Mark R. Pickering

A perceptually efficient VBR rate control algorithm

This paper describes a rate control algorithm for a variable bit-rate (VBR) video coder. The algorithm described varies the quantizer step size of the coder according to properties of an image sequence that affect the perception of errors. The algorithm also limits the output bit-rate of the coder without the use of buffers to more efficiently use network bandwidth. It is shown that a VBR encoder using this algorithm will provide decoded image sequences with a consistent perceived quality that is comparable with, or better than, the perceived quality of images coded with a CBR encoder.

Connecting Health and Technology (CHAT): protocol of a randomized controlled trial to improve nutrition behaviours using mobile devices and tailored text messaging in young adults

BackgroundIncreasing intakes of fruits and vegetables intake, in tandem with reducing consumption of energy-dense and nutrient poor foods and beverages are dietary priorities to prevent chronic disease. Although most adults do not eat enough fruit and vegetables, teenagers and young adults tend to have the lowest intakes. Young adults typically consume a diet which is inconsistent with the dietary recommendations. Yet little is known about the best approaches to improve dietary intakes and behaviours among this group. This randomised controlled trial aims to evaluate the effectiveness of using a mobile device to assess dietary intake, provide tailored dietary feedback and text messages to motivate changes in fruit, vegetable and junk food consumption among young adults.Methods/designThe CHAT project will involve the development of the mobile device food record (MDFR), and evaluation of dietary feedback and implementation of a 6-month intervention in young adults aged 18 to 30 years. The participants will be randomly assigned to one of three groups (1) Intervention Group 1: MDFR + Text Messages + Dietary Feedback; (2) Intervention Group 2: MDFR + Dietary Feedback; (3) Control Group 3: MDFR, no feedback. All groups will undertake a 3-day dietary record using the MDFR but only the Intervention Groups 1 and 2 will receive tailored dietary feedback at baseline and at 6-months which will consist of assessment of serves of fruits, vegetables and junk food in comparison to dietary recommendations. Tailored nutrition text messages will be sent to Intervention Group 1 over the 6 months. Data will be collected at baseline and again at the 6-month completion.DiscussionThis trial will test if applications running on mobile devices have potential to assess diet, provide tailored feedback and nutrition messages as an effective way of improving fruit and vegetable consumption and reducing energy-dense nutrient poor foods in young adults. The CHAT project will assess the impact of the intervention on behavioural intention to eat a more healthful diet. This innovative approach if successful may provide a means to deliver a low cost health promotion program that has the potential to reach large groups, particularly young adults.Trial registrationAustralian and New Zealand Clinical Trials Registry ACTRN12612000250831

A Video Watermarking Scheme Based on the Dual-Tree Complex Wavelet Transform

A watermarking scheme that discourages theater camcorder piracy through the enforcement of playback control is presented. In this method, the video is watermarked so that its display is not permitted if a compliant video player detects the watermark. A watermark that is robust to geometric distortions (rotation, scaling, cropping) and lossy compression is required in order to block access to media content that has been re-recorded with a camera inside a movie theater. We introduce a new video watermarking algorithm for playback control that takes advantage of the properties of the dual-tree complex wavelet transform. This transform offers the advantages of the regular and the complex wavelets (perfect reconstruction, shift invariance, and good directional selectivity). Our method relies on these characteristics to create a watermark that is robust to geometric distortions and lossy compression. The proposed scheme is simple to implement and outperforms comparable methods when tested against geometric distortions.

A new multi-modal similarity measure for fast gradient-based 2D-3D image registration

2D-3D image registration has been adopted in many clinical applications such as image-guided surgery and the kinematic analysis of bones in knee and ankle joints. In this paper we propose a new single-plane 2D-3D registration algorithm which requires far less iteration than previous techniques. The new algorithm includes a new multi-modal similarity measure and a novel technique for the analytic calculation of the required gradients. Our experimental results show that, when compared to existing gradient and non-gradient based techniques, the proposed algorithm has a wider range of initial poses for which registration can be achieved and requires significantly fewer iterations to converge to the true 3D position of the anatomical structure.

Multi-spectral remote sensing image registration via spatial relationship analysis on sift keypoints

Multi-sensor image registration is a challenging task in remote sensing. Considering the fact that multi-sensor devices capture the images at different times, multi-spectral image registration is necessary for data fusion of the images. Several conventional methods for image registration suffer from poor performance due to their sensitivity to scale and intensity variation. The scale invariant feature transform (SIFT) is widely used for image registration and object recognition to address these problems. However, directly applying SIFT to remote sensing image registration often results in a very large number of feature points or keypoints but a small number of matching points with a high false alarm rate. We argue that this is due to the fact that spatial information is not considered during the SIFT-based matching process. This paper proposes a method to improve SIFT-based matching by taking advantage of neighborhood information. The proposed method generates more correct matching points as the relative structure in different remote sensing images are almost static.

Efficient spatial-spectral compression of hyperspectral data

Mean-normalized vector quantization (M-NVQ) has been demonstrated to be the preferred technique for lossless compression of hyperspectral data. In this paper, a jointly optimized spatial M-NVQ/spectral DCT technique is shown to produce compression ratios significantly better than those obtained by the optimized spatial M-NVQ technique alone.

A robust codec for transmission of very low bit-rate video over channels with bursty errors

We describe a robust codec for the transmission of very low bit-rate video over channels with a variety of errors, including random and bursty bit errors and packet loss. The codec exploits adaptivity to give good performance with a low overhead. By only protecting macroblocks which would otherwise be poorly concealed by the decoder the codec allows adaptive selection of the parts of video to protect. For protection, it uses multiple description codes which indirectly provide frequency-based adaptivity by protecting the more significant DCT coefficients. Simulations show significant improvements in the performance of the codec when compared to codecs which use intra macroblock updating (raster scan and random) at the same overhead. The codec is efficient in its use of bits and has good error resilience properties both objectively and subjectively over a wide range of conditions. Further, transcoding of the received bit stream to the standard H.263 syntax is relatively easy.

Error resilience in video and multiplexing layers for very low bit-rate video coding systems

The transmission of audio-visual services on low-bit-rate, wireless telecommunications systems requires the use of coding techniques that are both efficient in their use of bits and robust against errors introduced in transmission. In this paper, we present efficient techniques for improving the error resilience of audio-visual services. These techniques are based on coding simultaneously for synchronization and error protection or detection. We apply the techniques to improve the performance of the multiplexing protocol (which combines the video and audio streams so that they can be transmitted on a single circuit), and also to improve the robustness of the coded video. We show through simulations that the techniques are efficient in their use of bits and effective against bursty errors common in wireless channels. For a simulation of the DECT channel at a bit-error rate of 10/sup -3/, the techniques give an order of magnitude improvement in the probability of lost packets in the multiplexer layer over more conventional techniques. In the video layer, the techniques give an improvement of between 1-2 dB over ITU-T Recommendation H.263. The techniques proposed for the video layer also have the advantage of permitting simple transcoding with bit streams complying with H.263.

Video Coding Using Elastic Motion Model and Larger Blocks

Motion-compensated prediction is the key to high-performance video coding. Previous works have explored alternatives to the classical translational motion model in video coding, but the cumulative rate-distortion performance has not been significant enough to see such approaches adopted in mainstream standards. In this paper, we propose a new extended prediction strategy that incorporates non-translational motion prediction. This method uses an elastic motion model with 2-D cosine basis functions to estimate non-translational motion between the blocks. To achieve superior performance, the proposed scheme takes advantage of larger blocks with multi-level partitioning. Experimental results show that this combined framework outperforms the existing techniques, including those available in the recent H.264 standard.

Imperceptible and Robust Blind Video Watermarking Using Chrominance Embedding: A Set of Approaches in the DT CWT Domain

Illegal distribution of a digital movie is a significant threat to the film industries. With the advent of high-speed broadband Internet access, a pirated copy of a digital video can be easily distributed to a global audience. Digital video watermarking is a possible means of limiting this type of digital distribution. In existing watermarking methods, the watermark is usually embedded into the luminance channel of a video frame, which affects imperceptibility. In addition, none of the existing techniques are robust to the combination of commonly used attacks, such as compression, upscaling, rotation, cropping, downscaling in resolution, frame rate conversion, and camcording. In this paper, we initially propose a basic blind digital video watermarking algorithm, where the watermark is embedded into one level of the dual-tree complex wavelet transform of the chrominance channel to provide high quality watermarked video and extracted using the same key that was used for embedding. This algorithm is robust to compression, upscaling, rotation, and cropping. An extension of this method extracts the watermark from any level(s) of the dual-tree complex wavelet transform depending on the resolution of the downscaled version of the watermarked frame rather than only from the embedding level to survive downscaling to an arbitrary resolution. Finally, the watermark of a frame is extracted from the information of that frame without using the key that was used during watermark embedding to provide robustness to temporal synchronization attacks, such as frame rate conversion. This scheme is also robust to compression, camcording, watermark estimation remodulation, temporal frame averaging, multiple watermark embedding, downscaling in resolution, and other geometric attacks, such as upscaling, rotation, and cropping.