PUMA publications for /user/thomasrichter/Quantization,Thu Mar 10 09:18:49 CET 2016Lake Buena Vista, Florida, USA2012 IEEE International Conference on Image Processing ICIP 2012sep1061 - 1064{SSPQ} - spatial domain perceptual image codec based on subsampling and perceptual quantization2013JPEG-LS Perceptual coding, distortion, just-noticeable perceptual quantization, A spatial domain perceptual image codec based on subsampling and perceptual quantization (SSPQ) guided by the just-noticeable distortion (JND) profile is proposed. SSPQ integrates perceptual image coding and progressive transmission in one framework. The input image is first subsampled by a factor of two in both dimensions and the subsampled image is compressed without loss. The subsampled image provides a basis for both predicting the input pixels by interpolation and estimating the JND values for each pixel. Residual quantization thresholds are set to the estimated JND values for a perceptually tuned compression. Quantized residuals are progressively encoded by a context-based Golomb coder with run-length coding capacity. Experimental results show over 50% improvement in compression performance on average for the proposed SSPQ codec compared to the lossless JPEG-LS.Thu Mar 10 09:18:49 CET 2016Snowbird, UTData Compression Conference (DCC), 2010mar79-88{S}patial {C}onstant {Q}uantization in {JPEG} {XR} is {N}early {O}ptimal2010Annealing, Distortion JPEG Quantization, Rate Simulated Theory, Variable XR, coding, compression, data distortion image optimisation, quantisation rate theory, vector The JPEG XR image compression standard, originally developed under the name
HD-Photo by Microsoft, offers the feature of spatial variably quantization;
its codestream syntax allows to select one out of a limited set of possible
quantizers per macro block and per frequency band. In this paper, an
algorithm is presented that finds the rate-distortion optimal set of quantizers,
and the optimal quantizer choice for each macro block. Even though it
seems plausible that this feature may provide a huge improvement for images
whose statistics is non-stationary, e.g. compound images, it is demonstrated that
the PSNR improvement is not larger than 0.3dB for a two-step heuristics
of feasible complexity, but improvements of up to 0.8dB for
compound images are possible by a much more complex optimization strategy.Thu Mar 10 09:18:49 CET 2016Snowbird, UTData Compression Conference (DCC), 2011mar474{D}eadzone {B}ased {R}ate {A}llocation for {JPEG} {XR}2011JPEG Optimal Quantization Quantization, Rate-Distortion XR!!, Similar to the JPEG image compression standard, the JPEG XR image
compression solely controls the image quality loss and hence the output rate
by means of the quantizer bucket sizes; a precise rate control mechanism
like the EBCOT rate allocation algorithm in JPEG 2000 is not specified, and
hence rate-distortion optimality of the quantizer is, in general, not given.
In this work, a simple rate-control mechanism for JPEG XR is introduced that
allows an efficient control of the quantizer towards rate-distortion
optimality. One possibility to implement this quantizer control would be to
use the spatial variable quantization feature of JPEG XR, but it was seen in
an earlier work that the additional side information required to transmit
the quantization setting almost compensates the PSNR gain of variable
quantization and complicates the rate allocation process by requiring an
additional quantizer allocation step.
However, while JPEG XR defines the image reconstruction process completely,
an encoder still has the freedom to select the deadzone size of the
quantizer; this mechanism has the additional advantage that no additional
side information needs to be transmitted and that the deadzone size is not,
unlike the quantizer bucket size, constrained to a set of pre-defined
values specified in the standard.
It is found that the image quality of JPEG XR can be improved by about 0.2
to 0.4 dB by performing a rate-distortion optimal selection of the deadzone;
this gain is seen to be comparable to the PSNR loss of a JPEG 2000 codec
where, for experimental reasons, EBCOT rate control has been turned off.