A jpeg Huffman decoding circuit and its decoding method

Abstract

The invention discloses a joint photographic experts group (JPEG) Huffman decoding circuit and a decoding method thereof; in a JPEG file header Huffman mark decoding phase, the decoding method comprises the following steps that: (1) a Huffman minimal codeword table is established according to the number of Huffman codewords under different lengths, the bit widths of 16 codewords in the minimal codeword table are respectively 1 bit, 2 bits, 3 bits, 4 bits, 5 bits, 6 bits, 7 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits and 8 bits; (2) a Huffman minimal codeword address table is established according to the number of the Huffman codewords under different lengths; (3) the length of the current Huffman codeword is calculated according to sixteen comparison results which are in parallel and are smaller than a comparator, a run-length encoding value is worked out according to the minimum codeword address table and the decoding data is calculated, wherein the 16 bit widths which are smaller than the comparator are respectively 1 bit, 2 bits, 3 bits, 4 bits, 5 bits, 6 bits, 7 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits, 8 bits and 8 bits.

Description

technical field [0001] The invention relates to a JPEG Huffman decoding circuit and a decoding method thereof. Background technique [0002] Huffman coding is a commonly used lossless compression technology based on probability and statistics. It uses longer bits to encode codewords with higher probability of occurrence, and uses shorter bits to encode codewords with lower probability of occurrence. Thus a compression ratio very close to the theoretical limit is achieved. [0003] Traditional Huffman decoding is usually implemented by bit-by-bit comparison. This method first needs to reconstruct the Huffman code table used for decoding according to the encoding information. The code table needs to occupy a large storage space. The example in the JPEG standard The typical code table length is about 4Kbit. Secondly, the method of bit-by-bit comparison usually requires multiple clock cycles to decode a codeword, which greatly limits the decoding rate. [0004] The prior art ...

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Problems solved by technology

[0005] However, since the length of the Huffman code word in the JPEG code stream is up to 16 bits, the minimum code word table bit width in the above method is 16 bits. In addition, when the input code stream is compared with the minimum code word table, 16 lengths are required Only comparators with 1, 2, 3, ..., 15, 16 can decode the current codeword length, which will reduce the decoding speed and increase the hardware cost of the chip

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