Team Imedia

Overall Objectives
Scientific Foundations
Application Domains
New Results
Other Grants and Activities

Section: New Results



Keywords : CBIR, image retrieval by content, relevance feedback, user interface, video retrieval.

Participants : Raffi Enficiaud, Nicolas Hervé, Jean-Paul Chieze, Mondher Khadhraoui, Souheil Selmi, Alexis Joly, Nozha Boujemaa.

As each year, the integration of latest research results has been achieved.

Some OS specific dependencies, on which we were working in 2008, were now tested on several platforms such as different Unices (32 and 64 bits), Mac OSX and with different compilers. The program now runs safely on all these architectures. To achieve that, we progressively moved to the Boost library (threads, unit tests , graphs, linear algebra supports) which is known for its quality, portability and permissive licence. The dependencies of the core software were also cleaned, and we are now able to build easily the software from scratch, which was previously possible only at the expense of a lot of time. A particular care was taken concerning the licence issues of these dependencies.

A lot of efforts were also put on the quality and stability of the program in order to develop new functionalities without introducing regressions, and to safely deploy MAESTRO on distant servers within the scope of industrial partnerships (need of VITALAS, Pl@ntNet,...). Automatic reports are built at each modification of the code repository, for several architectures and platforms in a distributed manner.

PMH library

Keywords : indexing structure, hashing, locality sensitive hashing, approximate similarity search, nearest neighbours, multi-probe.

Participants : Alexis Joly, Olivier Buisson [ INA ] .

During year 2009, we finalized jointly with INA a release version v1 of PMH library. The global architecture of the library was modified in order to make it more flexible and generic. Several parts of of indexing chain have been isolated in independent modules: a Transformer module that enables to project original data in new feature space, a scalar Quantizer module, a multi-dimensional Quantizer module that enables the creation of the hash keys and a query modeller that enables to learn the prior probability tables for a given query model. Several new functionalities were also added, the most important one being the ability to search directly on binary compressed signatures instead of original space signatures. The second main new functionality is a two-level hierarchy of hash tables that allows to bridge the previous limit of hash key sizes induced by memory limitations. Other new functionalities include new metrics, new scalar quantization and new hash function families. Discussions with INA regarding licencing of the software are currently engaged with the objective to have an open source licence next year. Finally, new research results on random maximum margin hashing have been implemented for experiments and should be fully integrated in the next few months.


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