Compression

Lossy
- Huffman
- Run length
- Lempel Ziv
- eg. Text & Program
Lossless
- JPEG
- MPEG
- MP3
- Images, Videos, Audio
Run Length Compression
- AAAABBCCC
  - -> 3A2B3C
- 0000011111000111
  - -> 0:4, 1:5, 0:3, 1:3
  - -> 00100 00101 00011 00011
- Good for bit stream with continuous value
Huffman (Entropy) Coding
- Entropy means the minimum number of bits needed per symbol on average
- Count all occurrences of the symbol
- Take the smallest pair and work until one left
- Prefix free
  - Unary Code
  - Gamma code
  - Delta code
    - Difference with prev value
    - When coded 0 entropy
  - Omega code
Lempel Ziv Coding
- Dictionary-based encoding
- Two steps:
  - Building index dictionary
  - Compressing words with index
- LZW
  - PKZIP
- LZSS
  - Winrar
- Deflate
  - GZIP, WinZip
- LZMA - 7ZIP
Perceptual Transform Coders for audio/images/video
- Fourier
- DCT
- Vector Quantization
Image and Video compression applications and algorithms
- JPEG
- H.263
- MPEG Video
- MPEG Audio
Entropy Coding
- Sum of log(2)p

The main difference between LZ77 and LZSS is that in LZ77 the dictionary reference could actually be longer than the string it was replacing.

LZSS is primarily used across.

Represent the symbols using the minimum number of bits.

zlib, LZO, LZF, FastLZ, and QuickLZ.

Snappy