Victor H. S. Ha

Portable receivers for digital multimedia broadcasting

A new national standard for digital multimedia broadcasting (DMB) has been announced in Korea to provide high quality digital audio, video, and data broadcasting services to fixed, mobile, and portable receivers. We have developed the worlds first DSP/FPGA implementation of the portable DMB receiver, complete with an RF receiver, a 6.4-inch LCD display, and audio/video/data decoders. In this paper, we present the design, implementation, and performance of this portable DMB receiver. First, we provide a brief overview of the DMB system and the audio/video coding tools supported by it, i.e., MPEG-4 BSAC and MPEG-4 Part 10 AVC/H.264. We discuss the low-power high-performance design of the DMB receiver, focusing particularly on the audio/video decoding parts. Finally, we illustrate the performance of the portable DMB receiver that operates in real-time at the overall frequency of 25 MHz.

Affine-permutation invariance of 2-D shapes

Shapes provide a rich set of clues on the identity and topological properties of an object. In many imaging environments, however, the same object appears to have different shapes due to distortions such as translation, rotation, reflection, scaling, or skewing. Further, the order by which the objects feature points are scanned changes, i.e., the order of the pixels may be permuted. Relating two-dimensional shapes of the same object distorted by different affine and permutation transformations is a challenge. We introduce a shape invariant that we refer to as the intrinsic shape of an object and describe an algorithm, BLAISER, to recover it. The intrinsic shape is invariant to affine-permutation distortions. It is a uniquely defined representative of the equivalence class of all affine-permutation distortions of the same object. BLAISER computes the intrinsic shape from any arbitrarily affine-permutation distorted image of the object, without prior knowledge regarding the distortions or the undistorted shape of the object. The critical step of BLAISER is the determination of the shape orientation and we provide a detailed discussion on this topic. The operations of BLAISER are based on low-order moments of the input shape and, thus, robust to error and noise. Examples illustrate the performance of the algorithm.

Affine invariant wavelet transform

We present a two-dimensional wavelet transform that is invariant to affine distortions of the input signal. Affine distortions include geometric effects such as translation, reflection, uniform and anisotropic scaling, rotation, and shearing of the input signal. Invariance of the wavelet transform to affine distortions is achieved in our work by developing an algorithm that reduces replicas of a signal related by affine distortions to a unique prototype signal. The affine invariant wavelet transform is then defined as the two-dimensional wavelet transform of the prototype signal, which provides the wavelet coefficients that are invariant to affine distortions of the input signal. We describe our algorithm and show examples that demonstrate our claims.

Affine-permutation symmetry: invariance and shape space

Studying similarity of objects by looking at their shapes arises naturally in many applications. However, under different viewpoints one and the same object appears to have different shapes. In addition, the correspondences between their feature points are unknown to the viewer. In this paper, we introduce the concept of intrinsic shape of an object that is invariant to affine-permutation shape distortions. We study geometry of the intrinsic shape space in the framework of differentiable manifolds with the emphasis on the computational aspects. We represent the intrinsic shape space as a folded Grassmann manifold. This allows us to easily analyze and compare different intrinsic shapes under the affine-permutation distortion without explicitly computing and recovering these intrinsic shapes. We present the mathematical equations for connecting two intrinsic shapes by a geodesic, measuring their similarity, and morphing one intrinsic shape onto another.

Performance evaluation of Eureka-147 with RS(204, 188) code for mobile multimedia broadcasting

The demand for mobile multimedia broadcasting service is increasing consistently as more people expect seamless outdoor connections and communication capabilities. In this paper, we introduce the digital multimedia broadcasting (DMB) system based on Eureka-147 that has been tentatively adopted in Korea. Since Eureka-147 is originally designed for broadcasting digital audio data, it provides a bit error rate (BER) of about 10-4 while the transmission of compressed video data, for example, requires the BER of about 10-9. To deal with this mismatch, the Korean DMB standard is considering the addition of the RS(204,188) coder to Eureka-147. In this paper, we apply the RS(204,188) coder to the Eureka-147 and present the simulation results on the performance of this modified system at various transmission and protection modes. We conclude that the addition of RS(204,188) coder to Eureka-147 in the Korean DMB system results in the satisfactory level of BER for mobile multimedia broadcasting services.

Design and implementation of H.264-based video decoder for digital multimedia broadcasting

In Korea, a nation-wide digital multimedia broadcasting (DMB) service was to be launched in 2004 to provide high quality digital audio, video and data broadcasting to mobile, portable, and fixed receivers. We have developed the worlds first FPGA implementation of a portable DMB receiver complete with an RF receiver, a 6.4-inch LCD display, and audio/video/data decoders. We present the real-time video decoder designed and implemented for this DMB receiver. The video coding in DMB, is based on the newest international video coding standard known as MPEG-4 Part 10 AVC/H.264. We describe the low-power high-performance design of the H.264-based DMB video decoder and illustrate its performance based on the FPGA implementation.

Efficient 2D shape orientation

In this paper, we study the reorientation of 2D shapes. We describe an algorithm that removes orientational ambiguity from arbitrarily oriented 2D shapes. The algorithm is robust to error in pixel locations as well as in the presence of occluded or added pixels. After reorientation, the resulting shape is in a normalized orientation and can then be used effectively in post-processing stages of such applications as pattern detection, recognition, and registration. The algorithm combines a new measure of shape orientation, the variable-size window orientation indicator index (/spl Delta/-OII), and the point-based reorientation algorithm (PRA) that we presented before. We test the new algorithm against an extensive database of complex 2D shapes.

Real-time audio/video decoders for digital multimedia broadcasting

A new national standard for digital multimedia broadcasting (DMB) has been drafted in Korea to provide high quality digital audio, video, and data broadcasting services to fixed, mobile, and portable receivers. We have developed the worlds first DSP/FPGA implementation of the portable DMB receiver, complete with an RF receiver, a 6.4-inch LCD display, and audio/video/data decoders. In this paper, we present the design, implementation, and performance of this portable DMB receiver. First, we provide a brief overview of the DMB system and the audio/video coding tools supported by it, i.e., MPEG-4 BSAC and MPEG-4 Part 10 AVC/H.264. We discuss the low-power high-performance design of the DMB receiver, focusing particularly on the audio/video decoding parts. Finally, we illustrate the performance of the portable DMB receiver that operates in real-time at the overall frequency of 25 MHz.

Dynamic range compression and contrast enhancement for digital images in the compressed domain

We develop a simple and efficient algorithm for dynamic range compression and contrast enhancement of digital images in the compressed domain. The basic idea of our approach is to separate illumination and reflectance components of an image in the compressed domain. We adjust the amount of contribution of the illumination component to effectively compress the dynamic range of the image. For contrast enhancement, we modify the reflectance component based on a new measure of the spectral contents of the image. The spectral content measure is computed from the energy distribution across different spectral bands in a discrete cosine transform (DCT) block. The advantages of the proposed algorithm are (1) high dynamic range scenes are effectively mapped to the smaller dynamic range of the image, (2) the details in very dark or bright areas become clearly visible, (3) the computational cost is low, and (4) the compressibility of the original image is not affected by the algorithm. We evaluate the performance of the proposed algorithm with well-known existing methods, such as histogram equalization and -rooting algorithm, using a few different enhancement quality metrics.

Three-dimensional intrinsic shape

In this paper, we define the intrinsic shape of an object in three-dimensional (3D) space as the shape invariant, to affine-permutation geometric shape distortions. We present an algorithm that blindly recovers from an arbitrarily affine-permutation distorted shape its intrinsic shape. This algorithm referred to us 3D BLAlSER (blind algorithm for intrinsic shape recovery) executes as one of its steps 3D PRA (point-based reorientation algorithm). 3D PRA reorients (blindly) rotated versions of the same object so that they become exactly aligned. 3D PRA extends 2D PRA to 3D space, but is much more complicated due to the multiple axes of rotation and the associated fold numbers. We describe the algorithms of 3D BLAISER and 3D PRA in detail.