Kega Video

• FourCC: KGV1
• Sample: http://samples.mplayerhq.hu/V-codecs/kgv1.avi

Codec used for capturing videos in some Sega emulator called Kega.

It produces output in RGB565 and coding is LZ-like.

Frame starts with two bytes which code real dimensions as multiple of 8 minus 1 block (i.e. width = (src[0] + 1) * 8;, same for height), the rest is coded data.

Coded data consists of 16-bit LSB control words with possible extensions:

1. 111x xxyy yyyy yyyy - copy (y+3) pixels from positive offset offsets[x]. If offsets[x] is not yet defined for this frame, read 24-bit LSB word after this code word. Naturally, this is possible only in interframes.
2. 110y yyyy yyyy yyyy - read run length value minus four from next byte (i.e. run = get_byte() + 4) and copy pixels from negative offset y+1 (e.g. offset 0 means RLE, offset 1 means repeating last two pixels, etc.)
3. 101y yyyy yyyy yyyy - same as above but always copy 3 pixels from given offset
4. 100y yyyy yyyy yyyy - same as above but always copy 2 pixels from given offset
5. 0ppp pppp pppp pppp - p is pixel value, simply output it.

Implementing decoder is left as an exercise for reader.