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Implementacja w układach FPGA dekompresji danych zgodnie ze standardem Deflate

Jamro E., Wiatr K.

Pomiary Automatyka Kontrola

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2013

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R. 59, nr 8

739--741

PL

Otwarty standard kompresji danych, Deflate, jest szeroko stosowanym standardem w plikach .gz / .zip i stanowi kombinację kompresji metodą LZ77 / LZSS oraz kodowania Huffmana. Niniejszy artykuł opisuje implementację w układach FPGA dekompresji danych według tego standardu. Niniejszy moduł jest w stanie dokonać dekompresji co najmniej 1B na takt zegara, co przy zegarze 100MHz daje 100MB/s. Aby zwiększyć szybkość, możliwa jest praca wielu równoległych modułów dla różnych strumieni danych wejściowych.

EN

This paper describes FPGA implementation of the Deflate standard decoder. Deflate [1] is a commonly used compression standard employed e.g. in zip and gz files. It is based on dictionary compression (LZ77 / LZSS) [4] and Huffman coding [5]. The proposed Huffman decoded is similar to [9], nevertheless several improvements are proposed. Instead of employing barrel shifter a different translation function is proposed (see Tab. 1). This is a very important modification as the barrel shifter is a part of the time-critical feedback loop (see Fig. 1). Besides, the Deflate standard specifies extra bits, which causes that a single input word might be up to 15+13=28 bits wide, but this width is very rare. Consequently, as the input buffer might not feed the decoder width such wide input date, a conditional decoding is proposed, for which the validity of the input data is checked after decoding the input symbol, thus when the actual input symbol bit widths is known. The implementation results (Tab. 2) show that the occupied hardware resources are mostly defined by the number of BRAM modules, which are mostly required by the 32kB dictionary memory. For example, comparable logic (LUT / FF) resources to the Deflate standard decoder are required by the AXI DMA module which transfers data to / from the decoder.

2

Sprzętowa akceleracja wybranych algorytmów kompresji obrazu nieruchomego w standardzie JPEG

Koryciak S., Dąbrowska-Boruch A., Wiatr K.

Pomiary Automatyka Kontrola

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2012

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R. 58, nr 7

593-595

PL

Artykuł opisuje opracowanie akceleratora dla wybranych algorytmów kompresji obrazu nieruchomego. Do jego sprzętowej realizacji został wykorzystany język opisu sprzętu VHDL. Wynikiem pracy była skuteczna implementacja na układ programowalny dekompresora obrazów nieruchomych zapisanych w standardzie JPEG ISO/IEC 10918-1(1993), trybie Baseline będącym podstawowym i obowiązkowym trybem dla tego standardu. Szczególną uwagę poświęcono wyborowi i implementacji dwóch najważniejszych zdaniem autora algorytmów występujących w omawianym standardzie.

EN

Image compression is one of the most important topics in the industry, commerce and scientific research. Image compression algorithms need to perform a large number of operations on a large number of data. In the case of compression and decompression of still images the time needed to process a single image is not critical. However, the assumption of this project was to build a solution which would be fully parallel, sequential and synchronous. The paper describes the development of an accelerator for selected still image compression algorithms. In its hardware implementation there was used the hardware description language VHDL. The result of this work was a successful implementation on a programmable system decompressor of still images saved in JPEG standard ISO / IEC 10918-1 (1993), Baseline mode, which is a primary, fundamental, and mandatory mode for this standard. The modular system and method of connection allows the continuous input data stream. Particular attention was paid to selection and implementation of two major, in the authors opinion, algorithms occuring in this standard. Executing the IDCT module uses an algorithm transformation IDCT-SQ modified by the authors of this paper. It provides a full pipelining by applying the same kind of arithmetic operations between each stage. The module used to decode Huffman's code proved to be a bottleneck

3

Selective low bit-rate image compression using wavelet transform

Santos Conde J., Niederholz J., Hosticka B.

Image Processing & Communications

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2000

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Vol. 6, no 1-2

45-55

EN

A novel image compression approach reaching very low bit-rates by utilization of region of interest information in the transform domain of the discrete wavelet transform (DWT) is introduced. The content-dependent image coding scheme yields an improved quality in the regions of interest while the background regions distant from the center of interest are smooth. Coding distortions are visible for very low bit-rates outside the regions of interest which is tolerable for the purpose of content dependent image compression. The significance of certain image regions can be selected interactively or determined by appropriate image segmentation schemes. Qualitative results are presented for several compression ratios and a comparison with JPEG compression is made.