JVET-F0041 AHG8: Platform independent floating point to integer conversion for 360Lib [Y. He, P. Hanhart, Y. Ye (InterDigital)]

Reviewed in BoG JVET-F0106.

The 360Lib software supports projection format conversion among different projection formats and spherical metrics calculation. To keep high precision, floating point computation is applied in 360Lib-2.1 when computing geometry coordinates for both projection format conversion and quality metric calculation. While generating and cross checking the 360° CTC simulation results as defined in JVET-E1030, it was found that 360Lib-2.1 may generate slightly different results depending on the OS and also the compiler version of the simulation platform. This document proposes a fix to the platform-dependent problem by converting floating point precision to fixed point precision and then converting to integer precision, rather than converting directly from floating point to integer. It was reported that, with the proposed fix, the simulations on Windows and on Linux platforms, as well as using different gcc versions on Linux, all achieve the same results. It is therefore asserted that this fix resolves the platform-dependence problem in the 360Lib-2.1 software. Compared to the 360Lib-2.1 anchors, in terms of end-to-end spherical quality metrics, there is no BD rate loss for luma for all projection formats. For chroma, there is no BD loss for all projection formats except the OHP projection format, where a small chroma BD loss of 0.1% was observed.

Decision (SW): Adopt JVET-F0041 (confirmed in JVET plenary).

JVET-F0041 AHG8: Platform independent floating point to integer conversion for 360Lib [Y. He, P. Hanhart, Y. Ye (InterDigital)]