Robert Prandolini

Architecture, philosophy, and performance of JPIP: internet protocol standard for JPEG2000

JPEG2000 is a family of technologies based on the image compression system defined in IS 15444-1. Presently, the ISO/IEC Joint Technical Committee of Photographic Experts (JPEG) is developing an international standard for interactivity with JPEG2000 files, called JPIP; it will become Part 9 of the standard. One of the main goals of JPIP is to exploit the multi-resolution and spatially random access properties of JPEG2000, to permit “smart dissemination” of the data for client-server based applications. The purpose of this paper is to discuss the principles and philosophy of operation underlying the JPIP standard, to outline aspects of the architecture of JPIP systems, and to report on the performance of a prototype implementation.

Coding of surveillance imagery for interpretability using local dimension estimates

This paper introduces a novel image coding principle: the coding of an image to maximize its interpretability versus bit-rate performance. For large surveillance images it would be more appropriate if the encoded wavelet coefficients were prioritized in their order of importance for interpretability. This paper presents one method for such a system. The importance values are derived from the estimates of the local dimension in image regions, which is a measure on the local image dynamics. The scale of the area used for the estimates is dyadic and maps to the image scale-space. The wavelet coefficients from a Mallat decomposition are prioritized according to their importance, based on the local information dimension estimates. Subjective evaluations have shown that this importance prioritization schema is preferred over the traditional progressive PSNR optimal approach. The paper will discuss the implementation of an importance prioritization schema for the EBCOT image coder, which is the algorithm used in JPEG2000. The concept of importance prioritization for interpretability may benefit future low bit-rate image and video coding.

Importance assignment to regions in surveillance imagery to aid visual examination and interpretation of compressed images

A simple bottom-up, context-free, algorithm for the identification of regions-of-interest in surveillance imagery that correlates well with the visual attention processes in humans is presented. The aim is to develop new criteria related to human performance in visual examination and interpretation, and perhaps to be able to design a more biologically plausible perceptive JPEG2000 image compression system. The paper introduces a quadtree computational platform to assign the importance of regions in an importance map, using several bottom-up, low-level factors, which have been found to influence visual attention. This technique is useful for images with objects or structures with importance dependent on resolution and field of view. Further work incorporating higher-level visual factors and context dependent criteria will allow regions of importance to be determined with greater accuracy.

Importance coding of still imagery based on importance maps of visually interpretable regions

The paper proposes a general framework for the importance coding of still images to maximise the interpretability versus bitrate performance. The interpretability of an image to achieve maximum content recognition is important in a diverse range of applications such as surveillance and medical. Importance coding aims to address this problem by prioritisation of the encoded image bit-stream based on the importance of regions in an image. Consequently, the most important features required for interpretability are encoded and transmitted earlier in the encoded image bit-stream. The notion of importance maps, which provide a systematic approach for the assignment of relative importance of regions in an image, are presented and its use in importance coding is developed. One highly desirable advantage of the proposed importance coding framework is that it can be implemented by the EBCOT (embedded block coding with optimised truncation) coder, which has been selected as the core-coding algorithm in JPEG 2000.

Use of UDP for efficient imagery dissemination

In the defence organization, imagery represents an important information source for users in the tactical, operational and strategic environments. Its wider dissemination may rely on deployed communication networks that are often unstable with high bit error rates and outages. This paper presents efficient techniques for imagery dissemination using the user datagram protocol (UDP). The use of UDP is compared with the popular transmission control protocol and shown to be superior in performance for error prone IP networks. We have employed a wavelet based coder producing an embedded bit-stream. The packetization of the bit-stream is investigated and we show that it is better to tile an image into independent embedded bit-streams when the network performance is poor. Variable-size tiling is compared with, and shown to be superior to, a fixed-size tiling approach. Selective re-transmission of lost packets is implemented for efficient imagery dissemination using UDP. The selective re- transmission scheme is a function of network bandwidth, delay times, error rates and the significance of the packet.

Importance prioritization coding in JPEG2000 for interpretability with application to surveillance imagery

Surveillance imagery is used for supporting the decision processes in strategic, operational and tactical tasks. The visual tasks associated with the interpretation of such imagery may require the detection of targets or the recognition of image contents. It is important for an image compression scheme to be tuned to maximise the imagerys interpretability (or content recognition) performance. Importance prioritisation coding of an image, where image contents are prioritised in order of importance for interpretability, is hence a very desirable feature for such applications. The paper presents a flexible framework for such prioritisation in JPEG2000 using regions of interests (ROIs) and importance maps. The coding scheme allows multiple and arbitrary shaped ROIs to be defined at different spatial locations, sub-band orientations and scale, and subsequently be prioritised using arbitrary importance scores. No ROI or importance map information need to be signalled to the decoder, and progressive lossy to lossless reconstruction of ROIs and the background is also possible. Furthermore, the prioritisation maintains the JPEG2000 code-stream syntax and can be decoded by any generic JPEG2000 decoder.

Digital coding of covert audio for monitoring and storage

This paper offers an overview of the requirements of digital covert audio acquisition (DCAA) and presents a codec that provides both real-time monitoring and efficient on-site storage. The codec incorporates an M-band discrete wavelet transform (DWT) subband decomposition with lattice vector quantisation (LVQ) of the wavelet coefficients to compress high quality covert audio to less then 32 kbps. Both objective quality measures for the monitoring channel and average growth rate of the on-site storage are presented to demonstrate that the proposed codec achieves the requirements of a covert audio acquisition system.

Importance coding of surveillance imagery for interpretability using quadtree dynamic importance maps

This paper presents an importance coding technique to improve the interpretability versus bit-rate performance for an image compression system. The term interpretability is a subjective image quality measure of the content recognition performance by trained image analysts. A quadtree dynamics importance map is used to aid the prioritisation of the image encoded bit-stream according to its importance for interpretability. The importance map is generated using several bottom-up, context-free features for the identification of regions-of-interest in surveillance imagery that correlate well with visual attention processes in humans. Traditional PSNR progressive coders rely on descending wavelet coefficient magnitudes to prioritise the encoded bit-stream. The importance coder discussed in the paper is designed such that the JPEG2000 standard can implement the importance prioritisation schema (without the need to send the importance map information). Subjective evaluations indicate that the proposed schema is better than traditional PSNR progressive coders for the purpose of very low bitrate content recognition.