Data Compression (AQA GCSE Computer Science): Flashcards
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What does RLE stand for?
What does RLE stand for?
Run-Length Encoding
What does RLE store instead of repeated data?
What does RLE store instead of repeated data?
Number of repetitions followed by the actual value
What type of data does RLE compress best?
What type of data does RLE compress best?
Data with consecutive repeated elements
RLE encoding of: AAAABBBBBCCCCCCCC
RLE encoding of: AAAABBBBBCCCCCCCC
(4,A)(5,B)(7,C)
Is RLE lossy or lossless?
Is RLE lossy or lossless?
Lossless - no data is lost
Bits for colour & count in RLE image encoding
Bits for colour & count in RLE image encoding
1 bit for colour, 7 bits for count
When does RLE achieve optimal compression?
When does RLE achieve optimal compression?
Long sequences of repeated values or solid colour areas
When does RLE fail or increase file size?
When does RLE fail or increase file size?
Random data with few repetitions or lots of detail
RLE advantage: Implementation
RLE advantage: Implementation
Simple to implement and understand
RLE advantage: Speed
RLE advantage: Speed
Fast compression & decompression, minimal processing
Can RLE make files larger?
Can RLE make files larger?
Yes, when data has few repetitions
RLE format: What comes first?
RLE format: What comes first?
Count first, then value