2001.03.30 14:23 "RLE compression", by Raphaël Marc

2001.03.31 02:35 "RE: RLE compression", by Gavin Gee

Packbits is definitely in this category. However, if you mean "run length encoding" in a generic sense, CCITTFAX Huffman RLE (K=0), G3 (K>=1) & G4 (K<0) do have encoded horizontal runs of white & black pixels internally. The bits used to represent the runs, however, is completely different. The TIFF spec has details on how the horizontal runs are encoded if you're interested.