Deliverable 5.2 - the School of Engineering and Design - Brunel ...
Deliverable 5.2 - the School of Engineering and Design - Brunel ...
Deliverable 5.2 - the School of Engineering and Design - Brunel ...
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ICT Project 3D VIVANT– <strong>Deliverable</strong> <strong>5.2</strong>Contract no.:248420Search & Retrieval Mechanisms &Tools3 DATABASE PREPARATIONA fundamental step in <strong>the</strong> preparation <strong>of</strong> a multimedia database in order to be searchable is to extractdescriptor vectors that represent each multimedia object. In <strong>the</strong> case <strong>of</strong> 3DVIVANT S&R frameworkthis also st<strong>and</strong>s true. This section describes <strong>the</strong> database structure, <strong>the</strong> descriptors extraction process<strong>and</strong> <strong>the</strong> final indexing structure creation to enable multimedia similarity search. This process is alsoknown as <strong>of</strong>fline process as it is depicted in Figure 5.OfflineContentRepositoryPre-ProcessingLow-level FeatureExtractionDescriptorsBrowsing / Selectingexisting objectFeatureRetrievalFeatureMatchingResultsSubmitting newobjectPre-ProcessingLow-level FeatureExtractionOnlineFigure 5: Dynamic behaviour <strong>of</strong> <strong>the</strong> search <strong>and</strong> retrieval framework.The steps <strong>of</strong> <strong>the</strong> <strong>of</strong>fline process are discussed in <strong>the</strong> following subsections. Section 3.1 refers to <strong>the</strong>database structure, section 3.2 describes <strong>the</strong> descriptors extraction process <strong>and</strong> <strong>the</strong> user’s options,section 3.3 discusses <strong>the</strong> codebook generation process <strong>and</strong> <strong>the</strong> extracted histograms (bag <strong>of</strong> words)<strong>and</strong> finally section 3.5 describes <strong>the</strong> creation <strong>of</strong> indexes for fast similarity search inside <strong>the</strong> database.3.1 DATABASE STRUCTUREIn 3DVIVANT <strong>the</strong> database is actually a filesystem structure that contains all <strong>the</strong> necessary data <strong>and</strong>metadata. The structure aims to organize <strong>the</strong> data in a) <strong>the</strong> raw multimedia files b) <strong>the</strong> features files c)<strong>the</strong> bag-<strong>of</strong>-words files d) <strong>and</strong> finally <strong>the</strong> index files. The filesystem structure is presented in Figure 6.In <strong>the</strong> “data” directory <strong>of</strong> <strong>the</strong> filesystem, <strong>the</strong> raw data are separated based on <strong>the</strong> modality in order todrive <strong>the</strong> appropriate descriptor extraction algorithms properly for each modality. Moreover, <strong>the</strong>proposed structure enables easier reference <strong>of</strong> <strong>the</strong> multimedia objects in <strong>the</strong> retrieval process.The decision to select <strong>the</strong> S&R database to be a filesystem structure is supported by variousarguments. First, a filesystem database is very easy to create even for a novice user. The possibility4/03/2013 12