On2 VP4

• FourCC: VP40
• Company: On2
• Samples: http://samples.mplayerhq.hu/V-codecs/VP4/

This codec has source code base common with its predecessor but sets version to 2.

Frame header

The same as VP3 with some extensions.

• Frame type - 1 bit
• Unused - 1 bit
• DCT Q mask - 6 bits

For frame type 0 (BASE_FRAME):

• version byte 0 - 8 bits
• version - 5 bits (should be 2)
• key frame type - 1 bit
• spare bits - 2 bits
• ??? - 8 bits
• ??? - 8 bits
• ??? - 5 bits
• ??? - 3 bits
• ??? - 5 bits
• ??? - 3 bits
• ??? - 2 bits