• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 75
  • 17
  • 8
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 100
  • 100
  • 33
  • 33
  • 32
  • 31
  • 30
  • 29
  • 25
  • 20
  • 17
  • 17
  • 15
  • 15
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Efficient and perceptual picture coding techniques. / CUHK electronic theses & dissertations collection

January 2009 (has links)
In the first part, some efficient algorithms are proposed to reduce the complexity of H.264 encoder, which is the latest state-of-the-art video coding standard. Intra and Inter mode decision play a vital role in H.264 encoder and can reduce the spatial and temporal redundancy significantly, but the computational cost is also high. Here, a fast Intra mode decision algorithm and a fast Inter mode decision algorithm are proposed. Experimental results show that the proposed algorithms not only save a lot of computational cost, but also maintain coding performance quite well. Moreover, a real time H.264 baseline codec is implemented on mobile device. Based on our real time H.264 codec, an H.264 based mobile video conferencing system is achieved. / The objective of this thesis is to develop some efficient and perceptual image and video coding techniques. Two parts of the work are investigated in this thesis. / The second part of this thesis investigates two kinds of perceptual picture coding techniques. One is the just noticeable distortion (JND) based picture coding. Firstly, a DCT based spatio-temporal JND model is proposed, which is an efficient model to represent the perceptual redundancies existing in images and is consistent with the human visual system (HVS) characteristic. Secondly, the proposed JND model is incorporated into image and video coding to improve the perceptual quality. Based on the JND model, a transparent image coder and a perceptually optimized H.264 video coder are implemented. Another technique is the image compression scheme based on the recent advances in texture synthesis. In this part, an image compression scheme is proposed with the perceptual visual quality as the performance criterion instead of the pixel-wise fidelity. As demonstrated in extensive experiments, the proposed techniques can improve the perceptual quality of picture coding significantly. / Wei Zhenyu. / Adviser: Ngan Ngi. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 148-154). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
52

Novel error resilient techniques for the robust transport of MPEG-4 video over error-prone networks. / CUHK electronic theses & dissertations collection

January 2004 (has links)
Bo Yan. / "May 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 117-131). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.
53

Arbitrary block-size transform video coding. / CUHK electronic theses & dissertations collection

January 2011 (has links)
Besides ABT with higher order transform, a transform based template matching is also investigated. A fast method of template matching, called Fast Walsh Search, is developed. This search method has similar accuracy as exhaustive search but significantly lower computation requirement. / In this thesis, the development of simple but efficient order-16 transforms will be shown. Analysis and comparison with existing order-16 transforms have been carried out. The proposed order-16 transforms were integrated to the existing coding standard reference software individually so as to achieve a new ABT system. In the proposed ABT system, order-4, order-8 and order-16 transforms coexist. The selection of the most appropriate transform is based on the rate-distortion performance of these transforms. A remarkable improvement in coding performance is shown in the experiment results. A significant bit rate reduction can be achieved with our proposed ABT system with both subjective and objective qualities remain unchanged. / Prior knowledge of the coefficient distribution is a key to achieve better coding performance. This is very useful in many areas in coding such as rate control, rate distortion optimization, etc. It is also shown that coefficient distribution of predicted residue is closer to Cauchy distribution rather than traditionally expected Laplace distribution. This can effectively improve the existing processing techniques. / Three kinds of order-l 6 orthogonal DCT-like integer transforms are proposed in this thesis. The first one is the simple integer transform, which is expanded from existing order-8 ICT. The second one is the hybrid integer transform from the Dyadic Weighted Walsh Transform (DWWT). It is shown that it has a better performance than simple integer transform. The last one is a recursive transform. Order-2N transform can be derived from order-N one. It is very close to the DCT. This recursive transform can be implemented in two different ways and they are denoted as LLMICT and CSFICT. They have excellent coding performance. These proposed transforms are investigated and are implemented into the reference software of H.264 and AVS. They are also compared with other order-16 orthogonal integer transform. Experimental results show that the proposed transforms give excellent coding performance and ease to compute. / Transform is a very important coding tool in video coding. It decorrelates the pixel data and removes the redundancy among pixels so as to achieve compression. Traditionally, order-S transform is used in video and image coding. Latest video coding standards, such as H.264/AVC, adopt both order-4 and order-8 transforms. The adaptive use of more than one transforms of different sizes is known as Arbitrary Block-size Transform (ABT). Transforms other than order-4 and order-8 can also be used in ABT. It is expected larger transform size such as order-16 will benefit more in video sequences with higher resolutions such as nap and 1a8ap sequences. As a result, order-16 transform is introduced into ABT system. / Fong, Chi Keung. / Adviser: Wai Kuen Cham. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
54

Adaptive unequal error protection for wireless video transmissions

Yang, Guanghua, January 2006 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.
55

Spatial motion vector recovery in wireless high definition video transmission using H.264 over WLANs

Gatimu, Kevin 08 June 2012 (has links)
Mobile devices are becoming more prevalent and complex. As a result, the wireless communication aspect of these devices is becoming increasingly significant. At the same time, video demands in terms of availability and quality are also on the uprise. High definition (HD) video is the standard of choice for meeting today's video demands. However, HD video is characterized by high data rates. Therefore, there is heightened interest in the 60-GHz spectrum as it is suitable for streaming uncompressed HD video. On the other hand, 802.11 wireless technology, compared to 60-GHz, is much more established and widely available and able to cater to a wide variety of devices. HD video compressed using H.264 can be wirelessly streamed via 802.11 wireless networks. However, such wireless networks are prone to packet losses, which result in degraded perceptual quality of video. It is thus important to perform error concealment in order to improve the visual quality of degraded video. Among the key techniques in performing error concealment on video compressed with H.264 is spatial motion vector recovery. This paper proposes a new spatial motion vector recovery technique (MI-WAM) that takes advantage of properly decoded motion vectors. MI-WAM and pre-existing MV recovery techniques are used to provide different corresponding macroblock candidates that compete for the best concealment of each lost macroblock in what will be referred to as competitive motion vector recovery (CMVR). / Graduation date: 2012
56

Source-channel coding for robust image transmission and for dirty-paper coding

Sun, Yong 25 April 2007 (has links)
In this dissertation, we studied two seemingly uncorrelated, but conceptually related problems in terms of source-channel coding: 1) wireless image transmission and 2) Costa ("dirty-paper") code design. In the first part of the dissertation, we consider progressive image transmission over a wireless system employing space-time coded OFDM. The space-time coded OFDM system based on a newly built broadband MIMO fading model is theoretically evaluated by assuming perfect channel state information (CSI) at the receiver for coherent detection. Then an adaptive modulation scheme is proposed to pick the constellation size that offers the best reconstructed image quality for each average signal-to-noise ratio (SNR). A more practical scenario is also considered without the assumption of perfect CSI. We employ low-complexity decision-feedback decoding for differentially space- time coded OFDM systems to exploit transmitter diversity. For JSCC, we adopt a product channel code structure that is proven to provide powerful error protection and bursty error correction. To further improve the system performance, we also apply the powerful iterative (turbo) coding techniques and propose the iterative decoding of differentially space-time coded multiple descriptions of images. The second part of the dissertation deals with practical dirty-paper code designs. We first invoke an information-theoretical interpretation of algebraic binning and motivate the code design guidelines in terms of source-channel coding. Then two dirty-paper code designs are proposed. The first is a nested turbo construction based on soft-output trellis-coded quantization (SOTCQ) for source coding and turbo trellis- coded modulation (TTCM) for channel coding. A novel procedure is devised to balance the dimensionalities of the equivalent lattice codes corresponding to SOTCQ and TTCM. The second dirty-paper code design employs TCQ and IRA codes for near-capacity performance. This is done by synergistically combining TCQ with IRA codes so that they work together as well as they do individually. Our TCQ/IRA design approaches the dirty-paper capacity limit at the low rate regime (e.g., < 1:0 bit/sample), while our nested SOTCQ/TTCM scheme provides the best performs so far at medium-to-high rates (e.g., >= 1:0 bit/sample). Thus the two proposed practical code designs are complementary to each other.
57

Foveated video compression and visual communications over wireless and wireline networks /

Lee, Sanghoon, January 2000 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 184-197). Available also in a digital version from Dissertation Abstracts.
58

Full motion multiparty videoconferencing using motion compensated visual pattern image sequence coding /

Barnett, Barry Stanley, January 2000 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 209-216). Available also in a digital version from Dissertation Abstracts.
59

Multi-user wireless link for real-time video transfer for defence applications /

Daniels, William Mathew. Unknown Date (has links)
The Real Time Multi- User Wireless Video Link is being developed with the aim of enhancing the capabilities of soldiers by improving their ability to detect, acquire, locate and engage targets by day or night and in all visibility conditions. The primary objective of this work, undertaken as part of the LAND 125 Soldier Combat System Project, is to improve soldiers capabilities by removing the need for cables between a thermal weapon sight mounted on a weapon and a visual display mounted on a soldier's helmet. It improves their ability by enabling them to more easily travel through difficult terrain and enables them to navigate obstacles more easily. The main aim of this project is to transmit video from a source mounted on top of the soldiers weapon to a helmet mounted display. Once this is achieved then the system can be expanded to enable video to be securely transferred to a remote base, enabling the base station to accurately monitor the situation. It could also be used to review the success of missions and for training purposes. / This system also has many commercial applications for example monitoring in hazardous areas, surveillance, high quality video transmission/storage, law enforcement, fire fighting and tele-medicine. In this thesis the requirements of this system and the detailed design techniques are presented. / Thesis (MEng(ComputerSystemsEng))--University of South Australia, 2004.
60

Applications of multi-channel filter banks to textured image segmentation

Davis, Craig Alton, Denney, Thomas Stewart, January 2006 (has links) (PDF)
Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Page generated in 0.1017 seconds