values encoded as three-bit signed values, so the negative values get codes after the positive values. The trees are built as canonical huffman trees

• -1: 2 bit
• 0: 1 bit
• +1: 2 bit

• -2: 3 bit
• -1: 3 bit
• 0: 1 bit
• +1: 3 bit
• +2: 3 bit

• -4: 5 bit
• -3: 4 bit
• -2: 4 bit
• -1: 3 bit
• 0: 1 bit
• +1: 3 bit
• +2: 4 bit
• +3: 5 bit

• -4: 5 bit
• -3: 5 bit
• -2: 4 bit
• -1: 3 bit
• 0: 1 bit
• +1: 3 bit
• +2: 4 bit
• +3: 4 bit