YLC

• Website: http://spring-fragrance.mints.ne.jp/aviutl/ (Japanese)
• FourCC: YLC0
• Sample: http://samples.libav.org/V-codecs/ylc0.avi

The website names it as "YUY2 Lossless Codec".

Format

bytes  0- 3 'YLC0'
bytes  4- 7 zero
bytes  8-11 offset to luma plane (should be 16)
bytes 12-15 offset to chroma plane

Bitstream is read as 32-bit little-endian words MSB.

Luma plane contains residues stored as exp-Golomb codes (unary-coded exponent + N bits of mantiss).

Chroma plane contains chroma values coded in groups and uses static Huffman trees:

 if (get_bit()) {
     val = decode_sym(tree1);
     if (val < 0xE1) {
         output chroma_table[val];
     } else {
         for (i = 0; i < (val - 0xDF); i++)
             output {0, 0, 0, 0}
     }
 } else {
     u0 = decode_sym(tree2);
     v0 = decode_sym(tree3);
     u1 = decode_sym(tree2);
     v1 = decode_sym(tree4);

     output { u0, v0, u0 + u1, v1 }
 }

Looks like for luma plane median prediction is used and for chroma only left prediction is used.