JPEG is a popular DCT-based still image compression standard, which has played an important role in image storage and transmission since its development. Several papers have been published to improve the performance of JPEG. Advanced image coding (AIC) combines intra frame block prediction from H.264 with a JPEG-style DCT, followed by context adaptive binary arithmetic coding (CABAC) used in H.264. It performs much better than JPEG and close to JPEG-2000. In this paper, we propose a modified AIC (M-AIC) by replacing the CABAC in AIC with a Huffman coder and an adaptive arithmetic coder. The simulation results demonstrate that M-AIC performs much better than JPEG, close to JPEG-2000 and AIC, and a little bit better than AIC in some low bit rate range.

Modified Advanced Image Coding

An encoder (10) is provided for encoding input data (D1) to generate corresponding encoded output data (D2). The encoder (10) includes a data processing arrangement for generating a run-length encoded (RLE) representation of the input data (D1). Moreover, the encoder (10) is operable to split the run-length encoded (RLE) representation into a plurality of parts (A, B), wherein at least one part is associated with original symbols and at least another part is associated with counters representative of occurrence of the original symbols. Furthermore, the encoder (10) is operable to encode the plurality of parts (A, B) separately to generate the encoded output data (D2). There is also provided a corresponding decoder (50) for decoding the encoded data (D2) to generate corresponding decoded output data (D3). Additionally, there is provided a codec (20) including the aforesaid encoder (10) and decoder (50). Optionally, the original symbols include at least one of: characters, alphabetic elements, numbers, bits, bytes, words.

Data encoder, data decoder and method

The present disclosure provides a method for data compression In one embodiment the method may include converting data from a first color space to a second color space to generate converted data The method may further include receiving said converted data at a discrete cosine transform (DCT), said DCT being configured to generate at least one DCT coefficient The method may additionally include receiving said at least one DCT coefficient from said discrete cosine transform at a quantizer, said quantizer being configured to quantize said at least one DCT coefficient and to provide at least one quantized coefficient to an entropy encoder, said entropy encoder including a first Huffman table corresponding to a number of bits used to encode an amplitude of a non-zero AC coefficient

Separate huffman coding of runlength and size data of dct coefficients

Image compression is an efficient method used to reduce the size of the image. JPEG algorithm has been considered as one of the famous techniques used for image compression. This paper proposed and implemented an optimized hardware solution called Hybrid Compression using Faster Color Conversion and Run Length (HC-FCC-RL) algorithm for JPEG algorithm based on FPGA to reduce the latency and accelerate the compression process. The paper also proposed a Fast Color Conversion with Approximation (FCCA) step to accelerate the conversion process from RGB to YC b C r . Using approximate techniques will reduce the number of resources used as well as the latency with some percentage error. In addition, the paper proposed a Parallel Run Length (P-RL) algorithm to speed up the design. The enhancement approach in this paper aimed to optimize the overall design of the JPEG algorithm targeting color images. The HC-FCC-RL architecture was implemented in Verilog, synthesized on FPGA board and evaluated. The color conversion architecture uses 331 logic elements, a latency of 13.930ns for converting the three colors component of blocks and a power dissipation of 861.03mW. The percentage errors for the color conversion is 11.6%, 1.8% and 5.3% for Y, C b , Cr components, respectively. The P-RL performs better than existing work by saving 48.36 % in logic elements, 53.79 % in latency and 62.86% in power dissipation. The proposed work demonstrated superior performance compared to current work in the literature.

Enhanced JPEG Algorithm for Colored Images Based on FPGA Implementation

We introduce an entropy coding method to enhance the compression efficiency of JPEG. Because run-length coding and earlytermination work more effectively for longer zero sequences, we extract ones and negative ones from the coefficients and reduce the magnitude of all coefficients by one. The extracted coefficients are encoded with a designated entropy coding method. The proposed method can transmit images in two parts progressively, where the first contains JPEG-compatible image with a small amount of degradation and the second is used to add fine details. Our method improves the compression ratio by more than 5% without sacrificing the efficiency of JPEG. key words: JPEG, entropy coding, sub-stream extraction

On Improving JPEG Entropy Coding by means of Sub-Stream Extraction

A number of image compression systems have been developed to save storage space and transmission bandwidth. The field of image compression has witnessed a lot of research on improving JPEG or evolving a codec with better performance. In the JPEG standard, run length encoding is used to code the string of zeros resulting from crude quantization of AC coefficients. In this paper we propose modified runlength JPEG (MR-JPEG), which uses separate coding of three symbols (RUNLENGTH, SIZE, AMPLITUDE) to code the information. To compare the results with the earlier scheme, we use two parameters-maximum difference (MD) for perceptual quality measurement and size (in KB's) for compression. Our results show that for large size images (512times512 and above), proposed scheme demonstrates higher compression with better quality.

V. Bhandari

Papers

Modified Runlength Coding for Improved JPEG Performance