Indeo 2

• FourCCs: RT21
• Company: Intel, then Ligos
• Samples: http://samples.mplayerhq.hu/V-codecs/RT21/

First this codec was called "Real-Time Video 2" (hence the FourCC), then was renamed to Indeo.

This codec operates with static Huffman-coded deltas. For intraframes those are the deltas to the previous line of current frame. For interframe deltas between this and previous frame are stored.