  Scene recognition with RGB images has been extensively studied and has
reached very remarkable recognition levels, thanks to convolutional neural
networks (CNN) and large scene datasets. In contrast, current RGB-D scene data
is much more limited, so often leverages RGB large datasets, by transferring
pretrained RGB CNN models and fine-tuning with the target RGB-D dataset.
However, we show that this approach has the limitation of hardly reaching
bottom layers, which is key to learn modality-specific features. In contrast,
we focus on the bottom layers, and propose an alternative strategy to learn
depth features combining local weakly supervised training from patches followed
by global fine tuning with images. This strategy is capable of learning very
discriminative depth-specific features with limited depth images, without
resorting to Places-CNN. In addition we propose a modified CNN architecture to
further match the complexity of the model and the amount of data available. For
RGB-D scene recognition, depth and RGB features are combined by projecting them
in a common space and further leaning a multilayer classifier, which is jointly
optimized in an end-to-end network. Our framework achieves state-of-the-art
accuracy on NYU2 and SUN RGB-D in both depth only and combined RGB-D data.
