Xu Liu

Bio: Xu Liu is an academic researcher from University of Maryland, College Park. The author has contributed to research in topics: Camera phone & Mobile device. The author has an hindex of 8, co-authored 11 publications receiving 270 citations. Previous affiliations of Xu Liu include Ricoh.

System And Method For Camera Imaging Data Channel

Abstract: A system and method for using cameras to download data to cell phones or other devices as an alternative to CDMA/GPRS, BlueTooth, Infrared or cable connections. The data is encoded as a sequence of images such as 2D bar codes, which can be displayed in any flat panel display, acquired by a camera, and decoded by software embedded in the device. The decoded data is written to a file. The system and method meet the following challenges: (1) To encode arbitrary data as a sequence of images. (2) To process captured images under various lighting variations and perspective distortions while maintaining real time performance. (3) To decode the processed images robustly even when partial data is lost.

VCode—Pervasive Data Transfer Using Video Barcode

Abstract: In this paper, we describe a novel data transfer scheme that uses the camera in a smart phone as an alternative data channel. The data is encoded as a sequence of 2-D barcode images, displayed on a flat panel display, acquired by the camera, and decoded in real time by the software embedded in device. The decoded data is written to a file. Compared with existing data channels, such as CDMA/GPRS, cables, Bluetooth, and Infrared, our method relies on visual communication and does not require special hardware or data plans. Users only need to point the camera at a monitor displaying the VCode to download. Technical challenges to overcome include correction of perspective distortion, compensation for contrast variation, and efficient implementation of small footprint software into a mobile device. We address these challenges and present our solution in detail. We have implemented a prototype which allows users to download various types of files successfully, including pictures, ring tones and Java games onto camera phones running Symbian and Windows Mobile platforms. We discuss the limitations of our solution and outline future work to overcome these limitations.

Mobile Retriever: access to digital documents from their physical source

Abstract: In this paper, we describe an image based document retrieval system which runs on camera enabled mobile devices. “Mobile Retriever” aims to seamlessly link physical and digital documents by allowing users to snap a picture of the text of a document and retrieve its electronic version from a database. Experiments show that for a database of 100,093 pages, the correct document can be retrieved in less than 4 s at a success rate over 95%. Our system extracts token pairs from the text, to efficiently index and retrieve candidate pages using only a small portion of the image. We use token triplets that define the orientation of three corresponding tokens to effectively prune the false positives and identify the correct page to retrieve. We stress the importance of geometrical relationship between feature points and show its effectiveness in our camera based image retrieval system.

Document Image Mosaicing with Mobile Phones

Abstract: This paper presents a novel user interaction concept for document image scanning with mobile phones. A high resolution mosaic image is constructed in two main stages. Firstly, online camera motion estimation is applied to the phone to assist the user to capture small image patches of the document page. Automatic image stitching process with the help of estimated device motion is carried out to reconstruct the full view of the document. Experiments on document images captured and processed with mosaicing software clearly show the feasibility of the approach.

A camera-based mobile data channel: capacity and analysis

Abstract: In this paper we propose a novel application, color Video Code (V-Code) and analyze its data transmission capacity through camera-based mobile data channels. Users can use the camera on a mobile device (PDA or camera phone) as a passive and pervasive data channel to download data encoded as a sequence of color visual patterns. The color V-Code is animated on a display, acquired by the camera and decoded by the pre-embedded software in the mobile device. One interesting question is what is the data transmission capacity it can achieve, theoretically and practically. To answer this question we build a camera channel model to measure color degradation using information theory and show that the capacity of the camera channel can be improved with the optimized color selection through color calibration. After initialization color models are learned automatically as downloading proceeds. We address the problem of precise registration, and implemented a fast perspective correction method to accelerate the decoder in real-time on a resource constrained device. With the optimized color set and efficient implementation we achieve a transmission bit rate of 15.4kbps on a common iMate Jamin phone (200MHz CPU). This speed is faster than the average GPRS bit rate (12kbps).

Smartphone-based methods and systems

Abstract: Arrangements involving portable devices (e.g., smartphones and tablet computers) are disclosed. One arrangement enables a content creator to select software with which that creator's content should be rendered—assuring continuity between artistic intention and delivery. Another utilizes a device camera to identify nearby subjects, and take actions based thereon. Others rely on near field chip (RFID) identification of objects, or on identification of audio streams (e.g., music, voice). Some technologies concern improvements to the user interfaces associated with such devices. Others involve use of these devices in connection with shopping, text entry, sign language interpretation, and vision-based discovery. Still other improvements are architectural in nature, e.g., relating to evidence-based state machines, and blackboard systems. Yet other technologies concern use of linked data in portable devices—some of which exploit GPU capabilities. Still other technologies concern computational photography. A great variety of other features and arrangements are also detailed.

Information communication method

Abstract: An information communication method of transmitting a signal is provided that uses a change in luminance. The method includes determining a pattern of the change in luminance by modulating the signal to be transmitted, and transmitting the signal by a light emitter changing in luminance according to the determined pattern. The pattern of the change in luminance is a pattern in which one of two different luminance values occurs in each arbitrary position in a predetermined duration. The determining a pattern of change in luminance includes dividing the predetermined duration into four duration units, so that one of two different luminance value occurs in one duration unit of the four duration units and the other luminance value of the two different luminance value occurs in three duration units of the four duration units, the three duration units are other than the one duration unit.

Methods and arrangements for smartphone payments and transactions

Abstract: The disclosure relates to digital signal processing such as digital watermarking, and the utilization of portable devices (e.g., smartphones) for such signal processing. One claim recites a smartphone comprising: a touch screen display; memory for storing a payload and for storing a digital image depicting a virtual card; means for processing the payload with an erasure code generator, in which the erasure code generator produces a plurality of outputs corresponding to the payload; means for embedding a first of the plurality of outputs in a first version of the digital image and proceeding with embedding until each of the plurality of outputs are respectively embedded in one of a plurality of versions of the digital image; and means for displaying embedded versions of the digital image so that a receiver analyzing captured image data representing the touch screen display can recover the payload. Of course, other claims and combinations are disclosed too.