Codebook

About: Codebook is a research topic. Over the lifetime, 8492 publications have been published within this topic receiving 115995 citations.

Bounding part scores for rapid detection with deformable part models

Abstract: Computing part scores is the main computational bottleneck in object detection with Deformable Part Models. In this work we introduce an efficient method to obtain bounds on part scores, which we then integrate with deformable model detection. As in [1] we rapidly approximate the inner product between a weight vector and HOG-based features by quantizing the HOG cells onto a codebook and replace their inner product with the lookup of a precomputed score. The novelty in our work consists in combining this lookup-based estimate with the codebook quantization error so as to construct probabilistic bounds to the exact inner product. In particular we use Chebyshev's inequality to obtain probably correct bounds for the inner product at each image location. We integrate these bounds with both the Dual-Tree Branch-and-Bound work of [2,3] and the Cascade-DPMs of [4]; in both cases the bounds are used in a first phase to conservatively construct a short-list of locations, for which the exact inner products are subsequently evaluated. We quantitatively evaluate our method and demonstrate that it allows for approximately a twofold speedup over both [2] and [4] with negligible loss in accuracy.

High-rate concatenated space-time block code M-TCM designs

Abstract: In this paper, a new technique to design improved high-rate space-time (ST) codes is proposed based on the concept of concatenated ST block code (STBC) and outer trellis-coded modulation (M-TCM) encoder constructions. Unlike the conventional rate-lossy STBC-MTCM schemes, the proposed designs produce higher rate ST codes by expanding the codebook of the inner orthogonal STBC. The classic set partitioning concept is adopted to realize the STBC-MTCM designs with large coding gains. The proposed expanded STBC-MTCM designs for the two-, three-, and four-transmitter cases are illustrated. Simulation results show the proposed STBC-MTCM designs significantly outperform the traditional ST-TCM schemes. Furthermore, decoding complexity of the proposed scheme is low because signal orthogonality is exploited to ease data decoding.

Multiple-stage vector excitation coding of speech waveforms

Abstract: An approach to vector-excitation-coding (VXC) speech compression utilizing multiple-stage vector quantization (VQ) is considered. Called multiple-stage VXC (MSVXC), this technique facilitates the use of high-dimensional excitation vectors at medium-band rates without substantially increasing computation. The basic approach consists of successively approximating the input speech vector in several cascaded VQ stages, where the input vector for each stage is the quantization error vector from the preceding stage. It is shown that if a number of VQ stages is increased sufficiently, MSVXC can be expressed as a form of transform coding, in which the computationally intensive excitation codebook search is completely eliminated. >

Reference signaling scheme using compressed feedforward codebooks for multi-user multiple input multiple output (MU-MIMO) systems

Abstract: A multi-user multiple-input multiple-output (MIMO) downlink beamforming system with limited feed forward is provided to enable precoding matrix information to be efficiently provided to a subset of user equipment devices, where zero-forcing transmit beamformers are computed at the base station and assembled into a precoding matrix. The precoding matrix is encoded using a compact reference signal codebook for forward link signaling, either by sending bits indicating the index of the transmission matrix used, or by transmitting one or more precoded pilots or reference signals wherein the pilot signals are precoded using vectors uniquely representative of the transmission matrix used which includes candidate reference signal matrices which meet a predetermined condition number requirement, such as a condition number threshold. The precoding matrix information is extracted at the user equipment devices using the compact reference signal codebook and used by the MMSE receiver to generate receive beamformers.

Image vector quantization with a perceptually-based cell classifier

Abstract: Vector quantization (VQ) has made it possible to utilize perceptually meaningful techniques for direct space-domain image coding. A simple 2 or 3 way classified codebook approach [2,3] allocates the perceptually important edges with more resolution than the easily encoded monotone regions of an image. In this paper, we introduce a major extension of the classification approach to include edge orientation and location, thereby exploiting an important feature of the human visual mechanism. In particular, each 4 × 4 block of pixels is classified into one of 31 classes for the case of 16 dimensional VQ. The encoding and codebook design complexity is significantly reduced, allowing us to use large codebooks designed from a large database of training images. We present images encoded at 0.7 and 0.8 bits per pixel using this scheme with 16- dimensional vectors. Only a small fraction of one bit per pixel is needed to code the monotone regions of an image; the rest of the bitrate is used to achieve a high level of edge integrity.