution allows you to set the range of volumes storable for each sample. If you have a low sampling resolution then the range of volumes will be very limited, if you have a high sampling resolution then the file size may become unfeasible. The sampling resolution for a CD is 16 bits used per sample.

9. 4 BIT RESOLUTION THE CURRENT INDUSTRY STANDARD IS?

10. Bit rate - the number of bits required to store 1 second of sound To work out the size of a sound sample requires the following equation: File Size = Sample Rate * Sample Resolution * Length of sound This is the same as saying: File Size = Bit Rate * Length of sound Example: Sound File Sizes If you wanted to record a 30 second voice message on your mobile phone you would use the following: Sample Rate = 8,000Hz Sample Resolution = 16 bit Length of Sound = 30 seconds Therefore the total file size would be: 8,000 * 16 * 30 = 3 840 000 Bits = 480 000 Bytes

11. Using the grid below, plot the following sample points for a sample resolution of 3 bits per sample: 000 001 100 101 100 011 100 110 111 101

12. Sample the sound wave below and convert it into binary form: 101 101 101 011 001 000 001 001 100 100

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