Compression algorithm incorporating a feedback loop for dynamic selection of a predefined Huffman dictionary

A method of implementing a feedback loop for selecting a preset Huffman dictionary from a bank of predefined Huffman dictionaries for use in a hardware data encoder, said method comprising:

• speculatively selecting for encoding of input data, a dictionary from a bank of predefined dictionaries, in accordance with a predefined criteria by analyzing a predetermined portion of the input data with the dictionaries of the bank of dictionaries;
• encoding the input data by an encoder, using the selected dictionary;
• monitoring the performance of the selected dictionary as compared to other dictionaries in the bank;
• and
• switching to encoding the input data in accordance with a different selected dictionary if such switching is determined to be advantageous based on the monitoring.

A feedback loop for selecting a preset Huffman dictionary from a bank of predefined Huffman dictionaries for use in a hardware data encoder, comprising:

• a repetition removal encoder operative to count the frequency of appearances of literals, lengths and distances in an input data block;
• a plurality of preset encoders and a static Huffman encoder;
• a preset selector operative to speculatively choose one of said preset encoders;
• a feedback loop circuit operative to count the length of symbols output by each preset encoder;
• and
• if the preset encoder corresponding to the lowest length is not the currently selected encoder, then end current block and said preset selector operative to change its choice of optimal preset encoder to the preset encoder corresponding to the lowest length,
• wherein said feedback loop is operative to measure the difference in compression ratio between the optimal compression ratio and that achieved by the currently selected preset encoder, and if the difference is greater than a threshold, discard encoded data of a current data block and have it re-encoded with the new optimal preset encoder.

A data encoder, comprising:

• a repetition removal encoder operative to receive input data, encode the data by removing repetitions and representing the data by literals lengths and distances, and count the frequency of appearances of literals, lengths and distances in the encoded data;
• a selector operative to choose one of a plurality of predefined Huffman dictionaries to be used in encoding the output of the repetition removal encoder;
• a Huffman encoder operative to encode the output of the repetition removal encoder, using the dictionary selected by the selector;
• and
• a feedback loop circuit operative to apply multiple predefined analyzing schemes on the data output from said repetition removal encoder, without actually encoding the data output in accordance with other predefined dictionaries, so as to evaluate the efficiency of the selected dictionary currently used by the Huffman encoder;
• wherein the selector is operative to change its choice of dictionary responsive to output from the feedback loop circuit.