1. Low Bit Rate Video Coding with Geometric Transformation
Nuno Rodrigues, Vitor Silva, Sérgio Faria
nuno.rodrigues, vitor.silva,
Abstract
New coding Techniques where tested
Geometric Transformations (GT) have been used to compensate complex object movements
In this work, GT are applied in the pixel domain, to allow the recovering of non-uniform intensity changes, as well as uncovered background, in Low BR Video Coding
BMA improved with compensation in the luminance domain BMAI
BMGT improved with compensation in the luminance domain BMGTI
Experimental Results
For Sergio Sequence coded with Motion Compensation only at approximately 70 kbps using blocks of 16x16 pixels
Block Matching with Geometric Transform
Blocks of pixels in the current frame are deformed appropriately, to best model the complex motion
Although BMGT is appropriate to compensate complex motion, there are still some problems, namely:
non-uniform intensity changes
masking and uncovered background
Sergio Sequence: 72 images where a head moves 180º from left to right has a large component of uncovered background from left face initially hidden
Conclusions
The new transformations in the pixel domain allow the estimation of rotation, scaling and masking with uncovered background, instead of only translational movements.
Using them, several images in a sequence can be encoded without encoding the residual error, for very low bit rate video coding applications.
Motion Compensation Enhancement
Transformations are applied to the elements of the image blocks in order to approximate the reference (P) and the reconstructed (Q) blocks.
Future Work
The compensation values c and b are determined using a least square approximation, in order to minimize the cumulative quadratic error:
Investigate the performance of this new kind of transformations in the coding of Stereo Sequences, as a way of exploring the redundancy between the two views of a scene, as well as the spatial and temporal redundancy of a normal sequence.