I moved to the Matroska project as a founding member when it split from the MCF project. I was involved in much of the discussion during the early stages of development of the Matroska container format. At the time I was most fluent with Java, and I wrote some basic classes to read the EBML file format which were later extended to support reading of Matroska files.
I also wrote the original code to allow storing MPEG-1/MPEG-2 video in the container and this was incorporated into MKVMerge. This involved reading the MPEG video specs and parsing the bitstream syntax to break the stream into individual frame elements and translating the metadata for frames to the Matroska format.