4. Data Compression Free Online FlashCards

What is data compression?

Data compression represents information with fewer bits than an uncompressed representation, reducing storage requirements and transmission time.

What is redundancy in data compression?

Redundancy is repeated, predictable, or perceptually unimportant information that can be represented more efficiently.

How does run-length encoding reduce repetition?

Run-length encoding replaces repeated values with a value and a count; for example, AAAAABBB becomes 5A3B.

How does Huffman coding exploit statistical redundancy?

Huffman coding assigns short codes to frequent symbols and longer codes to rare symbols, exploiting statistical redundancy.

What is spatial redundancy?

Spatial redundancy occurs when nearby pixels have similar colors; storing differences between neighbors can use fewer bits than storing each color independently.

What is temporal redundancy?

Temporal redundancy occurs when consecutive audio or video frames are similar, allowing later frames to store only changes from a complete frame.

What is perceptual redundancy?

Perceptual redundancy is information people may not notice, such as tiny color changes or sounds masked by louder sounds; lossy compression may remove it.

How is compression ratio calculated?

Compression ratio = original size ÷ compressed size. A 10 MB file reduced to 2 MB has a ratio of 5:1.

What does lossless compression guarantee?

Lossless compression reconstructs the original data exactly, bit for bit, without discarding information.

How does LZ77 perform dictionary coding?

Dictionary coding replaces repeated strings with references to dictionary entries. LZ77 refers to earlier matching sequences within a sliding window.

What is the purpose of PNG filtering?

PNG filters transform scanlines to make patterns easier to compress; the filters themselves do not reduce bytes and can be reversed exactly.

What does lossy compression do?

Lossy compression produces an approximation by discarding information judged less important, often using models of visual or auditory perception.