Modified Huffman
From Just Solve the File Format Problem
Modified Huffman, sometimes called MH, is a data compression algorithm used in 1-dimensional CCITT Group 3 to compress bi-level images. The data is first run-length encoded, and then Huffman coding is applied to the run lengths.
It's not clear whether "Modified Huffman" can also refer to the general concept of RLE combined with Huffman coding.
Specifications
See CCITT Group 3.
