 In the common case a single bit is used per symbol per table and the worst case—going from length 1 to length 20—would require approximately 37 bits.As a result of the earlier MTF encoding, code lengths would start at 2–3 bits long (very frequently used codes) and gradually increase, meaning that the delta format is fairly efficient, requiring around 300 bits (38 bytes) per full Huffman table.A bitmap is used to show which symbols are used inside the block and should be included in the Huffman trees.