Dr. Edward T. Chang Profile

Dr. Edward T. Chang

at Apple Inc

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Publications (7)

Proceedings Article | 20 February 2007 Paper

Kernel-size selection for defect pixel identification and correction

Edward Chang

Proceedings Volume 6502, 65020J (2007) https://doi.org/10.1117/12.705383

KEYWORDS: Image processing, Image sensors, Imaging systems, Filtering (signal processing), Data modeling, Sensors, Computer simulations, Signal processing, Digital imaging, Digital image processing

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Proceedings Article | 29 January 2007 Paper

Performance evaluation of digital still camera image processing pipelines

Dirk Hertel, Edward Chang, Loren Shih, Jason Sproul

Proceedings Volume 6494, 64940A (2007) https://doi.org/10.1117/12.705380

KEYWORDS: Image quality, Image processing, Image sensors, Cameras, Image analysis, Visualization, Digital cameras, Digital image processing, Imaging systems, Data modeling

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Proceedings Article | 22 March 1999 Paper

Color filter array recovery using a threshold-based variable number of gradients

Edward Chang, Shiufun Cheung, Davis Pan

Proceedings Volume 3650, (1999) https://doi.org/10.1117/12.342861

KEYWORDS: Optical filters, Sensors, Image resolution, Algorithm development, Color difference, Digital cameras, Cameras, Image quality, Digital photography, Detection and tracking algorithms

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Proceedings Article | 24 January 1997 Paper

Disk-based storage for scalable video

Edward Chang, Avideh Zakhor

Proceedings Volume 3020, (1997) https://doi.org/10.1117/12.264289

KEYWORDS: Video, Video compression, Neodymium, Data storage, Visualization, 3D video compression, Televisions, Data storage servers, Switches, Failure analysis

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Proceedings Article | 25 March 1996 Paper

Cost analysis for VBR video servers

Edward Chang, Avideh Zakhor

Proceedings Volume 2667, (1996) https://doi.org/10.1117/12.235891

KEYWORDS: Video, Control systems, Computer simulations, Rubidium, Data modeling, Device simulation, Data storage, Statistical analysis, Information operations, Convolution

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In this paper we compare techniques for storage and real-time retrieval of Variable Bit Rate (VBR) video data for multiple simultaneous users. The motivation for considering VBR is that video results in inherently time varying data, and as such, with the same average bit rate, higher quality can be achieved with VBR than with Constant Bit Rate (CBR). We propose and compare the following three classes of VBR data placement and retrieval techniques: Constant Time Length (CTL) places and retrieves data in blocks corresponding to equal playback durations, Constant Data Length (CDL) places and retrieves constant-sized data blocks, and a hybrid solution uses CDL placement but retrieves a variable number of blocks in each service round. We have found that CTL data placement has much lower buffer requirements than CDL but suffers from fragmentation during video editing. We show hybrid placement to have both advantages of high efficiency and low fragmentation. We also address the issue of admission control policies by comparing statistical and deterministic techniques. `Statistical' admission control uses statistics of the stored data to ensure that the probability of `overload' does not exceed a prespecified threshold. `Deterministic' control uses the actual stored video bit traces to regulate the number of admitted users. We consider two types of deterministic admission control: data-limit and ideal deterministic. Data-limit admission control admits users based on precomputing the total amount of data requested by all users in future service rounds. In contrast, ideal deterministic admission control not only precomputes the total amount of data requested, but also assumes we have control of data placement at the disk sector level in order to precompute the future seek and rotation times. We provide a cost/benefit analysis of the above placement/retrieval/admission control techniques and conclude that CTL and hybrid placement/retrieval techniques can reduce the total system cost by up to a factor of 3 in comparison with the strategy of padding the VBR video trace to achieve a constant data rate. For read-only systems, CTL has the lowest cost per user. For writable systems, the hybrid technique achieves a good compromise between low cost and low fragmentation. We find that all forms of deterministic admission control can outperform statistical, but the greatest gain comes from using ideal deterministic admission control. We note, however, that this admission control may be difficult to implement on standard disk controllers. Finally, we have implemented a full disk model simulator that operates 1000 times faster than the real-time disk. Results using the simulator are very close to those measured on the real disk, making the simulator useful for future experiments.

Proceedings Article | 1 April 1994 Paper

Scalable video data placement on parallel disk arrays

Edward Chang, Avideh Zakhor

Proceedings Volume 2185, (1994) https://doi.org/10.1117/12.171778

KEYWORDS: Video, Neodymium, Video compression, Data modeling, Scalable video coding, Data storage, Performance modeling, Switching, Televisions, Scattering

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Proceedings Article | 4 May 1993 Paper

Introduction to homogeneous networks

William Wolfe, Jay Rothman, James MacMillan, Edward Chang

Proceedings Volume 1831, (1993) https://doi.org/10.1117/12.143836

KEYWORDS: Mobile robots, Neurons, Network architectures, Performance modeling, Content addressable memory, Matrices, Network security, Fourier transforms, Convolution, Optimization (mathematics)

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