Kostya's Boring Codec World

There’s Bink variant without any samples known but with decoder present — Bink version d (aka Bink 0.6b). While it’s version closer to Bink-b (aka 0.5b) it’s the same in operation principles with all later variants (telltale sign is integer DCT instead of floating point one in Bink-b). Here are some details on how it differs from later Bink variants.

The main difference is lack of scaled blocks, hence block types got reshuffled as well:

• type 1 — pattern run
• type 2 — intra DCT block
• type 3 — inter DCT block
• type 4 — inter DCT block (lossless)
• type 5 — single colour fill block
• type 6 — pattern (2-color) block
• type 7 — motion block (looks like it uses overlapped copy like Bink-b though)
• type 8 — raw block

In other words it’s not that special and demonstrates the evolution of Bink versions.

This codec is a collaborative effort — both me and some bogan from Melbo have been slacking on it for quite a long time.

Strewth, it’s almost the same as its successor, the real Bink known everywhere (Bink-b or 0.5 is not even mentioned in official Bink history). The main differences are lack of Huffman coding (all bundle elements are just stored in predefined number of bits), different scan-run coding (instead of storing it in a separate bundle, run values are stored in bitstream with minimum number of bits needed to code the biggest run from that point, i.e. 6 bits at the beginning but less than five bits for runs in the second half of block) and DCT uses floating-point coefficients (though the same ones for all practical purposes).

The only thing that differs significantly is motion compensation. Bink version b seems to use the same frame for all coming decoding and actually motion compensation in the first frame copies already decoded block from the same frame. After discovering that fact I was able to obtain perfect first frame in many cases and sometimes the rest of video was also decoded fine except for few glitches. The only puzzling thing is that vertical motion vector offset in the first frame seems to have slightly different value, so <-8,15> actually means “copy data from the previous left block” and <0,7> means “copy data from the top block” while such translation is not needed for all next frames.

Since all known samples are from the Heroes of Might and Magic III game and they are duplicated with Smacker samples, there’s not much interest on finishing that decoder and integrating it into current FFmpeg Bink decoder (I’ve done it as a dirty hack). So no prawn cracker for you, mate.

Update: proof-of-a-concept hack (produces minor artifacts too) can be downloaded here.

I don’t think you’ll ever encounter Bink video version ‘b’, known samples were dug out from game data of certain New World Computing games. And looks like they are not supported by official software anymore. But why that can stop us from looking at it?

This information is based on findings by certain FFmpeag deaveloper and me looking at disassembly for similarities with newer Bink version.

The main difference is that this version does not employ Huffman coding at all. All bundle data is stored in raw form, 4-11 bits per entry depending on bundle type. Number of elements in bundle is stored as 13-bit number, newer version uses different number of bits depending on plane width.

Also this Bink used floating-point version of DCT (but constants are the same as in integer version employed by latter codec version).

Coding methods (block types) are in totally different order as well. And 8×8 -> 16×16 scaling block type was not devised in that time either. Bundles contain slightly different data as well — for example, quantisers and number of residue masks are there but pattern run block uses diminishing number of bits to code runs instead of reading it from bundle (indeed, if you have to decode 48 more block elements you need to read 6 bits but when there are mere 7 block elements left 3 bits are enough).

I’ve not looked too close at DCT coefficient/residue coding methods but they seem to resemble those used in newer version of codec.

Short conclusion: while Bink video codec steadily improved, most concepts are remained the same (but there’s a bigger leap between versions ‘b’ and ‘f’ than between ‘f’ and ‘i’, the latter are almost backwards compatible). And maybe we’ll see decoder for it in FFmpeg for completeness sake.