Visualizing complex urban environments has been an active research topic due to its wide variety of applications in city planning: road construction, emergency facilities planning, and optimal placement of wireless carrier base stations. Traditional 2D visualizations have been around for a long time but they only provide a schematic line-drawing bird's eye view and are sometimes confusing to understand due to the lack of depth information. Early versions of 3D systems have been developed for very expensive graphics workstations which seriously limited the availability. In this paper we describe a 3D visualization system for a desktop PC which integrates multiple resolutions of data and provides a realistic view of the urban environment.
The hybrid coding scheme is employed in all established coding standards. A forward motion vector field is estimated and applied for motion compensation. The remaining prediction error and the motion vectors are transmitted to the decoder. The discrete cosine transform is used for transform coding of the prediction error. The extension of this coding scheme to scalability is not easily achieved and the performance of standard video coders when using scalability options can often be reduced to the performance of simulcast coding. In this paper a hierarchical spatial scalable wavelet video coder is presented. A backward motion compensation scheme is used and no motion vectors have to be transmitted. In this coding scheme the lowpass band of the decomposition is coded first without motion compensation using DPCM. The coarser levels of the signal decomposition which are known to both, the encoder and the decoder, are then employed for motion estimation of the next levels. Due to the hierarchical structure of the presented scheme the impact of quantization is strongly interdependent between the decomposition levels. In contrast to still image coding quantization affects the reconstruction quality as well as the motion estimation and motion compensation efficiency. In this paper the bit allocation for the decomposition levels of the hierarchical wavelet video coder is investigated.
Temporal redundancies are the key to high compression ratios in video coding. In order to improve the prediction gain of motion compensation the concept of long-term memory motion- compensated prediction has been developed. More frames than the previously decoded frame can be taken into account for motion compensation. Usually the motion is estimated in the encoder, where all unencoded frames are accessible. We investigate the applicability of long-term memory motion- compensated prediction to a scalable wavelet video coding scheme using backward motion compensation, where the motion is estimated in both, the encoder and the decoder.
A fast full search block matching algorithm is developed. The matching criterion is the sum of absolute differences or the mean square error. The algorithm evaluates lower bounds for the matching criteria for subdivided blocks in order to reduce the number of search positions. It also uses the lower bounds for a fast calculation of the matching criterion for the remaining search positions. The computational complexity of the algorithm is evaluated and compared to the three-step search strategy. The search result of the algorithm is identical to the search result of the exhaustive search.
A new fast block matching algorithm is presented. The sum of absolute differences (SAD) and the mean square error (MSE) are used to find a suitable motion vector. A lower bound for both error measures is exploited to reduce the number of search positions and therefore the computational requirements. The error measures for the remaining search positions are calculated simultaneously so that the computational load for these calculations only slightly increases. The algorithm is compared to a fast full search block matching algorithm based on the same concept but only using the SAD or the MSE as the matching criterion. It is shown that the algorithm using both error measures combines the advantages of both algorithms using only on the SAD or the MSE.
KEYWORDS: Computer programming, Autoregressive models, Matrices, Motion estimation, Motion models, Video coding, Quantization, Control systems, Solids, Low bit rate video
The hybrid coding scheme is modified. The discrete cosine transform used for encoding displaced frame differences is replaced by a predefined set of transform matrices based on autoregressive models up to the fourth order. The autoregressive models are parameterized using reflection coefficients. It is shown that the coding efficiency can be improved though side information for the chosen transform has to be transmitted to the decoder.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.