Its a 2048 raw software screen buffer, with two 2-bit pixels per byte (one 2-bit pixel per nibble). Don't ask which pixel is which -- I always get confused by it! Just try it, and flip the order if you get "lucky" on the first try.

Buffer layout is row0, row1, .. row31. Each row is 128 pixels (64 bytes).

Look at /proc/empeg_screen.raw for an example.