公开(公告)号：US20150146107A1

公开(公告)日：2015-05-28

申请号：US14502733

申请日：2014-09-30

Applicant: Apple Inc.

Inventor： Ken Greenebaum ,  Ian Hendry ,  David Hayward

IPC: H04N9/64

CPC classification number: H04N9/646 ,  H04N1/644 ,  H04N5/202

Abstract: Media is usually encoded using a non-linear transfer function that approximates human perception to more efficiently allocate codes to areas of dynamic range where human observers are more easily able to perceive differences in signal strength. Many common media operations, e.g., scaling, rotating, and gamut converting, must be performed in a linear representation to be correct and artifact-free. The non-linear transfer functions used are often pure-power functions, such as “gamma” functions. To avoid banding after transformation, as many as 17 bits are needed in the linear-space with 8-bit input. Thus, methods, computer readable media, and systems for reducing the number of bits required in the linear domain are described herein that substitute a piecewise linear function (e.g., a line segment followed by an offset curve) for a pure-power gamma function, such that a slope limit is applied to constrain the number of (additional) linear bits required (over the input precision).

Abstract translation: 媒体通常使用非线性传递函数进行编码，该函数近似于人类的感知，以更有效地将代码分配给动态范围的区域，人类观察者更容易察觉到信号强度的差异。 必须在线性表示中执行许多常见的媒体操作，例如缩放，旋转和色域转换，以使其正确无误。 所使用的非线性传递函数通常是纯功率功能，例如“gamma”功能。 为了避免转换后的带状，在8位输入的线性空间中需要多达17位。 因此，本文描述了用于减少线性域中所需的位数的方法，计算机可读介质和系统，其将用于纯功率伽马函数的分段线性函数（例如，线段跟随偏移曲线）代替， 使得施加斜率限制来约束所需的（附加）线性位数（超过输入精度）。