36 research outputs found
Neighborhood Selection for Thresholding-based Subspace Clustering
Subspace clustering refers to the problem of clustering high-dimensional data
points into a union of low-dimensional linear subspaces, where the number of
subspaces, their dimensions and orientations are all unknown. In this paper, we
propose a variation of the recently introduced thresholding-based subspace
clustering (TSC) algorithm, which applies spectral clustering to an adjacency
matrix constructed from the nearest neighbors of each data point with respect
to the spherical distance measure. The new element resides in an individual and
data-driven choice of the number of nearest neighbors. Previous performance
results for TSC, as well as for other subspace clustering algorithms based on
spectral clustering, come in terms of an intermediate performance measure,
which does not address the clustering error directly. Our main analytical
contribution is a performance analysis of the modified TSC algorithm (as well
as the original TSC algorithm) in terms of the clustering error directly.Comment: ICASSP 201
Practical Full Resolution Learned Lossless Image Compression
We propose the first practical learned lossless image compression system,
L3C, and show that it outperforms the popular engineered codecs, PNG, WebP and
JPEG 2000. At the core of our method is a fully parallelizable hierarchical
probabilistic model for adaptive entropy coding which is optimized end-to-end
for the compression task. In contrast to recent autoregressive discrete
probabilistic models such as PixelCNN, our method i) models the image
distribution jointly with learned auxiliary representations instead of
exclusively modeling the image distribution in RGB space, and ii) only requires
three forward-passes to predict all pixel probabilities instead of one for each
pixel. As a result, L3C obtains over two orders of magnitude speedups when
sampling compared to the fastest PixelCNN variant (Multiscale-PixelCNN).
Furthermore, we find that learning the auxiliary representation is crucial and
outperforms predefined auxiliary representations such as an RGB pyramid
significantly.Comment: Updated preprocessing and Table 1, see A.1 in supplementary. Code and
models: https://github.com/fab-jul/L3C-PyTorc
The Possibility of Transfer(?): A Comprehensive Approach to the International Criminal Tribunal for Rwanda’s Rule 11bis To Permit Transfer to Rwandan Domestic Courts
We present a learned image compression system based on GANs, operating at
extremely low bitrates. Our proposed framework combines an encoder,
decoder/generator and a multi-scale discriminator, which we train jointly for a
generative learned compression objective. The model synthesizes details it
cannot afford to store, obtaining visually pleasing results at bitrates where
previous methods fail and show strong artifacts. Furthermore, if a semantic
label map of the original image is available, our method can fully synthesize
unimportant regions in the decoded image such as streets and trees from the
label map, proportionally reducing the storage cost. A user study confirms that
for low bitrates, our approach is preferred to state-of-the-art methods, even
when they use more than double the bits.Comment: E. Agustsson, M. Tschannen, and F. Mentzer contributed equally to
this work. ICCV 2019 camera ready versio