4.5 Fundamentals of data representation Flashcards
Why might you prefer to use sound synthesis over recording an orchestra?
- 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
Why might you not want to use sound synthesis?
- Sound synthesis struggles to recreate the sounds made by traditional instruments
- Sound synthesis struggles to recreate the human voice
What does MIDI stand for?
Musical Instrument Digital Interface
What does a MIDI File Consist of?
List of Event Messages that explain what notes must be played, when they must played, and how long or loud each note should be.
What are some examples of event messages?
- Digital signals that specify notation, pitch, and intensity
- Control signals for parameters such as volume and vibrato
- Clock signals to set the tempo
What number base is Denary/Decimal?
Base 10
What is Hexidecimal useful for?
Representing large numbers since you need fewer digits. 2 hex digits = 1 byte
i.e. Representing colours
What is Floating point binary?
When you have binary with a decimal point that can “float” meaning that it can be placed anywhere in the number.
What is fixed point binary
Binary where you have a decimal point in a fixed place, and fractional parts to the right of the point
What is binary?
Base 2, meaning it only uses 2 characters, 0 and 1, known as bits
What is 4 bits/half a byte called?
A nibble
What errors can you encounter when doing binary arithmetic?
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
What does it mean when deciding between range vs accuracy
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
How many permutations can you have in a byte?
256
How do you subtract binary?
Convert the number you’re subtracting into two’s compliment and then add the two numbers
How do you find the maximum values represented by a number base with a specific number of digits?
B^n
Where B is the number base and
n is the number of digits
How do you convert hexidecimal to denary
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.
How do you convert Hexidecimal to binary?
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
How do you convert floating point to denary?
- Work out the value of the exponent
- Denormalise the mantissa (using the exponent) – Moving the the point
- Calculate the denary value as normal
How do you convert denary to floating point binary?
- Convert denary to fixed point binary
- Normalise the number
- Check what exponent you need to get back to the original number
- Convert the exponent to binary
- Put the mantissa and the exponent together, making sure you use the correct number of bits for each number
How do you convert binary to hexidecimal?
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
Define two’s compliment?
When the most significant bit in binary is negative, allowing you to represent negative numbers with binary
Define normalised
The first two bits are different from each other
Define negative fixed point binary
Mixes Two’s Complement and fixed point binary by having the most significant bit be negative whilst also having numbers after a decimal point.
Define mantissa
The normalised number that has to be multiplied by 2x to get back to the original number
Define Hexidecimal
Base 16 number system
16 different digits - 0 to 9 and A (10) to F (15)
Define an exponent
A number that is used as the power of two when working with floating point binary
Define a byte
A string of 8 bits.
Define a bit
A bit is a Binary Digit.
Whats the difference between analogue and digital signals?
Analogue = continuiusly varying signal (wavy line signal) Digital = discrete signal (on or off)
What is the full range of human hearing?
20Hz to 20kHz
What is a Kibibyte?
1024 Bytes
What is a Kilobyte?
1,000 bytes
What is a megabyte?
1,000,000 Bytes
What does the Digital to Analogue Converter (DAC) do?
Converts digital data into analogue sound
How is sound encoded when it is stored in a computer system?
Soundwave is recorded and sampled at regular intervals.
Amplitude is represented by a number
How do you input analogue data into a computer?
Use an analogue to digital converter (ADC)
How do you find the file size of an audio file
2 Equations
File size = Sample rate x Sample resolution x Length of sound
File size = Bit rate x Length of sound
Define Sound Synthesis
Electronically Generated sounds that mimic musical instruments or the human voice
Define sampling
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.
Define Nyquists-Theorem
The sample rate should be at a frequency which is at least twice the value of the highest frequency in the sampled signal
Define frequency
How many full waves go past per second, reflects the pitch of the sound
Define Bit rate
Bit rate is the number of bits used per second
Define amplitude
The height of the wave, represents how loud the sound is
