Computer Science - 1.3 Compression

Why is compression needed?

Data files can be very large, causing slower transmission, especially in uncompressed folders where each folder is copied individually.

Type of Compression

Lossy and Lossless

Lossy Compression Characteristics

• Reduces Resolution

• Data is Lost Permenantly

• Discards Parts Of Data That Are Imperceptible

Lossless Compression Characteristics

• No data is lost (file is identical to original)

• Used when data integrity is critical

• Uses replacement algorithms like RLE (Run Length Encoding)

RLE (Run Length Encoding)

Compresses adjacent identical pixels/characters. Encodes the run into two values: the character/pixel value and the number of repetitions.

Easy Definition: Repeated sequences of the same characters are replaced by a single copy of the character and a count of the number of characters.

General Method to Reduce Image File Sizes

• Reduce resolution

• Lower bit depth

• Crop unnecessary parts

General Method to Reduce Video File Size

Reduce frame rate

General Method to Reduce Audio File Size

Lower sampling rate/resolution

Compression Conclusion

Improves storage and speeds up transmission. Lossless methods preserve accuracy; lossy methods prioritize size and speed.