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Computer science paper 2 > 4.5 Fundamentals of data representation > Flashcards

4.5 Fundamentals of data representation Flashcards

1
Q

Why might you prefer to use sound synthesis over recording an orchestra?

A
  • Sound synthesis produces smaller file sizes without loss of quality
  • Sound synthesis allows for easy editing of files after they have been recorded
  • Sound synthesis allows for sounds that would be unachievable using traditional instuments
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2
Q

Why might you not want to use sound synthesis?

A
  • Sound synthesis struggles to recreate the sounds made by traditional instruments
  • Sound synthesis struggles to recreate the human voice
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3
Q

What does MIDI stand for?

A

Musical Instrument Digital Interface

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4
Q

What does a MIDI File Consist of?

A

List of Event Messages that explain what notes must be played, when they must played, and how long or loud each note should be.

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5
Q

What are some examples of event messages?

A
  • Digital signals that specify notation, pitch, and intensity
  • Control signals for parameters such as volume and vibrato
  • Clock signals to set the tempo
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6
Q

What number base is Denary/Decimal?

A

Base 10

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7
Q

What is Hexidecimal useful for?

A

Representing large numbers since you need fewer digits. 2 hex digits = 1 byte
i.e. Representing colours

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8
Q

What is Floating point binary?

A

When you have binary with a decimal point that can “float” meaning that it can be placed anywhere in the number.

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9
Q

What is fixed point binary

A

Binary where you have a decimal point in a fixed place, and fractional parts to the right of the point

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10
Q

What is binary?

A

Base 2, meaning it only uses 2 characters, 0 and 1, known as bits

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11
Q

What is 4 bits/half a byte called?

A

A nibble

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12
Q

What errors can you encounter when doing binary arithmetic?

A

Cancellation : Adding a very small number to a very large number will not change the result

Underflow : The result of a calculation is too small to fit into the available number of bits

Overflow : The result of a calculation is too big to fit into the available number of bits.

Rounding : Some number just can’t be represented using binary. Rounding errors can be represented in absolute, relative and percentage forms

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13
Q

What does it mean when deciding between range vs accuracy

A

Since we can never accurately represent some fractional numbers in binary (for instance 1/3), we often must accept a certain amount of inaccuracy. However, it is possible to change the position of the binary point to alter the balance between range and accuracy

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14
Q

How many permutations can you have in a byte?

A

256

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15
Q

How do you subtract binary?

A

Convert the number you’re subtracting into two’s compliment and then add the two numbers

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16
Q

How do you find the maximum values represented by a number base with a specific number of digits?

A

B^n
Where B is the number base and
n is the number of digits

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17
Q

How do you convert hexidecimal to denary

A

16^2 16^1 16^0

Use those headings, convert each hex digit to denary and then multiply by its heading.
Total each of the values you get at the end.

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18
Q

How do you convert Hexidecimal to binary?

A

Convert each of the hexideciamal digits to denary seperately then convert each denary value into 4 bit unsigned binary and then just put the binary together

19
Q

How do you convert floating point to denary?

A
  1. Work out the value of the exponent
  2. Denormalise the mantissa (using the exponent) – Moving the the point
  3. Calculate the denary value as normal
20
Q

How do you convert denary to floating point binary?

A
  1. Convert denary to fixed point binary
  2. Normalise the number
  3. Check what exponent you need to get back to the original number
  4. Convert the exponent to binary
  5. Put the mantissa and the exponent together, making sure you use the correct number of bits for each number
21
Q

How do you convert binary to hexidecimal?

A

Split the binary into sections of 4 bits and convert each of them to denary, then convert to denary values to Hex values and just put them together

22
Q

Define two’s compliment?

A

When the most significant bit in binary is negative, allowing you to represent negative numbers with binary

23
Q

Define normalised

A

The first two bits are different from each other

24
Q

Define negative fixed point binary

A

Mixes Two’s Complement and fixed point binary by having the most significant bit be negative whilst also having numbers after a decimal point.

25
Q

Define mantissa

A

The normalised number that has to be multiplied by 2x to get back to the original number

26
Q

Define Hexidecimal

A

Base 16 number system

16 different digits - 0 to 9 and A (10) to F (15)

27
Q

Define an exponent

A

A number that is used as the power of two when working with floating point binary

28
Q

Define a byte

A

A string of 8 bits.

29
Q

Define a bit

A

A bit is a Binary Digit.

30
Q

Whats the difference between analogue and digital signals?

A 
Analogue = continuiusly varying signal (wavy line signal)
Digital = discrete signal (on or off)
31
Q

What is the full range of human hearing?

A

20Hz to 20kHz

32
Q

What is a Kibibyte?

A

1024 Bytes

33
Q

What is a Kilobyte?

A

1,000 bytes

34
Q

What is a megabyte?

A

1,000,000 Bytes

35
Q

What does the Digital to Analogue Converter (DAC) do?

A

Converts digital data into analogue sound

36
Q

How is sound encoded when it is stored in a computer system?

A

Soundwave is recorded and sampled at regular intervals.

Amplitude is represented by a number

37
Q

How do you input analogue data into a computer?

A

Use an analogue to digital converter (ADC)

38
Q

How do you find the file size of an audio file

2 Equations

A

File size = Sample rate x Sample resolution x Length of sound

File size = Bit rate x Length of sound

39
Q

Define Sound Synthesis

A

Electronically Generated sounds that mimic musical instruments or the human voice

40
Q

Define sampling

A

Sampling is the process of converting sound waves into digital form by taking a series of readings at fixed intervals in order to create discrete digital data.

41
Q

Define Nyquists-Theorem

A

The sample rate should be at a frequency which is at least twice the value of the highest frequency in the sampled signal

42
Q

Define frequency

A

How many full waves go past per second, reflects the pitch of the sound

43
Q

Define Bit rate

A

Bit rate is the number of bits used per second

44
Q

Define amplitude

A

The height of the wave, represents how loud the sound is

Computer science paper 2 (7 decks)

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