Raj Talluri

Position estimation for an autonomous mobile robot in an outdoor environment

The position estimation problem for an autonomous land vehicle navigating in an unstructured mountainous terrain is solved. A digital elevation map (DEM) of the area is assumed to be given. It is also assumed that the robot is equipped with a camera that can be panned and tilted, a compass, and an altimeter. No recognizable landmarks are assumed to be present, and the robot is not assumed to have an initial estimate of its position. The solution structures the problem as a constrained search paradigm by searching the DEM for the possible robot location. The shape and position of the horizon line in the image plane and the known camera geometry of the perspective projection are used as parameters. Geometric constraints are used to prune the search space significantly. The algorithm is made robust to errors in the imaging process by accounting for worst case errors. The approach is tested using real terrain data of areas in Colorado and Texas. >

A robust, scalable, object-based video compression technique for very low bit-rate coding

This paper describes an object-based video coding scheme (OBVC) that was proposed by Texas Instruments to the emerging ISO MPEG-4 video compression standardization effort. This technique achieves efficient compression by separating coherently moving objects from stationary background and compactly representing their shape, motion, and the content. In addition to providing improved coding efficiency at very low bit rates, the technique provides the ability to selectively encode, decode, and manipulate individual objects in a video stream. This technique supports all three MPEG-4 functionalities tested in the November 1995 tests, namely, improved coding efficiency, error resilience, and content scalability. This paper also describes the error protection and concealment schemes that enable robust transmission of compressed video over noisy communication channels such as analog phone lines and wireless links. The noise introduced by the communication channel is characterized by both burst errors and random bit errors. Applications of this object-based video coding technology include videoconferencing, video telephony, desktop multimedia, and surveillance video.

Unequal error protection of MPEG-4 compressed video

The MPEG-4 video compression standard incorporates several techniques to create error-resilient coded video. These techniques are effective against a certain level of errors. However, wireless channels often have very high error rates; thus channel coding is needed to reduce the number of errors in the compressed bitstream that is sent to the MPEG-4 video decoder. The structure of an MPEG-4 compressed bitstream lends itself to using unequal error protection to ensure fewer errors in the important portions of the bitstream. This paper discuses how unequal error protection can be used with the MPEG-4 error resilience tools and describes several experiments using both unequal and equal error protection on video sent through a simulated GSM channel. The results of these experiments show that when the bit error rate is high, unequal error protection can improve reconstructed video quality by as much as 1 dB compared with equal error protection.

Programmable DSP platform for digital still cameras

This paper presents a programmable DSP platform for digital still cameras based on the Texas Instruments TMS320C54x family. One major advantage of this platform is that, after capturing an image from a CCD sensor, processing the raw image, and compressing the image for storage is performed on the digital signal processor (DSP). This provides a short shot-to-shot delay and a high degree of flexibility. The system realized also allows instant viewing and selective storing of captured images. This paper outlines the various processing stages necessary to take the raw CCD data and produce a JPEG compressed bit stream and highlighting the advantages of DSPs for this application. The programmable nature of this platform allows for the exploration of different image processing and compression techniques. The low power nature of the digital signal processor provides long battery life.

Anatomy of a portable digital mediaprocessor

Portable devices equipped with imaging, video, and audio functionality are proliferating rapidly, and manufacturers are shipping hundreds of millions of such devices. A general-purpose processor (GPP) typically consumes tens of watts to nearly a hundred watts, while a high-performance digital still cameras main processor consumes only hundreds of milliwatts to nearly half a watt. Designing a mediaprocessor with performance comparable to that of a GPP at a power budget two orders of magnitude lower and a cost more than an order of magnitude lower poses quite a challenge. To meet requirements and reduce overall system cost, mediaprocessor designers must integrate the device with an extensive set of peripherals. For performance, cost, and power reasons, application-specific integrated circuits have traditionally been the most popular choice for portable media systems. We discuss the architecture of the DM310, a highly integrated portable digital mediaprocessor, manufactured in a 0.13-micron process.

Tools for robust image and video coding in JPEG-2000 and MPEG-4 standards

In this paper, we review the tools for error resilient image and video coding that have already been incorporated in the upcoming ISO/IEC MPEG4 and JPEG2000 video and image coding standards. We also review the ongoing work that are being currently conducted at the evolving JPEG2000 standard. The methodology adopted by the MPEG and JPEG standards bodies for developing error resilience tools is also discussed. Finally, we provide performance data on the effectiveness of these error resilience tools under various channel conditions.

Image map correspondence for mobile robot self-location using computer graphics

The use of computer graphics in estimating the position of an autonomous mobile robot navigating in an outdoor mountainous environment is discussed. A digital elevation map (DEM) of the area in which the robot is to navigate is given, and the robot is equipped with a camera that can be panned and tilted, a compass, and an altimeter. The position of the robot is estimated by establishing a correspondence between the images acquired by the camera on the robot (actual images) and the images generated from the DEM (predicted images) using computer graphics techniques. Features are extracted from the predicted images and the actual images that are used in establishing the correspondence. The features used are the horizon line contours (HLCs) in the images. To reduce the search space a constrained search paradigm is used. Geometric constraints help prune the search space significantly. >

MPEG-4 Video and Image Coding on Digital Signal Processors

The emerging MPEG-4 standard encompasses a wide variety of applications, many of which are suitable for implementation on a Digital Signal Processor (DSP). In particular, consumer products with embedded multimedia capability, such as set-top boxes and wireless communicators, are suitable for DSP-based implementation. With a programmable approach, various algorithmic tradeoffs can be made, based on processing capability. For best performance, careful attention must be paid to memory allocation, data transfer, and ordering of instructions to best match the DSP architecture. We discuss implementing simple profile MPEG-4 video on the low-power TMS320C54x, core profile on the TMS320C6x, and scalable texture profile, which could be implemented on either processor family.

Wireless MPEG-4 video on Texas Instruments DSP chips

Technology has advanced in recent years to the point where multimedia communicators are beginning to emerge. These communicators are low-power, portable devices that can transmit and receive multimedia data through the wireless network. Due to the high computational complexity involved and the low-power constraint in wireless applications, these devices require the use of processors that are powerful and are at the same time very power-efficient. In order to facilitate interoperability, it is important that these devices use standardized compression and communication algorithms. As a first step in implementing multimedia terminals, Texas Instruments (TI) has demonstrated real-time MPEG-4 video decoding (simple profile) on TMS320C54x, TIs low power, high performance DSP chip. In addition, TI has outlined a system-level solution to transmitting video across wireless networks, including channel coding and communication protocols.

DSP-based real-time video encoding

This paper describes the implementation of H.263 real-time video encoding on TI TMS320C6X. This series of DSPs utilize a common core based on VelociTITM, the advanced Very Long Instruction Word (VLIW) DSP architecture, which makes them ideal for the high performance embedded multimedia applications. In this paper we discuss in detail the used methodologies to structure video coding algorithm in order to exploit the DSP architecture. In particular, a novel DSP- friendly motion estimation algorithm has been developed to achieve the good trade-off between the coding efficiency and coding complexity. This algorithm plays a key role for the realization of real-time video encoding on DSPs. On the EVM board of this kind of DSP (CPU frequency 167 MHz), we were able to demonstrate the H.263 baseline video encoding, CIF (352 X 288), 1Mbit/s at a speed of about 30 fps. Multimedia applications such as consumer set-top boxes, videophones, videoconferencing, network camera will benefit from this performance.