further fixes for signed timestamp rescale introduced by db0079c
further fixes for signed timestamp rescale introduced by db0079c

gpac/gpac,gpac/gpac,rbouqueau/gpac,rbouqueau/gpac,gpac/gpac,gpac/gpac,rbouqueau/gpac,gpac/gpac,rbouqueau/gpac,gpac/gpac,rbouqueau/gpac,rbouqueau/gpac,rbouqueau/gpac,rbouqueau/gpac,gpac/gpac,gpac/gpac