Different types if compression

• What is running length encoding? A method of encoding data that uses the number of bits used to represent each character
• What is dictionary encoding? A method of encoding that uses the dictionary of words to represent the data.
• What is lossless compression? A method of reducing the file size of a file without losing any original data. (Data can be recovered from compressed data)
• Whats lossy compression? Some data is permanently removed from the file. Significantly reduce file size, but original data cant be recovered.
• Advantage of lossless compression? Data can be fully recovered. Redundant data is removed
• Describe rle. Sequence of pixels of the same colour, num of consecutive pixels of same colour are counted. Pair of values which consist of the length of the run and colour of the pixels in the run.
• Vector graphics


  No loss in quality when enlarged

  Easier to edit objects

  Less storage space used.

  Disadvantage- nit good for photographs/photo-realistic images
• Butmapled graphics


  Blurry or pixilated when enlarged

  Use more storage space

  Can easily edit pixels
• Midi is a sequence of event messages which store the recorded sound .(duration of the note, instrument its played on, volume of the nite)
• Analogue to digital conversion sensor outputs a digital signal, device takes reading of analogue signal at regular intervals. And records value in a process called sampling
• Digital to analogue conversion - dac is use ld, device reads a but pattern representing the analogue signal and outputs an electrical current.
• Drawbacks of midi - not good for speech

  Can sound too synthesised
• Positivea of midi

  Easy to edit notes

  Midi file size is smaller than sampled audio size

  No loss if quality when edited