Low-complexity wavelet-based scalable image & video coding for home-use surveillance

We study scalable image and video coding for the surveillance of rooms and personal environments based on inexpensive cameras and portable devices. The scalability is achieved through a multi-level 2D dyadic wavelet decomposition featuring an accurate low-cost integer wavelet implementation with lifting. As our primary contribution, we present a modification to the SPECK wavelet coefficient encoding algorithm to significantly improve the efficiency of an embedded system implementation. The modification consists of storing the significance of all quadtree nodes in a buffer, where each node comprises several coefficients. This buffer is then used to efficiently construct the code with minimal and direct memory access. Our approach allows efficient parallel implementation on multi-core computer systems and gives a substantial reduction of memory access and thus power consumption. We report experimental results, showing an approximate gain factor of 1,000 in execution time compared to a straightforward SPECK implementation, when combined with code optimization on a common digital signal processor. This translates to 75 full color 4CIF 4:2:0 encoding cycles per second, clearly demonstrating the realtime capabilities of the proposed modification

Complexity reduction of wavelet codecs through modified quality control

Integer-to-integer wavelets are employed for low-complexity image encoders in embedded applications and used in combination with wavelet coefficient coders, such as EZW, SPIHT, SPECK and TSSP. In scalable coders bitstream creation is computationally expensive when individual coefficients are manipulated. In this paper, we study two options that move the quality control to earlier stages in the encoding process to alleviate this complexity problem: (1) to stage one of the TSSP and (2) to the integer wavelet transform. By inserting special functions based on premature bit-plane dropping, we effectively implement a quality-control step prior to the coefficient coding. For a typical usage scenario with full HD images, with option (1) we achieve an improvement of the processing speed of TSSP by 28%, while retaining the original bitstream and thus the ratedistortion performance. Furthermore, we have found that option (2) is generically applicable to other bit-plane based codecs, while offering nearly the same processing speed

Robust automatic ship tracking in harbours using active cameras

Radar is commonly used to detect and track ships in maritime surveillance. Unfortunately the systems are costly and do not provide any visual information about the object's type. To complement the ship identity information given by a radar system, we propose a supplementary system using active visual cameras that can robustly detect and track ships in harbours. By combining a high-quality, non real-time robust object detector with a feature point tracker with low computational complexity, it is possible to track ships in real time over long intervals and large distances. In addition to controlling pan and tilt, we dynamically control camera zoom to provide a high resolution image of the tracked object over a large range of distances. The tracking system is improved by a special motion estimation model for the feature points, which also incorporates zooming of the camera. The system is robust and sustains tracking even under challenging conditions, such as multiple viewpoints, a large variety of ships and various weather conditions. During experiments, various types of ships were successfully tracked for up to 18 minutes, and over a distance of almost 1.5km in the port of Rotterdam. The proposed system is generic and can be utilized in various tracking applications, by training the detector for a different object class

Enhanced prediction for motion estimation in scalable video coding

In this paper, we present a temporal candidate generation scheme that can be applied to motion estimators in Scalable Video Codecs (SVCs). For bidirectional motion estimation, usually a test is made for each block to determine which motion compensation direction is preferred: forward, bidirectional or backward. Instead of simply using the last computed motion vector field (backward or forward), giving an asymmetry in the estimation, we involve both vector fields to generate a single candidate field for a more stable and improved prediction. This field is generated with the aid of mode decision information of the codec. This single field of motion vector candidates serves two purposes: (1) it initializes the next recursion and (2) it is the foundation for the succeeding scale in the scalable coding. We have implemented this improved candidate system for both HPPS as EPZS motion estimators in a scalable video codec. We have found that it reduces the errors caused by occlusion of moving objects or image boundaries. For EPZS, only a small improvement is observed compared to the simple candidate scheme. However, for HPPS improvements are more significant: when looking at individual levels, motion compensation performance improves by up to 0.84 dB and when implemented in SVC, HPPS slightly outperforms EPZS

Low-complexity wavelet-based scalable image & video coding for home-use surveillance

We study scalable image and video coding for the surveillance of rooms and personal environments based on inexpensive cameras and portable devices. The scalability is achieved through a multi-level 2D dyadic wavelet decomposition featuring an accurate low-cost integer wavelet implementation with lifting. As our primary contribution, we present a modification to the SPECK wavelet coefficient encoding algorithm to significantly improve the efficiency of an embedded system implementation. The modification consists of storing the significance of all quadtree nodes in a buffer, where each node comprises several coefficients. This buffer is then used to efficiently construct the code with minimal and direct memory access. Our approach allows efficient parallel implementation on multi-core computer systems and gives a substantial reduction of memory access and thus power consumption. We report experimental results, showing an approximate gain factor of 1,000 in execution time compared to a straightforward SPECK implementation, when combined with code optimization on a common digital signal processor. This translates to 75 full color 4CIF 4:2:0 encoding cycles per second, clearly demonstrating the realtime capabilities of the proposed modification

Robust automatic ship tracking in harbours using active cameras

Radar is commonly used to detect and track ships in maritime surveillance. Unfortunately the systems are costly and do not provide any visual information about the object's type. To complement the ship identity information given by a radar system, we propose a supplementary system using active visual cameras that can robustly detect and track ships in harbours. By combining a high-quality, non real-time robust object detector with a feature point tracker with low computational complexity, it is possible to track ships in real time over long intervals and large distances. In addition to controlling pan and tilt, we dynamically control camera zoom to provide a high resolution image of the tracked object over a large range of distances. The tracking system is improved by a special motion estimation model for the feature points, which also incorporates zooming of the camera. The system is robust and sustains tracking even under challenging conditions, such as multiple viewpoints, a large variety of ships and various weather conditions. During experiments, various types of ships were successfully tracked for up to 18 minutes, and over a distance of almost 1.5km in the port of Rotterdam. The proposed system is generic and can be utilized in various tracking applications, by training the detector for a different object class

Real-time scalable video codec implementation for surveillance

In this paper, we discuss the design and real-time implementation of a Scalable Video Codec (SVC) for surveillance applications. We present a complexity-scalable temporal wavelet transform and the implementation of a multi-level 2D 5/3 wavelet transform, using the lifting framework. We have employed SIMD (Single Instruction Multiple Data) and DMA (Direct Memory Access) techniques, where the proposed process of background DMA transfers is so effective, that the ALUs are always supplied with input data. We have realized the execution of a 4-level transform at 4CIF (CCIR-601) broadcast resolution in 3.65 Mcycles, including memory stalls, on a TMS320DM642 DSP. At a clock rate of 600 MHz, this translates to more than 160 transforms per second. For our complete SVC, we achieve a frame rate of 12.5-15 fps depending on scene activity. ©2009 IEEE