Restauration des pistes sonores optiques cinématographiques : approche par traitement d'images
Abdelǎali Hassaïne · HAL (Le Centre pour la Communication Scientifique Directe) · 2009
The restoration of old motion picture films is an active research field. The restoration of the optical soundtrack however has only been performed at the audio domain, in spite of the fact that it is recorded as a continuous image located between the images of the film and the sprocket holes. Two types of optical soundtracks exist: the most widespread are variable area soundtracks, which contain a transparent region located between two symmetrical opaque regions. The width of the transparent region is directly proportional to the audio signal amplitude. For the restoration of this kind of soundtracks, we developed algorithms for the correction of azimuth deviation, the detection of the symmetry axis and for the symmetry enforcement. A segmentation step is then performed for defects removal. The second type is called variable density soundtracks, in which, the intensity of each line is proportional to the audio signal amplitude. For the restoration of those soundtracks, we developed an algorithm for azimuth correction. A clipping algorithm is then performed for defects removal. We have also studied the problem of badly exposed optical soundtracks. This problem is due to light propagation during the duplications of the film. We developed several morphological methods for the detection and the restoration of this kind of defects. The evaluation of our restoration system is first done by sound experts. We have also set up blind listening tests in order to have a more objective assessment.