C2 - Signalling
Digital Storage
Image Processing
Sampling Signals
Transmitting Signals
Two types of data
Digital
Analogue
Can only have set values in order to be processed by computers
Can have potentially any value as it's constantly changing
Pixels
An individual square of an image that has a specific value
Resolution = Pixel Width x Pixel Height
Bits
An electronic signal represented by either a 1 or 0
Each pixel value is encoded with a No. of bits
No. of Values Possible with x bits
No. of bits needed to encode x data
No. of Bits = No. of Pixels x Bits per Pixel
Bandwidth
The Freq of a signal
Even though signals transmitted have varying freq, the freq is modulated so only a given range can be used
Bits per sec
Mean Smoothing
Median Smoothing
Edge Detection
- Takes a mean average of the pixels surround each pixel - Lost of Quality
- Takes a median average of the pixels which efficiently removes noise
For each pixel value, multiply it by 4, subtract the NESW pixels
If the result is -ve result becomes 0 leaving a crisp edge
Analogue signals constantly vary
When noise is picked up (due to interference) the reconstructed signal can look very different
Noise doesn't affect digital signals due to the value limit the signal can have
How many bits is used is how it is coded
If 2 Bit coding is used, there are 2^2 possible values for the signal
Resolution of the sample is the smallest change in p.d that can be determined
Resolution = p.d change / No. of levels
The minimum sampling rate should be 2x Max Freq
Low sampling can result in aliases
Low freq signals that are not part of the original
Rate of Transmission = Samples per sec x Bits per Sample
Where Samples per sex should be 2x Max Freq
Bits per Sample
Time Taken to Transmit
No. of bits to transmit / Rate of transmission
Bit Rate
Samples per Sec x Bits per Sample
Duration of Signal
No. of Bits in Signal / Bit Rate