It is really a coincidence that about a week after I looked at their Pyramid codec I got reminded that there’s another codec of theirs exists, probably related to the WNV1 codec I REd back in 2005.
So apparently the codec codes YUY2 in 8×8 blocks. Each block is prefixed with a bit telling whether it’s a coded or skipped block. Coded block have additional 4-bit mode that seems to determine which quantisation they’ll use. The data is packed as deltas to the previously decoded value (per-component) using static codebook with values in -7..7 range (plus scaling by shifting left). There’s also an escape value in case raw value should be read instead. Overall it feels like Winnov Video 1 coding.
In other words, nothing remarkable but still a bit more advanced than usual DPCM-based intermediate codecs.