DCI Specs - Digital Cinema Initiatives

3.2.1.6. Transfer FunctionThe CIE XYZ tristimulus values must be calculated with a normalizing constant that setsthe Y tristimulus value equal to the absolute luminance 4 in cd/m 2 . With this specificationof the color, the following equations define the encoding transfer function. 53.2.1.7. Bit DepthThe bit depth for each code value for a color component shall be 12 bits. This yields 36bits per pixel.3.2.1.8. Aspect RatioSome examples for the accommodation of images of various aspect ratios in thecontainers are shown in Table 3.Where:Ph = number of active horizontal pixels in imagePv = number of active vertical pixels in imageAR = the aspect ratio of the image (ratio of width to height, expressedas a decimal)Level Ph Pv AR PixelAspectRatio1 4096 1716 239 1:11 3996 2160 1.85 1:12 2048 858 2.39 1:12 1998 1080 1.85 1:1Table 3: Example Image Aspect Ratios4 The peak luminance as shown in the transfer function equation is 52.37 cd/m 2 . The extra headroom is reserved toaccommodate a range of white points including D 55 , D 61 and D 65 , while still supporting the reference white luminance of48 cd/m 2 as specified in SMPTE 196E for Digital Cinema-Screen Luminance Level, Chromaticity and Uniformity.5 The INT operator returns the value of 0 for fractional parts in the range of 0 to 0.4999… and +1 for fractional parts in therange 0.5 to 0.9999…, i.e., it rounds up fractions above 0.5.DCI Digital Cinema System Specification v.1.2 Page 28