Abstract
The issue of backwards compatible image and video coding gained
some attention in both MPEG and JPEG, let it be as extension for HEVC,
let it be as the JPEG XT standardization initiative of the SC29WG1
committee. The coding systems work all on the principle of a base
layer operating in the low-dynamic range regime, using a tone-mapped
version of the HDR material as input, and an extension layer invisible
to legacy applications. The extension layer allows implementations
conforming to the full standard to reconstruct the original image in
the high-dynamic range regime. What is also common to all approaches
is the rate-allocation problem: How can one split the rate between
base and extension layer to ensure optimal coding? In this work, an
explicit answer is derived for a simplified model of a two-layer
compression system in the high bit-rate approximation. For a HDR to
LDR tone mapping that approximates the well-known sRGB non-linearity
of ? = 2.4 and a Laplacian probability density function, explicit
results in the form of the Lambert-W-function are derived. The
theoretical results are then verified in experiments using a JPEG XT
demo implementation.
Users
Please
log in to take part in the discussion (add own reviews or comments).