In lossless compression methods, the received data are the exact replica of the sent data.
In run-length encoding, repeated occurrences of a symbol are replaced by a symbol and the number of occurrences of the symbol.
In Huffman coding, the code length is a function of symbol frequency; more frequent symbols have shorter codes than less frequent symbols.
In LZ(Lempel Ziv) encoding, repeated strings or words are stored in variables.
An index to the variable replaces the string or word.
LZ encoding requires a dictionary and an algorithm at both sender and receiver.
Joint Photographic Experts Group (JPEG) is a method to compress pictures and graphics.
The JPEG process involves blocking, the discrete cosine transform, quantization, and
lossless compression.Motion Pictures Experts Group (MPEG) is a method to compress video.
MPEG involves both spatial compression and temporal compression.
The former is similar to JPEG, and the latter removes redundant frames.
To temporally compress data, the MPEG method divides frames into 3 categories: I-frames, P-frames, and B-frames.