What is Lossy Compression?

Reduces file size by PERMANENTLY removing data
Original cannot be perfectly recreated
Removes details human senses can't detect (or barely notice)
Typical reduction: 80-95% smaller (massive savings!)

When to Use Lossy:

Photos: Vacation pics, social media - slight quality loss unnoticeable
Music: Streaming, portable devices - most people can't tell difference
Video: YouTube, Netflix - optimized for human perception
General rule: Media for human consumption where exact precision isn't critical

Common Lossy Formats:

JPEG (.jpg): Photos - 90-95% compression, widely supported
MP3: Music - 90% smaller than WAV, near-CD quality
MP4, H.264, H.265: Video - streaming, YouTube, Netflix
AAC: Music - Apple's audio format (iTunes, iPhone)
WebP: Web images - Google's format (better than JPEG)

This key facts covers Lossy Compression - Good Enough Quality within Compression for GCSE Computer Science. Revise Compression in 3.3 Data Representation for GCSE Computer Science with 16 exam-style questions and 16 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 6 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.

Practice questions for Compression

Which statement correctly describes lossy compression?

A. The original file can be perfectly restored after decompression.
B. Data is permanently removed and the original cannot be exactly recreated.
C. The compressed file is always the same size as the original.
D. No data is removed during the compression process.

1 markfoundation

Explain how run-length encoding (RLE) works to compress data.

3 marksstandard

Lossy Compression - Good Enough Quality

Practice questions for Compression

Quick recall flashcards

16 questions on Compression: practise free