In the recent month I was not very productive, so I’d like to talk about codecs that I’m not likely to finish soon (not that I’m going to finish any codec soon anyway).
Here’s the best output I could get from G2M2 or G2M3 data by decoding JPEG part of the tiles. ELS part still needs some work since it’s boring â€” 10-neighbour prediction, differential pixel decoding and other wonders of binary coder.
Certain Intermediate Codec
I managed to reverse engineer some parts of it. First you have so-called fixed header, then you have strip sizes and then strip data with some header as well. The way it’s coded is also more or less clear. But some connecting details â€” like how those strips are divided (now it looks like 96×1 macroblocks or equally ridiculous).
Since it’s QuickTime it’s hard to say where are the entry points to the codec and what functions are invoked.
Also the only usable binary (with debug symbols) is PowerPC only. It’s nice platform but I still need to learn some of its peculiarities.
It turns out that it is slightly simplified variant of TwinVQ. It does not have variable-length codes, all values are read as fixed bits (depending on sampling rate and bitrate of course). The only catch is that it’s hard to find where such description is retrieved or generated. And existing codebooks are somewhat different.